B4J Question Convert Java code to B4J and InitializeNewInstance.

[zed]

First of all, I found the JAVA code on the net, but I'm having a bit of trouble implementing it in B4J.
Following Cableguy message

JNA SendMessage - I need help!

Hi guys... I need to send a message to a Form Handler, basically "intercepting" the WM_NCHITTEST Message ( This allows your custom maximize button to be registered as the standard one) and Return HTMAXBUTTON (thus making the OS believe my custom Maximize button is the Native one). Getting the...

www.b4x.com

I coded this.

'This procedure works well to recover the HWND
Private Sub GetHWND
    Dim user32 As JavaObject
    user32 = user32.InitializeStatic("com.sun.jna.platform.win32.User32").GetField("INSTANCE")
 
    Dim hwnd As JavaObject = user32.RunMethod("GetActiveWindow",Null)
    Log("hwnd : "&hwnd)
    
    ' Access the pointer
    Dim pointer As JavaObject = hwnd.RunMethod("getPointer", Null)

    ' Extract the value from the pointer with NativeValue()
    Dim native As JavaObject
    native.InitializeStatic("com.sun.jna.Pointer")

    Dim hwndLong As Long = native.RunMethod("nativeValue", Array(pointer))

    Log("HWND (Long) : " & hwndLong)

    If hwndLong > 0 Then
        HookWindowProcedure(hwndLong)
    Else
        Log("Error: Invalid HWND")
    End If
End Sub

How to intercept WM_NCHITTEST message and return HTMAXBUTTON in B4J with JNA

I have a sample code in Java to adapt to B4J.

import com.sun.jna.platform.win32.User32;
import com.sun.jna.platform.win32.WinDef.*;
import com.sun.jna.platform.win32.WinUser.*;
import com.sun.jna.Callback;

public class MonWndProc implements Callback {
    public LRESULT callback(HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam) {
        if (uMsg == WinUser.WM_NCHITTEST) {
            return new LRESULT(WinUser.HTMAXBUTTON); // Indique que le bouton max est actif
        }
        return User32.INSTANCE.DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
}

Adaptation in B4J.

Sub HookWindowProcedure(hwnd As Long)
    Dim User32 As JavaObject
    User32.InitializeStatic("com.sun.jna.platform.win32.User32")

    Dim WndProc As JavaObject
    WndProc.InitializeNewInstance("MonWndProc", Null) ' <-- What is the classname

    User32.RunMethod("SetWindowLongPtr", Array(hwnd, -4, WndProc))
End Sub

MyWndProc is a class that implements Callback and intercepts WM_NCHITTEST.
SetWindowLongPtr overrides the window procedure to use MyWndProc.
HTMAXBUTTON tricks Windows into thinking the custom button is the native maximize button.
What is the classname ?

And finally.

Sub CustomWndProc(hwnd As String, uMsg As Int, wParam As Long, lParam As Long) As Long
    If uMsg = 132 Then ' WM_NCHITTEST
        Return 9 ' HTMAXBUTTON
    End If

    Dim User32 As JavaObject
    User32.InitializeStatic("com.sun.jna.platform.win32.User32")
    Return User32.RunMethod("DefWindowProc", Array(hwnd, uMsg, wParam, lParam))
End Sub

Here are the Logs

WARNING: package com.sun.javafx.embed.swing.oldimpl not in javafx.swing
Waiting for debugger to connect...
Program started.
hwnd1 : (HWND) native@0xbc0568
HWND (Long) : 12322152
Error occurred on line: 50 (Main)
java.lang.ClassNotFoundException: java$lang$MonWndProc
    at anywheresoftware.b4j.object.JavaObject.getCorrectClassName(JavaObject.java:289)
    at anywheresoftware.b4j.object.JavaObject.InitializeNewInstance(JavaObject.java:84)
    at b4j.example.main._hookwindowprocedure(main.java:144)
    at b4j.example.main._appstart(main.java:114)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:629)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:237)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:111)
    at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:100)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:98)
    at b4j.example.main.start(main.java:38)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:1589)

Thank you for any help you can give me

 

[Erel]

public class MonWndProc implements Callback {

This should be:

public static class MonWndProc implements Callback {

And the class name is: "b4j.example.main$MonWndProc"

 

[zed]

Should I put the java block
#if java
----
#end if

Because in this case, there is a compilation error.

B4J Version : 10.00
Analyse du code.    (0.00s)
    Java Version : 19
Building folders structure.    (0.02s)
Compilation du code.    (0.00s)
Compilation du code des layouts.    (0.00s)
Organiser les bibliothèques.    (0.00s)
Compilation du code Java.    Error
B4J line: 59
End Sub
src\b4j\example\main.java:198: error: cannot find symbol
        if (uMsg == WinUser.WM_NCHITTEST) {
                    ^
  symbol:   variable WinUser
  location: class MonWndProc
1 error
only showing the first 1 errors, of 2 total; use -Xmaxerrs if you would like to see more

the error comes from line 8 of the java code

 

[PaulMeuris]

This might help...
https://stackoverflow.com/questions/68500278/jna-does-not-have-a-function-from-the-windows-api

 

[zed]

Thanks for the link, but it doesn't really help me.
Why WinUser.WM_NCHITTEST is not working.
I will continue my investigation, but any help is appreciated.