Allow SkLazyPixelRef to use SkScaledImageCache

tests/CachedDecodingPixelRefTest.cpp

Index: tests/CachedDecodingPixelRefTest.cpp
diff --git a/tests/CachedDecodingPixelRefTest.cpp b/tests/CachedDecodingPixelRefTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b45b10d0f7de926be68979b2a0fac76746f93596
--- /dev/null
+++ b/tests/CachedDecodingPixelRefTest.cpp
@@ -0,0 +1,208 @@
+/*
+ * 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 "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkData.h"
+#include "SkForceLinking.h"
+#include "SkImageDecoder.h"
+#include "SkImagePriv.h"
+#include "SkLazyPixelRef.h"
+#include "SkScaledImageCache.h"
+#include "SkStream.h"
+#include "Test.h"
+
+__SK_FORCE_IMAGE_DECODER_LINKING;
+
+/**
+ * Fill this bitmap with some color.
+ */
+static void make_test_image(SkBitmap* bm) {
+    static const int W = 50, H = 50;
+    static const SkBitmap::Config config = SkBitmap::kARGB_8888_Config;
+    bm->setConfig(config, W, H);
+    bm->allocPixels();
+    bm->eraseColor(SK_ColorBLACK);
+    SkCanvas canvas(*bm);
+    SkPaint paint;
+    paint.setColor(SK_ColorBLUE);
+    canvas.drawRectCoords(0, 0, SkIntToScalar(W/2),
+                          SkIntToScalar(H/2), paint);
+    paint.setColor(SK_ColorWHITE);
+    canvas.drawRectCoords(SkIntToScalar(W/2), SkIntToScalar(H/2),
+                          SkIntToScalar(W), SkIntToScalar(H), paint);
+}
+
+/**
+ * encode this bitmap into some data via SkImageEncoder
+ */
+static SkData* create_data_from_bitmap(const SkBitmap& bm,
+                                       SkImageEncoder::Type type) {
+    SkDynamicMemoryWStream stream;
+    if (SkImageEncoder::EncodeStream(&stream, bm, type, 100)) {
+        return stream.copyToData();
+    }
+    return NULL;
+}
+
+/**
+ *  A simplified version of SkBitmapFactory
+ */
+static bool simple_bitmap_factory(SkBitmapFactory::DecodeProc proc,
+                                  SkData* data,
+                                  SkBitmap* dst,
+                                  SkBitmap::Allocator* allocator = NULL) {
+    SkImage::Info info;
+    if (!proc(data->data(), data->size(), &info, NULL)) {
+        return false;
+    }
+    dst->setConfig(SkImageInfoToBitmapConfig(info), info.fWidth,
+                    info.fHeight, 0, info.fAlphaType);
+    SkAutoTUnref<SkLazyPixelRef> ref(SkNEW_ARGS(SkLazyPixelRef,
+                                                (data, proc, NULL)));
+    if (allocator) {
+        ref->setAllocator(allocator);
+    }
+    dst->setPixelRef(ref);
+    return true;
+}
+
+static void compare_bitmaps(skiatest::Reporter* reporter,
+                            const SkBitmap& b1, const SkBitmap& b2,
+                            bool pixelPerfect = true) {
+    REPORTER_ASSERT(reporter, b1.empty() == b2.empty());
+    REPORTER_ASSERT(reporter, b1.width() == b2.width());
+    REPORTER_ASSERT(reporter, b1.height() == b2.height());
+    REPORTER_ASSERT(reporter, b1.isNull() == b2.isNull());
+    SkAutoLockPixels autoLockPixels1(b1);
+    SkAutoLockPixels autoLockPixels2(b2);
+    REPORTER_ASSERT(reporter, b1.isNull() == b2.isNull());
+    if (b1.isNull() || b1.empty()) {
+        return;
+    }
+    REPORTER_ASSERT(reporter, NULL != b1.getPixels());
+    REPORTER_ASSERT(reporter, NULL != b2.getPixels());
+    if ((!(b1.getPixels())) || (!(b2.getPixels()))) {
+        return;
+    }
+    if ((b1.width() != b2.width()) ||
+        (b1.height() != b2.height())) {
+        return;
+    }
+    if (!pixelPerfect) {
+        return;
+    }
+    int pixelErrors = 0;
+    for (int y = 0; y < b2.height(); ++y) {
+        for (int x = 0; x < b2.width(); ++x) {
+            if (b1.getColor(x, y) != b2.getColor(x, y)) {
+                ++pixelErrors;
+            }
+        }
+    }
+    REPORTER_ASSERT(reporter, 0 == pixelErrors);
+}
+
+/**
+ *  This checks to see that a SkLazyPixelRef works as advertized.
