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Apply clip in device space for onDrawBehind().

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The back image for saveBehind was in the device's space, but clipping
when drawing to that same region used clipRegion(), which is affected
by the global-to-device matrix. This change switches to using clipRect()
and a temporary whack of the local-to-device matrix to identity so that
we can exactly specify the same rectangle in the device space.

This is important once image filters start changing the global-to-device
matrix to no longer be integer-translations.

Change-Id: I40b37700b9cbf787e81931fdfe109968452533e1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/341158
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>
This commit is contained in:
Michael Ludwig 2020-12-07 19:55:04 -05:00 committed by Skia Commit-Bot
parent e5d9bbfa5b
commit 8685c31dd1
1 changed files with 23 additions and 10 deletions
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33
src/core/SkCanvas.cpp
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@ -2274,6 +2274,11 @@ void SkCanvas::onDrawRegion(const SkRegion& region, const SkPaint& paint) {
}
void SkCanvas::onDrawBehind(const SkPaint& paint) {
SkBaseDevice* dev = this->getTopDevice();
if (!dev) {
return;
}
SkIRect bounds;
SkDeque::Iter iter(fMCStack, SkDeque::Iter::kBack_IterStart);
for (;;) {
@ -2282,6 +2287,9 @@ void SkCanvas::onDrawBehind(const SkPaint& paint) {
return; // no backimages, so nothing to draw
}
if (rec->fBackImage) {
// drawBehind should only have been called when the saveBehind record is active;
// if this fails, it means a real saveLayer was made w/o being restored first.
SkASSERT(dev == rec->fTopLayer->fDevice.get());
bounds = SkIRect::MakeXYWH(rec->fBackImage->fLoc.fX, rec->fBackImage->fLoc.fY,
rec->fBackImage->fImage->width(),
rec->fBackImage->fImage->height());
@ -2289,22 +2297,27 @@ void SkCanvas::onDrawBehind(const SkPaint& paint) {
}
}
// The backimage location (and thus bounds) were defined in the device's space, so mark it
// as a clip. We use a clip instead of just drawing a rect in case the paint has an image
// filter on it (which is applied before any auto-layer so the filter is clipped).
dev->save();
{
// We also have to temporarily whack the device matrix since clipRegion is affected by the
// global-to-device matrix and clipRect is affected by the local-to-device.
SkAutoDeviceTransformRestore adtr(dev, SkMatrix::I());
dev->clipRect(SkRect::Make(bounds), SkClipOp::kIntersect, /* aa */ false);
// ~adtr will reset the local-to-device matrix so that drawPaint() shades correctly.
}
DRAW_BEGIN(paint, nullptr)
while (iter.next()) {
SkBaseDevice* dev = iter.fDevice;
dev->save();
// We use clipRegion because it is already defined to operate in dev-space
// (i.e. ignores the ctm). However, it is going to first translate by -origin,
// but we don't want that, so we undo that before calling in.
SkRegion rgn(bounds.makeOffset(dev->getOrigin()));
dev->clipRegion(rgn, SkClipOp::kIntersect);
dev->drawPaint(draw.paint());
dev->restore(fMCRec->fMatrix);
iter.fDevice->drawPaint(draw.paint());
}
DRAW_END
dev->restore(fMCRec->fMatrix);
}
void SkCanvas::onDrawOval(const SkRect& oval, const SkPaint& paint) {