Handle hotplug events as described instead of rescanning

Hotplug events say which display they're for and whether the display
was connected or disconnected. Before, this info was ignored, and the
event just triggered a rescan of all displays. If a display was
disconnected and then reconnected quickly, the rescan would treat this
as a no-op or a device property change and wouldn't turn the display
on.

Now the display manager attempts to update its state with the change
the event describes. So a quick disconnect/connect cycle will cause
the display to be turned on since the display manager will have
updated its internal state to reflect the disconnect event, and will
treat the connect event as a new display rather than a device property
change.

Bug: 7491120
Change-Id: Ia83f7c96b7f16f4c1bed2a73e9b56b0bf7ee3984

1 files changed, 34 insertions, 23 deletions

diff --git a/services/java/com/android/server/display/LocalDisplayAdapter.java b/services/java/com/android/server/display/LocalDisplayAdapter.java
index b37d57fbb0ff..ee2d617944a9 100644
--- a/services/java/com/android/server/display/LocalDisplayAdapter.java
+++ b/services/java/com/android/server/display/LocalDisplayAdapter.java
@@ -60,31 +60,38 @@ final class LocalDisplayAdapter extends DisplayAdapter {
         super.registerLocked();
 
         mHotplugReceiver = new HotplugDisplayEventReceiver(getHandler().getLooper());
-        scanDisplaysLocked();
-    }
 
-    private void scanDisplaysLocked() {
         for (int builtInDisplayId : BUILT_IN_DISPLAY_IDS_TO_SCAN) {
-            IBinder displayToken = Surface.getBuiltInDisplay(builtInDisplayId);
-            if (displayToken != null && Surface.getDisplayInfo(displayToken, mTempPhys)) {
-                LocalDisplayDevice device = mDevices.get(builtInDisplayId);
-                if (device == null) {
-                    // Display was added.
-                    device = new LocalDisplayDevice(displayToken, builtInDisplayId, mTempPhys);
-                    mDevices.put(builtInDisplayId, device);
-                    sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_ADDED);
-                } else if (device.updatePhysicalDisplayInfoLocked(mTempPhys)) {
-                    // Display properties changed.
-                    sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_CHANGED);
-                }
-            } else {
-                LocalDisplayDevice device = mDevices.get(builtInDisplayId);
-                if (device != null) {
-                    // Display was removed.
-                    mDevices.remove(builtInDisplayId);
-                    sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_REMOVED);
-                }
+            tryConnectDisplayLocked(builtInDisplayId);
+        }
+    }
+
+    private void tryConnectDisplayLocked(int builtInDisplayId) {
+        IBinder displayToken = Surface.getBuiltInDisplay(builtInDisplayId);
+        if (displayToken != null && Surface.getDisplayInfo(displayToken, mTempPhys)) {
+            LocalDisplayDevice device = mDevices.get(builtInDisplayId);
+            if (device == null) {
+                // Display was added.
+                device = new LocalDisplayDevice(displayToken, builtInDisplayId, mTempPhys);
+                mDevices.put(builtInDisplayId, device);
+                sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_ADDED);
+            } else if (device.updatePhysicalDisplayInfoLocked(mTempPhys)) {
+                // Display properties changed.
+                sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_CHANGED);
             }
+        } else {
+            // The display is no longer available. Ignore the attempt to add it.
+            // If it was connected but has already been disconnected, we'll get a
+            // disconnect event that will remove it from mDevices.
+        }
+    }
+
+    private void tryDisconnectDisplayLocked(int builtInDisplayId) {
+        LocalDisplayDevice device = mDevices.get(builtInDisplayId);
+        if (device != null) {
+            // Display was removed.
+            mDevices.remove(builtInDisplayId);
+            sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_REMOVED);
         }
     }
 
@@ -191,7 +198,11 @@ final class LocalDisplayAdapter extends DisplayAdapter {
         @Override
         public void onHotplug(long timestampNanos, int builtInDisplayId, boolean connected) {
             synchronized (getSyncRoot()) {
-                scanDisplaysLocked();
+                if (connected) {
+                    tryConnectDisplayLocked(builtInDisplayId);
+                } else {
+                    tryDisconnectDisplayLocked(builtInDisplayId);
+                }
             }
         }
     }