System File Chooser: support system message dialog with custom buttons on Windows (not yet used in SystemFileChooser

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLinuxLibrary.java

@@ -146,7 +146,8 @@ public class FlatNativeLinuxLibrary
 	 * @param owner the owner of the file dialog; or {@code null}
 	 * @param open if {@code true}, shows the open dialog; if {@code false}, shows the save dialog
 	 * @param title text displayed in dialog title; or {@code null}
-	 * @param okButtonLabel text displayed in default button; or {@code null}. Use '_' for mnemonics (e.g. "_Choose")
+	 * @param okButtonLabel text displayed in default button; or {@code null}.
+	 *        Use '_' for mnemonics (e.g. "_Choose")
 	 *        Use '__' for '_' character (e.g. "Choose__and__Quit").
 	 * @param currentName user-editable filename currently shown in the filename field in save dialog; or {@code null}
 	 * @param currentFolder current directory shown in the dialog; or {@code null}
@@ -189,7 +190,9 @@ public class FlatNativeLinuxLibrary
 	 *        this will appear as title in a larger bold font
 	 * @param secondaryText secondary text; shown below of primary text; or {@code null}
 	 * @param defaultButton index of the default button, which can be pressed using ENTER key
-	 * @param buttons texts of the buttons; if no buttons given the a default "OK" button is shown
+	 * @param buttons texts of the buttons; if no buttons given the a default "OK" button is shown.
+	 *        Use '_' for mnemonics (e.g. "_Choose")
+	 *        Use '__' for '_' character (e.g. "Choose__and__Quit").
 	 * @return index of pressed button; or -1 for ESC key
 	 *
 	 * @since 3.6

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeWindowsLibrary.java

@@ -18,6 +18,7 @@ package com.formdev.flatlaf.ui;
 
 import java.awt.Color;
 import java.awt.Window;
+import javax.swing.JOptionPane;
 import com.formdev.flatlaf.util.SystemInfo;
 
 /**
@@ -204,7 +205,8 @@ public class FlatNativeWindowsLibrary
 	 * @param owner the owner of the file dialog; or {@code null}
 	 * @param open if {@code true}, shows the open dialog; if {@code false}, shows the save dialog
 	 * @param title text displayed in dialog title; or {@code null}
-	 * @param okButtonLabel text displayed in default button; or {@code null}. Use '&' for mnemonics (e.g. "&Choose").
+	 * @param okButtonLabel text displayed in default button; or {@code null}.
+	 *        Use '&' for mnemonics (e.g. "&Choose").
 	 *        Use '&&' for '&' character (e.g. "Choose && Quit").
 	 * @param fileNameLabel text displayed in front of the filename text field; or {@code null}
 	 * @param fileName user-editable filename currently shown in the filename field; or {@code null}
@@ -240,6 +242,29 @@ public class FlatNativeWindowsLibrary
 		boolean approve( String[] files, long hwndFileDialog );
 	}
 
+	/**
+	 * Shows a modal Windows message dialog.
+	 * <p>
+	 * For use in {@link FileChooserCallback} only.
+	 *
+	 * @param hwndParent the parent of the message box
+	 * @param messageType type of message being displayed:
+	 *        {@link JOptionPane#ERROR_MESSAGE}, {@link JOptionPane#INFORMATION_MESSAGE},
+	 *        {@link JOptionPane#WARNING_MESSAGE}, {@link JOptionPane#QUESTION_MESSAGE} or
+	 *        {@link JOptionPane#PLAIN_MESSAGE}
+	 * @param title dialog box title; or {@code null} to use title from parent window
+	 * @param text message to be displayed
+	 * @param defaultButton index of the default button, which can be pressed using ENTER key
+	 * @param buttons texts of the buttons.
+	 *        Use '&amp;' for mnemonics (e.g. "&amp;Choose").
+	 *        Use '&amp;&amp;' for '&amp;' character (e.g. "Choose &amp;&amp; Quit").
+	 * @return index of pressed button; or -1 for ESC key
+	 *
+	 * @since 3.6
+	 */
+	public native static int showMessageDialog( long hwndParent, int messageType,
+		String title, String text, int defaultButton, String... buttons );
+
 	/**
 	 * Shows a Windows message box
 	 * <a href="https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messagebox">MessageBox</a>.
@@ -251,10 +276,8 @@ public class FlatNativeWindowsLibrary
 	 * @param caption dialog box title
 	 * @param type see <a href="https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messagebox#parameters">MessageBox parameter uType</a>
 	 * @return see <a href="https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messagebox#return-value">MessageBox Return value</a>
-	 * @return index of pressed button; or -1 for ESC key
 	 *
 	 * @since 3.6
 	 */
-	public native static int showMessageDialog( long hwndParent,
+	public native static int showMessageBox( long hwndParent, String text, String caption, int type );
-		String text, String caption, int type );
 }

