Do not leave the tab folder GC in advanced graphics mode - #3529
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vogella merged 1 commit intoAug 18, 2026
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CTabFolderRenderer.drawDirtyIndicator() uses alpha and anti-aliasing, which switch the GC to GDI+ on Windows and are not undone by restoring alpha and anti-aliasing. All tabs share one GC and the selected tab is painted last, so tabs painted after a dirty indicator were measured with GDI+ text metrics and their text was elided, and on the double-buffered paint they lost their clipping because getClipping(Region) no longer round-trips. Leave the advanced mode again after drawing the indicator and restore the clipping, which setAdvanced(false) resets. This is a no-op on GTK and macOS. Adds a regression test and a manual test. Repainting also gets faster, as only the indicator is drawn in GDI+ instead of every tab after it: about 20% on a folder with 20 dirty tabs. Fixes eclipse-platform#3522
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@HeikoKlare please test your example. I think RC1 freeze starts tomorrow at least that was what i saw in the email so the freeze check might to eager. |
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@Phillipus please also test it in your RCP app. |
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@vogella Confirmed that this PR fixes it. Thanks! |
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Thank you for the quick fix. It solves the issue for me as well.
The change looks like a good, local workaround for the underlying issue in the GC implementation that we can still bring into the upcoming release.
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Fixes #3522
CTabFolderRenderer.drawDirtyIndicator()uses alpha and anti-aliasing, which switch the GC to GDI+ on Windows and are not undone by restoring alpha and anti-aliasing. All tabs share one GC and the selected tab is painted last, so tabs painted after a dirty indicator were measured with GDI+ text metrics and their text was elided, and on the double-buffered paint they lost their clipping becausegetClipping(Region)no longer round-trips. That is the jumping text of this issue and the vanishing tab @Phillipus reported in it.The fix leaves the advanced mode again after drawing the indicator and restores the clipping, which
setAdvanced(false)resets. It is a no-op on GTK and macOS, where the GC is always advanced.Verified on Windows 11 at 150% and emulated 100% zoom: both symptoms reproduce on master and are gone with the change, the tab strip is then pixel identical for every repaint geometry, and repainting is about 20% faster on a folder with 20 dirty tabs. The new regression test fails without the change and passes with it.
Test_org_eclipse_swt_custom_CTabFoldershows the same 3 failures as clean master at 150% zoom.