We want to give SkPixelRef a way to signal over to GrResourceCache that it's become pointless to keep around textures based on that SkPixelRef when its pixels change, so that it can be a good citizen and free those textures.
This adds an invalidation listener mechanism to SkPixelRef to let it send this message while still staying ignorant of who's listening.
These messages are tricky to deliver. The SkPixelRefs they originates from and the GrResourceCaches they ultimately end up at may be on different threads; neither class is threadsafe; their object lifetimes are totally independent; it's a many-senders-to-many-receivers relation; and neither codebase should really know about the other.
So I've added a per-message-type global message bus to broadcast messages to threadsafe inboxes. Anyone can post() a message, which will show up in all the inboxes of that type, read whenever the inbox's owner calls poll(). The implementation is _dumb_; it can be improved in several dimensions (inbox size limits, lock-free message delivery) if we find the need.
I took some care to make sure not to send the invalidation message for any SkPixelRef that's sharing a generation ID with another SkPixelRef.
BUG=
R=bsalomon@google.com, scroggo@google.com, reed@google.com
Author: mtklein@google.com
Review URL: https://codereview.chromium.org/26734003
git-svn-id: http://skia.googlecode.com/svn/trunk@11949 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/PixelRefTest.cpp b/tests/PixelRefTest.cpp
new file mode 100644
index 0000000..ce2575e
--- /dev/null
+++ b/tests/PixelRefTest.cpp
@@ -0,0 +1,49 @@
+#include "Test.h"
+#include "TestClassDef.h"
+
+#include "SkPixelRef.h"
+#include "SkMallocPixelRef.h"
+
+namespace {
+
+class TestListener : public SkPixelRef::GenIDChangeListener {
+public:
+ explicit TestListener(int* ptr) : fPtr(ptr) {}
+ void onChange() SK_OVERRIDE { (*fPtr)++; }
+private:
+ int* fPtr;
+};
+
+} // namespace
+
+DEF_TEST(PixelRef_GenIDChange, r) {
+ SkMallocPixelRef pixelRef(NULL, 0, NULL); // We don't really care about the pixels here.
+
+ // Register a listener.
+ int count = 0;
+ pixelRef.addGenIDChangeListener(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.addGenIDChangeListener(SkNEW_ARGS(TestListener, (&count)));
+ pixelRef.notifyPixelsChanged();
+ REPORTER_ASSERT(r, 1 == count);
+
+ // Quick check that NULL is safe.
+ REPORTER_ASSERT(r, 0 != pixelRef.getGenerationID());
+ pixelRef.addGenIDChangeListener(NULL);
+ pixelRef.notifyPixelsChanged();
+}