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LibGfx: Decouple glyph positions calculation from draw_text_run()

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This change separates a part of the `draw_text_run()` function, which
is responsible for calculating the positions for glyphs that need to be
painted, into a separate function called `get_glyph_run()`.

It is a part of the preparation for text run painting using OpenGL,
where we can't immediately blit glyph bitmaps but instead need to
prepare a sequence of quads for them in advance.
This commit is contained in:
Aliaksandr Kalenik 2023-11-05 00:17:04 +01:00 • committed by Andreas Kling
parent 3ac77dac99
commit efdbd8238e
4 changed files with 121 additions and 61 deletions
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37
Userland/Libraries/LibGfx/TextLayout.h
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@ -75,23 +75,33 @@ enum class IncludeLeftBearing {
No
};
struct GlyphPosition {
struct DrawGlyph {
FloatPoint position;
float glyph_width;
AK::Utf8CodePointIterator& it;
u32 code_point;
Font const* font;
};
struct DrawEmoji {
IntPoint position;
Gfx::Bitmap const* emoji;
Font const* font;
};
using DrawGlyphOrEmoji = Variant<DrawGlyph, DrawEmoji>;
Variant<DrawGlyph, DrawEmoji> prepare_draw_glyph_or_emoji(FloatPoint point, Utf8CodePointIterator& it, Font const& font);
template<typename Callback>
void for_each_glyph_position(FloatPoint start, Utf8View text, Font const& font, Callback callback, IncludeLeftBearing include_left_bearing = IncludeLeftBearing::No)
void for_each_glyph_position(FloatPoint baseline_start, Utf8View string, Font const& font, Callback callback, IncludeLeftBearing include_left_bearing = IncludeLeftBearing::No)
{
float space_width = font.glyph_width(' ') + font.glyph_spacing();
u32 last_code_point = 0;
auto point = start;
auto point = baseline_start;
point.translate_by(0, -font.pixel_metrics().ascent);
for (auto code_point_iterator = text.begin(); code_point_iterator != text.end(); ++code_point_iterator) {
for (auto code_point_iterator = string.begin(); code_point_iterator != string.end(); ++code_point_iterator) {
auto code_point = *code_point_iterator;
if (should_paint_as_space(code_point)) {
point.translate_by(space_width, 0);
@ -106,18 +116,19 @@ void for_each_glyph_position(FloatPoint start, Utf8View text, Font const& font,
auto it = code_point_iterator; // The callback function will advance the iterator, so create a copy for this lookup.
auto glyph_width = font.glyph_or_emoji_width(it) + font.glyph_spacing();
auto glyph_point = point;
if (include_left_bearing == IncludeLeftBearing::Yes)
glyph_point += FloatPoint(font.glyph_left_bearing(code_point), 0);
auto glyph_or_emoji = prepare_draw_glyph_or_emoji(point, code_point_iterator, font);
if (include_left_bearing == IncludeLeftBearing::Yes) {
if (glyph_or_emoji.has<DrawGlyph>())
glyph_or_emoji.get<DrawGlyph>().position += FloatPoint(font.glyph_left_bearing(code_point), 0);
}
callback(GlyphPosition {
.position = glyph_point,
.glyph_width = glyph_width,
.it = code_point_iterator });
callback(glyph_or_emoji);
point.translate_by(glyph_width, 0);
last_code_point = code_point;
}
}
Vector<DrawGlyphOrEmoji> get_glyph_run(FloatPoint baseline_start, Utf8View const& string, Font const& font, IncludeLeftBearing include_left_bearing = IncludeLeftBearing::No);
}