Change ParagraphBuilder to replace the parent style's font families with the child style's font families (#10074)

jason-simmons · web-flow · commit f7e0614b8876 · 2019-07-23T17:57:56.000-07:00
Previously ParagraphBuilder was concatenating the child's fonts to the parent's font list, causing the parent's fonts to take precedence. Fixes flutter/flutter#35992
diff --git a/lib/ui/text/paragraph_builder.cc b/lib/ui/text/paragraph_builder.cc
@@ -438,8 +438,10 @@ void ParagraphBuilder::pushStyle(tonic::Int32List& encoded,
   }
 
   if (mask & tsFontFamilyMask) {
-    style.font_families.insert(style.font_families.end(), fontFamilies.begin(),
-                               fontFamilies.end());
+    // The child style's font families override the parent's font families.
+    // If the child's fonts are not available, then the font collection will
+    // use the system fallback fonts (not the parent's fonts).
+    style.font_families = fontFamilies;
   }
 
   if (mask & tsFontFeaturesMask) {

Original file line number	Diff line number	Diff line change
`@@ -438,8 +438,10 @@ void ParagraphBuilder::pushStyle(tonic::Int32List& encoded,`
`438`	`438`	`}`
`439`	`439`
`440`	`440`	`if (mask & tsFontFamilyMask) {`
`441`		`- style.font_families.insert(style.font_families.end(), fontFamilies.begin(),`
`442`		`- fontFamilies.end());`
	`441`	`+ // The child style's font families override the parent's font families.`
	`442`	`+ // If the child's fonts are not available, then the font collection will`
	`443`	`+ // use the system fallback fonts (not the parent's fonts).`
	`444`	`+ style.font_families = fontFamilies;`
`443`	`445`	`}`
`444`	`446`
`445`	`447`	`if (mask & tsFontFeaturesMask) {`