4coder/4ed_buffer.cpp

/*
 * Mr. 4th Dimention - Allen Webster
 *
 * 06.01.2017
 *
 * The 4coder base buffer data structure.
 *
 */

// TOP

//
// Buffer low level operations
//

internal void
write_cursor_with_index(Cursor_With_Index *positions, i32 *count, i32 pos){
    positions[(*count)].index = *count;
    positions[(*count)].pos = pos;
    ++(*count);
}

// TODO(allen): Rewrite this without being a dumbass.
// TODO(allen): Rewrite this without being a dumbass.
// TODO(allen): Rewrite this without being a dumbass.
#define CursorSwap__(a,b) { Cursor_With_Index t = a; a = b; b = t; }

// TODO(allen): Rewrite this without being a dumbass.
internal void
buffer_quick_sort_cursors(Cursor_With_Index *positions, i32 start, i32 pivot){
    i32 mid = start;
    i32 pivot_pos = positions[pivot].pos;
    for (i32 i = mid; i < pivot; ++i){
        if (positions[i].pos < pivot_pos){
            CursorSwap__(positions[mid], positions[i]);
            ++mid;
        }
    }
    CursorSwap__(positions[mid], positions[pivot]);
    
    if (start < mid - 1) buffer_quick_sort_cursors(positions, start, mid - 1);
    if (mid + 1 < pivot) buffer_quick_sort_cursors(positions, mid + 1, pivot);
}

// TODO(allen): Rewrite this without being a dumbass.
internal void
buffer_quick_unsort_cursors(Cursor_With_Index *positions, i32 start, i32 pivot){
    i32 mid = start;
    i32 pivot_index = positions[pivot].index;
    for (i32 i = mid; i < pivot; ++i){
        if (positions[i].index < pivot_index){
            CursorSwap__(positions[mid], positions[i]);
            ++mid;
        }
    }
    CursorSwap__(positions[mid], positions[pivot]);
    
    if (start < mid - 1) buffer_quick_unsort_cursors(positions, start, mid - 1);
    if (mid + 1 < pivot) buffer_quick_unsort_cursors(positions, mid + 1, pivot);
}

#undef CursorSwap__

internal void
buffer_sort_cursors(Cursor_With_Index *positions, i32 count){
    if (count > 0){
        buffer_quick_sort_cursors(positions, 0, count - 1);
    }
}

internal void
buffer_unsort_cursors(Cursor_With_Index *positions, i32 count){
    if (count > 0){
        buffer_quick_unsort_cursors(positions, 0, count - 1);
    }
}

internal void
buffer_update_cursors(Cursor_With_Index *sorted_positions, i32 count, i32 start, i32 end, i32 len, b32 lean_right){
    i32 shift_amount = (len - (end - start));
    Cursor_With_Index *position = sorted_positions + count - 1;
    
    if (lean_right){
        for (; position >= sorted_positions && position->pos > end; --position){
            position->pos += shift_amount;
        }
        for (; position >= sorted_positions && position->pos >= start; --position){
            position->pos = start + len;
        }
    }
    else{
        for (; position >= sorted_positions && position->pos > end; --position){
            position->pos += shift_amount;
        }
        for (; position >= sorted_positions && position->pos >= start; --position){
            position->pos = start;
        }
    }
}

internal i32
buffer_batch_debug_sort_check(Buffer_Edit *sorted_edits, i32 edit_count){
    Buffer_Edit *edit = sorted_edits;
    i32 i = 0, start_point = 0;
    i32 result = 1; 
    
    for (i = 0; i < edit_count; ++i, ++edit){
        if (start_point > edit->start){
            result = 0; break;
        }
        start_point = (edit->end < edit->start + 1)?(edit->start + 1):(edit->end);
    }
    
    return(result);
}

// TODO(allen): This now relies on Edit and Edit_Array from 4ed_edit.h even though we sort of think of that
// as cheating... gotta rethink the separation of buffer from everything else moving forward or something.

internal i32
buffer_batch_edit_update_cursors(Cursor_With_Index *sorted_positions, i32 count, Edit_Array sorted_edits, b32 lean_right){
    Cursor_With_Index *position = sorted_positions;
    Cursor_With_Index *one_past_last_position = sorted_positions + count;
    Edit *edit = sorted_edits.vals;
    Edit *one_past_last_edit = sorted_edits.vals + sorted_edits.count;
    
    i32 shift_amount = 0;
    if (lean_right){
        for (;edit < one_past_last_edit && position < one_past_last_position;
             ++edit){
            i32 start = edit->range.first;
            i32 end = edit->range.one_past_last;
            
            for (;position->pos < start && position < one_past_last_position;
                 ++position){
                position->pos += shift_amount;
            }
            
            i32 new_end = start + edit->length + shift_amount;
            for (;position->pos <= end && position < one_past_last_position;
                 ++position){
                position->pos = new_end;
            }
            
            shift_amount += (edit->length - (end - start));
        }
    }
    else{
        for (;edit < one_past_last_edit && position < one_past_last_position;
             ++edit){
            i32 start = edit->range.first;
            i32 end = edit->range.one_past_last;
            
            for (;position->pos < start && position < one_past_last_position;
                 ++position){
                position->pos += shift_amount;
            }
            
            i32 new_end = start + shift_amount;
            for (;position->pos <= end && position < one_past_last_position;
                 ++position){
                position->pos = new_end;
            }
            
            shift_amount += (edit->length - (end - start));
        }
    }
    
    for (;position < one_past_last_position;
         ++position){
        position->pos += shift_amount;
    }
    
    for (;edit < one_past_last_edit;
         ++edit){
        shift_amount += (edit->length - (edit->range.one_past_last - edit->range.first));
    }
    
    return(shift_amount);
}

//////////////////////////////////////

internal i32
eol_convert_in(char *dest, char *src, i32 size){
    i32 i = 0;
    i32 j = 0;
    i32 k = 0;
    
    for (; j < size && src[j] != '\r'; ++j);
    memcpy(dest, src, j);
    
    if (j < size){
        k = 1;
        ++j;
        for (i = j; i < size; ++i){
            if (src[i] == '\r'){
                memcpy(dest + j - k, src + j, i - j);
                ++k;
                j = i+1;
            }
        }
        memcpy(dest + j - k, src + j, i - j);
        j = i - k;
    }
    
    return(j);
}

internal i32
eol_in_place_convert_in(char *data, i32 size){
    i32 i = 0;
    i32 j = 0;
    i32 k = 0;
    
    for (; j < size && data[j] != '\r'; ++j);
    
    if (j < size){
        k = 1;
        ++j;
        for (i = j; i < size; ++i){
            if (data[i] == '\r'){
                memmove(data + j - k, data + j, i - j);
                ++k;
                j = i+1;
            }
        }
        memmove(data + j - k, data + j, i - j);
        j = i - k;
    }
    
    return(j);
}

// TODO(allen): iterative memory check?
internal i32
eol_convert_out(char *dest, i32 max, char *src, i32 size, i32 *size_out){
    i32 result = 1;
    i32 i = 0;
    i32 j = 0;
    
    for (; i < size; ++i, ++j){
        if (src[i] == '\n'){
            dest[j] = '\r';
            ++j;
            dest[j] = '\n';
        }
        else dest[j] = src[i];
    }
    
    *size_out = j;
    return(result);
}

// TODO(allen): iterative memory check?
internal i32
eol_in_place_convert_out(char *data, i32 size, i32 max, i32 *size_out){
    i32 result = 1;
    i32 i = 0;
    
    for (; i < size; ++i){
        if (data[i] == '\n'){
            memmove(data + i + 1, data + i, size - i);
            data[i] = '\r';
            ++i;
            ++size;
        }
    }
    
