Add methods to SkLayerDrawLooper to allow adding layers on top

tests/LayerDrawLooperTest.cpp

Index: tests/LayerDrawLooperTest.cpp
diff --git a/tests/LayerDrawLooperTest.cpp b/tests/LayerDrawLooperTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..7b85fc814a0b92f5b1f5cd0cf2d5ac3689d18974
--- /dev/null
+++ b/tests/LayerDrawLooperTest.cpp
@@ -0,0 +1,154 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "Test.h"
+#include "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkDraw.h"
+#include "SkDevice.h"
+#include "SkLayerDrawLooper.h"
+#include "SkMatrix.h"
+#include "SkPaint.h"
+#include "SkRect.h"
+#include "SkRefCnt.h"
+#include "SkScalar.h"
+#include "SkXfermode.h"
+
+namespace {
+
+class FakeDevice : public SkDevice {
+public:
+    FakeDevice() : SkDevice(SkBitmap::kARGB_8888_Config, 100, 100) { }
+
+    virtual void drawRect(const SkDraw& draw, const SkRect& r, const SkPaint& paint) {
+        fLastMatrix = *draw.fMatrix;
+        SkDevice::drawRect(draw, r, paint);
+    }
+
+    SkMatrix fLastMatrix;
+};
+
+} // namespace
+
+static void test_frontToBack(skiatest::Reporter* reporter) {
+    SkAutoTUnref<SkLayerDrawLooper> looper(SkNEW(SkLayerDrawLooper));
+    SkLayerDrawLooper::LayerInfo layerInfo;
+
+    // Add the front layer, with the defaults.
+    (void)looper->addLayer(layerInfo);
+
+    // Add the back layer, with some layer info set.
+    layerInfo.fOffset.set(SkFloatToScalar(10.0f), SkFloatToScalar(20.0f));
+    layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
+    SkPaint* layerPaint = looper->addLayer(layerInfo);
+    layerPaint->setXfermodeMode(SkXfermode::kSrc_Mode);
+
+    FakeDevice device;
+    SkCanvas canvas(&device);
+    SkPaint paint;
+    looper->init(&canvas);
+
+    // The back layer should come first.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrc_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(10.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(20.0f) == device.fLastMatrix.getTranslateY());
+    paint.reset();
+
+    // Then the front layer.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateY());
+
+    // Only two layers were added, so that should be the end.
+    REPORTER_ASSERT(reporter, !looper->next(&canvas, &paint));
+}
+
+static void test_backToFront(skiatest::Reporter* reporter) {
+    SkAutoTUnref<SkLayerDrawLooper> looper(SkNEW(SkLayerDrawLooper));
+    SkLayerDrawLooper::LayerInfo layerInfo;
+
+    // Add the back layer, with the defaults.
+    (void)looper->addLayerOnTop(layerInfo);
+
+    // Add the front layer, with some layer info set.
+    layerInfo.fOffset.set(SkFloatToScalar(10.0f), SkFloatToScalar(20.0f));
+    layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
+    SkPaint* layerPaint = looper->addLayerOnTop(layerInfo);
+    layerPaint->setXfermodeMode(SkXfermode::kSrc_Mode);
+
+    FakeDevice device;
+    SkCanvas canvas(&device);
+    SkPaint paint;
+    looper->init(&canvas);
+
+    // The back layer should come first.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateY());
+    paint.reset();
+
+    // Then the front layer.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrc_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(10.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(20.0f) == device.fLastMatrix.getTranslateY());
+
+    // Only two layers were added, so that should be the end.
+    REPORTER_ASSERT(reporter, !looper->next(&canvas, &paint));
+}
+
+static void test_mixed(skiatest::Reporter* reporter) {
+    SkAutoTUnref<SkLayerDrawLooper> looper(SkNEW(SkLayerDrawLooper));
+    SkLayerDrawLooper::LayerInfo layerInfo;
+
+    // Add the back layer, with the defaults.
+    (void)looper->addLayer(layerInfo);
+
+    // Add the front layer, with some layer info set.
+    layerInfo.fOffset.set(SkFloatToScalar(10.0f), SkFloatToScalar(20.0f));
+    layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
+    SkPaint* layerPaint = looper->addLayerOnTop(layerInfo);
+    layerPaint->setXfermodeMode(SkXfermode::kSrc_Mode);
+
+    FakeDevice device;
+    SkCanvas canvas(&device);
+    SkPaint paint;
+    looper->init(&canvas);
+
+    // The back layer should come first.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(0.0f) == device.fLastMatrix.getTranslateY());
+    paint.reset();
+
+    // Then the front layer.
+    REPORTER_ASSERT(reporter, looper->next(&canvas, &paint));
+    REPORTER_ASSERT(reporter, SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrc_Mode));
+    canvas.drawRect(SkRect::MakeWH(SkFloatToScalar(50.0f), SkFloatToScalar(50.0f)), paint);
+    REPORTER_ASSERT(reporter, SkFloatToScalar(10.0f) == device.fLastMatrix.getTranslateX());
+    REPORTER_ASSERT(reporter, SkFloatToScalar(20.0f) == device.fLastMatrix.getTranslateY());
+
+    // Only two layers were added, so that should be the end.
+    REPORTER_ASSERT(reporter, !looper->next(&canvas, &paint));
+}
+
+static void TestLayerDrawLooper(skiatest::Reporter* reporter) {
+    test_frontToBack(reporter);
+    test_backToFront(reporter);
+    test_mixed(reporter);
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("LayerDrawLooper", TestLayerDrawLooperClass, TestLayerDrawLooper)