Purge clip masks when they are no longer findable.

This improves memory usage when the content contains frequently changing clips implemented as masks.

BUG=chromium:676459

Change-Id: I06ea5f9fe1cff9564ea136bad9fe97f6ecd77ad9
Reviewed-on: https://skia-review.googlesource.com/6629
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/include/private/SkMessageBus.h b/include/private/SkMessageBus.h
new file mode 100644
index 0000000000..79f5c026dc
--- /dev/null
+++ b/include/private/SkMessageBus.h
@@ -0,0 +1,110 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkMessageBus_DEFINED
+#define SkMessageBus_DEFINED
+
+#include "SkMutex.h"
+#include "SkOnce.h"
+#include "SkTArray.h"
+#include "SkTDArray.h"
+#include "SkTypes.h"
+
+template <typename Message>
+class SkMessageBus : SkNoncopyable {
+public:
+    // Post a message to be received by all Inboxes for this Message type.  Threadsafe.
+    static void Post(const Message& m);
+
+    class Inbox {
+    public:
+        Inbox();
+        ~Inbox();
+
+        // Overwrite out with all the messages we've received since the last call.  Threadsafe.
+        void poll(SkTArray<Message>* out);
+
+    private:
+        SkTArray<Message>  fMessages;
+        SkMutex            fMessagesMutex;
+
+        friend class SkMessageBus;
+        void receive(const Message& m);  // SkMessageBus is a friend only to call this.
+    };
+
+private:
+    SkMessageBus();
+    static SkMessageBus* Get();
+
+    SkTDArray<Inbox*> fInboxes;
+    SkMutex           fInboxesMutex;
+};
+
+// This must go in a single .cpp file, not some .h, or we risk creating more than one global
+// SkMessageBus per type when using shared libraries.  NOTE: at most one per file will compile.
+#define DECLARE_SKMESSAGEBUS_MESSAGE(Message)                      \
+    template <>                                                    \
+    SkMessageBus<Message>* SkMessageBus<Message>::Get() {          \
+        static SkOnce once;                                        \
+        static SkMessageBus<Message>* bus;                         \
+        once([] { bus = new SkMessageBus<Message>(); });           \
+        return bus;                                                \
+    }
+
+//   ----------------------- Implementation of SkMessageBus::Inbox -----------------------
+
+template<typename Message>
+SkMessageBus<Message>::Inbox::Inbox() {
+    // Register ourselves with the corresponding message bus.
+    SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
+    SkAutoMutexAcquire lock(bus->fInboxesMutex);
+    bus->fInboxes.push(this);
+}
+
+template<typename Message>
+SkMessageBus<Message>::Inbox::~Inbox() {
+    // Remove ourselves from the corresponding message bus.
+    SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
+    SkAutoMutexAcquire lock(bus->fInboxesMutex);
+    // This is a cheaper fInboxes.remove(fInboxes.find(this)) when order doesn't matter.
+    for (int i = 0; i < bus->fInboxes.count(); i++) {
+        if (this == bus->fInboxes[i]) {
+            bus->fInboxes.removeShuffle(i);
+            break;
+        }
+    }
+}
+
+template<typename Message>
+void SkMessageBus<Message>::Inbox::receive(const Message& m) {
+    SkAutoMutexAcquire lock(fMessagesMutex);
+    fMessages.push_back(m);
+}
+
+template<typename Message>
+void SkMessageBus<Message>::Inbox::poll(SkTArray<Message>* messages) {
+    SkASSERT(messages);
+    messages->reset();
+    SkAutoMutexAcquire lock(fMessagesMutex);
+    fMessages.swap(messages);
+}
+
+//   ----------------------- Implementation of SkMessageBus -----------------------
+
+template <typename Message>
+SkMessageBus<Message>::SkMessageBus() {}
+
+template <typename Message>
+/*static*/ void SkMessageBus<Message>::Post(const Message& m) {
+    SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
+    SkAutoMutexAcquire lock(bus->fInboxesMutex);
+    for (int i = 0; i < bus->fInboxes.count(); i++) {
+        bus->fInboxes[i]->receive(m);
+    }
+}
+
+#endif  // SkMessageBus_DEFINED