    *size_out = size;
    return(result);
}

//////////////////////////////////////

//
// Implementation of the gap buffer
//

internal i32
buffer_good(Gap_Buffer *buffer){
    i32 good = (buffer->data != 0);
    return(good);
}

internal i32
buffer_size(Gap_Buffer *buffer){
    i32 size = buffer->size1 + buffer->size2;
    return(size);
}

internal Gap_Buffer_Init
buffer_begin_init(Gap_Buffer *buffer, u8 *data, umem size){
    Gap_Buffer_Init init;
    init.buffer = buffer;
    init.data = (char*)data;
    init.size = (i32)size;
    return(init);
}

internal b32
buffer_init_need_more(Gap_Buffer_Init *init){
    return(init->buffer->data == 0);
}

internal i32
buffer_init_page_size(Gap_Buffer_Init *init){
    return(init->size * 2);
}

internal void
buffer_init_provide_page(Gap_Buffer_Init *init, void *page, i32 page_size){
    Gap_Buffer *buffer = init->buffer;
    buffer->data = (char*)page;
    buffer->max = page_size;
}

internal b32
buffer_end_init(Gap_Buffer_Init *init){
    Gap_Buffer *buffer = init->buffer;
    b32 result = false;
    
    if (buffer->data != 0 && buffer->max >= init->size){
        i32 size = init->size;
        i32 size2 = (size >> 1);
        i32 osize1 = size - size2;
        i32 size1 = osize1;
        
        if (size1 > 0){
            size1 = eol_convert_in(buffer->data, init->data, size1);
            if (size2 > 0){
                size2 = eol_convert_in(buffer->data + size1, init->data + osize1, size2);
            }
        }
        
        buffer->size1 = size1;
        buffer->size2 = size2;
        buffer->gap_size = buffer->max - size1 - size2;
        memmove(buffer->data + size1 + buffer->gap_size, buffer->data + size1, size2);
        
        result = true;
    }
    
    return(result);
}

internal b32
buffer_stringify_loop(Gap_Buffer_Stream *stream, Gap_Buffer *buffer, i32 start, i32 end){
    b32 result = false;
    
    if (0 <= start && start < end && end <= buffer->size1 + buffer->size2){
        stream->buffer = buffer;
        stream->absolute_end = end;
        
        if (start < buffer->size1){
            if (buffer->size1 < end){
                stream->separated = true;
            }
            else{
                stream->separated = false;
            }
            stream->data = buffer->data;
        }
        else{
            stream->separated = false;
            stream->data = buffer->data + buffer->gap_size;
        }
        
        if (stream->separated){
            stream->end = buffer->size1;
        }
        else{
            stream->end = end;
        }
        
        if (stream->end > stream->absolute_end){
            stream->end = stream->absolute_end;
        }
        
        result = true;
    }
    
    if (!result && stream->use_termination_character){
        stream->buffer = buffer;
        stream->absolute_end = end;
        stream->use_termination_character = true;
        stream->data = (&stream->terminator) - buffer->size1 - buffer->size2;
        stream->end = stream->absolute_end + 1;
        result = true;
    }
    
    return(result);
}

internal b32
buffer_stringify_next(Gap_Buffer_Stream *stream){
    b32 result = 0;
    Gap_Buffer *buffer = stream->buffer;
    if (stream->separated){
        stream->data = buffer->data + buffer->gap_size;
        stream->end = stream->absolute_end;
        stream->separated = 0;
        result = 1;
    }
    
    if (result == 0){
        if (stream->use_termination_character){
            stream->use_termination_character = 0;
            stream->data = (&stream->terminator) - buffer->size1 - buffer->size2;
            stream->end = stream->absolute_end + 1;
            result = 1;
        }
    }
    
    return(result);
}

internal i32
buffer_replace_range_compute_shift(i32 start, i32 end, i32 len){
    return(len - (end - start));
}

internal b32
buffer_replace_range(Gap_Buffer *buffer, i32 start, i32 end, char *str, i32 len, i32 shift_amount, i32 *request_amount){
    char *data = buffer->data;
    i32 size = buffer_size(buffer);
    b32 result = false;
    i32 move_size = 0;
    
    Assert(0 <= start);
    Assert(start <= end);
    Assert(end <= size);
    
    if (shift_amount + size <= buffer->max){
        if (end < buffer->size1){
            move_size = buffer->size1 - end;
            memmove(data + buffer->size1 + buffer->gap_size - move_size, data + end, move_size);
            buffer->size1 -= move_size;
            buffer->size2 += move_size;
        }
        if (start > buffer->size1){
            move_size = start - buffer->size1;
            memmove(data + buffer->size1, data + buffer->size1 + buffer->gap_size, move_size);
            buffer->size1 += move_size;
            buffer->size2 -= move_size;
        }
        
        memcpy(data + start, str, len);
        buffer->size2 = size - end;
        buffer->size1 = start + len;
        buffer->gap_size -= shift_amount;
        
        Assert(buffer->size1 + buffer->size2 == size + shift_amount);
        Assert(buffer->size1 + buffer->gap_size + buffer->size2 == buffer->max);
    }
    else{
        *request_amount = round_up_i32(2*(shift_amount + size), KB(4));
        result = true;
    }
    
    return(result);
}

internal b32
buffer_batch_edit_step(Buffer_Batch_State *state, Gap_Buffer *buffer, Edit_Array sorted_edits, i32 *request_amount){
    b32 result = false;
    
    i32 shift_total = state->shift_total;
    i32 i = state->i;
    
    Edit *edit = sorted_edits.vals + i;
    for (; i < sorted_edits.count; ++i, ++edit){
        char *str = edit->str;
        i32 length = edit->length;
        i32 start = edit->range.first + shift_total;
        i32 end = edit->range.one_past_last + shift_total;
        i32 shift_amount = buffer_replace_range_compute_shift(start, end, length);
        result = buffer_replace_range(buffer, start, end, str, length, shift_amount, request_amount);
        if (result){
            break;
        }
        shift_total += shift_amount;
    }
    
    state->shift_total = shift_total;
    state->i = i;
    
    return(result);
}

internal void*
buffer_edit_provide_memory(Gap_Buffer *buffer, void *new_data, i32 new_max){
    void *result = buffer->data;
    i32 size = buffer_size(buffer);
    i32 new_gap_size = new_max - size;
    
    Assert(new_max >= size);
    
    memcpy(new_data, buffer->data, buffer->size1);
    memcpy((char*)new_data + buffer->size1 + new_gap_size, buffer->data + buffer->size1 + buffer->gap_size, buffer->size2);
    
    buffer->data = (char*)new_data;
    buffer->gap_size = new_gap_size;
    buffer->max = new_max;
    
    return(result);
}

//
// High level buffer operations
//

internal String_Const_u8_Array
buffer_get_chunks(Cursor *cursor, Gap_Buffer *buffer, Buffer_Get_Chunk_Mode mode){
    i32 total_count = (buffer->size1 > 0) + (buffer->size2 > 0) + (mode == BufferGetChunk_ZeroTerminated);
    String_Const_u8_Array result = {};
    result.vals = push_array(cursor, String_Const_u8, total_count);
    if (buffer->size1 > 0){
        result.vals[result.count] = SCu8(buffer->data, buffer->size1);
        result.count += 1;
    }
    if (buffer->size2 > 0){
        result.vals[result.count] = SCu8(buffer->data + buffer->size1 + buffer->gap_size, buffer->size2);
        result.count += 1;
    }
    if (mode == BufferGetChunk_ZeroTerminated){
        result.vals[result.count] = SCu8();
        result.count += 1;
    }
    return(result);
}

