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-rw-r--r--layout/svg/nsSVGOuterSVGFrame.cpp56
1 files changed, 33 insertions, 23 deletions
diff --git a/layout/svg/nsSVGOuterSVGFrame.cpp b/layout/svg/nsSVGOuterSVGFrame.cpp
index 434676010..b1ee54eb9 100644
--- a/layout/svg/nsSVGOuterSVGFrame.cpp
+++ b/layout/svg/nsSVGOuterSVGFrame.cpp
@@ -979,46 +979,56 @@ nsSVGOuterSVGAnonChildFrame::GetType() const
return nsGkAtoms::svgOuterSVGAnonChildFrame;
}
-bool
-nsSVGOuterSVGAnonChildFrame::IsSVGTransformed(Matrix* aOwnTransform,
- Matrix* aFromParentTransform) const
+static Matrix
+ComputeOuterSVGAnonChildFrameTransform(const nsSVGOuterSVGAnonChildFrame* aFrame)
{
// Our elements 'transform' attribute is applied to our nsSVGOuterSVGFrame
// parent, and the element's children-only transforms are applied to us, the
// anonymous child frame. Since we are the child frame, we apply the
// children-only transforms as if they are our own transform.
- SVGSVGElement* content = static_cast<SVGSVGElement*>(mContent);
+ SVGSVGElement* content = static_cast<SVGSVGElement*>(aFrame->GetContent());
if (!content->HasChildrenOnlyTransform()) {
- return false;
+ return Matrix();
}
// Outer-<svg> doesn't use x/y, so we can pass eChildToUserSpace here.
gfxMatrix ownMatrix =
content->PrependLocalTransformsTo(gfxMatrix(), eChildToUserSpace);
- if (ownMatrix.IsIdentity()) {
- return false;
+ if (ownMatrix.HasNonTranslation()) {
+ // viewBox, currentScale and currentTranslate should only produce a
+ // rectilinear transform.
+ MOZ_ASSERT(ownMatrix.IsRectilinear(),
+ "Non-rectilinear transform will break the following logic");
+
+ // The nsDisplayTransform code will apply this transform to our frame,
+ // including to our frame position. We don't want our frame position to
+ // be scaled though, so we need to correct for that in the transform.
+ CSSPoint pos = CSSPixel::FromAppUnits(aFrame->GetPosition());
+ CSSPoint scaledPos = CSSPoint(ownMatrix._11 * pos.x, ownMatrix._22 * pos.y);
+ CSSPoint deltaPos = scaledPos - pos;
+ ownMatrix *= gfxMatrix::Translation(-deltaPos.x, -deltaPos.y);
}
- if (aOwnTransform) {
- if (ownMatrix.HasNonTranslation()) {
- // Note: viewBox, currentScale and currentTranslate should only
- // produce a rectilinear transform.
- MOZ_ASSERT(ownMatrix.IsRectilinear(),
- "Non-rectilinear transform will break the following logic");
-
- // The nsDisplayTransform code will apply this transform to our frame,
- // including to our frame position. We don't want our frame position to
- // be scaled though, so we need to correct for that in the transform.
- CSSPoint pos = CSSPixel::FromAppUnits(GetPosition());
- CSSPoint scaledPos = CSSPoint(ownMatrix._11 * pos.x, ownMatrix._22 * pos.y);
- CSSPoint deltaPos = scaledPos - pos;
- ownMatrix *= gfxMatrix::Translation(-deltaPos.x, -deltaPos.y);
- }
+ return gfx::ToMatrix(ownMatrix);
+}
- *aOwnTransform = gfx::ToMatrix(ownMatrix);
+// We want this frame to be a reference frame. An easy way to achieve that is
+// to always return true from this method, even for identity transforms.
+// This frame being a reference frame ensures that the offset between this
+// <svg> element and the parent reference frame is completely absorbed by the
+// nsDisplayTransform that's created for this frame, and that this offset does
+// not affect our descendants' transforms. Consequently, if the <svg> element
+// moves, e.g. during scrolling, the transform matrices of our contents are
+// unaffected. This simplifies invalidation.
+bool
+nsSVGOuterSVGAnonChildFrame::IsSVGTransformed(Matrix* aOwnTransform,
+ Matrix* aFromParentTransform) const
+{
+ if (aOwnTransform) {
+ *aOwnTransform = ComputeOuterSVGAnonChildFrameTransform(this);
}
return true;