flatlaf-natives/flatlaf-natives-windows/src/main/cpp/Runtime.cpp

@@ -36,8 +36,11 @@
  * @author Karl Tauber
  */
 
+HINSTANCE _instance;
+
 extern "C"
 BOOL WINAPI _DllMainCRTStartup( HINSTANCE instance, DWORD reason, LPVOID reserved ) {
+	_instance = instance;
 	return TRUE;
 }
 

flatlaf-natives/flatlaf-natives-windows/src/main/cpp/WinMessageDialog.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2024 FormDev Software GmbH
+ * Copyright 2025 FormDev Software GmbH
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 #define _NO_CRT_STDIO_INLINE
 
 #include <windows.h>
+#include <stdio.h>
 #include "JNIUtils.h"
 #include "com_formdev_flatlaf_ui_FlatNativeWindowsLibrary.h"
 
@@ -26,8 +27,24 @@
  * @since 3.6
  */
 
+#define ID_BUTTON1		101
+
+// declare external fields
+extern HINSTANCE _instance;
+
+// declare internal methods
+static byte* createInMemoryTemplate( HWND owner, int messageType, LPCWSTR title, LPCWSTR text,
+	int defaultButton, int buttonCount, LPCWSTR* buttons );
+static INT_PTR CALLBACK messageDialogProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam );
+static int textLengthAsDLUs( HDC hdc, LPCWSTR str, int strLen );
+static LONG pixel2dluX( LONG px );
+static LONG pixel2dluY( LONG px );
+static LONG dluX2pixel( LONG dluX );
+static LPWORD lpwAlign( LPWORD lpIn );
+
+
 extern "C"
-JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_showMessageDialog
+JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_showMessageBox
 	( JNIEnv* env, jclass cls, jlong hwndParent, jstring text, jstring caption, jint type )
 {
 	// convert Java strings to C strings
@@ -36,3 +53,326 @@ JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_show
 
