Pre-crop filled rects to avoid scissor

gm/croppedrects.cpp

+/*
+ * Copyright 2016 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 "SkPath.h"
+#include "SkRandom.h"
+#include "SkRRect.h"
+#include "SkSurface.h"
+
+namespace skiagm {
+
+constexpr SkRect kSrcImageClip{75, 75, 275, 275};
+
+/*
+ * The purpose of this test is to exercise all three codepaths in GrDrawContext (drawFilledRect,
+ * fillRectToRect, fillRectWithLocalMatrix) that pre-crop filled rects based on the clip.
+ *
+ * The test creates an image of a green square surrounded by red background, then draws this image
+ * in various ways with the red clipped out. The test is successful if there is no visible red
+ * background, scissor is never used, and ideally, all the rectangles draw in one batch.
+ */
+class CroppedRectsGM : public GM {
+private:
+    SkString onShortName() override final { return SkString("croppedrects"); }
+    SkISize onISize() override { return SkISize::Make(500, 500); }
+
+    void onOnceBeforeDraw() override {
+        sk_sp<SkSurface> srcSurface = SkSurface::MakeRasterN32Premul(500, 500);
+        SkCanvas* srcCanvas = srcSurface->getCanvas();
+
+        srcCanvas->clear(SK_ColorRED);
+
+        SkPaint paint;
+        paint.setColor(0xff00ff00);
+        srcCanvas->drawRect(kSrcImageClip, paint);
+
+        constexpr SkScalar kStrokeWidth = 10;
+        SkPaint stroke;
+        stroke.setStyle(SkPaint::kStroke_Style);
+        stroke.setStrokeWidth(kStrokeWidth);
+        stroke.setColor(0xff008800);
+        srcCanvas->drawRect(kSrcImageClip.makeInset(kStrokeWidth / 2, kStrokeWidth / 2), stroke);
+
+        fSrcImage = srcSurface->makeImageSnapshot(SkBudgeted::kYes, SkSurface::kNo_ForceUnique);
+        fSrcImageShader = fSrcImage->makeShader(SkShader::kClamp_TileMode,
+                                                SkShader::kClamp_TileMode);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->clear(SK_ColorWHITE);
+
+        {
+            // GrDrawContext::drawFilledRect.
+            SkAutoCanvasRestore acr(canvas, true);
+            SkPaint paint;
+            paint.setShader(fSrcImageShader);
+            paint.setFilterQuality(kNone_SkFilterQuality);
+            canvas->clipRect(kSrcImageClip);
+            canvas->drawPaint(paint);
+        }
+
+        {
+            // GrDrawContext::fillRectToRect.
+            SkAutoCanvasRestore acr(canvas, true);
+            SkPaint paint;
+            paint.setFilterQuality(kNone_SkFilterQuality);
+            SkRect drawRect = SkRect::MakeXYWH(350, 100, 100, 300);
+            canvas->clipRect(drawRect);
+            canvas->drawImageRect(fSrcImage.get(),
+                                  kSrcImageClip.makeOutset(0.5f * kSrcImageClip.width(),
+                                                           kSrcImageClip.height()),
+                                  drawRect.makeOutset(0.5f * drawRect.width(), drawRect.height()),
+                                  &paint);
+        }
+
+        {
+            // GrDrawContext::fillRectWithLocalMatrix.
+            SkAutoCanvasRestore acr(canvas, true);
+            SkPath path;
+            path.moveTo(kSrcImageClip.fLeft - kSrcImageClip.width(), kSrcImageClip.centerY());
+            path.lineTo(kSrcImageClip.fRight + 3 * kSrcImageClip.width(), kSrcImageClip.centerY());
+            SkPaint paint;
+            paint.setStyle(SkPaint::kStroke_Style);
+            paint.setStrokeWidth(2 * kSrcImageClip.height());
+            paint.setShader(fSrcImageShader);
+            paint.setFilterQuality(kNone_SkFilterQuality);
+            canvas->translate(-90, 263);
+            canvas->scale(300 / kSrcImageClip.width(), 100 / kSrcImageClip.height());
+            canvas->clipRect(kSrcImageClip);
+            canvas->drawPath(path, paint);
+        }
+
+        // TODO: assert the draw target only has one batch in the post-MDB world.
+    }
+
+    sk_sp<SkImage> fSrcImage;
+    sk_sp<SkShader> fSrcImageShader;
+
+    typedef GM INHERITED;
+};
+
+DEF_GM( return new CroppedRectsGM(); )
+
+}