internal String_Const_u8_Array
buffer_get_chunks(Cursor *cursor, Gap_Buffer *buffer){
    return(buffer_get_chunks(cursor, buffer, BufferGetChunk_Basic));
}

internal String_Const_u8_Array
buffer_chunks_clamp(String_Const_u8_Array chunks, Range_i64 range){
    i64 real_position = 0;
    for (i32 i = 0; i < chunks.count; i += 1){
        Range_i64 chunk_range = Ii64(real_position, real_position + chunks.strings[i].size);
        Range_i64 clamped_range = Ii64(clamp(range.min, chunk_range.min, range.max),
                                       clamp(range.min, chunk_range.max, range.max));
        chunks.strings[i].str += clamped_range.min - chunk_range.min;
        chunks.strings[i].size = range_size(clamped_range);
        real_position += range_size(chunk_range);
    }
    for (; chunks.count > 0 && chunks.strings[0].size == 0;){
        chunks.strings += 1;
        chunks.count -= 1;
    }
    for (; chunks.count > 0 && chunks.strings[chunks.count - 1].size == 0;){
        chunks.count -= 1;
    }
    return(chunks);
}

internal void
buffer_stringify(Gap_Buffer *buffer, i32 start, i32 end, char *out){
    Gap_Buffer_Stream stream = {};
    
    i32 i = start;
    if (buffer_stringify_loop(&stream, buffer, i, end)){
        b32 still_looping = 0;
        do{
            i32 size = stream.end - i;
            memcpy(out, stream.data + i, size);
            i = stream.end;
            out += size;
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
}

internal void
buffer_stringify_range(Gap_Buffer *buffer, Range range, char *out){
    buffer_stringify(buffer, range.first, range.one_past_last, out);
}

internal i32
buffer_convert_out(Gap_Buffer *buffer, char *dest, i32 max){
    Gap_Buffer_Stream stream = {};
    i32 i = 0;
    i32 size = buffer_size(buffer);
    Assert(size + buffer->line_count <= max);
    
    i32 pos = 0;
    if (buffer_stringify_loop(&stream, buffer, 0, size)){
        b32 still_looping = 0;
        do{
            i32 chunk_size = stream.end - i;
            i32 out_size = 0;
            i32 result = eol_convert_out(dest + pos, max - pos, stream.data + i, chunk_size, &out_size);
            Assert(result);
            i = stream.end;
            pos += out_size;
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    return(pos);
}

internal i32
buffer_count_newlines(Gap_Buffer *buffer, i32 start, i32 end){
    Gap_Buffer_Stream stream = {};
    i32 i = start;
    i32 count = 0;
    
    Assert(0 <= start);
    Assert(start <= end);
    Assert(end <= buffer_size(buffer));
    
    if (buffer_stringify_loop(&stream, buffer, i, end)){
        b32 still_looping = 0;
        do{
            for (; i < stream.end; ++i){
                count += (stream.data[i] == '\n');
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    return(count);
}

// TODO(allen): Rewrite this with a duff routine
// Also make it so that the array goes one past the end
// and stores the size in the extra spot.
internal i32
buffer_measure_starts(Buffer_Measure_Starts *state, Gap_Buffer *buffer){
    Gap_Buffer_Stream stream = {};
    i32 size = buffer_size(buffer);
    i32 start = state->start, i = state->i;
    i32 *start_ptr = buffer->line_starts + state->count;
    i32 *start_end = buffer->line_starts + buffer->line_max;
    i32 result = 1;
    
    if (buffer_stringify_loop(&stream, buffer, i, size)){
        b32 still_looping = 0;
        do{
            for (; i < stream.end; ++i){
                char ch = stream.data[i];
                if (ch == '\n'){
                    if (start_ptr == start_end){
                        goto buffer_measure_starts_widths_end;
                    }
                    
                    *start_ptr++ = start;
                    start = i + 1;
                }
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    Assert(i == size);
    
    if (start_ptr == start_end){
        goto buffer_measure_starts_widths_end;
    }
    *start_ptr++ = start;
    result = 0;
    
    buffer_measure_starts_widths_end:;
    state->i = i;
    state->count = (i32)(start_ptr - buffer->line_starts);
    state->start = start;
    
    if (!result){
        buffer->line_count = state->count;
    }
    
    return(result);
}

internal void
buffer_measure_character_starts(System_Functions *system, Gap_Buffer *buffer, i32 *character_starts, i32 mode, i32 virtual_white){
    Assert(mode == 0);
    
    Gap_Buffer_Stream stream = {};
    i32 i = 0;
    i32 size = buffer_size(buffer);
    
    i32 line_index = 0;
    i32 character_index = 0;
    
    b32 skipping_whitespace = 0;
    
    character_starts[line_index++] = character_index;
    
    if (virtual_white){
        skipping_whitespace = 1;
    }
    
    Translation_State tran = {};
    Translation_Emits emits = {};
    
    stream.use_termination_character = 1;
    stream.terminator = '\n';
    if (buffer_stringify_loop(&stream, buffer, i, size)){
        b32 still_looping = 0;
        do{
            for (; i < stream.end; ++i){
                u8 ch = (u8)stream.data[i];
                
                translating_fully_process_byte(&tran, ch, i, size, &emits);
                
                for (TRANSLATION_DECL_EMIT_LOOP(J, emits)){
                    TRANSLATION_DECL_GET_STEP(step, behavior, J, emits);
                    
                    if (behavior.do_newline){
                        ++character_index;
                        character_starts[line_index++] = character_index;
                        if (virtual_white){
                            skipping_whitespace = 1;
                        }
                    }
                    else if (behavior.do_codepoint_advance || behavior.do_number_advance){
                        if (ch != ' ' && ch != '\t'){
                            skipping_whitespace = 0;
                        }
                        
                        if (!skipping_whitespace){
                            ++character_index;
                        }
                    }
                }
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    Assert(line_index-1 == buffer->line_count);
}

// duff-routine defines
#define DrCase(PC) case PC: goto resumespot_##PC
#define DrYield(PC, n) { *S_ptr = S; S_ptr->__pc__ = PC; return(n); resumespot_##PC:; }
#define DrReturn(n) { *S_ptr = S; S_ptr->__pc__ = -1; return(n); }

internal Buffer_Layout_Stop
buffer_measure_wrap_y(Buffer_Measure_Wrap_State *S_ptr, Buffer_Measure_Wrap_Params params, f32 line_shift, b32 do_wrap, i32 wrap_unit_end){
    Buffer_Measure_Wrap_State S = *S_ptr;
    Buffer_Layout_Stop S_stop;
    
    switch (S.__pc__){
        DrCase(1);
        DrCase(2);
        DrCase(3);
        DrCase(4);
    }
    
    S.size = buffer_size(params.buffer);
    
    if (params.virtual_white){
        S_stop.status = BLStatus_NeedLineShift;
        S_stop.line_index = S.line_index;
        S_stop.wrap_line_index = S.current_wrap_index;
        S_stop.pos = S.i;
        DrYield(1, S_stop);
    }
    
    S.x = line_shift;
    params.wrap_line_index[S.line_index++] = 0;
    
    if (params.virtual_white){
        S.skipping_whitespace = true;
    }
    
    S.first_of_the_line = 1;
    if (buffer_stringify_loop(&S.stream, params.buffer, S.i, S.size)){
        S.still_looping = 0;
        do{
            for (; S.i < S.stream.end; ++S.i){
                {
                    u8 ch = (u8)S.stream.data[S.i];
                    
                    if (ch != ' ' && ch != '\t'){
                        S.skipping_whitespace = false;
                    }
                    
                    translating_fully_process_byte(&S.tran, ch, S.i, S.size, &S.emits);
                }
                
                for (TRANSLATION_EMIT_LOOP(S.J, S.emits)){
                    TRANSLATION_GET_STEP(S.step, S.behavior, S.J, S.emits);
                    
                    if (S.behavior.do_newline){
                        ++S.current_wrap_index;
                        params.wrap_line_index[S.line_index++] = S.current_wrap_index;
                        
