Subpixel layout: setSimpleLineLayoutEnabled() produces different layout when line position has CSS px fractions.

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[zalan]

fast/forms/textAreaLineHeight-simple-lines.html

[zalan]

SimpleLineLayout's paintFlow() needs to call roundedIntPoint() on paint offset to match InlineTextBox's paint positioning.

something along these lines:

--- a/Source/WebCore/rendering/SimpleLineLayoutFunctions.cpp
+++ b/Source/WebCore/rendering/SimpleLineLayoutFunctions.cpp
@@ -80,9 +80,10 @@ void paintFlow(const RenderBlockFlow& flow, const Layout& layout, PaintInfo& pai
     GraphicsContextStateSaver stateSaver(context, textPaintStyle.strokeWidth > 0);
 
     updateGraphicsContext(context, textPaintStyle);
+    LayoutPoint adjustedPaintOffset = roundedIntPoint(paintOffset);
 
     LayoutRect paintRect = paintInfo.rect;
-    paintRect.moveBy(-paintOffset);
+    paintRect.moveBy(-adjustedPaintOffset);
 
     auto resolver = runResolver(flow, layout);
     auto range = resolver.rangeForRect(paintRect);
@@ -92,9 +93,9 @@ void paintFlow(const RenderBlockFlow& flow, const Layout& layout, PaintInfo& pai
             continue;
         TextRun textRun(run.text());
         textRun.setTabSize(!style.collapseWhiteSpace(), style.tabSize());
-        context.drawText(font, textRun, run.baseline() + paintOffset);
+        context.drawText(font, textRun, run.baseline() + adjustedPaintOffset);
         if (debugBordersEnabled)
-            paintDebugBorders(context, run.rect(), paintOffset);
+            paintDebugBorders(context, run.rect(), adjustedPaintOffset);
     }
 }

[zalan]

Created attachment 221206 [details]
test case

[zalan]

*** Bug 126893 has been marked as a duplicate of this bug. ***

[zalan]

*** Bug 126894 has been marked as a duplicate of this bug. ***

[zalan]

additional failed cases (from dupes)

LayoutTests/fast/shapes/shape-inside/shape-inside-circle-padding.html
LayoutTests/fast/shapes/shape-inside/shape-inside-circle.html
LayoutTests/fast/shapes/shape-inside/shape-inside-ellipse-padding.html
LayoutTests/fast/shapes/shape-inside/shape-inside-ellipse.html
LayoutTests/fast/shapes/shape-inside/shape-inside-rounded-rectangle-fit-002.html
LayoutTests/fast/shapes/shape-inside/shape-inside-subpixel-rectangle-top.html

LayoutTests/fast/regions/floats-basic-in-variable-width-regions.html
LayoutTests/fast/regions/overflow-moving-below-floats-in-variable-width-regions.html
LayoutTests/fast/regions/overflow-not-moving-below-floats-in-variable-width-regions.html
LayoutTests/fast/regions/overflow-size-change-in-variable-width-regions.html
LayoutTests/fast/regions/overflow-size-change-with-stacking-context.html
LayoutTests/fast/regions/selection/selecting-text-through-different-region-flows.html

[zalan]

actually fast/shapes/shape-inside/shape-inside-subpixel-rectangle-top.html doesnt get fixed by this. For that, webkit.org/b/124784 needs revisiting.

[zalan]

*** Bug 126891 has been marked as a duplicate of this bug. ***

[zalan]

fast/css/word-spacing-between-blocks.html
fast/css/word-spacing-between-inlines.html

[zalan]

Created attachment 221530 [details]
Patch

[zalan]

Created attachment 221531 [details]
Patch

[zalan]

<rdar://problem/15855703>

[Antti Koivisto]

Comment on attachment 221531 [details]
Patch

r=me

[WebKit Commit Bot]

Comment on attachment 221531 [details]
Patch

Clearing flags on attachment: 221531

Committed r162340: <http://trac.webkit.org/changeset/162340>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.