RFR: 8090267: JFXPanel Input Problem

[Martin Fox]

On Tue, 4 Jul 2023 05:54:54 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> When Japanse (IME on) is inputted to the TextFIeld, which is on JFXPanel, 
> small window for inputting appears on top-left side of screen
> 
> ![image](https://github.com/openjdk/jfx/assets/43534309/65833d59-528e-4087-9992-9f86b8b8c47f)
> 
> For swing-interop case, WmImeStartComposition starts composition in native ImmSetCompositionWindow window as "m_useNativeCompWindow" below is true for FX
> https://github.com/openjdk/jdk/blob/514816ed7d7dea1fb13d32b80aef89774bee13d3/src/java.desktop/windows/native/libawt/windows/awt_Component.cpp#L3957
> 
> m_useNativeCompWindow is true because during sun.awt.im.InputContext#focusGained() calls activateInputMethod which calls WInputMethod.activate() which calls haveActiveClient() which checks for
> clientComponent.getInputMethodRequests().
> Now, in JFXPanel, getInputMethodRequests() returns null as setEmbeddedScene() is not called yet.
> Since getInputMethodRequests() returns null, haveActiveClient() is false which calls enableNativeIME() with 1 [thereby native composition window is enabled]
> https://github.com/openjdk/jdk/blob/514816ed7d7dea1fb13d32b80aef89774bee13d3/src/java.desktop/windows/classes/sun/awt/windows/WInputMethod.java#L316
> 
> Proposed fix is to ensure there is an active client "initially" so that enableNativeIME() is called with 0 and no native compostion window is shown.
> getInputMethodRequests() is called in setEmbeddedScene() so as to make sure getInputMethodRequest() is initialised to correct "InputMethodSupport.InputMethodRequestsAdapter.fxRequests" object and not NULL.
> 
> AFter fix
> ![image](https://github.com/openjdk/jfx/assets/43534309/ec3d8343-9295-4950-885b-f9983b9b017a)

It turns out this PR didn't introduce new problems, it just exposed existing ones. The AWT EventQueue thread is calling into the InputMethodRequests at the same time as the JavaFX thread is updating and drawing the text field. If the timing is right (or wrong) both threads can trigger glyph layout in the same Text object at the same time. The result is the sort of erratic behavior seen here.

I've entered [JDK-8322784](https://bugs.openjdk.org/browse/JDK-8322784).

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

PR Comment: https://git.openjdk.org/jfx/pull/1169#issuecomment-1872276763