[Skia] Text rendered as much less heavy compared to other browsers

Scony · Scony · commit 461326156329 · 2026-03-05T04:23:28.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=309152 Reviewed by Carlos Garcia Campos. This change makes all the text rendered by skia look right - i.e. just like in other browsers - by incorrectly blending in linear color space despite target being in non-linear color space. Until this patch, the rendering was done mathematically correct i.e. the blending was done with respect to target's color space. However, historically, many fonts were designed for incorrect blending and hence they look the most "correct" in such a circumstances. As skia internally implements so called "gamma hack", this change tweaks SkSurfaceProps to properly tune it so that text looks correct. Despite chromium uses 0.2 for contrast and 1.2 for gamma, this change chooses 0 for contrast and 1 for gamma, as the results are visually indistinguishable and yet in some reftests, the differences between anti-aliased pixels are smaller. So in other words, this change makes text anti-aliasing more stable (uniform) when it comes to very small, sub-pixel positioning differences. No new tests. Canonical link: https://commits.webkit.org/308692@main
diff --git a/LayoutTests/fast/snapshot/nested-stacking-context.html b/LayoutTests/fast/snapshot/nested-stacking-context.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html>
 <head>
-<meta name="fuzzy" content="maxDifference=0-1; totalPixels=0-10000" />
+<meta name="fuzzy" content="maxDifference=0-2; totalPixels=0-10000" />
 <style>
 #box {
     width: 100px;
diff --git a/LayoutTests/imported/w3c/web-platform-tests/css/css-text-decor/text-shadow/color-inherit.html b/LayoutTests/imported/w3c/web-platform-tests/css/css-text-decor/text-shadow/color-inherit.html
@@ -1,5 +1,6 @@
 <!DOCTYPE HTML>
 <link rel="help" href="https://drafts.csswg.org/css-text-decor-3/#text-shadow-property">
 <link rel="match" href="color-inherit-ref.html">
+<meta name="fuzzy" content="maxDifference=0-1; totalPixels=0-1">
 <div style="position: absolute; top: 24px; left: 24px; color: blue; text-shadow: 3px 3px;">Hello</div>
 
diff --git a/LayoutTests/imported/w3c/web-platform-tests/css/css-view-transitions/table-caption.html b/LayoutTests/imported/w3c/web-platform-tests/css/css-view-transitions/table-caption.html
@@ -7,6 +7,7 @@
 <link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
 <link rel="author" href="https://mozilla.org" title="Mozilla">
 <link rel="match" href="table-caption-ref.html">
+<meta name="fuzzy" content="maxDifference=0-1; totalPixels=0-3">
 <style>
   table {
     view-transition-name: table;
diff --git a/LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/selectors/cue_function/bold_object/bold_timestamp_future.html b/LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/selectors/cue_function/bold_object/bold_timestamp_future.html
@@ -2,6 +2,7 @@
 <html class="reftest-wait">
 <title>WebVTT rendering, bold object transition with timestamp, ::cue(b:future) selector</title>
 <link rel="match" href="bold_timestamp_future-ref.html">
+<meta name="fuzzy" content="maxDifference=0-1; totalPixels=0-1">
 <style>
 html { overflow:hidden }
 body { margin:0 }
diff --git a/LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/selectors/cue_function/not_root_selector.html b/LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/selectors/cue_function/not_root_selector.html
@@ -2,6 +2,7 @@
 <html class="reftest-wait">
 <title>WebVTT rendering, ::cue(:not(:root)) should not match the root</title>
 <link rel="match" href="not_root_selector-ref.html">
+<meta name="fuzzy" content="maxDifference=0-1; totalPixels=0-1">
 <style>
 html { overflow:hidden }
 body { margin:0 }
diff --git a/Source/WebCore/platform/graphics/FontRenderOptions.h b/Source/WebCore/platform/graphics/FontRenderOptions.h
@@ -81,6 +81,12 @@ class FontRenderOptions {
 #if USE(CAIRO)
     const cairo_font_options_t* fontOptions() const { return m_fontOptions.get(); }
 #elif USE(SKIA)
+    // Custom text settings make text look better at the expense of incorrect blending which is industry standard.
+    static constexpr SkScalar s_textContrast { 0 };
+    static constexpr SkScalar s_textGamma { 1 };
+
+    SkSurfaceProps createSurfaceProps(uint32_t flags = 0) const { return { flags, subpixelOrder(), s_textContrast, s_textGamma }; }
+
     SkFontHinting hinting() const;
     SkFont::Edging antialias() const;
     SkPixelGeometry subpixelOrder() const;
diff --git a/Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp b/Source/WebCore/platform/graphics/skia/GraphicsContextSkia.cpp
@@ -1154,7 +1154,7 @@ static sk_sp<SkSurface> createAcceleratedSurface(const IntSize& size)
     RELEASE_ASSERT(grContext);
 
     auto imageInfo = SkImageInfo::Make(size.width(), size.height(), kRGBA_8888_SkColorType, kPremul_SkAlphaType, SkColorSpace::MakeSRGB());
-    SkSurfaceProps properties { 0, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
     auto surface = SkSurfaces::RenderTarget(grContext, skgpu::Budgeted::kNo, imageInfo, PlatformDisplay::sharedDisplay().msaaSampleCount(), kTopLeft_GrSurfaceOrigin, &properties);
     if (!surface || !surface->getCanvas())
         return nullptr;
diff --git a/Source/WebCore/platform/graphics/skia/ImageBufferSkiaAcceleratedBackend.cpp b/Source/WebCore/platform/graphics/skia/ImageBufferSkiaAcceleratedBackend.cpp
@@ -121,7 +121,7 @@ std::unique_ptr<ImageBufferSkiaAcceleratedBackend> ImageBufferSkiaAcceleratedBac
         flags |= SkSurfaceProps::kDynamicMSAA_Flag;
         msaaSampleCount = 1;
     }
-    SkSurfaceProps properties { flags, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps(flags);
     auto surface = SkSurfaces::RenderTarget(grContext, skgpu::Budgeted::kNo, imageInfo, msaaSampleCount, kTopLeft_GrSurfaceOrigin, &properties);
     if (!surface || !surface->getCanvas())
         return nullptr;
diff --git a/Source/WebCore/platform/graphics/skia/ImageBufferSkiaUnacceleratedBackend.cpp b/Source/WebCore/platform/graphics/skia/ImageBufferSkiaUnacceleratedBackend.cpp
@@ -46,7 +46,7 @@ std::unique_ptr<ImageBufferSkiaUnacceleratedBackend> ImageBufferSkiaUnaccelerate
         return nullptr;
 