                        if (params.virtual_white){
                            S_stop.status          = BLStatus_NeedLineShift;
                            S_stop.line_index      = S.line_index - 1;
                            S_stop.wrap_line_index = S.current_wrap_index;
                            S_stop.pos             = S.i+1;
                            DrYield(2, S_stop);
                        }
                        
                        S.x = line_shift;
                        
                        if (params.virtual_white){
                            S.skipping_whitespace = 1;
                        }
                        S.first_of_the_line = 1;
                    }
                    else if (S.behavior.do_number_advance || S.behavior.do_codepoint_advance){
                        if (!S.skipping_whitespace){
                            if (S.behavior.do_codepoint_advance){
                                S.current_adv = font_get_glyph_advance(params.face, S.step.value);
                            }
                            else{
                                S.current_adv = params.face->byte_advance;
                            }
                            
                            S.did_wrap = false;
                            if (S.step.i >= S.wrap_unit_end){
                                S_stop.status          = BLStatus_NeedWrapDetermination;
                                S_stop.line_index      = S.line_index - 1;
                                S_stop.wrap_line_index = S.current_wrap_index;
                                S_stop.pos             = S.step.i;
                                S_stop.x               = S.x;
                                DrYield(4, S_stop);
                                
                                S.wrap_unit_end = wrap_unit_end;
                                
                                if (do_wrap && !S.first_of_the_line){
                                    S.did_wrap = true;
                                    ++S.current_wrap_index;
                                    
                                    if (params.virtual_white){
                                        S_stop.status          = BLStatus_NeedWrapLineShift;
                                        S_stop.line_index      = S.line_index - 1;
                                        S_stop.wrap_line_index = S.current_wrap_index;
                                        S_stop.pos             = S.step.i;
                                        DrYield(3, S_stop);
                                    }
                                    
                                    S.x = line_shift + S.current_adv;
                                }
                            }
                            
                            if (!S.did_wrap){
                                S.x += S.current_adv;
                            }
                            
                            S.first_of_the_line = 0;
                        }
                    }
                }
            }
            S.still_looping = buffer_stringify_next(&S.stream);
        }while(S.still_looping);
    }
    
    ++S.current_wrap_index;
    params.wrap_line_index[S.line_index++] = S.current_wrap_index;
    
    Assert(S.line_index-1 == params.buffer->line_count);
    
    S_stop.status = BLStatus_Finished;
    DrReturn(S_stop);
}

#undef DrCase
#undef DrYield
#undef DrReturn

internal void
buffer_remeasure_starts(Gap_Buffer *buffer, i32 line_start, i32 line_end, i32 line_shift, i32 text_shift){
    i32 *starts = buffer->line_starts;
    i32 line_count = buffer->line_count;
    
    Assert(0 <= line_start);
    Assert(line_start <= line_end);
    Assert(line_end < line_count);
    Assert(line_count + line_shift <= buffer->line_max);
    
    ++line_end;
    
    // Adjust
    if (text_shift != 0){
        i32 line_i = line_end;
        starts += line_i;
        for (; line_i < line_count; ++line_i, ++starts){
            *starts += text_shift;
        }
        starts = buffer->line_starts;
    }
    
    // Shift
    i32 new_line_count = line_count;
    i32 new_line_end = line_end;
    if (line_shift != 0){
        new_line_count += line_shift;
        new_line_end += line_shift;
        
        memmove(starts + line_end + line_shift, starts + line_end, sizeof(i32)*(line_count - line_end));
    }
    
    // Iteration data (yikes! Need better loop system)
    Gap_Buffer_Stream stream = {};
    i32 size = buffer_size(buffer);
    i32 char_i = starts[line_start];
    i32 line_i = line_start;
    
    // Line start measurement
    i32 start = char_i;
    
    if (buffer_stringify_loop(&stream, buffer, char_i, size)){
        b32 still_looping = 0;
        do{
            for (; char_i < stream.end; ++char_i){
                u8 ch = (u8)stream.data[char_i];
                
                if (ch == '\n'){
                    starts[line_i] = start;
                    ++line_i;
                    start = char_i + 1;
                    
                    // TODO(allen): I would like to know that I am not guessing here,
                    // so let's try to turn the && into an Assert.
                    if (line_i >= new_line_end && (line_i >= new_line_count || start == starts[line_i])){
                        goto buffer_remeasure_starts_end;
                    }
                }
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    // TODO(allen): I suspect this can just go away.
    if (char_i == size){
        starts[line_i++] = start;
    }
    
    buffer_remeasure_starts_end:;
    Assert(line_count >= 1);
    buffer->line_count = new_line_count;
}

internal void
buffer_remeasure_character_starts(System_Functions *system, Gap_Buffer *buffer, i32 line_start, i32 line_end, i32 line_shift, i32 *character_starts, i32 mode, i32 virtual_whitespace){
    Assert(mode == 0);
    
    i32 new_line_count = buffer->line_count;
    
    Assert(0 <= line_start);
    Assert(line_start <= line_end);
    Assert(line_end < new_line_count - line_shift);
    
    ++line_end;
    
    // Shift
    i32 line_count = new_line_count;
    i32 new_line_end = line_end;
    if (line_shift != 0){
        line_count -= line_shift;
        new_line_end += line_shift;
        
        memmove(character_starts + line_end + line_shift, character_starts + line_end, sizeof(i32)*(line_count - line_end + 1));
    }
    
    // Iteration data
    Gap_Buffer_Stream stream = {};
    i32 size = buffer_size(buffer);
    i32 char_i = buffer->line_starts[line_start];
    i32 line_i = line_start;
    
    // Character measurement
    i32 last_char_start = character_starts[line_i];
    i32 current_char_start = last_char_start;
    
    b32 skipping_whitespace = 0;
    
    if (virtual_whitespace){
        skipping_whitespace = 1;
    }
    
    // Translation
    Translation_State tran = {};
    Translation_Emits emits = {};
    
    stream.use_termination_character = 1;
    stream.terminator = '\n';
    if (buffer_stringify_loop(&stream, buffer, char_i, size)){
        b32 still_looping = 0;
        do{
            for (; char_i < stream.end; ++char_i){
                u8 ch = (u8)stream.data[char_i];
                translating_fully_process_byte(&tran, ch, char_i, size, &emits);
                
                for (TRANSLATION_DECL_EMIT_LOOP(J, emits)){
                    TRANSLATION_DECL_GET_STEP(step, behavior, J, emits);
                    
                    if (behavior.do_newline){
                        character_starts[line_i++] = last_char_start;
                        ++current_char_start;
                        last_char_start = current_char_start;
                        if (virtual_whitespace){
                            skipping_whitespace = 1;
                        }
                        
                        if (line_i >= new_line_end){
                            goto buffer_remeasure_character_starts_end;
                        }
                    }
                    else if (behavior.do_codepoint_advance || behavior.do_number_advance){
                        if (ch != ' ' && ch != '\t'){
                            skipping_whitespace = 0;
                        }
                        
                        if (!skipping_whitespace){
                            ++current_char_start;
                        }
                    }
                }
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    Assert(line_i >= new_line_end);
    
    buffer_remeasure_character_starts_end:;
    