 	return ::MessageBox( reinterpret_cast<HWND>( hwndParent ), ctext, ccaption, type );
 }
+
+extern "C"
+JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_showMessageDialog
+	( JNIEnv* env, jclass cls, jlong hwndParent, jint messageType, jstring title,
+		jstring text, jint defaultButton, jobjectArray buttons )
+{
+	HWND owner = reinterpret_cast<HWND>( hwndParent );
+
+	// convert Java strings to C strings
+	AutoReleaseString ctitle( env, title );
+	AutoReleaseString ctext( env, text );
+	AutoReleaseStringArray cbuttons( env, buttons );
+
+	// get title from parent window if necessary
+	WCHAR parentTitle[100];
+	if( ctitle == NULL )
+		::GetWindowText( owner, parentTitle, 100 );
+
+	byte* templ = createInMemoryTemplate( owner, messageType, (ctitle != NULL) ? ctitle : parentTitle,
+		ctext, defaultButton, cbuttons.count, cbuttons );
+	if( templ == NULL )
+		return -1;
+
+	LRESULT ret = ::DialogBoxIndirect( _instance, (LPDLGTEMPLATE) templ, owner, messageDialogProc );
+	delete templ;
+	return (ret >= ID_BUTTON1) ? ret - ID_BUTTON1 : -1;
+}
+
+
+// all values in DLUs
+
+#define INSETS_TOP				16
+#define INSETS_LEFT				12
+#define INSETS_RIGHT			12
+#define INSETS_BOTTOM			8
+
+#define ICON_TEXT_GAP			8
+
+#define LABEL_MIN_WIDTH			100
+#define LABEL_MAX_WIDTH			250
+#define LABEL_HEIGHT			8
+
+#define BUTTON_WIDTH			50
+#define BUTTON_HEIGHT			14
+#define BUTTON_GAP				5
+#define BUTTON_TOP_GAP			16
+#define BUTTON_LEFT_RIGHT_GAP	8
+
+// based on https://learn.microsoft.com/en-us/windows/win32/dlgbox/using-dialog-boxes#creating-a-template-in-memory
+static byte* createInMemoryTemplate( HWND owner, int messageType, LPCWSTR title, LPCWSTR text,
+	int defaultButton, int buttonCount, LPCWSTR* buttons )
+{
+	//---- calculate layout (in DLUs) ----
+
+	HDC hdc = GetDC( owner );
+
+	// layout icon
+	LPWSTR icon;
+	switch( messageType ) {
+		case /* JOptionPane.ERROR_MESSAGE */       0: icon = IDI_ERROR; break;
+		case /* JOptionPane.INFORMATION_MESSAGE */ 1: icon = IDI_INFORMATION; break;
+		case /* JOptionPane.WARNING_MESSAGE */     2: icon = IDI_WARNING; break;
+		case /* JOptionPane.QUESTION_MESSAGE */    3: icon = IDI_QUESTION; break;
+		default:
+		case /* JOptionPane.PLAIN_MESSAGE */      -1: icon = NULL; break;
+	}
+	int ix = INSETS_LEFT;
+	int iy = INSETS_TOP;
+	int iw = pixel2dluX( ::GetSystemMetrics( SM_CXICON ) );
+	int ih = pixel2dluY( ::GetSystemMetrics( SM_CYICON ) );
+
+	// layout text
+	int tx = ix + (icon != NULL ? iw + ICON_TEXT_GAP : 0);
+	int ty = iy;
+	int tw = 0;
+	int th = 0;
+	if( text == NULL )
+		text = L"";
+	LPWSTR wrappedText = new WCHAR[wcslen( text ) + 1];
+	wcscpy( wrappedText, text );
+	LPWSTR lineStart = wrappedText;
+	for( LPWSTR t = wrappedText; ; t++ ) {
+		if( *t != '\n' && *t != 0 )
+			continue;
+
+		// calculate line width (in pixels) and number of charaters that fit into LABEL_MAX_WIDTH
+		int lineLen = t - lineStart;
+		int fit = 0;
+		SIZE size{ 0 };
+		if( !::GetTextExtentExPoint( hdc, lineStart, lineLen, dluX2pixel( LABEL_MAX_WIDTH ), &fit, NULL, &size ) )
+			break;
+
+		if( fit < lineLen ) {
+			// wrap too long line --> try to wrap at space character
+			bool wrapped = false;
+			for( LPWSTR t2 = lineStart + fit - 1; t2 > lineStart; t2-- ) {
+				if( *t2 == ' ' || *t2 == '\t' ) {
+					*t2 = '\n';
