RFR: 8303038: Glass gtk3 sends scroll events with delta(x, y) = 0 [v4]

[Thiago Milczarek Sayao]

On Wed, 1 Mar 2023 15:07:37 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Thiago Milczarek Sayao has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename var
>
> modules/javafx.graphics/src/main/native-glass/gtk/glass_window.cpp line 390:
> 
>> 388:         if (gdk_window_get_events(gdk_window) & GDK_SMOOTH_SCROLL_MASK) {
>> 389:             is_smooth = true;
>> 390:             if (event->direction == GDK_SCROLL_SMOOTH) {
> 
> When would `GDK_SMOOTH_SCROLL_MASK` be set with direction not equal to `GDK_SCROLL_SMOOTH`? In this case, you will use a dx and dy value of 0 (which will at least now be ignored with your fix). Is this correct?

Correct.

`direction`:
The direction to scroll to (one of `GDK_SCROLL_UP`, `GDK_SCROLL_DOWN`, `GDK_SCROLL_LEFT`, `GDK_SCROLL_RIGHT ` or `GDK_SCROLL_SMOOTH`).

If the device supports it and if event mask is set to contain `GDK_SMOOTH_SCROLL_MASK `, gdk will send `GDK_SCROLL_SMOOTH` with the deltas equivalent to the device sensor. But it will also send the others for compatibilty (I guess).

We set to receive all events. When gtk3 introduced `GDK_SMOOTH_SCROLL_MASK` (*) we started receiving it but not accounting it, so resulting in deltas = `0`.

(*) It's set on `WindowContextTop` constructor.

> modules/javafx.graphics/src/main/native-glass/gtk/glass_window.cpp line 419:
> 
>> 417:         // Note: For gtk negatives values means UP/LEFT, JavaFx is opposite
>> 418:         dx = (dx != 0) ? dx * -1 : 0;
>> 419:         dy = (dy != 0) ? dy * -1 : 0;
> 
> Is avoiding a possible negative 0 is really necessary? If not, this could simplify to `dx *= -1;` and `dy *= -1;`

Will double check it, but I think I spaced out.

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PR: https://git.openjdk.org/jfx/pull/1044