On Wed, 8 Oct 2025 01:20:41 GMT, Sergey Bylokhov <[email protected]> wrote:
> The bug happens when List.select(int) is used in multiple selection mode. It > only appears when the List is added to a Frame, because in that case, the > selection is handled by the platform peer, and the internal logic in the List > class is skipped. > > To fix this, the code now uses > [addSelectionInterval](https://github.com/openjdk/jdk/blob/910bb68e5191f830ff6f3dff5753e4e5f6214a7b/src/java.desktop/share/classes/javax/swing/ListSelectionModel.java#L93) > instead of setSelectedIndex. This method works correctly for multiple > selection mode when using JList as the delegate on macOS. > > I added DeselectionUnitTest and SelectionUnitTest tests for some selection > and deselection cases. At first, it was one big test, but I split it because > it got too large. > > **Notes on invalid index handling** > According to the java.awt.List > [spec](https://github.com/openjdk/jdk/blob/0e5655e6680762a99b5aecb58369b880ea913565/src/java.desktop/share/classes/java/awt/List.java#L573), > using invalid indexes is undefined behavior. For now, I have decided not to > validate these cases fully in this patch, but I did add a check in the > `LWListPeer.select()` to handle them more safely. > > The previously used setSelectedIndex method > [ignored](https://github.com/openjdk/jdk/blob/0e5655e6680762a99b5aecb58369b880ea913565/src/java.desktop/share/classes/javax/swing/JList.java#L2229) > indexes greater than the list size, unlike addSelectionInterval. So I added > an explicit check to skip all indexes larger than the list size. > > Later, I discovered that passing a negative index not only causes an > exception (which is acceptable, since it's undefined behavior), but also > leaves the peer in an inconsistent state. This happens because > setSkipStateChangedEvent(false) at the end of LWListPeer.select() is not > called if an exception is thrown. > > To prevent this, I added a check to skip all negative values as well. As a > result, the peer now cleanly ignores all out-of-range indexes. > > **Description of how invalid indexes are handled on other platforms:** > - The shared code in java.awt.List stores elements and selection separately, > so it accepts invalid indexes. This can cause exceptions if the selection and > data become out of sync. > - On Windows, all invalid indexes are ignored, except for the special value > -1, which is used to select or deselect all elements. This happens because > the indexes are passed to the win api without validation. > - XAWT uses the same logic as the shared code, so it can throw the same > exceptions if the data... src/java.desktop/macosx/classes/sun/lwawt/LWListPeer.java line 150: > 148: } > 149: } > 150: Note: `getDelegate().getView().addSelectionInterval(index, index);` `getDelegate().getView().removeSelectionInterval(index, index);` just shortcuts for: `getDelegate().getView().getSelectionModel().addSelectionInterval(index, index);` `getDelegate().getView().getSelectionModel().removeSelectionInterval(index, index);` ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/27682#discussion_r2412303830