    // Adjust
    if (line_i <= new_line_end){
        i32 character_shift = current_char_start - character_starts[line_i];
        
        if (character_shift != 0){
            character_starts += line_i;
            for (; line_i <= new_line_count; ++line_i, ++character_starts){
                *character_starts += character_shift;
            }
        }
    }
}

internal void
buffer_remeasure_wrap_y(Gap_Buffer *buffer, i32 line_start, i32 line_end, i32 line_shift,
                        f32 *wraps, f32 font_height, f32 *adv, f32 max_width){
    i32 new_line_count = buffer->line_count;
    
    Assert(0 <= line_start);
    Assert(line_start <= line_end);
    Assert(line_end < new_line_count - line_shift);
    
    ++line_end;
    
    // Shift
    i32 line_count = new_line_count;
    i32 new_line_end = line_end;
    if (line_shift != 0){
        line_count -= line_shift;
        new_line_end += line_shift;
        
        memmove(wraps + line_end + line_shift, wraps + line_end, sizeof(i32)*(line_count - line_end + 1));
    }
    
    // Iteration data (yikes! Need better loop system)
    Gap_Buffer_Stream stream = {};
    i32 size = buffer_size(buffer);
    i32 char_i = buffer->line_starts[line_start];
    i32 line_i = line_start;
    
    // Line wrap measurement
    f32 last_wrap = wraps[line_i];
    f32 current_wrap = last_wrap;
    f32 x = 0.f;
    
    if (buffer_stringify_loop(&stream, buffer, char_i, size)){
        b32 still_looping = 0;
        do{
            for (; char_i < stream.end; ++char_i){
                u8 ch = (u8)stream.data[char_i];
                
                if (ch == '\n'){
                    wraps[line_i] = last_wrap;
                    ++line_i;
                    current_wrap += font_height;
                    last_wrap = current_wrap;
                    x = 0.f;
                    
                    // TODO(allen): I would like to know that I am not guessing here.
                    if (line_i >= new_line_end){
                        goto buffer_remeasure_wraps_end;
                    }
                }
                else{
                    f32 current_adv = adv[ch];
                    if (x + current_adv > max_width){
                        current_wrap += font_height;
                        x = current_adv;
                    }
                    else{
                        x += current_adv;
                    }
                }
            }
            still_looping = buffer_stringify_next(&stream);
        }while(still_looping);
    }
    
    wraps[line_i++] = last_wrap;
    
    buffer_remeasure_wraps_end:;
    
    // Adjust
    if (line_i <= new_line_end){
        f32 y_shift = current_wrap - wraps[line_i];
        
        if (y_shift != 0){
            wraps += line_i;
            for (; line_i <= new_line_count; ++line_i, ++wraps){
                *wraps += y_shift;
            }
        }
    }
}

internal i32
binary_search(i32 *array, i32 value, i32 l_bound, i32 u_bound){
    i32 start = l_bound, end = u_bound;
    i32 i = 0;
    
    if (value < 0){
        value = 0;
    }
    
    for (;;){
        i = (start + end) >> 1;
        if (array[i] < value){
            start = i;
        }
        else if (array[i] > value){
            end = i;
        }
        else{
            break;
        }
        Assert(start < end);
        if (start == end - 1){
            i = start;
            break;
        }
    }
    
    return(i);
}

// TODO(allen): CHECK
internal i32
buffer_get_line_index_range(Gap_Buffer *buffer, i32 pos, i32 l_bound, i32 u_bound){
    Assert(0 <= l_bound);
    Assert(l_bound <= u_bound);
    Assert(u_bound <= buffer->line_count);
    
    Assert(buffer->line_starts != 0);
    
    i32 i = binary_search(buffer->line_starts, pos, l_bound, u_bound);
    return(i);
}

internal i32
buffer_get_line_number(Gap_Buffer *buffer, i32 pos){
    i32 result = buffer_get_line_index_range(buffer, pos, 0, buffer->line_count);
    return(result);
}

internal i32
buffer_get_line_index_from_character_pos(i32 *character_starts, i32 pos, i32 l_bound, i32 u_bound){
    i32 i = binary_search(character_starts, pos, l_bound, u_bound);
    return(i);
}

internal i32
buffer_get_line_index_from_wrapped_y(i32 *wrap_line_index, f32 y, i32 line_height, i32 l_bound, i32 u_bound){
    i32 wrap_index = floor32(y/line_height);
    i32 i = binary_search(wrap_line_index, wrap_index, l_bound, u_bound);
    return(i);
}

internal Partial_Cursor
buffer_partial_from_pos(Gap_Buffer *buffer, i32 pos){
    Partial_Cursor result = {};
    
    i32 size = buffer_size(buffer);
    pos = clamp(0, pos, size);
    
    i32 line_index = buffer_get_line_index_range(buffer, pos, 0, buffer->line_count);
    result.pos = pos;
    result.line = line_index + 1;
    result.character = pos - buffer->line_starts[line_index] + 1;
    
    return(result);
}

internal Partial_Cursor
buffer_partial_from_line_character(Gap_Buffer *buffer, i32 line, i32 character){
    Partial_Cursor result = {};
    
    i32 line_index = line - 1;
    i32 last_line_index = buffer->line_count - 1;
    line_index = clamp(0, line_index, last_line_index);
    
    i32 size = buffer_size(buffer);
    
    i32 this_start = buffer->line_starts[line_index];
    i32 max_character = (size - this_start) + 1;
    if (line_index < last_line_index){
        i32 next_start = buffer->line_starts[line_index + 1];
        max_character = (next_start - this_start);
    }
    
    i32 adjusted_pos = 0;
    if (character > 0){
        if (character > max_character){
            adjusted_pos = max_character - 1;
        }
        else{
            adjusted_pos = character - 1;
        }
    }
    else if (character == 0){
        adjusted_pos = 0;
    }
    else{
        if (-character > max_character){
            adjusted_pos = 0;
        }
        else{
            adjusted_pos = max_character + character;
        }
    }
    
    result.pos = this_start + adjusted_pos;
    result.line = line_index + 1;
    result.character = character;
    
    return(result);
}

// dialogical-routine defines
#define DrCase(PC) case PC: goto resumespot_##PC
#define DrYield(PC, n) { *S_ptr = S; S_ptr->__pc__ = PC; return(n); resumespot_##PC:; }
#define DrReturn(n) { *S_ptr = S; S_ptr->__pc__ = -1; return(n); }

internal Buffer_Layout_Stop
buffer_cursor_seek(Buffer_Cursor_Seek_State *S_ptr, Buffer_Cursor_Seek_Params params, f32 line_shift, b32 do_wrap, i32 wrap_unit_end){
    Buffer_Cursor_Seek_State S = *S_ptr;
    Buffer_Layout_Stop S_stop;
    
    switch (S.__pc__){
        DrCase(1);
        DrCase(2);
        DrCase(3);
        DrCase(4);
    }
    
    S.font_height = (i32)(params.face->height);
    
    S.xy_seek = (params.seek.type == buffer_seek_wrapped_xy || params.seek.type == buffer_seek_unwrapped_xy);
    S.size = buffer_size(params.buffer);
    
    // Get cursor hint
    {
        i32 line_index = 0;
        switch (params.seek.type){
            case buffer_seek_pos:
            {
                params.seek.pos = clamp(0, params.seek.pos, S.size);
                
                line_index = buffer_get_line_number(params.buffer, (i32)params.seek.pos);
            }break;
            
            case buffer_seek_character_pos:
            {
                i32 line_count = params.buffer->line_count;
                i32 max_character = params.character_starts[line_count] - 1;
                params.seek.pos = clamp(0, params.seek.pos, max_character);
                
                line_index = buffer_get_line_index_from_character_pos(params.character_starts, (i32)params.seek.pos, 0, params.buffer->line_count);
            }break;
            
            case buffer_seek_line_char:
            {
                line_index = (i32)params.seek.line - 1;
                line_index = clamp_bot(0, line_index);
            }break;
            
            case buffer_seek_unwrapped_xy:
            {
                line_index = (i32)(params.seek.y / S.font_height);
                line_index = clamp_bot(0, line_index);
            }break;
            
            case buffer_seek_wrapped_xy:
            {
                line_index = buffer_get_line_index_from_wrapped_y(params.wrap_line_index, params.seek.y, S.font_height, 0, params.buffer->line_count);
            }break;
            
            default: InvalidPath;
        }
        
        i32 safe_line_index = line_index;
        if (line_index >= params.buffer->line_count){
            safe_line_index = params.buffer->line_count-1;
        }
        
