RFR: 8324941: POC for Headless platform for JavaFX [v4]
Andy Goryachev
angorya at openjdk.org
Fri Jun 27 20:41:47 UTC 2025
On Mon, 23 Jun 2025 08:26:30 GMT, Johan Vos <jvos at openjdk.org> wrote:
>> After spending a year in the sandbox repository, the Headless Platform is now ready to be reviewed in the main repository.
>>
>> ### the Headless Platform
>> The Headless Platform is a top-level com.sun.glass.ui platform that replaces the second-level Monocle-Headless subplatform, that is part of the top-level Monocle platform.
>> The platform can be used like any other platform, especially for running headless JavaFX applications, or for running tests (e.g. on CI systems)
>>
>> ### changes
>> The code for the Headless Platform is in a new package com.sun.glass.ui.headless in the javafx.graphics module, and it does not require a code change in other packages.
>> This PR adds a simple change in the `build.gradle` file, to make the Headless Platform the standard when running headless tests (instead of using Monocle/Headless)
>>
>> ### enable the Headless Platform
>> Setting the system property `glass.platform` to `Headless` will select the Headless Platform instead of the default one (either gtk, mac or win).
>>
>> ### testing
>> `gradlew --info -PHEADLESS_TEST=true -PFULL_TEST=true :systemTests:cleanTest :systemTests:test`
>> runs all the system tests, apart from the robot tests. There are 2 failing tests, but there are valid reasons for those to fail.
>>
>> ### robot tests
>> Most of the robot tests are working on headless as well. add `-PUSE_ROBOT` to test those.
>
> Johan Vos has updated the pull request incrementally with one additional commit since the last revision:
>
> Process reviewer comments
Added a little code to the monkey tester to take a snapshot of the scene.
Here is the result launching it on the headless platform on macOS 15.5:
Good job!
Question: While the screen size is limited in this version to 1000x1000, the size of the snapshot exceeds that. Is that expected?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessApplication.java line 22:
> 20: private final NestedRunnableProcessor processor = new NestedRunnableProcessor();
> 21: private final HeadlessWindowManager windowManager = new HeadlessWindowManager();
> 22: private Screen[] screens = null;
minor: no need to assign null, also L24
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessApplication.java line 41:
> 39: @Override
> 40: protected void _invokeAndWait(Runnable runnable) {
> 41: throw new UnsupportedOperationException("Not supported yet.");
is there a follow-up bug for this, or the list of things to do?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessApplication.java line 92:
> 90: @Override
> 91: protected void staticCursor_setVisible(boolean visible) {
> 92: throw new UnsupportedOperationException("Not supported yet.");
should it be a no-op instead? will cursor be supported at all?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessRobot.java line 109:
> 107: }
> 108: int modifiers = 0;
> 109: view.notifyMouse(mouseEvent, buttonEvent, (int)mouseX-wx, (int)mouseY-wy, (int)mouseX, (int)mouseY, modifiers, false, false);
should the coordinates be rounded instead of floor'ed (cast to int)?
(also in other places below)
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessRobot.java line 161:
> 159: int repeat = Math.abs(wheelAmt);
> 160: for (int i = 0; i < repeat; i++) {
> 161: view.notifyScroll((int) mouseX, (int) mouseY, wx, wy, 0, dff, 0, 0, 0, 0, 0, multiplierX, multiplierY);
are all parameters correct? `modifiers` and `lines`, specifically?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessRobot.java line 179:
> 177: public void getScreenCapture(int x, int y, int width, int height, int[] data, boolean scaleToFit) {
> 178: checkWindowFocused();
> 179: ((HeadlessWindow)activeWindow).getScreenCapture(x, y, width, height, data, scaleToFit);
maybe the `activeWindow` can be declared as `HeadlessWindow` to avoid casting
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessRobot.java line 231:
> 229: if (windows.isEmpty()) return null;
> 230: if (windows.size() == 1) return (HeadlessWindow)windows.get(0);
> 231: return (HeadlessWindow)windows.get(windows.size() -1);
call me old fashioned, but would a straightforward reverse `for` loop be better in this case? no unnecessary memory allocations required.
here and in two methods below?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessWindow.java line 19:
> 17:
> 18: private static final AtomicInteger ptrCount = new AtomicInteger(0);
> 19: private long ptr;
since `ptr` is long, should `ptrCount` be `AtomicLong`?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessWindow.java line 316:
> 314: int b = rgba & 0xFF;
> 315:
> 316: Color color = Color.color(
could use `Color::rgb(int,int,int,double)`;
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessWindow.java line 329:
> 327: for (int j = 0; j < width; j++) {
> 328: int idx = i * width + j;
> 329: int fidx = (y + i) * 1000 + x + j;
where does 1000 come from?
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessWindow.java line 341:
> 339: int offsetX = this.getX();
> 340: int offsetY = this.getY();
> 341: int stride = 1000;
same magic 1000 here
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/HeadlessWindow.java line 356:
> 354:
> 355: void clearRect(int x0, int w0, int y0, int h0) {
> 356: int stride = 1000;
and here...
modules/javafx.graphics/src/main/java/com/sun/glass/ui/headless/NestedRunnableProcessor.java line 40:
> 38: latch.await();
> 39: } catch (InterruptedException e) {
> 40: e.printStackTrace();
should we print here or send to `Application.reportException(e)` ?
-------------
PR Comment: https://git.openjdk.org/jfx/pull/1836#issuecomment-3014300491
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172457055
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172458562
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172463000
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172698720
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172703243
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172705046
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172729945
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172790233
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172819470
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172820759
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172821109
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172821466
PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2172827253
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