Draw the mouse cursor in Chromoting Android client

remoting/android/java/src/org/chromium/chromoting/DesktopView.java

Index: remoting/android/java/src/org/chromium/chromoting/DesktopView.java
diff --git a/remoting/android/java/src/org/chromium/chromoting/DesktopView.java b/remoting/android/java/src/org/chromium/chromoting/DesktopView.java
index b1eac42633a5f3d16d6dc682c98d45519852a106..8e56fa6917fe553bbe13a4263e481932d639d439 100644
--- a/remoting/android/java/src/org/chromium/chromoting/DesktopView.java
+++ b/remoting/android/java/src/org/chromium/chromoting/DesktopView.java
@@ -11,6 +11,7 @@ import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Matrix;
 import android.graphics.Paint;
+import android.graphics.Point;
 import android.os.Bundle;
 import android.os.Looper;
 import android.text.InputType;
@@ -67,6 +68,12 @@ public class DesktopView extends SurfaceView implements Runnable, SurfaceHolder.
     private int mScreenWidth;
     private int mScreenHeight;
 
+    /**
+     * Specifies the position, in image coordinates, at which the cursor image will be drawn.
+     * This will normally be at the location of the most recently injected motion event.
+     */
+    private Point mCursorPosition;
+
     /** Specifies the dimension by which the zoom level is being lower-bounded. */
     private Constraint mConstraint;
 
@@ -98,6 +105,7 @@ public class DesktopView extends SurfaceView implements Runnable, SurfaceHolder.
         mTransform = new Matrix();
         mScreenWidth = 0;
         mScreenHeight = 0;
+        mCursorPosition = new Point();
 
         mConstraint = Constraint.UNDEFINED;
         mRecheckConstraint = false;
@@ -216,6 +224,12 @@ public class DesktopView extends SurfaceView implements Runnable, SurfaceHolder.
 
         canvas.drawColor(Color.BLACK);
         canvas.drawBitmap(image, 0, 0, new Paint());
+        Bitmap cursorBitmap = JniInterface.getCursorBitmap();
+        if (cursorBitmap != null) {
+            Point hotspot = JniInterface.getCursorHotspot();
+            canvas.drawBitmap(cursorBitmap, mCursorPosition.x - hotspot.x,

[solb, 2013/09/14 00:29:41]

It might be good to synchronize this on mCursorPosition so that a poorly-timed
mouse click can't result in the cursor's being drawn in an odd position.

[Lambros, 2013/09/14 01:16:48]

Good catch! Done.

+                              mCursorPosition.y - hotspot.y, new Paint());
+        }
         getHolder().unlockCanvasAndPost(canvas);
     }
 
@@ -242,6 +256,8 @@ public class DesktopView extends SurfaceView implements Runnable, SurfaceHolder.
         synchronized (mTransform) {
             mScreenWidth = width;
             mScreenHeight = height;
+            mCursorPosition.x = width / 2;

[solb, 2013/09/14 00:29:41]

Synchronizing these on mTransform does no good, since they're never used within
a the critical period of its rendering.  Might be better to lock on
mCursorPosition itself?

[Lambros, 2013/09/14 01:16:48]

Done.

+            mCursorPosition.y = height / 2;
 
             if (mRecheckConstraint) {
                 mConstraint = Constraint.UNDEFINED;
@@ -299,8 +315,15 @@ public class DesktopView extends SurfaceView implements Runnable, SurfaceHolder.
         mTransform.invert(canvasToImage);
         canvasToImage.mapPoints(coordinates);
 
+        mCursorPosition.x = (int)coordinates[0];

[solb, 2013/09/14 00:29:41]

I think these two lines should also be synchronized on mCursorPosition.

[Lambros, 2013/09/14 01:16:48]

Done. I've also added a synchronize around mTransform, hope that's OK.

+        mCursorPosition.y = (int)coordinates[1];
+
         // Coordinates are now relative to the image, so transmit them to the host.
-        JniInterface.mouseAction((int)coordinates[0], (int)coordinates[1], button, pressed);
+        JniInterface.mouseAction(mCursorPosition.x, mCursorPosition.y, button, pressed);
+
+        // TODO(lambroslambrou): Optimize this to repaint only the areas covered by the old and new
+        // cursor positions.
+        JniInterface.redrawGraphics();
     }
 
     /**