Fix failed filter followed by an affects-transparent-black filter.

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 1e2cdacb97ef5eab26c8e8089b1ade73856062af..01b0401a57de2eada03c4a66e7d81237ccbc7cdc 100644
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -57,13 +57,18 @@ sk_sp<SkSpecialImage> SkColorFilterImageFilter::onFilterImage(SkSpecialImage* so
                                                               SkIPoint* offset) const {
     SkIPoint inputOffset = SkIPoint::Make(0, 0);
     sk_sp<SkSpecialImage> input(this->filterInput(0, source, ctx, &inputOffset));
-    if (!input) {
+
+    SkIRect bounds;
+    SkIRect inputBounds;
+    if (fColorFilter->affectsTransparentBlack()) {

[robertphillips, 2016/03/30 17:12:28]

// If the color filter affects transparent black the bounds have to be the
entire clip

?

[Stephen White, 2016/04/04 21:50:55]

Done. (Isn't that what the code says? :) )

+        inputBounds = ctx.clipBounds();
+    } else if (!input) {
         return nullptr;
+    } else {
+        inputBounds = SkIRect::MakeXYWH(inputOffset.x(), inputOffset.y(),
+                                        input->width(), input->height());
     }
 

[robertphillips, 2016/03/30 17:12:28]

Can we move 'bounds' down here ?

[Stephen White, 2016/04/04 21:50:55]

Done.

-    SkIRect bounds;
-    const SkIRect inputBounds = SkIRect::MakeXYWH(inputOffset.fX, inputOffset.fY,
-                                                  input->width(), input->height());
     if (!this->applyCropRect(ctx, inputBounds, &bounds)) {
         return nullptr;
     }
@@ -77,18 +82,24 @@ sk_sp<SkSpecialImage> SkColorFilterImageFilter::onFilterImage(SkSpecialImage* so
     SkCanvas* canvas = surf->getCanvas();
     SkASSERT(canvas);
 
-    // TODO: it seems like this clear shouldn't be necessary (see skbug.com/5075)
-    canvas->clear(0x0);
-
     SkPaint paint;
 
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     paint.setColorFilter(fColorFilter);
 
-    input->draw(canvas,
-                SkIntToScalar(inputOffset.fX - bounds.fLeft),
-                SkIntToScalar(inputOffset.fY - bounds.fTop),
-                &paint);
+    // TODO: it seems like this clear shouldn't be necessary (see skbug.com/5075)
+    if (fColorFilter->affectsTransparentBlack()) {

[robertphillips, 2016/03/30 17:12:28]

// The following SkSpecialImage::draw call may not fill the entire canvas. This
drawPaint call insures transparent black gets handled everywhere

?

[Stephen White, 2016/04/04 21:50:55]

Done.

+        canvas->drawPaint(paint);
+    } else {

[robertphillips, 2016/03/30 17:12:28]

can we move the "TODO:" comment in here ?

[Stephen White, 2016/03/30 19:16:08]

Well, technically it applies to the drawPaint(), since there's overdraw there as
well. I'll generalize the comment.

(If I felt courageous, I'd put a clip around the drawPaint & clear that excludes
the input bounds. That should take care of the overdraw.)

[Stephen White, 2016/04/04 21:50:55]

Done.

+        canvas->clear(0x0);
+    }
+
+    if (input) {
+        input->draw(canvas,
+                    SkIntToScalar(inputOffset.fX - bounds.fLeft),
+                    SkIntToScalar(inputOffset.fY - bounds.fTop),
+                    &paint);
+    }
 
     offset->fX = bounds.fLeft;
     offset->fY = bounds.fTop;