[Regression] Webkit "-apple-system" font fallback token handles font …

…weights of PingFang incorrectly. https://bugs.webkit.org/show_bug.cgi?id=177345 <rdar://problem/32975942> Reviewed by Jon Lee. Source/WebCore: This bug has a fairly insideous cause. In particular, the system font fallback path follows system conventions, which are not the same as the CSS fallback path. For example, the Chinese fallback of San Francisco weight 600 is Ping Fang weight 500. This doesn't match our assumptions in CSS, because Ping Fang does have a 600 weight, which CSS would think is closer. However, the whole point of system-ui is that it follows the system fallback path, not CSS's. Therefore, falling back from a bold system-ui request to a non-bold fallback font is correct and expected, and we shouldn't synthesize bold in this situation. Test: fast/text/system-ui-chinese-bold-fallback.html * platform/graphics/cocoa/FontFamilySpecificationCoreText.cpp: (WebCore::FontFamilySpecificationCoreText::fontRanges const): LayoutTests: * fast/text/system-ui-chinese-bold-fallback.html: Canonical link: https://commits.webkit.org/194649@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@223589 268f45cc-cd09-0410-ab3c-d52691b4dbfc
WebKit · Oct 18, 2017 · b17a107d56ebf8f6344473290ccc146a31e557e3 · b17a107
1 parent e4f08b1
commit b17a107d56ebf8f6344473290ccc146a31e557e3
Showing 5 changed files with 50 additions and 1 deletion.
diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
@@ -1,3 +1,13 @@
+2017-10-17  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        [Regression] Webkit "-apple-system" font fallback token handles font weights of PingFang incorrectly.
+        https://bugs.webkit.org/show_bug.cgi?id=177345
+        <rdar://problem/32975942>
+
+        Reviewed by Jon Lee.
+
+        * fast/text/system-ui-chinese-bold-fallback.html:
+
 2017-10-17  Dean Jackson  <dino@apple.com>
 
         webgl/1.0.2/conformance/canvas/drawingbuffer-static-canvas-test.html failing

diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
@@ -1,3 +1,24 @@
+2017-10-17  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        [Regression] Webkit "-apple-system" font fallback token handles font weights of PingFang incorrectly.
+        https://bugs.webkit.org/show_bug.cgi?id=177345
+        <rdar://problem/32975942>
+
+        Reviewed by Jon Lee.
+
+        This bug has a fairly insideous cause. In particular, the system font fallback path follows
+        system conventions, which are not the same as the CSS fallback path. For example, the Chinese
+        fallback of San Francisco weight 600 is Ping Fang weight 500. This doesn't match our
+        assumptions in CSS, because Ping Fang does have a 600 weight, which CSS would think is closer.
+        However, the whole point of system-ui is that it follows the system fallback path, not CSS's.
+        Therefore, falling back from a bold system-ui request to a non-bold fallback font is correct
+        and expected, and we shouldn't synthesize bold in this situation.
+
+        Test: fast/text/system-ui-chinese-bold-fallback.html
+
+        * platform/graphics/cocoa/FontFamilySpecificationCoreText.cpp:
+        (WebCore::FontFamilySpecificationCoreText::fontRanges const):
+
 2017-10-17  Chelsea Pugh  <cpugh@apple.com>
 
         [iOS] Don't turn fields yellow after filling credentials

diff --git a/Source/WebCore/platform/graphics/cocoa/FontFamilySpecificationCoreText.cpp b/Source/WebCore/platform/graphics/cocoa/FontFamilySpecificationCoreText.cpp
@@ -60,7 +60,7 @@ FontRanges FontFamilySpecificationCoreText::fontRanges(const FontDescription& fo
     bool syntheticBold, syntheticOblique;
     std::tie(syntheticBold, syntheticOblique) = computeNecessarySynthesis(fontForSynthesisComputation.get(), fontDescription).boldObliquePair();
 
-    FontPlatformData fontPlatformData(font.get(), size, syntheticBold, syntheticOblique, fontDescription.orientation(), fontDescription.widthVariant(), fontDescription.textRenderingMode());
+    FontPlatformData fontPlatformData(font.get(), size, false, syntheticOblique, fontDescription.orientation(), fontDescription.widthVariant(), fontDescription.textRenderingMode());
 
     return FontRanges(FontCache::singleton().fontForPlatformData(fontPlatformData));
 }

diff --git a/fast/text/system-ui-chinese-bold-fallback-expected.html b/fast/text/system-ui-chinese-bold-fallback-expected.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+This makes sure that drawing Chinese characters in a weight 600 system font doesn't cause synthetic bold.
+<div style="font: 600 16px system-ui; font-synthesis: none;">&#x4eca;</div>
+</body>
+</html>
diff --git a/fast/text/system-ui-chinese-bold-fallback.html b/fast/text/system-ui-chinese-bold-fallback.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+This makes sure that drawing Chinese characters in a weight 600 system font doesn't cause synthetic bold.
+<div style="font: 600 16px system-ui;">&#x4eca;</div>
+</body>
+</html>