+					int w = textLengthAsDLUs( hdc, lineStart, t2 - lineStart );
+					tw = max( tw, w );
+					th += LABEL_HEIGHT;
+
+					// continue wrapping after inserted line break
+					t = t2;
+					lineStart = t + 1;
+					wrapped = true;
+					break;
+				}
+			}
+			if( !wrapped ) {
+				// not able to wrap at word --> break long word
+				int breakIndex = (lineStart + fit) - wrappedText;
+				int w = textLengthAsDLUs( hdc, lineStart, breakIndex );
+				tw = max( tw, w );
+				th += LABEL_HEIGHT;
+
+				// duplicate string
+				LPWSTR wrappedText2 = new WCHAR[wcslen( wrappedText ) + 1 + 1];
+				// use wcscpy(), instead of wcsncpy(), because this method is inlined and does not require linking to runtime lib
+				wcscpy( wrappedText2, wrappedText );
+				wrappedText2[breakIndex] = '\n';
+				wcscpy( wrappedText2 + breakIndex + 1, wrappedText + breakIndex );
+
+				// delete old text
+				delete[] wrappedText;
+				wrappedText = wrappedText2;
+
+				// continue wrapping after inserted line break
+				t = wrappedText + breakIndex;
+				lineStart = t + 1;
+			}
+		} else {
+			// line fits into LABEL_MAX_WIDTH
+			int w = pixel2dluX( size.cx );
+			tw = max( tw, w );
+			th += LABEL_HEIGHT;
+			lineStart = t + 1;
+		}
+
+		if( *t == 0 )
+			break;
+	}
+	tw = min( max( tw, LABEL_MIN_WIDTH ), LABEL_MAX_WIDTH );
+	th = max( th, LABEL_HEIGHT );
+	if( icon != NULL && th < ih )
+		ty += (ih - th) / 2; // vertically center text
+
+	// layout buttons
+	int* bw = new int[buttonCount];
+	int buttonTotalWidth = BUTTON_GAP * (buttonCount - 1);
+	for( int i = 0; i < buttonCount; i++ ) {
+		int w = textLengthAsDLUs( hdc, buttons[i], -1 ) + 16;
+		bw[i] = max( BUTTON_WIDTH, w );
+		buttonTotalWidth += bw[i];
+	}
+
+	// layout dialog
+	int dx = 0;
+	int dy = 0;
+	int dw = max( tx + tw + INSETS_RIGHT, BUTTON_LEFT_RIGHT_GAP + buttonTotalWidth + BUTTON_LEFT_RIGHT_GAP );
+	int dh = max( iy + ih, ty + th ) + BUTTON_TOP_GAP + BUTTON_HEIGHT + INSETS_BOTTOM;
+
+	// center dialog in owner
+	RECT ownerRect{ 0 };
+	if( ::GetClientRect( owner, &ownerRect ) ) {
+		dx = (pixel2dluX( ownerRect.right - ownerRect.left ) - dw) / 2;
+		dy = (pixel2dluY( ownerRect.bottom - ownerRect.top ) - dh) / 2;
+	}
+
+	// layout button area
+	int bx = dw - buttonTotalWidth - BUTTON_LEFT_RIGHT_GAP;
+	int by = dh - BUTTON_HEIGHT - INSETS_BOTTOM;
+
+	// (approximately) calculate memory size needed for in-memory template
+	int templSize = (sizeof(DLGTEMPLATE) + /*menu*/ 2 + /*class*/ 2 + /*title*/ 2)
+		+ ((sizeof(DLGITEMTEMPLATE) + /*class*/ 4 + /*title/icon*/ 4 + /*creation data*/ 2) * (/*icon+text*/2 + buttonCount))
+		+ (title != NULL ? wcslen( title ) * sizeof(wchar_t) : 0)
+		+ (wcslen( wrappedText ) * sizeof(wchar_t));
+	for( int i = 0; i < buttonCount; i++ )
+		templSize += (wcslen( buttons[i] ) * sizeof(wchar_t));
+
+	templSize += (2 * (1 + 1 + buttonCount)); // necessary for DWORD alignment
+	templSize += 100; // some reserve
+
+	// allocate memory for in-memory template
+	byte* templ = new byte[templSize];
+	if( templ == NULL )
+		return NULL;
+
+
+	//---- define dialog box ----
+
+	LPDLGTEMPLATE lpdt = (LPDLGTEMPLATE) templ;
+	lpdt->style = WS_POPUP | WS_BORDER | WS_SYSMENU | DS_MODALFRAME | WS_CAPTION;
+	lpdt->cdit = /*text*/ 1 + buttonCount; // number of controls
+	lpdt->x = dx;
+	lpdt->y = dy;
+	lpdt->cx = dw;
+	lpdt->cy = dh;
+
