Proactive SkPixelRef invalidation

tests/PixelRefTest.cpp

+#include "Test.h"
+#include "TestClassDef.h"
+
+#include "SkPixelRef.h"
+#include "SkMallocPixelRef.h"
+
+namespace {
+
+class TestListener : public SkPixelRef::InvalidationListener {
+public:
+    explicit TestListener(int* ptr) : fPtr(ptr) {}
+    void onInvalidate() SK_OVERRIDE { (*fPtr)++; }
+private:
+    int* fPtr;
+};
+
+}  // namespace
+
+DEF_TEST(PixelRef_Invalidation, r) {
+    SkMallocPixelRef pixelRef(NULL, 0, NULL);  // We don't really care about the pixels here.
+
+    // Register a listener.
+    int count = 0;
+    pixelRef.addInvalidationListener(SkNEW_ARGS(TestListener, (&count)));
+    REPORTER_ASSERT(r, 0 == count);
+
+    // No one has looked at our pixelRef's generation ID, so invalidating it doesn't make sense.
+    // (An SkPixelRef tree falls in the forest but there's nobody around to hear it.  Do we care?)
+    pixelRef.notifyPixelsChanged();
+    REPORTER_ASSERT(r, 0 == count);
+
+    // Force the generation ID to be calculated.
+    REPORTER_ASSERT(r, 0 != pixelRef.getGenerationID());
+
+    // Our listener was dropped in the first call to notifyPixelsChanged().  This is a no-op.
+    pixelRef.notifyPixelsChanged();
+    REPORTER_ASSERT(r, 0 == count);
+
+    // Force the generation ID to be recalculated, then add a listener.
+    REPORTER_ASSERT(r, 0 != pixelRef.getGenerationID());
+    pixelRef.addInvalidationListener(SkNEW_ARGS(TestListener, (&count)));
+    pixelRef.notifyPixelsChanged();
+    REPORTER_ASSERT(r, 1 == count);
+
+    // Quick check that NULL is safe.

[scroggo, 2013/10/22 21:04:02]

Is the goal here to test that we don't crash? Can you put this inside SK_DEBUG
since it won't really test anything in Release mode?

[bsalomon, 2013/10/23 13:52:57]

¿If there was a bug it could crash in release, no?

[mtklein, 2013/10/23 15:28:10]

Right.  This is relevant in both Release and Debug.  I think this should stay
as-is.

+    REPORTER_ASSERT(r, 0 != pixelRef.getGenerationID());
+    pixelRef.addInvalidationListener(NULL);
+    pixelRef.notifyPixelsChanged();
+}