Fix several race conditions in internal/driver/glfw package

[fpabl0]

Description:

Fix several race conditions in internal/driver/glfw package.
To test this fix, run:

go test -race -gcflags=all=-d=checkptr=0 fyne.io/fyne/v2/internal/driver/glfw

The flag -gcflags=all=-d=checkptr=0 is to temporarily ignore the crash related to gl (#1957).

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

[fpabl0]

After testing a lot the test called TestWindow_Focus (have written a script to run the test again and again until it fails haha) , I finally found where is the data race and in consequence why this test occasionally fails. The race occurs here:

w.charInput(w.viewport, 'd')
w.keyPressed(w.viewport, glfw.KeyTab, 0, glfw.Press, 0)

charInput(...) always enqueue the event to be called in a go routine later.
w.keyPressed with glfw.KeyTab event runs immediately in the main loop. Internally, it does w.canvas.FocusNext() that triggers the FocusLost method on widget.Entry and so refreshing the entry.Text and ignoring the charInput events because of the data race.

So, the question is should we also enqueue w.canvas.FocusNext() event from keyPressed to ensure all these operations are running sequentially in the same go routine?

[andydotxyz]

So, the question is should we also enqueue w.canvas.FocusNext() event from keyPressed to ensure all these operations are running sequentially in the same go routine?

Yes I think that sounds correct

[andydotxyz]

Seems like good improvements thanks