From d8b57717793f069db2ccd7c8174d0822bd7de6e1 Mon Sep 17 00:00:00 2001
From: fs <fs@opera.com>
Date: Wed, 20 May 2015 00:52:17 -0700
Subject: [PATCH] Don't fail SkMergeImageFilter if one of the inputs are empty

If one of the inputs to a SkMergeImageFilter was clipped away or
otherwise caused the filterImage(...) invocation for it to return
false, the entire effect would be "failed" and return false --
regardless of if it had produced a result or not.
Instead of returning false directly if filterImage(...) for a source
returned false, consider all the inputs, and then only return false if
all of them do.

BUG=chromium:489046

Review URL: https://codereview.chromium.org/1133523006
---
 src/effects/SkMergeImageFilter.cpp | 7 ++++++-
 tests/ImageFilterTest.cpp          | 8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/effects/SkMergeImageFilter.cpp b/src/effects/SkMergeImageFilter.cpp
index f68d913378..4c5404d5fb 100755
--- a/src/effects/SkMergeImageFilter.cpp
+++ b/src/effects/SkMergeImageFilter.cpp
@@ -77,6 +77,7 @@ bool SkMergeImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src,
     SkCanvas canvas(dst);
     SkPaint paint;
 
+    bool didProduceResult = false;
     int inputCount = countInputs();
     for (int i = 0; i < inputCount; ++i) {
         SkBitmap tmp;
@@ -85,7 +86,7 @@ bool SkMergeImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src,
         SkImageFilter* filter = getInput(i);
         if (filter) {
             if (!filter->filterImage(proxy, src, ctx, &tmp, &pos)) {
-                return false;
+                continue;
             }
             srcPtr = &tmp;
         } else {
@@ -98,8 +99,12 @@ bool SkMergeImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& src,
             paint.setXfermode(NULL);
         }
         canvas.drawSprite(*srcPtr, pos.x() - x0, pos.y() - y0, &paint);
+        didProduceResult = true;
     }
 
+    if (!didProduceResult)
+        return false;
+
     offset->fX = bounds.left();
     offset->fY = bounds.top();
     *result = dst->accessBitmap(false);
diff --git a/tests/ImageFilterTest.cpp b/tests/ImageFilterTest.cpp
index 6c596156fe..0076ac56fb 100644
--- a/tests/ImageFilterTest.cpp
+++ b/tests/ImageFilterTest.cpp
@@ -442,6 +442,12 @@ DEF_TEST(ImageFilterDrawTiled, reporter) {
 
     SkAutoTUnref<SkImageFilter> rectShaderFilter(SkRectShaderImageFilter::Create(shader.get()));
 
+    SkAutoTUnref<SkShader> greenColorShader(SkShader::CreateColorShader(SK_ColorGREEN));
+    SkImageFilter::CropRect leftSideCropRect(SkRect::MakeXYWH(0, 0, 32, 64));
+    SkAutoTUnref<SkImageFilter> rectShaderFilterLeft(SkRectShaderImageFilter::Create(greenColorShader.get(), &leftSideCropRect));
+    SkImageFilter::CropRect rightSideCropRect(SkRect::MakeXYWH(32, 0, 32, 64));
+    SkAutoTUnref<SkImageFilter> rectShaderFilterRight(SkRectShaderImageFilter::Create(greenColorShader.get(), &rightSideCropRect));
+
     struct {
         const char*    fName;
         SkImageFilter* fFilter;
@@ -464,6 +470,8 @@ DEF_TEST(ImageFilterDrawTiled, reporter) {
                   kernelSize, kernel, gain, bias, SkIPoint::Make(1, 1),
                   SkMatrixConvolutionImageFilter::kRepeat_TileMode, false) },
         { "merge", SkMergeImageFilter::Create(NULL, NULL, SkXfermode::kSrcOver_Mode) },
+        { "merge with disjoint inputs", SkMergeImageFilter::Create(
+              rectShaderFilterLeft, rectShaderFilterRight, SkXfermode::kSrcOver_Mode) },
         { "offset", SkOffsetImageFilter::Create(SK_Scalar1, SK_Scalar1) },
         { "dilate", SkDilateImageFilter::Create(3, 2) },
         { "erode", SkErodeImageFilter::Create(2, 3) },