On Tue, 27 Oct 2020 10:38:34 GMT, Jose Pereda <jper...@openjdk.org> wrote:
>> As discussed in the [JBS >> issue](https://bugs.openjdk.java.net/browse/JDK-8199592), when snapping an >> already snapped value (either intentionally or by mistake), the result >> should be the same, otherwise we'll be jumping unnecessary from a valid >> pixel to another pixel. >> >> This PR provides a fix to `snapSizeXX` methods used in `Region`, which >> ultimately use `Math.ceil`, by subtracting an epsilon value to scaled value >> before ceiling, to ensure snapping a snapped value gives the same value. >> >> A test to verify `snapSizeX` and `snapSizeY` with 1000 random values, and 6 >> different UI scales is provided. >> For the 1.0, 1.25, 1.5 and 2.0 UI scales, the current approach works fine. >> Only for 1.75 and the random 1.374562997 value fails (the test fails for >> around 2% of the values with 1.75 and around 10% with 1.374562997). >> With the proposed fix, it doesn't fail at all. > > Jose Pereda has updated the pull request incrementally with one additional > commit since the last revision: > > Update JBS reference in RegionTest modules/javafx.graphics/src/main/java/javafx/scene/layout/Region.java line 303: > 301: } > 302: > 303: private static double scaledCeil(double value, double scale) { Can you explicitly add here that this method guarantees `scaledCeil(scaledCeil(val, scale), scale) == scaledCeil (val, scale)` It seems other code already assumed this, but it should not be taken for granted, so now that your fix assures this is the case, it can be taken for granted. ------------- PR: https://git.openjdk.java.net/jfx/pull/336
