Improve the VSYNC api a bit.

- add the ability to set the vsync delivery rate, when the rate is
set to N>1 (ie: receive every N vsync), SF process' is woken up for
all of vsync, but clients only see the every N events.

- add the concept of one-shot vsync events, with a call-back
to request the next one. currently the call-back is a binder IPC.

Change-Id: I09f71df0b0ba0d88ed997645e2e2497d553c9a1b

2 files changed, 32 insertions, 0 deletions

diff --git a/include/gui/DisplayEventReceiver.h b/include/gui/DisplayEventReceiver.h
index 8d07c0e..dccc164 100644
--- a/include/gui/DisplayEventReceiver.h
+++ b/include/gui/DisplayEventReceiver.h
@@ -94,6 +94,20 @@ public:
      */
     ssize_t getEvents(Event* events, size_t count);
 
+    /*
+     * setVsyncRate() sets the Event::VSync delivery rate. A value of
+     * 1 returns every Event::VSync. A value of 2 returns every other event,
+     * etc... a value of 0 returns no event unless  requestNextVsync() has
+     * been called.
+     */
+    status_t setVsyncRate(uint32_t count);
+
+    /*
+     * requestNextVsync() schedules the next Event::VSync. It has no effect
+     * if the vsync rate is > 0.
+     */
+    status_t requestNextVsync();
+
 private:
     sp<IDisplayEventConnection> mEventConnection;
     sp<BitTube> mDataChannel;
diff --git a/include/gui/IDisplayEventConnection.h b/include/gui/IDisplayEventConnection.h
index 8728bb5..86247de 100644
--- a/include/gui/IDisplayEventConnection.h
+++ b/include/gui/IDisplayEventConnection.h
@@ -33,9 +33,27 @@ class BitTube;
 class IDisplayEventConnection : public IInterface
 {
 public:
+
     DECLARE_META_INTERFACE(DisplayEventConnection);
 
+    /*
+     * getDataChannel() returns a BitTube where to receive the events from
+     */
     virtual sp<BitTube> getDataChannel() const = 0;
+
+    /*
+     * setVsyncRate() sets the vsync event delivery rate. A value of
+     * 1 returns every vsync events. A value of 2 returns every other events,
+     * etc... a value of 0 returns no event unless  requestNextVsync() has
+     * been called.
+     */
+    virtual void setVsyncRate(uint32_t count) = 0;
+
+    /*
+     * requestNextVsync() schedules the next vsync event. It has no effect
+     * if the vsync rate is > 0.
+     */
+    virtual void requestNextVsync() = 0;    // asynchronous
 };
 
 // ----------------------------------------------------------------------------