RFR: 8345538: Robot.mouseMove doesn't clamp bounds on macOS when trying to move mouse off screen [v11]

[Alexander Zvegintsev]

On Tue, 28 Jan 2025 23:21:26 GMT, Alisen Chung <achung at openjdk.org> wrote:

>> Currently on macOS when mouseMove is given an offscreen coordinate to move the mouse to, mouseMove will physically clamp to the edge of the screen, but if you try to grab the mouse location immediately after by using MouseInfo.getPointerInfo().getLocation() you will get the value of the offscreen point.
>> 
>> Windows and linux do this clamping and coordinate handling for us, but new distributions may not necessarily handle clamping the same way, so Robot should be checking for clamping rather than delegating it to native.
>> 
>> This fix updates shared code to cache the screen bounds and adds a check to not exceed the bounds in mouseMove. The caching is done in the Robot constructor, so if the screen bounds changes the constructor must be called again to update to the new bounds.
>
> Alisen Chung has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - helper function
>  - grab screen data on mouseMove

src/java.desktop/share/classes/java/awt/Robot.java line 229:

> 227: 
> 228:         GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
> 229:         GraphicsDevice[] gs = ge.getScreenDevices();

Suggestion:

        GraphicsDevice[] gds = ge.getScreenDevices();


I found that `gds` is a more common name in our code and testbase. At least for me, I immediately read `gds` as GraphicsDeviceS, array of `GraphicsDevice`.
Same applies for the test.

P.S. It's not a call to action, it's more of an invitation for discussion.

src/java.desktop/share/classes/java/awt/Robot.java line 258:

> 256: 
> 257:         if (leastXDiff > leastYDiff) {
> 258:             peer.mouseMove(finX2, finY2);

Let's say I have the following display configuration on Linux. Since it uses Xinerama, it shares the same coordinate system. 

java.awt.Rectangle[x=0,y=0,width=3440,height=1440]
java.awt.Rectangle[x=3440,y=0,width=1440,height=2560]

![image](https://github.com/user-attachments/assets/1953442c-fa18-49a0-99eb-b633152d83f6)

When I try to move the mouse to `x=20000,y=200`, I see that it clamps to `x=3439,y=200` (a point between 2 screens), while before it was `x=4879,y=200`(a rightmost point).

The old behavior seems more logical to me.

src/java.desktop/share/classes/java/awt/Robot.java line 268:

> 266:     private Point calcClosestPoint(int x, int y, Rectangle screenBounds) {
> 267:         return new Point(Math.min(Math.max(x, screenBounds.x), screenBounds.x + screenBounds.width-1),
> 268:                 Math.min(Math.max(y, screenBounds.y), screenBounds.y + screenBounds.height-1));

Suggestion:

        return new Point(Math.min(Math.max(x, screenBounds.x), screenBounds.x + screenBounds.width - 1),
                Math.min(Math.max(y, screenBounds.y), screenBounds.y + screenBounds.height - 1));


minor spacing issue

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PR Review Comment: https://git.openjdk.org/jdk/pull/22781#discussion_r1939749017
PR Review Comment: https://git.openjdk.org/jdk/pull/22781#discussion_r1939760680
PR Review Comment: https://git.openjdk.org/jdk/pull/22781#discussion_r1939747548