RFR: 8366739: ToolBar: overflow menu with fractional scale (2)

[Cormac Redmond]

On Sun, 21 Dec 2025 03:36:47 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Fix overflow menu triggering due to floating-point precision error.
>> 
>> At 1.25 display scaling on Windows, floating-point comparison errors (e.g. 109.60000000000001 > 109.6) cause the overflow menu to appear when the lefthand value is regarded as larger than the righthand value.
>> 
>> These should be treated as equal (and therefore not display the overflow menu).
>> 
>> This bug can happen in both horizontal and vertical toolbar orientation.
>> 
>> The new tests added fail without this fix, and pass with it. An existing test has been re-factored slightly to allow re-use and more flexibility in specifying the scene's root node.
>
> modules/javafx.controls/src/main/java/javafx/scene/control/skin/ToolBarSkin.java line 706:
> 
>> 704:             // Use a small epsilon (1e-9 / 0.000000001) to tolerate floating-point rounding error when comparing
>> 705:             // doubles. E.g. 117.60000000000001 should be regarded as equal to 117.6.
>> 706:             if (x - length > 1e-9) {
> 
> We don't really use tolerances like this in the UI code; instead the problem is almost always because some floating point operations were done, but the result wasn't (re)snapped.
> 
> In the code above I see that `x` is modified without re-snapping.  I think a `snapPositionX/Y` should be applied on `x`, something like this:
> 
>             if (node.isManaged()) {
>                 if (getSkinnable().getOrientation() == Orientation.VERTICAL) {
>                     x += snapPositionY(snapSizeY(node.prefHeight(-1)) + getSpacing());
>                 } else {
>                     x += snapPositionX(snapSizeX(node.prefWidth(-1)) + getSpacing());
>                 }
>             }

Thanks @hjohn.

The problem here is caused by the repeated operations on x itself (+=), not the added getSpacing(), so the bug _still_ happens with the above (although, I'm sure getSpacing() could be a causing factor also if the value was something particular; in my case I haven't noticed it so so far).

Anyway, this minor change fixes it and I think is in the spirit of your suggestion:


if (node.isManaged()) {
  if (getSkinnable().getOrientation() == Orientation.VERTICAL) {
    x = snapPositionY(x + snapSizeY(node.prefHeight(-1)) + getSpacing());
  } else {
    x = snapPositionX(x + snapSizeX(node.prefWidth(-1)) + getSpacing());
  }
}


Pushed now...

-------------

PR Review Comment: https://git.openjdk.org/jfx/pull/2016#discussion_r2637734595