     auto imageInfo = SkImageInfo::MakeN32Premul(backendSize.width(), backendSize.height(), parameters.colorSpace.platformColorSpace());
-    SkSurfaceProps properties = { 0, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
     auto surface = SkSurfaces::Raster(imageInfo, &properties);
     if (!surface || !surface->getCanvas())
         return nullptr;
diff --git a/Source/WebCore/platform/graphics/skia/PlatformDisplaySkia.cpp b/Source/WebCore/platform/graphics/skia/PlatformDisplaySkia.cpp
@@ -217,7 +217,7 @@ static unsigned initializeMSAASampleCount(GrDirectContext* grContext)
         // knows there are bugs. The only way to know whether our sample count will work is trying to create a
         // surface with that value and check whether it works.
         auto imageInfo = SkImageInfo::Make(512, 512, kRGBA_8888_SkColorType, kPremul_SkAlphaType, SkColorSpace::MakeSRGB());
-        SkSurfaceProps properties = { 0, FontRenderOptions::singleton().subpixelOrder() };
+        SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
         auto surface = SkSurfaces::RenderTarget(grContext, skgpu::Budgeted::kNo, imageInfo, sampleCount, kTopLeft_GrSurfaceOrigin, &properties);
 
         // If the creation of the surface failed, disable MSAA.
diff --git a/Source/WebCore/platform/graphics/skia/ShareableBitmapSkia.cpp b/Source/WebCore/platform/graphics/skia/ShareableBitmapSkia.cpp
@@ -60,7 +60,7 @@ CheckedUint32 ShareableBitmapConfiguration::calculateBytesPerRow(const IntSize&
 sk_sp<SkSurface> ShareableBitmap::createSurface()
 {
     ref();
-    SkSurfaceProps properties = { 0, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
     auto surface = SkSurfaces::WrapPixels(m_configuration.imageInfo(), mutableSpan().data(), bytesPerRow(), [](void*, void* context) {
         static_cast<ShareableBitmap*>(context)->deref();
     }, this, &properties);
diff --git a/Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedTileBuffer.cpp b/Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedTileBuffer.cpp
@@ -150,7 +150,7 @@ bool CoordinatedUnacceleratedTileBuffer::tryEnsureSurface()
 
     auto imageInfo = SkImageInfo::Make(m_size.width(), m_size.height(), kBGRA_8888_SkColorType, kPremul_SkAlphaType, SkColorSpace::MakeSRGB());
     // FIXME: ref buffer and unref on release proc?
-    SkSurfaceProps properties = { 0, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
     m_surface = SkSurfaces::WrapPixels(imageInfo, data(), imageInfo.minRowBytes64(), &properties);
     return true;
 }
@@ -200,7 +200,7 @@ bool CoordinatedAcceleratedTileBuffer::tryEnsureSurface()
     unsigned msaaSampleCount = PlatformDisplay::sharedDisplay().msaaSampleCount();
 #endif
 
-    SkSurfaceProps properties = { 0, FontRenderOptions::singleton().subpixelOrder() };
+    SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
     m_surface = SkSurfaces::WrapBackendTexture(PlatformDisplay::sharedDisplay().skiaGrContext(),
         backendTexture,
         kTopLeft_GrSurfaceOrigin,
diff --git a/Source/WebKit/WebProcess/WebPage/CoordinatedGraphics/AcceleratedSurface.cpp b/Source/WebKit/WebProcess/WebPage/CoordinatedGraphics/AcceleratedSurface.cpp
@@ -227,7 +227,7 @@ SkSurface* AcceleratedSurface::RenderTargetShareableBuffer::skiaSurface()
         if (!skiaGLContext->makeContextCurrent())
             return nullptr;
 
-        SkSurfaceProps properties { 0, FontRenderOptions::singleton().subpixelOrder() };
+        SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps();
         auto skiaSurface = SkSurfaces::WrapBackendRenderTarget(
             display.skiaGrContext(),
             renderTargetSkia,

Original file line number	Diff line number	Diff line change
`@@ -121,7 +121,7 @@ std::unique_ptr<ImageBufferSkiaAcceleratedBackend> ImageBufferSkiaAcceleratedBac`
`121`	`121`	`flags \|= SkSurfaceProps::kDynamicMSAA_Flag;`
`122`	`122`	`msaaSampleCount = 1;`
`123`	`123`	`}`
`124`		`- SkSurfaceProps properties { flags, FontRenderOptions::singleton().subpixelOrder() };`
	`124`	`+ SkSurfaceProps properties = FontRenderOptions::singleton().createSurfaceProps(flags);`
`125`	`125`	`auto surface = SkSurfaces::RenderTarget(grContext, skgpu::Budgeted::kNo, imageInfo, msaaSampleCount, kTopLeft_GrSurfaceOrigin, &properties);`
`126`	`126`	`if (!surface \|\| !surface->getCanvas())`
`127`	`127`	`return nullptr;`