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measure_text(): actually extend text bounding box with each new glyph advance.

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This commit is contained in:
Brian J. Burg 2012-10-15 13:44:20 -07:00
parent 47144ce3c3
commit e28827d1c0
1 changed files with 18 additions and 14 deletions
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32
src/servo/text/font.rs
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@ -52,22 +52,30 @@ pub trait FontMethods {
pub impl Font : FontMethods { pub impl Font : FontMethods {
fn measure_text(run: &TextRun, offset: uint, length: uint) -> RunMetrics { fn measure_text(run: &TextRun, offset: uint, length: uint) -> RunMetrics {
let em_size = self.metrics.em_size;
let em_ascent = self.metrics.em_ascent;
let em_descent = self.metrics.em_descent;
// TODO: alter advance direction for RTL // TODO: alter advance direction for RTL
// TODO: using inter-char and inter-word spacing settings when measuring text // TODO: using inter-char and inter-word spacing settings when measuring text
let mut advance = au(0); let mut advance = au(0);
let mut bounds = Rect(Point2D(au(0), self.metrics.em_size.scale_by(-self.metrics.em_ascent)), let mut bounds = Rect(Point2D(au(0), em_size.scale_by(-em_ascent)),
Size2D(au(0), self.metrics.em_size.scale_by(self.metrics.em_ascent + self.metrics.em_descent))); Size2D(au(0), em_size.scale_by(em_ascent + em_descent)));
do run.glyphs.iter_glyphs_for_range(offset, length) |_i, glyph| { do run.glyphs.iter_glyphs_for_range(offset, length) |_i, glyph| {
advance += glyph.advance() advance += glyph.advance();
bounds = bounds.translate(&Point2D(glyph.advance(), au(0)));
} }
// TODO: support loose and tight bounding boxes // TODO: support loose and tight bounding boxes; using the
// ascent+descent and advance is sometimes too generous and
// looking at actual glyph extents can yield a tighter box.
RunMetrics { advance_width: advance, let metrics = RunMetrics { advance_width: advance,
bounding_box: bounds, bounding_box: bounds,
ascent: self.metrics.em_size.scale_by(self.metrics.em_ascent), ascent: em_size.scale_by(em_ascent),
descent: self.metrics.em_size.scale_by(self.metrics.em_descent), descent: em_size.scale_by(em_descent),
} };
return metrics;
} }
fn buf(&self) -> @~[u8] { fn buf(&self) -> @~[u8] {
@ -97,11 +105,7 @@ fn Font(lib: @FontCache, fontbuf: @~[u8], native_font: NativeFont, metrics: Font
} }
} }
// TODO: what are the units of these metrics? CTFont metrics calls are // Most of these metrics are in terms of em. Use em_size to convert to au.
// font units for a specific point size, and these are normalized by
// font units-per-em. Are there some cases where these metrics depend
// on font size? If so, need to be careful about using same sizes on
// font creation, metrics gathering, and drawing.
struct FontMetrics { struct FontMetrics {
underline_size: float, underline_size: float,
underline_offset: float, underline_offset: float,