Prevent matrix stack from being corrupted if a rotated image filter is clipped out

Bug: skia:7765
Change-Id: Id76b63cebc25dcdff02d4ba3f6d6bba6f2b6b842
Reviewed-on: https://skia-review.googlesource.com/122782
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Robert Phillips <robertphillips@google.com>

2 files changed, 33 insertions, 0 deletions

diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 635f453bf7..7398f2819d 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -984,6 +984,7 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
     SkLazyPaint lazyP;
     SkImageFilter* imageFilter = paint ? paint->getImageFilter() : nullptr;
     SkMatrix stashedMatrix = fMCRec->fMatrix;
+    MCRec* modifiedRec = nullptr;
     SkMatrix remainder;
     SkSize scale;
     /*
@@ -1006,6 +1007,7 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
         stashedMatrix.decomposeScale(&scale, &remainder))
     {
         // We will restore the matrix (which we are overwriting here) in restore via fStashedMatrix
+        modifiedRec = fMCRec;
         this->internalSetMatrix(SkMatrix::MakeScale(scale.width(), scale.height()));
         SkPaint* p = lazyP.set(*paint);
         p->setImageFilter(SkImageFilter::MakeMatrixFilter(remainder,
@@ -1021,6 +1023,11 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
 
     SkIRect ir;
     if (!this->clipRectBounds(bounds, saveLayerFlags, &ir, imageFilter)) {
+        if (modifiedRec) {
+            // In this case there will be no layer in which to stash the matrix so we need to
+            // revert the prior MCRec to its earlier state.
+            modifiedRec->fMatrix = stashedMatrix;
+        }
         return;
     }
 
diff --git a/tests/CanvasTest.cpp b/tests/CanvasTest.cpp
index 95030a3e42..d61d195982 100644
--- a/tests/CanvasTest.cpp
+++ b/tests/CanvasTest.cpp
@@ -898,3 +898,29 @@ DEF_TEST(Canvas_degenerate_dimension, reporter) {
     }
 }
 
+#include "SkBlurImageFilter.h"
+
+DEF_TEST(Canvas_ClippedOutImageFilter, reporter) {
+    SkCanvas canvas(100, 100);
+
+    SkPaint p;
+    p.setColor(SK_ColorGREEN);
+    p.setImageFilter(SkBlurImageFilter::Make(3.0f, 3.0f, nullptr, nullptr));
+
+    SkRect blurredRect = SkRect::MakeXYWH(60, 10, 30, 30);
+
+    SkMatrix invM;
+    invM.setRotate(-45);
+    invM.mapRect(&blurredRect);
+
+    const SkRect clipRect = SkRect::MakeXYWH(0, 50, 50, 50);
+
+    canvas.clipRect(clipRect);
+
+    canvas.rotate(45);
+    const SkMatrix preCTM = canvas.getTotalMatrix();
+    canvas.drawRect(blurredRect, p);
+    const SkMatrix postCTM = canvas.getTotalMatrix();
+    REPORTER_ASSERT(reporter, preCTM == postCTM);
+}
+