Mirrors/servo
1
0
Fork 0
mirror of https://github.com/servo/servo.git synced 2025-06-06 16:45:39 +00:00
Code Issues Projects Releases Packages Wiki Activity

Ensure when calculating font metrics that the total line height matches requested line height.

Browse source 
This fixes rounding accuracy issues that could result in layout producing results off by a small number of Au.
This commit is contained in:
Glenn Watson 2016-02-17 09:42:21 +10:00
parent 7aedb9c7cd
commit 286130b051
4 changed files with 13 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

9
components/layout/inline.rs
View file

@ -1928,9 +1928,14 @@ impl InlineMetrics {
#[inline]
pub fn from_font_metrics(font_metrics: &FontMetrics, line_height: Au) -> InlineMetrics {
let leading = line_height - (font_metrics.ascent + font_metrics.descent);
// Calculating the half leading here and then using leading - half_leading
// below ensure that we don't introduce any rounding accuracy issues here.
// The invariant is that the resulting total line height must exactly
// equal the requested line_height.
let half_leading = leading.scale_by(0.5);
InlineMetrics {
block_size_above_baseline: font_metrics.ascent + leading.scale_by(0.5),
depth_below_baseline: font_metrics.descent + leading.scale_by(0.5),
block_size_above_baseline: font_metrics.ascent + half_leading,
depth_below_baseline: font_metrics.descent + leading - half_leading,
ascent: font_metrics.ascent,
}
}