Changeset 246431 in webkit

Timestamp:

Jun 14, 2019, 1:02:54 AM (7 years ago)

Author:

Carlos Garcia Campos

Message:

[cairo] Entering text into forms on github.com creates a trapezoid artifact
​https://bugs.webkit.org/show_bug.cgi?id=126124

Reviewed by Michael Catanzaro.

Mixing antialiasing modes in the same clip is not actually supported by cairo. In the case of rectangle clips we
are already ignoring the current antialiasing to not do any antialiasing. We could do the opposite for clips
receiving a path, we want to enforce antialiasing in that case since the paths might contain curves. Doing that
we ensure all calls to clip with a path use the same antialiasing, which is the case of the github bug.

• platform/graphics/cairo/CairoOperations.cpp:

(WebCore::Cairo::doClipWithAntialias): Helper to call cairo_clip() with the given antialising mode.
(WebCore::Cairo::clip): Use doClipWithAntialias().
(WebCore::Cairo::clipOut): Ditto.
(WebCore::Cairo::clipPath): Ditto.

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/graphics/cairo/CairoOperations.cpp (modified) (5 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-06-14  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        [cairo] Entering text into forms on github.com creates a trapezoid artifact
+        https://bugs.webkit.org/show_bug.cgi?id=126124
+
+        Reviewed by Michael Catanzaro.
+
+        Mixing antialiasing modes in the same clip is not actually supported by cairo. In the case of rectangle clips we
+        are already ignoring the current antialiasing to not do any antialiasing. We could do the opposite for clips
+        receiving a path, we want to enforce antialiasing in that case since the paths might contain curves. Doing that
+        we ensure all calls to clip with a path use the same antialiasing, which is the case of the github bug.
+
+        * platform/graphics/cairo/CairoOperations.cpp:
+        (WebCore::Cairo::doClipWithAntialias): Helper to call cairo_clip() with the given antialising mode.
+        (WebCore::Cairo::clip): Use doClipWithAntialias().
+        (WebCore::Cairo::clipOut): Ditto.
+        (WebCore::Cairo::clipPath): Ditto.
+
 2019-06-13  Myles C. Maxfield  <mmaxfield@apple.com>
 

trunk/Source/WebCore/platform/graphics/cairo/CairoOperations.cpp

@@ -1252 +1252 @@
 }
 
+static void doClipWithAntialias(cairo_t* cr, cairo_antialias_t antialias)
+{
+    auto savedAntialiasRule = cairo_get_antialias(cr);
+    cairo_set_antialias(cr, antialias);
+    cairo_clip(cr);
+    cairo_set_antialias(cr, savedAntialiasRule);
+}
+
 void clip(PlatformContextCairo& platformContext, const FloatRect& rect)
 {
@@ -1263 +1271 @@
     // when a transformation is applied to the GraphicsContext
     // while drawing the transformed layer.
-    cairo_antialias_t savedAntialiasRule = cairo_get_antialias(cr);
-    cairo_set_antialias(cr, CAIRO_ANTIALIAS_NONE);
-    cairo_clip(cr);
+    doClipWithAntialias(cr, CAIRO_ANTIALIAS_NONE);
     cairo_set_fill_rule(cr, savedFillRule);
-    cairo_set_antialias(cr, savedAntialiasRule);
 
     if (auto* graphicsContextPrivate = platformContext.graphicsContextPrivate())
@@ -1282 +1287 @@
     cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
     cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
-    cairo_clip(cr);
+    doClipWithAntialias(cr, CAIRO_ANTIALIAS_NONE);
     cairo_set_fill_rule(cr, savedFillRule);
 }
@@ -1296 +1301 @@
     cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
     cairo_set_fill_rule(cr, CAIRO_FILL_RULE_EVEN_ODD);
-    cairo_clip(cr);
+    // Enforce default antialias when clipping paths, since they can contain curves.
+    doClipWithAntialias(cr, CAIRO_ANTIALIAS_DEFAULT);
     cairo_set_fill_rule(cr, savedFillRule);
 }
@@ -1309 +1315 @@
     cairo_fill_rule_t savedFillRule = cairo_get_fill_rule(cr);
     cairo_set_fill_rule(cr, clipRule == WindRule::EvenOdd ? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
-    cairo_clip(cr);
+    // Enforce default antialias when clipping paths, since they can contain curves.
+    doClipWithAntialias(cr, CAIRO_ANTIALIAS_DEFAULT);
     cairo_set_fill_rule(cr, savedFillRule);