JDK-8220272: Found the problem + possible fix

[Nir Lisker]

Hi Thiago,

Anyone can create a PR on GitHub, see
https://github.com/javafxports/openjdk-jfx/blob/develop/.github/CONTRIBUTING.md
.

- Nir

On Mon, Apr 15, 2019 at 3:47 AM Thiago Milczarek Sayao <
thiago.sayao at clamed.com.br> wrote:

> * THE PROBLEM *
>
> In GlassApplication.cpp, the GDK_FOCUS_CHANGE event gets called from the
> last window to the first on my setup (I suspect "out-of-order" on some
> setups and even occasionally in the expected order). So the code to keep
> the latest enabled window fails (refering to WindowStage.java
> activeWindows) - that's why the "First Window" (on the code to reproduce
> the bug report) shows on top - because openjfx thinks it was the latest
> window. In WindowStage.java:
>
>     final void handleFocusDisabled() {
>         if (activeWindows.isEmpty()) {
>             return;
>         }
>         WindowStage window = activeWindows.get(activeWindows.size() - 1);
> //<-- HERE!!
>         window.setIconified(false);
>         window.requestToFront();
>         window.requestFocus();
>     }
>
> When there is a WINDOW_MODAL this code gets called because the modal
> window disable it's parents (so they do not get events - it's correct). So
> openjfx brings up what it thinks it's the latest window - but since the out
> of order GDK_FOCUS_CHANGE - it's the wrong window (activeWindows list has
> not the correct order).
>
> The Gtk docs states GDK_FOCUS_CHANGE is true "if the window has gained the
> keyboard focus" which may not be directly correlated to openjfx's
> WindowEvent.FOCUS_GAINED.
>
> * THE FIX *
>
> To fix this, WindowEvent.FOCUS_GAINED must be called in order of which
> window is shown (because the window is inserted on activeWindows at this
> event).
>
> So I have modified glass_window.cpp to immediately call
> WindowEvent.FOCUS_GAINED when showing the window:
>
> void WindowContextBase::set_visible(bool visible) {
>     if (visible) {
>         gtk_widget_show_all(gtk_widget);
>
>         //JDK-8220272 - fire event first because GDK_FOCUS_CHANGE is not
> always in order
>         if(jwindow && isEnabled()) {
>             mainEnv->CallVoidMethod(jwindow, jWindowNotifyFocus,
> com_sun_glass_events_WindowEvent_FOCUS_GAINED);
>         }
>     } else {
>         gtk_widget_hide(gtk_widget);
>         if (jview && is_mouse_entered) {
>             is_mouse_entered = false;
>             mainEnv->CallVoidMethod(jview, jViewNotifyMouse,
>                     com_sun_glass_events_MouseEvent_EXIT,
>                     com_sun_glass_events_MouseEvent_BUTTON_NONE,
>                     0, 0,
>                     0, 0,
>                     0,
>                     JNI_FALSE,
>                     JNI_FALSE);
>             CHECK_JNI_EXCEPTION(mainEnv)
>         }
>     }
> }
>
> Did some tests and it seems to fix the problem.
>
> I do not have permission to make a PR, so posting the fix here. Will
> happily do the PR if required.
>
> Thanks.
>
>