+	LPWORD lpw = (LPWORD) (lpdt + 1);
+	*lpw++ = 0; // no menu
+	*lpw++ = 0; // predefined dialog box class (by default)
+	if( title != NULL ) {
+		wcscpy( (LPWSTR) lpw, title );
+		lpw += wcslen( title ) + 1;
+	} else
+		*lpw++ = 0; // no title
+
+
+	//---- define icon ----
+
+	if( icon != NULL ) {
+		lpdt->cdit++;
+
+		lpw = lpwAlign( lpw );
+		LPDLGITEMTEMPLATE lpdit = (LPDLGITEMTEMPLATE) lpw;
+		lpdit->x = ix;
+		lpdit->y = iy;
+		lpdit->cx = iw;
+		lpdit->cy = ih;
+		lpdit->id = ID_BUTTON1 - 1;
+		lpdit->style = WS_CHILD | WS_VISIBLE | SS_ICON;
+
+		lpw = (LPWORD) (lpdit + 1);
+		*lpw++ = 0xffff; *lpw++ = 0x0082;		// Static class
+		*lpw++ = 0xffff; *lpw++ = (WORD) icon;	// icon
+		*lpw++ = 0;								// creation data
+	}
+
+
+	//---- define text ----
+
+	lpw = lpwAlign( lpw );
+	LPDLGITEMTEMPLATE lpdit = (LPDLGITEMTEMPLATE) lpw;
+	lpdit->x = tx;
+	lpdit->y = ty;
+	lpdit->cx = tw;
+	lpdit->cy = th;
+	lpdit->id = ID_BUTTON1 - 2;
+	lpdit->style = WS_CHILD | WS_VISIBLE | SS_LEFT | SS_NOPREFIX | SS_EDITCONTROL;
+
+	lpw = (LPWORD) (lpdit + 1);
+	*lpw++ = 0xffff; *lpw++ = 0x0082;										// Static class
+	wcscpy( (LPWSTR) lpw, wrappedText ); lpw += wcslen( wrappedText ) + 1;	// text
+	*lpw++ = 0;																// creation data
+
+
+	//---- define buttons ----
+
+	defaultButton = min( max( defaultButton, 0 ), buttonCount - 1 );
+	int buttonId = ID_BUTTON1;
+	for( int i = 0; i < buttonCount; i++ ) {
+		lpw = lpwAlign( lpw );
+		LPDLGITEMTEMPLATE lpdit = (LPDLGITEMTEMPLATE) lpw;
+		lpdit->x = bx;
+		lpdit->y = by;
+		lpdit->cx = bw[i];
+		lpdit->cy = BUTTON_HEIGHT;
+		lpdit->id = buttonId++;
+		lpdit->style = WS_CHILD | WS_VISIBLE | WS_TABSTOP | (i == 0 ? WS_GROUP : 0)
+			| BS_TEXT | (i == defaultButton ? BS_DEFPUSHBUTTON : BS_PUSHBUTTON);
+
+		lpw = (LPWORD) (lpdit + 1);
+		*lpw++ = 0xffff; *lpw++ = 0x0080;										// Button class
+		wcscpy( (LPWSTR) lpw, buttons[i] ); lpw += wcslen( buttons[i] ) + 1;	// text
+		*lpw++ = 0;																// creation data
+
+		bx += bw[i] + BUTTON_GAP;
+	}
+
+	delete[] wrappedText;
+	delete[] bw;
+	
+	return templ;
+}
+
+static BOOL CALLBACK focusDefaultButtonProc( HWND hwnd, LPARAM lParam ) {
+	if( ::GetWindowLong( hwnd, GWL_ID ) >= ID_BUTTON1 ) {
+		LONG style = ::GetWindowLong( hwnd, GWL_STYLE );
+		if( (style & BS_DEFPUSHBUTTON) != 0 ) {
+			::SetFocus( hwnd );
+			return FALSE;
+		}
+	}
+	return TRUE;
+}
+
+static INT_PTR CALLBACK messageDialogProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam ) {
+	if( uMsg == WM_INITDIALOG )
+		::EnumChildWindows( hwnd, focusDefaultButtonProc, 0 );
+	else if( uMsg == WM_COMMAND ) {
+		::EndDialog( hwnd, wParam );
+		return TRUE;
+	}
+	return FALSE;
+}
+
+static int textLengthAsDLUs( HDC hdc, LPCWSTR str, int strLen ) {
+	SIZE size{ 0 };
+	::GetTextExtentPoint32( hdc, str, (strLen >= 0) ? strLen : wcslen( str ), &size );
+	return pixel2dluX( size.cx );
+}
+
+static LONG pixel2dluX( LONG px ) {
+	return MulDiv( px, 4, LOWORD( ::GetDialogBaseUnits() ) );
+}
+
+static LONG pixel2dluY( LONG py ) {
+	return MulDiv( py, 8, HIWORD( ::GetDialogBaseUnits() ) );
+}
+
+static LONG dluX2pixel( LONG dluX ) {
+	return MulDiv( dluX, LOWORD( ::GetDialogBaseUnits() ), 4 );
+}
+
+static LPWORD lpwAlign( LPWORD lpIn ) {
+	ULONG_PTR ul = (ULONG_PTR) lpIn;
+	ul += 3;
+	ul >>= 2;
+	ul <<= 2;
+	return (LPWORD) ul;
+}