        // Build the cursor hint
        S.next_cursor.pos = params.buffer->line_starts[safe_line_index];
        S.next_cursor.character_pos = params.character_starts[safe_line_index];
        S.next_cursor.line = safe_line_index + 1;
        S.next_cursor.character = 1;
        S.next_cursor.wrap_line = params.wrap_line_index[safe_line_index] + 1;
        S.next_cursor.unwrapped_y = (f32)(safe_line_index * S.font_height);
        S.next_cursor.unwrapped_x = 0;
        S.next_cursor.wrapped_y = (f32)(params.wrap_line_index[safe_line_index] * S.font_height);
        S.next_cursor.wrapped_x = 0;
    }
    
    // Get the initial line shift.
    // Adjust the non-screen based coordinates to point to the first
    // non-virtual character of the line.
    if (params.virtual_white){
        S_stop.status          = BLStatus_NeedLineShift;
        S_stop.line_index      = (i32)S.next_cursor.line - 1;
        S_stop.wrap_line_index = (i32)S.next_cursor.wrap_line - 1;
        DrYield(1, S_stop);
        
        S.next_cursor.unwrapped_x += line_shift;
        S.next_cursor.wrapped_x += line_shift;
        
        S.stream.use_termination_character = 1;
        S.stream.terminator = '\n';
        if (buffer_stringify_loop(&S.stream, params.buffer, (i32)S.next_cursor.pos, S.size)){
            do{
                for (; S.next_cursor.pos < S.stream.end; ++S.next_cursor.pos){
                    u8 ch = (u8)S.stream.data[S.next_cursor.pos];
                    
                    if (ch != ' ' && ch != '\t'){
                        goto double_break_vwhite;
                    }
                    else{
                        ++S.next_cursor.character;
                    }
                }
                S.still_looping = buffer_stringify_next(&S.stream);
            }while(S.still_looping);
        }
        InvalidPath;
        double_break_vwhite:;
    }
    
    // If the caller just wants the hint, return that now.
    if (params.return_hint){
        *params.cursor_out = S.next_cursor;
        S_stop.status = BLStatus_Finished;
        DrReturn(S_stop);
    }
    
    // If we are already passed the point we want to be at, then just take this.
    S.this_cursor = S.next_cursor;
    switch (params.seek.type){
        case buffer_seek_pos:
        {
            if (S.next_cursor.pos >= params.seek.pos){
                goto buffer_cursor_seek_end;
            }
        }break;
        
        case buffer_seek_character_pos:
        {
            if (S.next_cursor.character_pos >= params.seek.pos){
                goto buffer_cursor_seek_end;
            }
        }break;
        
        case buffer_seek_line_char:
        {
            if ((S.next_cursor.line == params.seek.line &&
                 S.next_cursor.character >= params.seek.character) ||
                S.next_cursor.line > params.seek.line){
                goto buffer_cursor_seek_end;
            }
        }break;
        
        case buffer_seek_unwrapped_xy:
        {
            if (S.next_cursor.unwrapped_y > params.seek.y){
                goto buffer_cursor_seek_end;
            }
        }break;
        
        case buffer_seek_wrapped_xy:
        {
            if (S.next_cursor.wrapped_y > params.seek.y){
                goto buffer_cursor_seek_end;
            }
        }break;
    }
    
    // Main seek loop
    S.i = (i32)S.next_cursor.pos;
    
    S.stream = null_buffer_stream;
    S.stream.use_termination_character = 1;
    S.stream.terminator = 0;
    
    S.first_of_the_line = 1;
    if (buffer_stringify_loop(&S.stream, params.buffer, S.i, S.size)){
        S.still_looping = 0;
        do{
            for (; S.i < S.stream.end; ++S.i){
                {
                    u8 ch = (u8)S.stream.data[S.i];
                    translating_fully_process_byte(&S.tran, ch, S.i, S.size, &S.emits);
                }
                
                for (TRANSLATION_EMIT_LOOP(S.J, S.emits)){
                    TRANSLATION_GET_STEP(S.step, S.behavior, S.J, S.emits);
                    
                    S.prev_cursor = S.this_cursor;
                    S.this_cursor = S.next_cursor;
                    
                    if (S.behavior.do_newline){
                        ++S.next_cursor.character_pos;
                        ++S.next_cursor.line;
                        ++S.next_cursor.wrap_line;
                        S.next_cursor.unwrapped_y += S.font_height;
                        S.next_cursor.wrapped_y += S.font_height;
                        S.next_cursor.character = 1;
                        S.next_cursor.unwrapped_x = 0;
                        
                        if (params.virtual_white){
                            S_stop.status          = BLStatus_NeedLineShift;
                            S_stop.line_index      = (i32)S.next_cursor.line - 1;
                            S_stop.wrap_line_index = (i32)S.next_cursor.wrap_line - 1;
                            DrYield(2, S_stop);
                        }
                        
                        S.next_cursor.wrapped_x = line_shift;
                        S.first_of_the_line = 1;
                    }
                    else if (S.behavior.do_number_advance || S.behavior.do_codepoint_advance){
                        
                        if (S.behavior.do_codepoint_advance){
                            S.ch_width = font_get_glyph_advance(params.face, S.step.value);
                        }
                        else{
                            S.ch_width = params.face->byte_advance;
                        }
                        
                        if (S.step.i >= S.wrap_unit_end){
                            S_stop.status          = BLStatus_NeedWrapDetermination;
                            S_stop.line_index      = (i32)S.next_cursor.line - 1;
                            S_stop.wrap_line_index = (i32)S.next_cursor.wrap_line - 1;
                            S_stop.pos             = S.step.i;
                            S_stop.x               = S.next_cursor.wrapped_x;
                            DrYield(4, S_stop);
                            
                            S.wrap_unit_end = wrap_unit_end;
                            
                            if (do_wrap && !S.first_of_the_line){
                                S.next_cursor.wrapped_y += S.font_height;
                                
                                ++S.next_cursor.wrap_line;
                                if (params.virtual_white){
                                    S_stop.status          = BLStatus_NeedWrapLineShift;
                                    S_stop.line_index      = (i32)S.next_cursor.line - 1;
                                    S_stop.wrap_line_index = (i32)S.next_cursor.wrap_line - 1;
                                    DrYield(3, S_stop);
                                }
                                
                                S.next_cursor.wrapped_x = line_shift;
                                S.this_cursor = S.next_cursor;
                            }
                        }
                        
                        ++S.next_cursor.character_pos;
                        ++S.next_cursor.character;
                        S.next_cursor.unwrapped_x += S.ch_width;
                        S.next_cursor.wrapped_x += S.ch_width;
                        
                        S.first_of_the_line = 0;
                    }
                    
                    S.next_cursor.pos += S.step.byte_length;
                    
                    f32 x = 0, px = 0, y = 0, py = 0;
                    switch (params.seek.type){
                        case buffer_seek_pos:
                        if (S.this_cursor.pos >= params.seek.pos){
                            goto buffer_cursor_seek_end;
                        }break;
                        
