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LibGUI: Fix off-by-one error in rendering of highlighted text

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This fixes an off-by-one error in TextEditor's rendering of the syntax
highlighting as generated by Syntax::Highlighter and its subclasses.

Before, a single character span was e.g. (0-3) to (0-3), but this was
considered invalid by GUI::TextRange. Now, a single character span would
be e.g. (0-3) to (0-4).

This fix requires all Syntax::Highlighter subclasses to be adjusted, as
they all relied on the previous implementation. This will then also fix
a bug where single-character HTML tags wouldn't be highlighted.
This commit is contained in:
Max Wipfli 2021-06-03 23:09:35 +02:00 committed by Ali Mohammad Pur
parent 8f81d9ad90
commit a819f98956
Notes: sideshowbarker 2024-07-18 16:53:32 +09:00 
Author: https://github.com/MaxWipfli
Commit: https://github.com/SerenityOS/serenity/commit/a819f989569
Pull-request: https://github.com/SerenityOS/serenity/pull/7768
Issue: https://github.com/SerenityOS/serenity/issues/7349
Reviewed-by: https://github.com/alimpfard
1 changed files with 10 additions and 16 deletions
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26
Userland/Libraries/LibGUI/TextEditor.cpp
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@ -497,7 +497,9 @@ void TextEditor::paint_event(PaintEvent& event)
Gfx::IntRect span_rect = { visual_line_rect.location(), { 0, line_height() } };
auto draw_text_helper = [&](size_t start, size_t end, RefPtr<Gfx::Font>& font, Color& color, Optional<Color> background_color = {}, bool underline = false) {
size_t length = end - start + 1;
size_t length = end - start;
if (length == 0)
return;
auto text = visual_line_text.substring_view(start, length);
span_rect.set_width(font->width(text));
if (background_color.has_value()) {
@ -529,11 +531,7 @@ void TextEditor::paint_event(PaintEvent& event)
break;
}
if (span.range.start().line() == span.range.end().line() && span.range.end().column() < span.range.start().column()) {
if (span.range.end().column() == span.range.start().column() - 1) {
// span length is zero, just ignore
} else {
dbgln_if(TEXTEDITOR_DEBUG, "span form {}:{} to {}:{} has negative length => ignoring", span.range.start().line(), span.range.start().column(), span.range.end().line(), span.range.end().column());
}
dbgln_if(TEXTEDITOR_DEBUG, "span form {}:{} to {}:{} has negative length => ignoring", span.range.start().line(), span.range.start().column(), span.range.end().line(), span.range.end().column());
++span_index;
continue;
}
@ -556,21 +554,17 @@ void TextEditor::paint_event(PaintEvent& event)
}
size_t span_end;
bool span_consumned;
if (span.range.end().line() > line_index || span.range.end().column() >= start_of_visual_line + visual_line_text.length()) {
if (visual_line_text.length() == 0) {
// subtracting 1 would wrap around
// since there is nothing to draw here just move on
break;
}
span_end = visual_line_text.length() - 1;
if (span.range.end().line() > line_index || span.range.end().column() > start_of_visual_line + visual_line_text.length()) {
span_end = visual_line_text.length();
span_consumned = false;
} else {
span_end = span.range.end().column() - start_of_visual_line;
span_consumned = true;
}
if (span_start != next_column) {
// draw unspanned text between spans
draw_text_helper(next_column, span_start - 1, unspanned_font, unspanned_color);
draw_text_helper(next_column, span_start, unspanned_font, unspanned_color);
}
auto font = unspanned_font;
if (span.attributes.bold) {
@ -578,7 +572,7 @@ void TextEditor::paint_event(PaintEvent& event)
font = bold_font;
}
draw_text_helper(span_start, span_end, font, span.attributes.color, span.attributes.background_color, span.attributes.underline);
next_column = span_end + 1;
next_column = span_end;
if (!span_consumned) {
// continue with same span on next line
break;
@ -588,7 +582,7 @@ void TextEditor::paint_event(PaintEvent& event)
}
// draw unspanned text after last span
if (next_column < visual_line_text.length()) {
draw_text_helper(next_column, visual_line_text.length() - 1, unspanned_font, unspanned_color);
draw_text_helper(next_column, visual_line_text.length(), unspanned_font, unspanned_color);
}
// consume all spans that should end this line
// this is necessary since the spans can include the new line character