On Tue, 6 Jun 2023 16:07:53 GMT, Alexey Ivanov <[email protected]> wrote:
> **Problem description** > > If you grab the thumb of the scroll bar of `ScrollPane` and drag it slowly > and continuously up and down, you'll notice the UI stops rendering correctly: > the child component of the scroll pane will render on the left of the frame > itself, the inside of the scroll pane will be filled with the background > color of its child component. > > **Root cause** > > AWT calls the > [`::SetScrollInfo`](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setscrollinfo) > function on EDT when AWT processes scroll bar tracking events. This Windows > API is not thread-safe, calling this function on an incorrect thread leads to > leaking GDI objects. > > When the process reaches the limit on the number of GDI objects, it cannot > create new GDI objects, which results in rendering issues. > > **Fix** > > To resolve the problem, I modified the code so that `::SetScrollInfo` and > [`::GetScrollInfo`](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getscrollinfo) > are always called on the toolkit thread, all AWT components are created on > the toolkit thread. > > An automatic test is provided. The test scrolls the vertical scroll bar up > and down. Then the test takes a screenshot. When the bug is reproduced, the > robot cannot create new GDI objects to capture the screenshot and it throws > `OutOfMemoryError`. I have submitted the follow-up bugs. > Probably we should update the Java_sun_awt_windows_WScrollbarPeer_setValues > as well? it calls the SetScrollInfo. > [⇑](https://github.com/openjdk/jdk/pull/14338#issuecomment-1579851933) [JDK-8315690](https://bugs.openjdk.org/browse/JDK-8315690): Call ::SetScrollInfo on toolkit thread in awt.ScrollBar > In addition to that, `WScrollPanePeer.getScrollOffset` is unused, so it's > never called. > [⇑](https://github.com/openjdk/jdk/pull/14338#discussion_r1220111236) [JDK-8315691](https://bugs.openjdk.org/browse/JDK-8315691): Remove unused WScrollPanePeer.getScrollOffset method > There's also a specific `WM_AWT_SET_SCROLL_INFO` message to call > `::SetScrollInfo`. This message is never used, it can also be removed. > [⇑](https://github.com/openjdk/jdk/pull/14338#discussion_r1221395024) [JDK-8315693](https://bugs.openjdk.org/browse/JDK-8315693): Remove WM_AWT_SET_SCROLL_INFO message ------------- PR Comment: https://git.openjdk.org/jdk/pull/14338#issuecomment-1706567768