                        case buffer_seek_character_pos:
                        if (S.this_cursor.character_pos >= params.seek.pos){
                            goto buffer_cursor_seek_end;
                        }break;
                        
                        case buffer_seek_wrapped_xy:
                        {
                            x = S.this_cursor.wrapped_x;
                            px = S.prev_cursor.wrapped_x;
                            y = S.this_cursor.wrapped_y;
                            py = S.prev_cursor.wrapped_y;
                        }break;
                        
                        case buffer_seek_unwrapped_xy:
                        {
                            x = S.this_cursor.unwrapped_x;
                            px = S.prev_cursor.unwrapped_x;
                            y = S.this_cursor.unwrapped_y;
                            py = S.prev_cursor.wrapped_y;
                        }break;
                        
                        case buffer_seek_line_char:
                        if (S.this_cursor.line == params.seek.line && S.this_cursor.character >= params.seek.character){
                            goto buffer_cursor_seek_end;
                        }
                        else if (S.this_cursor.line > params.seek.line){
                            S.this_cursor = S.prev_cursor;
                            goto buffer_cursor_seek_end;
                        }break;
                    }
                    
                    if (S.xy_seek){
                        if (y > params.seek.y){
                            S.this_cursor = S.prev_cursor;
                            goto buffer_cursor_seek_end;
                        }
                        
                        if (y > params.seek.y - S.font_height && x >= params.seek.x){
                            if (!params.seek.round_down){
                                if (py >= y && !S.behavior.do_newline && (params.seek.x - px) < (x - params.seek.x)){
                                    S.this_cursor = S.prev_cursor;
                                }
                                goto buffer_cursor_seek_end;
                            }
                            
                            if (py >= y){
                                S.this_cursor = S.prev_cursor;
                            }
                            goto buffer_cursor_seek_end;
                        }
                    }
                    
                    if (S.next_cursor.pos > S.size){
                        goto buffer_cursor_seek_end;
                    }
                }
            }
            S.still_looping = buffer_stringify_next(&S.stream);
        }while(S.still_looping);
    }
    
    InvalidPath;
    
    buffer_cursor_seek_end:;
    *params.cursor_out = S.this_cursor;
    S_stop.status = BLStatus_Finished;
    DrReturn(S_stop);
}

#undef DrCase
#undef DrYield
#undef DrReturn

internal void
buffer_invert_edit_shift(Gap_Buffer *buffer, Buffer_Edit edit, Buffer_Edit *inverse, char *strings,
                         i32 *str_pos, i32 max, i32 shift_amount){
    i32 pos = *str_pos;
    i32 len = edit.end - edit.start;
    Assert(pos >= 0);
    Assert(pos + len <= max);
    *str_pos = pos + len;
    
    inverse->str_start = pos;
    inverse->len = len;
    inverse->start = edit.start + shift_amount;
    inverse->end = edit.start + edit.len + shift_amount;
    buffer_stringify(buffer, edit.start, edit.end, strings + pos);
}

internal void
buffer_invert_edit(Gap_Buffer *buffer, Buffer_Edit edit, Buffer_Edit *inverse, char *strings,
                   i32 *str_pos, i32 max){
    buffer_invert_edit_shift(buffer, edit, inverse, strings, str_pos, max, 0);
}

internal i32
buffer_invert_batch(Buffer_Invert_Batch *state, Gap_Buffer *buffer, Buffer_Edit *edits, i32 count,
                    Buffer_Edit *inverse, char *strings, i32 *str_pos, i32 max){
    i32 shift_amount = state->shift_amount;
    i32 i = state->i;
    Buffer_Edit *edit = edits + i;
    Buffer_Edit *inv_edit = inverse + i;
    i32 result = 0;
    
    for (; i < count; ++i, ++edit, ++inv_edit){
        if (*str_pos + edit->end - edit->start <= max){
            buffer_invert_edit_shift(buffer, *edit, inv_edit, strings, str_pos, max, shift_amount);
            shift_amount += (edit->len - (edit->end - edit->start));
        }
        else{
            result = 1;
            state->len = edit->end - edit->start;
        }
    }
    
    state->i = i;
    state->shift_amount = shift_amount;
    
    return(result);
}

typedef u32 Render_Item_Flag;
enum{
    RenderItemFlag_ForceEmit = 1,
    RenderItemFlag_NoAdvance = 2,
};

internal Render_Item_Write
write_render_item(Render_Item_Write write, i32 index, u32 codepoint, u32 flags,
                  Render_Item_Flag render_flags){
    if (write.item < write.item_end){
        f32 ch_width = font_get_glyph_advance(write.face, codepoint);
        
        b32 visible_on_layout = (write.x_min <= write.x + ch_width && write.x <= write.x_max);
        
        if (visible_on_layout || ((render_flags & RenderItemFlag_ForceEmit) != 0)){
            write.item->index = index;
            write.item->codepoint = codepoint;
            write.item->flags = flags;
            write.item->x0 = write.x;
            write.item->y0 = write.y;
            write.item->x1 = write.x + ch_width;
            write.item->y1 = write.y + write.font_height;
            ++write.item;
        }
        
        if ((render_flags & RenderItemFlag_NoAdvance) == 0){
            write.x += ch_width;
        }
    }
    return(write);
}

// duff-routine defines
#define DrCase(PC) case PC: goto resumespot_##PC
#define DrYield(PC, n) { *S_ptr = S; S_ptr->__pc__ = PC; return(n); resumespot_##PC:; }
#define DrReturn(n) { *S_ptr = S; S_ptr->__pc__ = -1; return(n); }

internal Buffer_Layout_Stop
buffer_render_data(Buffer_Render_State *S_ptr, Buffer_Render_Params params, f32 line_shift, b32 do_wrap, i32 wrap_unit_end){
    Buffer_Render_State S = *S_ptr;
    Buffer_Layout_Stop S_stop;
    
    S.write.item_end = params.items + params.max;
    
    switch (S.__pc__){
        DrCase(1);
        DrCase(2);
        DrCase(3);
        DrCase(4);
    }
    
    S.size = buffer_size(params.buffer);
    S.size = Min(S.size, params.one_past_last_abs_pos);
    S.shift_x = params.port_x - params.scroll_x;
    S.shift_y = params.port_y - params.scroll_y;
    
    if (params.wrapped){
        S.shift_y += params.start_cursor.wrapped_y;
    }
    else{
        S.shift_y += params.start_cursor.unwrapped_y;
    }
    
    S.line = (i32)params.start_cursor.line - 1;
    S.wrap_line = (i32)params.start_cursor.wrap_line - 1;
    
    if (params.virtual_white){
        S_stop.status          = BLStatus_NeedLineShift;
        S_stop.line_index      = S.line;
        S_stop.wrap_line_index = S.wrap_line;
        DrYield(1, S_stop);
    }
    
    S.write.item        = params.items;
    S.write.x           = S.shift_x + line_shift;
    S.write.y           = S.shift_y;
    S.write.system      = params.system;
    S.write.face        = params.face;
    S.write.font_height = (i32)params.face->height;
    S.write.x_min       = params.port_x;
    S.write.x_max       = params.port_x + params.clip_w;
    