flatlaf-natives/flatlaf-natives-windows/src/main/headers/com_formdev_flatlaf_ui_FlatNativeWindowsLibrary.h

@@ -124,9 +124,17 @@ JNIEXPORT jobjectArray JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibr
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeWindowsLibrary
  * Method:    showMessageDialog
- * Signature: (JLjava/lang/String;Ljava/lang/String;I)I
+ * Signature: (JILjava/lang/String;Ljava/lang/String;I[Ljava/lang/String;)I
  */
 JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_showMessageDialog
+  (JNIEnv *, jclass, jlong, jint, jstring, jstring, jint, jobjectArray);
+
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatNativeWindowsLibrary
+ * Method:    showMessageBox
+ * Signature: (JLjava/lang/String;Ljava/lang/String;I)I
+ */
+JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeWindowsLibrary_showMessageBox
   (JNIEnv *, jclass, jlong, jstring, jstring, jint);
 
 #ifdef __cplusplus

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSystemFileChooserWindowsTest.java

@@ -30,7 +30,10 @@ import java.awt.event.WindowListener;
 import java.awt.event.WindowStateListener;
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.prefs.Preferences;
 import javax.swing.*;
+import javax.swing.border.TitledBorder;
+import com.formdev.flatlaf.demo.DemoPrefs;
 import com.formdev.flatlaf.extras.components.*;
 import com.formdev.flatlaf.extras.components.FlatTriStateCheckBox.State;
 import com.formdev.flatlaf.ui.FlatNativeWindowsLibrary;
@@ -50,7 +53,7 @@ public class FlatSystemFileChooserWindowsTest
 			}
 
 			FlatTestFrame frame = FlatTestFrame.create( args, "FlatSystemFileChooserWindowsTest" );
-			addListeners( frame );
+//			addListeners( frame );
 			frame.showFrame( FlatSystemFileChooserWindowsTest::new );
 		} );
 	}
@@ -59,6 +62,10 @@ public class FlatSystemFileChooserWindowsTest
 		initComponents();
 
 		fileTypesField.setSelectedItem( null );
+
+		Preferences state = DemoPrefs.getState();
+		messageField.setText( state.get( "systemfilechooser.windows.message", "some message" ) );
+		buttonsField.setText( state.get( "systemfilechooser.windows.buttons", "OK" ) );
 	}
 
 	private void open() {
@@ -143,8 +150,8 @@ public class FlatSystemFileChooserWindowsTest
 			System.out.println( "  -- callback " + hwndFileDialog + "  " + Arrays.toString( files ) );
 			if( showMessageDialogOnOKCheckBox.isSelected() ) {
 				System.out.println( FlatNativeWindowsLibrary.showMessageDialog( hwndFileDialog,
-					"some text", "title",
+					JOptionPane.INFORMATION_MESSAGE,
-					/* MB_ICONINFORMATION */ 0x00000040 | /* MB_YESNO */ 0x00000004 ) );
+					null, "some text", 1, "Yes", "No" ) );
 			}
 			return true;
 		};
@@ -189,6 +196,28 @@ public class FlatSystemFileChooserWindowsTest
 			optionsClear.set( optionsClear.get() | option );
 	}
 
