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

[Kevin Rushforth]

On Fri, 24 Feb 2023 00:14:03 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> Simple fix to get the scroll deltas from GDK_SCROLL_SMOOTH. If we ignore this scroll event type, deltas are sent to java with the value equal to zero.
>> 
>> Here's whats happening:
>> 
>> We include all event masks, so when using gtk3 (>= 3.4.0) it includes `GDK_SMOOTH_SCROLL_MASK` meaning we receive duplicated events, one with  `direction = GDK_SMOOTH_SCROLL_MASK` and other with "legacy" direction (UP/DOWN).
>> 
>> When receiving the event corresponding to `GDK_SMOOTH_SCROLL_MASK` we ignored it causing it to send deltas (x,y) = 0.
>> 
>> The fix now checks if `GDK_SMOOTH_SCROLL_MASK` is supported and uses it, also adding smooth scroll functionality.
>
> Thiago Milczarek Sayao has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rename var

I haven't tested this, but I left a couple questions.

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?

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;`

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