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Bug 1458968 - Make the nsSVGOuterSVGAnonChildFrame a reference frame by always returning true from IsSVGTransformed. r=mattwoodrow

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This causes transforms of the <svg> contents to be unaffected by scrolling / offset changes of the <svg> element.

MozReview-Commit-ID: JtDmwppqBis
This commit is contained in:
Markus Stange 2018-05-22 21:41:30 -04:00 committed by Jeff Muizelaar
parent 495e546911
commit 1c9281028a
1 changed files with 34 additions and 25 deletions
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59
layout/svg/nsSVGOuterSVGFrame.cpp
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@ -1002,47 +1002,56 @@ nsSVGOuterSVGAnonChildFrame::Init(nsIContent* aContent,
}
#endif
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*>(GetContent());
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.
// XXX Yeah, this is a bit hacky.
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);
}
return 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) {
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.
// XXX Yeah, this is a bit hacky.
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);
}
*aOwnTransform = gfx::ToMatrix(ownMatrix);
*aOwnTransform = ComputeOuterSVGAnonChildFrameTransform(this);
}
return true;