On Thu, 23 Jul 2026 04:14:00 GMT, Jayathirth D V <[email protected]> wrote:
>> When we use XOR mode to clear the drawn content in Metal pipeline, it is >> leaving some traces. >> We noticed similar issue when Metal pipeline was under development: >> [JDK-8251167](https://bugs.openjdk.org/browse/JDK-8251167). But the fix is >> not complete and we still see some traces. Using uiScale 1.0 with >> contrasting background and foreground color reveals this not so easily >> noticeable issue. >> >> In case of Metal XOR mode is implemented using shaders and we are using an >> interpolated position passed from Vertex shader to determine the current >> position of fragment/pixel. We also add magic offsets to line vertices in >> MTLRenderer.DrawLine() and it can cause different approximations while >> calculating the interpolated position. >> >> Because of this we end up in mismatch between the pixel from which we are >> reading the content and the pixel to which we are writing. Instead of using >> interpolated position we should use the rasterized position present in >> fragment shader to pick the appropriate pixel. When we use rasterized >> position mismatch doesn't happen and XOR draw clears the content properly. >> >> We need this change in both `frag_col_xorMode` and `frag_txt_xorMode` >> shaders. Gradient and texture paint shaders are no-op in case of XOR as they >> use software loops, so no change is made in those shaders. Regression test >> is added only for color shader as mathematically i was able to reproduce >> issue only for color shader, but product fix is needed in case of text >> shader also. >> >> If we use rasterized position to pick pixels we don't need fix done under >> [JDK-8251167](https://bugs.openjdk.org/browse/JDK-8251167), so that change >> is also reverted. >> >> Code update is tested in CI and no regressions seen. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Jayathirth D V has updated the pull request incrementally with one additional > commit since the last revision: > > Make test generic Marked as reviewed by serb (Reviewer). ------------- PR Review: https://git.openjdk.org/jdk/pull/31981#pullrequestreview-4761851735
