Changeset 245191 in webkit

Timestamp:

May 10, 2019 1:30:05 PM (5 years ago)

Author:

Alan Bujtas

Message:

[iOS] baidu.com: Synthetic bold renders too far apart, appears doubled.
​https://bugs.webkit.org/show_bug.cgi?id=197781
<rdar://problem/48027412>

Reviewed by Simon Fraser.

Source/WebCore:

Synthetic bold is essentially two regular glyphs painted with an offset. While on macOS this offset is always 1px (CSS), on iOS larger font produces higher offset value. At paint time, this offset value (in CSS px unit) get converted
to a device pixel value taking context scale into account. This conversion ensures that the gap between the 2 regular glyphs won't get wider (in device pixels) as the user pinch zooms in.
This works as long as the scale on the context is >= 1. This patch ensures that a scaled down context won't blow up this gap.

Test: fast/text/large-synthetic-bold-with-scale-transform.html

• platform/graphics/cocoa/FontCascadeCocoa.mm:

(WebCore::FontCascade::drawGlyphs):

LayoutTests:

• fast/text/large-synthetic-bold-with-scale-transform-expected.html: Added.
• fast/text/large-synthetic-bold-with-scale-transform.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/text/large-synthetic-bold-with-scale-transform-expected.html (added)
• LayoutTests/fast/text/large-synthetic-bold-with-scale-transform.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/platform/graphics/cocoa/FontCascadeCocoa.mm (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2019-05-10  Zalan Bujtas  <zalan@apple.com>
+
+        [iOS] baidu.com: Synthetic bold renders too far apart, appears doubled.
+        https://bugs.webkit.org/show_bug.cgi?id=197781
+        <rdar://problem/48027412>
+
+        Reviewed by Simon Fraser.
+
+        * fast/text/large-synthetic-bold-with-scale-transform-expected.html: Added.
+        * fast/text/large-synthetic-bold-with-scale-transform.html: Added.
+
 2019-05-10  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-05-10  Zalan Bujtas  <zalan@apple.com>
+
+        [iOS] baidu.com: Synthetic bold renders too far apart, appears doubled.
+        https://bugs.webkit.org/show_bug.cgi?id=197781
+        <rdar://problem/48027412>
+
+        Reviewed by Simon Fraser.
+
+        Synthetic bold is essentially two regular glyphs painted with an offset. While on macOS this offset is always 1px (CSS), on iOS larger font produces higher offset value. At paint time, this offset value (in CSS px unit) get converted
+        to a device pixel value taking context scale into account. This conversion ensures that the gap between the 2 regular glyphs won't get wider (in device pixels) as the user pinch zooms in.
+        This works as long as the scale on the context is >= 1. This patch ensures that a scaled down context won't blow up this gap.
+
+        Test: fast/text/large-synthetic-bold-with-scale-transform.html
+
+        * platform/graphics/cocoa/FontCascadeCocoa.mm:
+        (WebCore::FontCascade::drawGlyphs):
+
 2019-05-10  Brent Fulgham  <bfulgham@apple.com>
 

trunk/Source/WebCore/platform/graphics/cocoa/FontCascadeCocoa.mm

@@ -277 +277 @@
         FloatSize horizontalUnitSizeInDevicePixels = contextCTM.mapSize(FloatSize(1, 0));
         float horizontalUnitLengthInDevicePixels = sqrtf(horizontalUnitSizeInDevicePixels.width() * horizontalUnitSizeInDevicePixels.width() + horizontalUnitSizeInDevicePixels.height() * horizontalUnitSizeInDevicePixels.height());
-        if (horizontalUnitLengthInDevicePixels)
-            syntheticBoldOffset /= horizontalUnitLengthInDevicePixels;
+        if (horizontalUnitLengthInDevicePixels) {
+            // Make sure that a scaled down context won't blow up the gap between the glyphs. 
+            syntheticBoldOffset = std::min(syntheticBoldOffset, syntheticBoldOffset / horizontalUnitLengthInDevicePixels);
+        }
     };