Native input dispatch rewrite work in progress.

The old dispatch mechanism has been left in place and continues to
be used by default for now.  To enable native input dispatch,
edit the ENABLE_NATIVE_DISPATCH constant in WindowManagerPolicy.

Includes part of the new input event NDK API.  Some details TBD.

To wire up input dispatch, as the ViewRoot adds a window to the
window session it receives an InputChannel object as an output
argument.  The InputChannel encapsulates the file descriptors for a
shared memory region and two pipe end-points.  The ViewRoot then
provides the InputChannel to the InputQueue.  Behind the
scenes, InputQueue simply attaches handlers to the native PollLoop object
that underlies the MessageQueue.  This way MessageQueue doesn't need
to know anything about input dispatch per-se, it just exposes (in native
code) a PollLoop that other components can use to monitor file descriptor
state changes.

There can be zero or more targets for any given input event.  Each
input target is specified by its input channel and some parameters
including flags, an X/Y coordinate offset, and the dispatch timeout.
An input target can request either synchronous dispatch (for foreground apps)
or asynchronous dispatch (fire-and-forget for wallpapers and "outside"
targets).  Currently, finding the appropriate input targets for an event
requires a call back into the WindowManagerServer from native code.
In the future this will be refactored to avoid most of these callbacks
except as required to handle pending focus transitions.

End-to-end event dispatch mostly works!

To do: event injection, rate limiting, ANRs, testing, optimization, etc.

Change-Id: I8c36b2b9e0a2d27392040ecda0f51b636456de25

1 files changed, 137 insertions, 0 deletions

diff --git a/include/utils/PollLoop.h b/include/utils/PollLoop.h
new file mode 100644
index 0000000..2ec39fe
--- /dev/null
+++ b/include/utils/PollLoop.h
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef UTILS_POLL_LOOP_H
+#define UTILS_POLL_LOOP_H
+
+#include <utils/Vector.h>
+#include <utils/threads.h>
+
+#include <poll.h>
+
+namespace android {
+
+/**
+ * A basic file descriptor polling loop based on poll() with callbacks.
+ */
+class PollLoop : public RefBase {
+protected:
+    virtual ~PollLoop();
+
+public:
+    PollLoop();
+
+    /**
+     * A callback that it to be invoked when an event occurs on a file descriptor.
+     * Specifies the events that were triggered and the user data provided when the
+     * callback was set.
+     *
+     * Returns true if the callback should be kept, false if it should be removed automatically
+     * after the callback returns.
+     */
+    typedef bool (*Callback)(int fd, int events, void* data);
+
+    /**
+     * Performs a single call to poll() with optional timeout in milliseconds.
+     * Invokes callbacks for all file descriptors on which an event occurred.
+     *
+     * If the timeout is zero, returns immediately without blocking.
+     * If the timeout is negative, waits indefinitely until awoken.
+     *
+     * Returns true if a callback was invoked or if the loop was awoken by wake().
+     * Returns false if a timeout or error occurred.
+     *
+     * This method must only be called on the main thread.
+     * This method blocks until either a file descriptor is signalled, a timeout occurs,
+     * or wake() is called.
+     * This method does not return until it has finished invoking the appropriate callbacks
+     * for all file descriptors that were signalled.
+     */
+    bool pollOnce(int timeoutMillis);
+
+    /**
+     * Wakes the loop asynchronously.
+     *
+     * This method can be called on any thread.
+     * This method returns immediately.
+     */
+    void wake();
+
+    /**
+     * Sets the callback for a file descriptor, replacing the existing one, if any.
+     * It is an error to call this method with events == 0 or callback == NULL.
+     *
+     * Note that a callback can be invoked with the POLLERR, POLLHUP or POLLNVAL events
+     * even if it is not explicitly requested when registered.
+     *
+     * This method can be called on any thread.
+     * This method may block briefly if it needs to wake the poll loop.
+     */
+    void setCallback(int fd, int events, Callback callback, void* data = NULL);
+
+    /**
+     * Removes the callback for a file descriptor, if one exists.
+     *
+     * When this method returns, it is safe to close the file descriptor since the poll loop
+     * will no longer have a reference to it.  However, it is possible for the callback to
+     * already be running or for it to run one last time if the file descriptor was already
+     * signalled.  Calling code is responsible for ensuring that this case is safely handled.
+     * For example, if the callback takes care of removing itself during its own execution either
+     * by returning false or calling this method, then it can be guaranteed to not be invoked
+     * again at any later time unless registered anew.
+     *
+     * This method can be called on any thread.
+     * This method may block briefly if it needs to wake the poll loop.
+     *
+     * Returns true if a callback was actually removed, false if none was registered.
+     */
+    bool removeCallback(int fd);
+
+private:
+    struct RequestedCallback {
+        Callback callback;
+        void* data;
+    };
+
+    struct PendingCallback {
+        int fd;
+        int events;
+        Callback callback;
+        void* data;
+    };
+
+    Mutex mLock;
+    Condition mAwake;
+    bool mPolling;
+
+    int mWakeReadPipeFd;
+    int mWakeWritePipeFd;
+
+    Vector<struct pollfd> mRequestedFds;
+    Vector<RequestedCallback> mRequestedCallbacks;
+
+    Vector<PendingCallback> mPendingCallbacks; // used privately by pollOnce
+
+    void openWakePipe();
+    void closeWakePipe();
+
+    ssize_t getRequestIndexLocked(int fd);
+    void wakeAndLock();
+};
+
+} // namespace android
+
+#endif // UTILS_POLL_LOOP_H