    S.byte_advance = params.face->byte_advance;
    
    if (params.virtual_white){
        S.skipping_whitespace = true;
    }
    
    S.first_of_the_line = true;
    S.first_of_the_wrap = true;
    S.i = (i32)params.start_cursor.pos;
    if (buffer_stringify_loop(&S.stream, params.buffer, S.i, S.size)){
        do{
            for (; S.i < S.stream.end; ++S.i){
                {
                    u8 ch = (u8)S.stream.data[S.i];
                    translating_fully_process_byte(&S.tran, ch, S.i, S.size, &S.emits);
                }
                
                for (TRANSLATION_EMIT_LOOP(S.J, S.emits)){
                    TRANSLATION_GET_STEP(S.step, S.behavior, S.J, S.emits);
                    
                    if (!S.behavior.do_newline && S.step.i >= S.wrap_unit_end){
                        S_stop.status          = BLStatus_NeedWrapDetermination;
                        S_stop.line_index      = S.line;
                        S_stop.wrap_line_index = S.wrap_line;
                        S_stop.pos             = S.step.i;
                        S_stop.x               = S.write.x - S.shift_x;
                        DrYield(4, S_stop);
                        
                        S.wrap_unit_end = wrap_unit_end;
                        
                        if (do_wrap && !S.first_of_the_line){
                            if (params.virtual_white){
                                S_stop.status          = BLStatus_NeedWrapLineShift;
                                S_stop.line_index      = S.line;
                                S_stop.wrap_line_index = S.wrap_line + 1;
                                DrYield(2, S_stop);
                            }
                            
                            ++S.wrap_line;
                            
                            if (params.wrapped){
                                switch (params.wrap_slashes){
                                    case WrapIndicator_Show_After_Line:
                                    {
                                        S.write = write_render_item(S.write, S.step.i-1, '\\', BRFlag_Ghost_Character, 0);
                                    }break;
                                    
                                    case WrapIndicator_Show_At_Wrap_Edge:
                                    {
                                        if (S.write.x < S.shift_x + params.width){
                                            S.write.x = S.shift_x + params.width;
                                        }
                                        S.write = write_render_item(S.write, S.step.i-1, '\\', BRFlag_Ghost_Character, 0);
                                    }break;
                                }
                                
                                S.write.x = S.shift_x + line_shift;
                                S.write.y += S.write.font_height;
                                S.first_of_the_wrap = true;
                            }
                        }
                    }
                    
                    if (S.write.y > params.height + params.port_y || S.write.item >= S.write.item_end){
                        goto buffer_get_render_data_end;
                    }
                    
                    if (S.behavior.do_newline){
                        {
                            Render_Item_Flag flags = 0;
                            if (S.first_of_the_wrap){
                                flags |= RenderItemFlag_ForceEmit;
                            }
                            S.write = write_render_item(S.write, S.step.i, ' ', 0, flags);
                        }
                        
                        if (params.virtual_white){
                            S_stop.status          = BLStatus_NeedLineShift;
                            S_stop.line_index      = S.line + 1;
                            S_stop.wrap_line_index = S.wrap_line + 1;
                            DrYield(3, S_stop);
                            S.skipping_whitespace = true;
                        }
                        
                        ++S.line;
                        ++S.wrap_line;
                        
                        S.write.x = S.shift_x + line_shift;
                        S.write.y += S.write.font_height;
                        
                        S.first_of_the_line = true;
                        S.first_of_the_wrap = true;
                    }
                    else if (S.behavior.do_codepoint_advance){
                        u32 n = S.step.value;
                        if (n != ' ' && n != '\t'){
                            S.skipping_whitespace = false;
                        }
                        
                        u32 I = S.step.i;
                        if (!S.skipping_whitespace){
                            Render_Item_Flag flags = 0;
                            if (S.first_of_the_wrap){
                                flags |= RenderItemFlag_ForceEmit;
                            }
                            switch (n){
                                case '\r':
                                {
                                    S.write = write_render_item(S.write, I, '\\', BRFlag_Special_Character, flags);
                                    S.write = write_render_item(S.write, I, 'r', BRFlag_Special_Character, flags);
                                }break;
                                
                                case '\t':
                                {
                                    S.ch_width = font_get_glyph_advance(params.face, '\t');
                                    
                                    f32 new_x = S.write.x + S.ch_width;
                                    S.write = write_render_item(S.write, I, ' ', 0, flags);
                                    S.write.x = new_x;
                                }break;
                                
                                default:
                                {
                                    S.write = write_render_item(S.write, I, n, 0, flags);
                                }break;
                            }
                        }
                        else if (S.first_of_the_wrap){
                            Render_Item_Flag flags = RenderItemFlag_ForceEmit|RenderItemFlag_NoAdvance;
                            S.write = write_render_item(S.write, I, ' ', 0, flags);
                        }
                        
                        S.first_of_the_line = false;
                        S.first_of_the_wrap = false;
                    }
                    else if (S.behavior.do_number_advance){
                        u8 n = (u8)S.step.value;
                        u32 I = S.step.i;
                        S.skipping_whitespace = false;
                        
                        S.ch_width = S.byte_advance;
                        f32 new_x = S.write.x + S.ch_width;
                        
                        u8 cs[3];
                        cs[0] = '\\';
                        byte_to_ascii(n, cs+1);
                        
                        Render_Item_Flag flags = 0;
                        if (S.first_of_the_wrap){
                            flags |= RenderItemFlag_ForceEmit;
                        }
                        S.write = write_render_item(S.write, I, cs[0], BRFlag_Special_Character, flags);
                        S.write = write_render_item(S.write, I, cs[1], BRFlag_Special_Character, flags);
                        S.write = write_render_item(S.write, I, cs[2], BRFlag_Special_Character, flags);
                        
                        Assert(S.write.x <= new_x);
                        S.write.x = new_x;
                        
                        S.first_of_the_line = false;
                        S.first_of_the_wrap = false;
                    }
                    
                    
                    if (!S.skipping_whitespace && !S.behavior.do_newline){
                        S.first_of_the_line = false;
                    }
                }
            }
            S.still_looping = buffer_stringify_next(&S.stream);
        }while(S.still_looping);
    }
    
    buffer_get_render_data_end:;
    if (S.write.y <= params.height + S.shift_y || S.write.item == params.items){
        S.write = write_render_item(S.write, S.size, ' ', 0, false);
    }
    
    *params.count = (i32)(S.write.item - params.items);
    Assert(*params.count <= params.max);
    
    S_stop.status = BLStatus_Finished;
    DrReturn(S_stop);
}

#undef DrYield
#undef DrReturn
#undef DrCase

internal Buffer_Chunk_Position
buffer_get_chunk_position(String_Const_u8_Array chunks, i32 buffer_size, i32 real_pos){
    Buffer_Chunk_Position pos = {};
    pos.real_pos = real_pos;
    pos.chunk_pos = real_pos;
    if (pos.real_pos != buffer_size){
        for (;(imem)(chunks.vals[pos.chunk_index].size) <= pos.chunk_pos;){
            Assert(pos.chunk_index < chunks.count);
            pos.chunk_pos -= (i32)chunks.vals[pos.chunk_index].size;
            pos.chunk_index += 1;
        }
    }
    else{
        pos.chunk_index = chunks.count - 1;
        pos.chunk_pos = (i32)chunks.vals[pos.chunk_index].size;
    }
    return(pos);
}

internal i32
buffer_chunk_position_iterate(String_Const_u8_Array chunks, Buffer_Chunk_Position *pos, Scan_Direction direction){
    i32 past_end = 0;
    pos->real_pos += direction;
    pos->chunk_pos += direction;
    if (pos->chunk_pos < 0){
        if (pos->chunk_index == 0){
            past_end = -1;
        }
        else{
            pos->chunk_index -= 1;
            pos->chunk_pos = (i32)chunks.vals[pos->chunk_index].size - 1;
        }
    }
    else if (pos->chunk_pos >= (imem)(chunks.vals[pos->chunk_index].size)){
        pos->chunk_index += 1;
        if (pos->chunk_index == chunks.count){
            past_end = 1;
        }
        else{
            pos->chunk_pos = 0;
        }
    }
    return(past_end);
}

// BOTTOM