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bug 686497 - avoid passing excessively long wavy-underline path to cairo for stroking. r=roc

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This commit is contained in:
Jonathan Kew
2011-09-16 20:23:29 +01:00
parent b38724baf4
commit 92578ba35f
6 changed files with 69 additions and 26 deletions
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39
layout/base/nsCSSRendering.cpp
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@@ -3367,6 +3367,7 @@ nsCSSRendering::DrawTableBorderSegment(nsRenderingContext& aContext,
void
nsCSSRendering::PaintDecorationLine(gfxContext* aGfxContext,
const gfxRect& aDirtyRect,
const nscolor aColor,
const gfxPoint& aPt,
const gfxSize& aLineSize,
@@ -3381,8 +3382,9 @@ nsCSSRendering::PaintDecorationLine(gfxContext* aGfxContext,
gfxRect rect =
GetTextDecorationRectInternal(aPt, aLineSize, aAscent, aOffset,
aDecoration, aStyle, aDescentLimit);
if (rect.IsEmpty())
if (rect.IsEmpty() || !rect.Intersects(aDirtyRect)) {
return;
}
if (aDecoration != NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE &&
aDecoration != NS_STYLE_TEXT_DECORATION_LINE_OVERLINE &&
@@ -3524,14 +3526,30 @@ nsCSSRendering::PaintDecorationLine(gfxContext* aGfxContext,
* 7. Repeat from 2 until reached to right-most edge of the area.
*/
rect.x += lineHeight / 2.0;
aGfxContext->NewPath();
gfxPoint pt(rect.TopLeft());
gfxFloat rightMost = pt.x + rect.Width() + lineHeight;
gfxFloat adv = rect.Height() - lineHeight;
gfxFloat flatLengthAtVertex = NS_MAX((lineHeight - 1.0) * 2.0, 1.0);
// figure out if we can trim whole cycles from the left and right edges
// of the line, to try and avoid creating an unnecessarily long and
// complex path
gfxFloat cycleLength = 2 * (adv + flatLengthAtVertex);
PRInt32 skipCycles = floor((aDirtyRect.x - rect.x) / cycleLength);
if (skipCycles > 0) {
rect.x += skipCycles * cycleLength;
rect.width -= skipCycles * cycleLength;
}
rect.x += lineHeight / 2.0;
gfxPoint pt(rect.TopLeft());
gfxFloat rightMost = pt.x + rect.Width() + lineHeight;
skipCycles = floor((rightMost - aDirtyRect.XMost()) / cycleLength);
if (skipCycles > 0) {
rightMost -= skipCycles * cycleLength;
}
aGfxContext->NewPath();
pt.x -= lineHeight;
aGfxContext->MoveTo(pt); // 1
@@ -3539,7 +3557,16 @@ nsCSSRendering::PaintDecorationLine(gfxContext* aGfxContext,
aGfxContext->LineTo(pt); // 2
PRBool goDown = PR_TRUE;
PRUint32 iter = 0;
while (pt.x < rightMost) {
if (++iter > 1000) {
// stroke the current path and start again, to avoid pathological
// behavior in cairo with huge numbers of path segments
aGfxContext->Stroke();
aGfxContext->NewPath();
aGfxContext->MoveTo(pt);
iter = 0;
}
pt.x += adv;
pt.y += goDown ? adv : -adv;