+	private void messageDialog() {
+		long hwnd = getHWND( SwingUtilities.windowForComponent( this ) );
+		String message = messageField.getText();
+		String[] buttons = buttonsField.getText().trim().split( "[,]+" );
+
+		Preferences state = DemoPrefs.getState();
+		state.put( "systemfilechooser.windows.message", message );
+		state.put( "systemfilechooser.windows.buttons", buttonsField.getText() );
+
+		System.out.println( FlatNativeWindowsLibrary.showMessageDialog( hwnd,
+			JOptionPane.WARNING_MESSAGE, null, message, 1, buttons ) );
+	}
+
+	private void messageBox() {
+		long hwnd = getHWND( SwingUtilities.windowForComponent( this ) );
+		String message = messageField.getText();
+
+		System.out.println( FlatNativeWindowsLibrary.showMessageBox( hwnd, message, null,
+			/* MB_ICONINFORMATION */ 0x00000040 | /* MB_YESNO */ 0x00000004 ) );
+	}
+
+	@SuppressWarnings( "unused" )
 	private static void addListeners( Window w ) {
 		w.addWindowListener( new WindowListener() {
 			@Override
@@ -278,6 +307,12 @@ public class FlatSystemFileChooserWindowsTest
 		supportStreamableItemsCheckBox = new FlatTriStateCheckBox();
 		allowMultiSelectCheckBox = new FlatTriStateCheckBox();
 		hidePinnedPlacesCheckBox = new FlatTriStateCheckBox();
+		messageDialogPanel = new JPanel();
+		messageLabel = new JLabel();
+		messageScrollPane = new JScrollPane();
+		messageField = new JTextArea();
+		buttonsLabel = new JLabel();
+		buttonsField = new JTextField();
 		okButtonLabelLabel = new JLabel();
 		okButtonLabelField = new JTextField();
 		fileNameLabelLabel = new JLabel();
@@ -301,6 +336,9 @@ public class FlatSystemFileChooserWindowsTest
 		openDirectButton = new JButton();
 		saveDirectButton = new JButton();
 		showMessageDialogOnOKCheckBox = new JCheckBox();
+		hSpacer1 = new JPanel(null);
+		messageDialogButton = new JButton();
+		messageBoxButton = new JButton();
 		filesScrollPane = new JScrollPane();
 		filesField = new JTextArea();
 
@@ -365,7 +403,8 @@ public class FlatSystemFileChooserWindowsTest
 				"[]0" +
 				"[]0" +
 				"[]0" +
-				"[]0"));
+				"[]0" +
+				"[grow]"));
 
 			//---- overwritePromptCheckBox ----
 			overwritePromptCheckBox.setText("overwritePrompt");
@@ -461,8 +500,41 @@ public class FlatSystemFileChooserWindowsTest
 			//---- hidePinnedPlacesCheckBox ----
 			hidePinnedPlacesCheckBox.setText("hidePinnedPlaces");
 			panel1.add(hidePinnedPlacesCheckBox, "cell 1 7");
+
+			//======== messageDialogPanel ========
+			{
+				messageDialogPanel.setBorder(new TitledBorder("MessageDialog"));
+				messageDialogPanel.setLayout(new MigLayout(
+					"hidemode 3",
+					// columns
+					"[fill]" +
+					"[grow,fill]",
+					// rows
+					"[grow,fill]" +
+					"[]"));
+
+				//---- messageLabel ----
+				messageLabel.setText("Message");
+				messageDialogPanel.add(messageLabel, "cell 0 0,aligny top,growy 0");
+
+				//======== messageScrollPane ========
+				{
+
+					//---- messageField ----
+					messageField.setColumns(40);
+					messageField.setRows(4);
+					messageScrollPane.setViewportView(messageField);
+				}
+				messageDialogPanel.add(messageScrollPane, "cell 1 0");
+
+				//---- buttonsLabel ----
+				buttonsLabel.setText("Buttons:");
+				messageDialogPanel.add(buttonsLabel, "cell 0 1");
+				messageDialogPanel.add(buttonsField, "cell 1 1");
+			}
+			panel1.add(messageDialogPanel, "cell 0 8 3 1,grow");
 		}
-		add(panel1, "cell 2 1 1 10,aligny top,growy 0");
+		add(panel1, "cell 2 1 1 10,growy");
 