+ */
+#include "TestClassDef.h"
+DEF_TEST(CachedDecodingPixelRefTest, reporter) {
+    SkBitmap original;
+    make_test_image(&original);
+    const size_t bitmapSize = original.getSize();
+    const size_t oldByteLimit = SkScaledImageCache::GetByteLimit();
+    REPORTER_ASSERT(reporter, (!(original.empty())) && (!(original.isNull())));
+
+    static const SkImageEncoder::Type types[] = {
+        SkImageEncoder::kPNG_Type,
+        SkImageEncoder::kJPEG_Type,
+        SkImageEncoder::kWEBP_Type
+    };
+
+    for (size_t i = 0; i < SK_ARRAY_COUNT(types); i++) {
+        SkImageEncoder::Type type = types[i];
+        SkAutoDataUnref encoded(create_data_from_bitmap(original, type));
+        REPORTER_ASSERT(reporter, encoded.get() != NULL);
+        if (NULL == encoded.get()) {
+            continue;
+        }
+        SkBitmap lazy;
+        static const SkBitmapFactory::DecodeProc decoder =
+            &(SkImageDecoder::DecodeMemoryToTarget);
+        bool success = simple_bitmap_factory(decoder, encoded.get(), &lazy);
+
+        REPORTER_ASSERT(reporter, success);
+
+        size_t bytesUsed = SkScaledImageCache::GetBytesUsed();
+
+        if (oldByteLimit < bitmapSize) {
+            SkScaledImageCache::SetByteLimit(bitmapSize + oldByteLimit);
+        }
+        void* lazyPixels = NULL;
+
+        // Since this is lazy, it shouldn't have fPixels yet!
+        REPORTER_ASSERT(reporter, NULL == lazy.getPixels());
+        {
+            SkAutoLockPixels autoLockPixels(lazy);  // now pixels are good.
+            lazyPixels = lazy.getPixels();
+            REPORTER_ASSERT(reporter, NULL != lazy.getPixels());
+            // first time we lock pixels, we should get bump in the size
+            // of the cache by exactly bitmapSize.
+            REPORTER_ASSERT(reporter, bytesUsed + bitmapSize
+                            == SkScaledImageCache::GetBytesUsed());
+            bytesUsed = SkScaledImageCache::GetBytesUsed();
+        }
+        // pixels should be gone!
+        REPORTER_ASSERT(reporter, NULL == lazy.getPixels());
+        {
+            SkAutoLockPixels autoLockPixels(lazy);  // now pixels are good.
+            REPORTER_ASSERT(reporter, NULL != lazy.getPixels());
+
+            // verify that the same pixels are used this time.
+            REPORTER_ASSERT(reporter, lazy.getPixels() == lazyPixels);
+        }
+
+        bool comparePixels = (SkImageEncoder::kPNG_Type == type);
+        // Only PNG is pixel-perfect.
+        compare_bitmaps(reporter, original, lazy, comparePixels);
+
+        // force the cache to clear by making it too small.
+        SkScaledImageCache::SetByteLimit(bitmapSize / 2);
+        compare_bitmaps(reporter, original, lazy, comparePixels);
+
+        // I'm pretty sure that the logic of the cache should mean
+        // that it will clear to zero, regardless of where it started.
+        REPORTER_ASSERT(reporter, SkScaledImageCache::GetBytesUsed() == 0);
+        // TODO(someone) - write a custom allocator that can verify
+        // that the memory where those pixels were cached really did
+        // get freed.
+
+        ////////////////////////////////////////////////////////////////////////
+        //  The following commented-out code happens to work on my
+        //  machine, and indicates to me that the SkLazyPixelRef is
+        //  behaving as designed.  But I don't know an easy way to
+        //  guarantee that a second allocation of the same size will
+        //  give a different address.
+        ////////////////////////////////////////////////////////////////////////
+        // {
+        //     // confuse the heap allocation system
+        //     SkAutoMalloc autoMalloc(bitmapSize);
+        //     REPORTER_ASSERT(reporter, autoMalloc.get() == lazyPixels);
+        //     {
+        //         SkAutoLockPixels autoLockPixels(lazy);
+        //         // verify that *different* pixels are used this time.
+        //         REPORTER_ASSERT(reporter, lazy.getPixels() != lazyPixels);
+        //         compare_bitmaps(reporter, original, lazy, comparePixels);
+        //     }
+        // }
+
+        // restore cache size
+        SkScaledImageCache::SetByteLimit(oldByteLimit);
+    }
+}
+