On Sat, 28 Jun 2025 04:28:23 GMT, Sergey Bylokhov <s...@openjdk.org> wrote:
>> src/java.desktop/share/classes/javax/swing/border/LineBorder.java line 166: >> >>> 164: Shape inner; >>> 165: >>> 166: int offs = clipRound(this.thickness * scaleFactor); >> >> Please double-check whether you need to use `Region.clipScale()` instead. >> >> I actually do not remember when to use one over the other. Maybe if you find >> a review request for the patch where these methods were added, you can >> confirm which one should be used. I checked the current source, and it seems >> that we randomly use one or the other, which seems incorrect. > > it might be possible we should use one for the left/top part and another for > the right/bottom so we will not create a gaps. > Please double-check whether you need to use Region.clipScale() instead. @mrserb We use `Region.clipRound` for converting coordinates in `SwingUtilities3.paintBorder`: https://github.com/openjdk/jdk/blob/a23de2ec090628b52532ee5d9bd4364a97499f5b/src/java.desktop/share/classes/com/sun/java/swing/SwingUtilities3.java#L231-L236 These formulas were introduced in #10681 ([JDK-8282958](https://bugs.openjdk.org/browse/JDK-8282958)); and after refactoring #11571 ([JDK-8294680](https://bugs.openjdk.org/browse/JDK-8294680)), the new formulas resolved [JDK-8294921](https://bugs.openjdk.org/browse/JDK-8294921) after #7449 ([JDK-8279614](https://bugs.openjdk.org/browse/JDK-8279614)) where there was a gap between the component edge and its border. These formulas specifically addressed the situation with gaps and were developed while we worked on making `LineBorder` and `EtchedBorder` render better at fractional scales. So, using `clipRound` seems good enough. Initially, [I suggested](https://bugs.openjdk.org/browse/JDK-8349188?focusedId=14758933&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14758933) using `(int) (this.thickness * scaleFactor)`, but `clipRound` gives better results. > I actually do not remember when to use one over the other. Maybe if you find > a review request for the patch where these methods were added, you can > confirm which one should be used. I couldn't find anything explaining where `clipScale` is better than `clipRound`. The discussion for [JDK-8000629](https://bugs.openjdk.org/browse/JDK-8000629) started in [March 2013](https://mail.openjdk.org/pipermail/awt-dev/2013-March/004486.html) and continued in [April 2013](https://mail.openjdk.org/pipermail/awt-dev/2013-April/004577.html). > I checked the current source, and it seems that we randomly use one or the > other, which seems incorrect. The javadoc for neither `clipScale` nor `clipRound` provides an example where each method is best suitable. So, it's not that surprising either is used randomly… It seems to me, that both [`clipScale`](https://github.com/openjdk/jdk/blob/a23de2ec090628b52532ee5d9bd4364a97499f5b/src/java.desktop/share/classes/sun/java2d/pipe/Region.java#L159) and [`clipRound`](https://github.com/openjdk/jdk/blob/a23de2ec090628b52532ee5d9bd4364a97499f5b/src/java.desktop/share/classes/sun/java2d/pipe/Region.java#L140) yield the same result. The former uses `Math.round`, whereas the latter uses `Math.ceil` after subtracting `0.5`. > it might be possible we should use one for the left/top part and another for > the right/bottom so we will not create a gaps. Perhaps… However, I'm pretty sure gaps are still possible whatever method we choose because fractional pixels don't fit nicely into the pixel grid. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/26025#discussion_r2173510928
