Implement correct clipping for image filters.

gm/imageblurtiled.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkBlurImageFilter.h"
+#include "SkRandom.h"
+
+#define WIDTH 640
+#define HEIGHT 480
+
+namespace skiagm {
+
+class ImageBlurTiledGM : public GM {
+public:
+    ImageBlurTiledGM(SkScalar sigmaX, SkScalar sigmaY)
+        : fSigmaX(sigmaX), fSigmaY(sigmaY) {
+    }
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("imageblurtiled");
+    }
+
+    virtual SkISize onISize() {
+        return make_isize(WIDTH, HEIGHT);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        SkPaint paint;
+        paint.setImageFilter(new SkBlurImageFilter(fSigmaX, fSigmaY))->unref();
+        const SkScalar tile_size = SkIntToScalar(128);
+        SkRect bounds;
+        canvas->getClipBounds(&bounds);
+        for (SkScalar y = bounds.top(); y < bounds.bottom(); y += tile_size) {
+            for (SkScalar x = bounds.left(); x < bounds.right(); x += tile_size) {
+                canvas->save();
+                canvas->clipRect(SkRect::MakeXYWH(x, y, tile_size, tile_size));
+                canvas->saveLayer(NULL, &paint);
+                const char* str[] = {
+                    "The quick",
+                    "brown fox",
+                    "jumped over",
+                    "the lazy dog.",
+                };
+                SkPaint textPaint;
+                textPaint.setAntiAlias(true);
+                textPaint.setTextSize(SkIntToScalar(100));
+                int posY = 0;
+                for (unsigned i = 0; i < SK_ARRAY_COUNT(str); i++) {
+                    posY += 100;
+                    canvas->drawText(str[i], strlen(str[i]), SkIntToScalar(0),
+                                     SkIntToScalar(posY), textPaint);
+                }
+                canvas->restore();
+                canvas->restore();
+            }
+        }
+    }
+
+private:
+    SkScalar fSigmaX;
+    SkScalar fSigmaY;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory1(void*) { return new ImageBlurTiledGM(3.0f, 3.0f); }
+static GMRegistry reg1(MyFactory1);
+
+}