Why does a custom Window Procedure stop processing window messages? - winapi

Question

I'm trying to configure a custom window procedure and it works. However, after a while, the window stops reacting to any input. It seems that the more rendering is going on in a scene, the sooner the window gets broken.
This even happens if my custom window procedure simply calls the default window.
Reproducer:
package com.example;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.BaseTSD;
import com.sun.jna.platform.win32.User32;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinUser;
import com.sun.jna.win32.W32APIOptions;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ProgressIndicator;
import javafx.stage.Stage;
import static com.sun.jna.platform.win32.WinUser.GWL_WNDPROC;
public class CustomWndProc {
public static void main(String[] args) {
CustomFrameApplication.launch(CustomFrameApplication.class, args);
}
public static class CustomFrameApplication extends Application {
#Override
public void start(Stage primaryStage) {
primaryStage.setScene(new Scene(new ProgressIndicator(ProgressIndicator.INDETERMINATE_PROGRESS)));
primaryStage.show();
HWND hwnd = new HWND();
hwnd.setPointer(User32.INSTANCE.GetActiveWindow().getPointer());
BaseTSD.LONG_PTR defaultWindowProc = User32.INSTANCE.GetWindowLongPtr(hwnd, GWL_WNDPROC);
WinUser.WindowProc windowProc = (hwnd1, uMsg, wParam, lParam) ->
User32Ex.INSTANCE.CallWindowProc(defaultWindowProc, hwnd1, uMsg, wParam, lParam);
User32Ex.INSTANCE.SetWindowLongPtr(hwnd, GWL_WNDPROC, windowProc);
}
}
public interface User32Ex extends User32 {
User32Ex INSTANCE = Native.load("user32", User32Ex.class, W32APIOptions.DEFAULT_OPTIONS);
Pointer SetWindowLongPtr(HWND hWnd, int nIndex, WindowProc wndProc);
LRESULT CallWindowProc(LONG_PTR proc, HWND hWnd, int uMsg, WPARAM uParam, LPARAM lParam);
}
}
Give it a few seconds or minutes and you won't be able to move, minimize, maximize or close the window anymore.
If you want guaranteed freeze, use a WebView instead of a ProgressIndicator:
WebView webView = new WebView();
webView.getEngine().load("https://www.google.com");
primaryStage.setScene(new Scene(webView));
I wondered if it has something to do that my code runs in the JavaFX Application thread (leading to some race condition) but I assume so does the default window procedure (how can I verify?).
I'm trying to build a JavaFX application that uses a custom frame.
Using JNA 5.5.0.

Answer 1

I think this is the right way to do it, but maybe I'm wrong..
I got the Information from:
Why my JNA using application doesn't react in a right way?
import com.sun.jna.LastErrorException;
import com.sun.jna.Native;
import com.sun.jna.platform.win32.BaseTSD;
import com.sun.jna.platform.win32.User32;
import com.sun.jna.platform.win32.WinDef;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.win32.W32APIOptions;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ProgressIndicator;
import javafx.stage.Stage;
public class CustomWndProc {
public static void main(String[] args) {
CustomFrameApplication.launch(CustomFrameApplication.class, args);
}
public static class CustomFrameApplication extends Application {
private BaseTSD.LONG_PTR baseWndProc;
public User32Ex.WNDPROC listener = new User32Ex.WNDPROC() {
public WinDef.LRESULT callback(HWND hWnd, int uMsg, WinDef.WPARAM uParam,
WinDef.LPARAM lParam) {
// TODO handle the window message
// calling the base WndProc
return User32Ex.INSTANCE.CallWindowProc(baseWndProc, hWnd, uMsg, uParam, lParam);
}
};
#Override
public void start(Stage primaryStage) {
primaryStage.setScene(new Scene(new ProgressIndicator(ProgressIndicator.INDETERMINATE_PROGRESS)));
primaryStage.show();
HWND hwnd = new HWND();
hwnd.setPointer(User32.INSTANCE.GetActiveWindow().getPointer());
this.baseWndProc = User32Ex.INSTANCE.GetWindowLongPtr(hwnd, User32Ex.GWL_WNDPROC);
User32Ex.INSTANCE.SetWindowLongPtr(hwnd, User32Ex.GWL_WNDPROC, this.listener);
}
}
public interface User32Ex extends User32 {
User32Ex INSTANCE = Native.load("user32", User32Ex.class, W32APIOptions.DEFAULT_OPTIONS);
interface WNDPROC extends StdCallCallback {
LRESULT callback(HWND hWnd, int uMsg, WPARAM uParam, LPARAM lParam);
}
LONG_PTR GetWindowLongPtr(HWND hWnd, int nIndex) throws LastErrorException;
LRESULT CallWindowProc(LONG_PTR proc, HWND hWnd, int uMsg, WPARAM uParam, WinDef.LPARAM lParam) throws LastErrorException;
LONG_PTR SetWindowLongPtr(HWND hWnd, int nIndex, WNDPROC wndProc) throws LastErrorException;
}
}