687778 - per-font feature settings are overridden by feature settings associated with a style rule

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[John Daggett (:jtd)]

Attachment: testcase showing missing ligature

The CSS3 Fonts spec allows both font feature settings on a per-font basis and within general style rules.  In other words, both forms below are allowed:

@font-face {
  font-family: MyFont;
  src: url(xxx);
  -moz-font-feature-settings: "dlig=1"; /* discretionary ligatures on by default */
}

p {
  -moz-font-feature-settings: "dlig=1";
}

However, the logic in gfxHarfBuzzShaper::InitTextRun only references the feature settings associated with the font if there are *no* style rule settings.  This is wrong, feature settings in style rules should override per-font settings but on a feature-by-feature basis.  With the content below, discretionary ligatures are not drawn:

@font-face {
  font-family: MyFont;
  src: url(xxx);
  -moz-font-feature-settings: "dlig=1"; /* discretionary ligatures on by default */
}

p {
  -moz-font-feature-settings: "xyzw=1"; /* random feature */
}

Comment 1

[John Daggett (:jtd)]

Attachment: testcase showing missing ligature

Added a test for not properly handling overridden features within the feature settings itself (i.e. "dlig=1, dlig=0" should be equivalent to "dlig=0").

Comment 2

[John Daggett (:jtd)]

This was fixed by bug 718539.