 		//---- okButtonLabelLabel ----
 		okButtonLabelLabel.setText("okButtonLabel");
@@ -548,6 +620,17 @@ public class FlatSystemFileChooserWindowsTest
 		//---- showMessageDialogOnOKCheckBox ----
 		showMessageDialogOnOKCheckBox.setText("show message dialog on OK");
 		add(showMessageDialogOnOKCheckBox, "cell 0 11 3 1");
+		add(hSpacer1, "cell 0 11 3 1,growx");
+
+		//---- messageDialogButton ----
+		messageDialogButton.setText("MessageDialog...");
+		messageDialogButton.addActionListener(e -> messageDialog());
+		add(messageDialogButton, "cell 0 11 3 1,alignx right,growx 0");
+
+		//---- messageBoxButton ----
+		messageBoxButton.setText("MessageBox...");
+		messageBoxButton.addActionListener(e -> messageBox());
+		add(messageBoxButton, "cell 0 11 3 1");
 
 		//======== filesScrollPane ========
 		{
@@ -598,6 +681,12 @@ public class FlatSystemFileChooserWindowsTest
 	private FlatTriStateCheckBox supportStreamableItemsCheckBox;
 	private FlatTriStateCheckBox allowMultiSelectCheckBox;
 	private FlatTriStateCheckBox hidePinnedPlacesCheckBox;
+	private JPanel messageDialogPanel;
+	private JLabel messageLabel;
+	private JScrollPane messageScrollPane;
+	private JTextArea messageField;
+	private JLabel buttonsLabel;
+	private JTextField buttonsField;
 	private JLabel okButtonLabelLabel;
 	private JTextField okButtonLabelField;
 	private JLabel fileNameLabelLabel;
@@ -621,6 +710,9 @@ public class FlatSystemFileChooserWindowsTest
 	private JButton openDirectButton;
 	private JButton saveDirectButton;
 	private JCheckBox showMessageDialogOnOKCheckBox;
+	private JPanel hSpacer1;
+	private JButton messageDialogButton;
+	private JButton messageBoxButton;
 	private JScrollPane filesScrollPane;
 	private JTextArea filesField;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSystemFileChooserWindowsTest.jfd

@@ -56,7 +56,7 @@ new FormModel {
 			add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
 				"$layoutConstraints": "insets 2,hidemode 3"
 				"$columnConstraints": "[left]para[left]para[left]"
-				"$rowConstraints": "[]0[]0[]0[][]0[]0[]0[]0"
+				"$rowConstraints": "[]0[]0[]0[][]0[]0[]0[]0[grow]"
 			} ) {
 				name: "panel1"
 				add( new FormComponent( "com.formdev.flatlaf.extras.components.FlatTriStateCheckBox" ) {
@@ -200,8 +200,45 @@ new FormModel {
 				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 					"value": "cell 1 7"
 				} )
+				add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
+					"$layoutConstraints": "hidemode 3"
+					"$columnConstraints": "[fill][grow,fill]"
+					"$rowConstraints": "[grow,fill][]"
+				} ) {
+					name: "messageDialogPanel"
+					"border": new javax.swing.border.TitledBorder( "MessageDialog" )
+					add( new FormComponent( "javax.swing.JLabel" ) {
+						name: "messageLabel"
+						"text": "Message"
+					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+						"value": "cell 0 0,aligny top,growy 0"
+					} )
+					add( new FormContainer( "javax.swing.JScrollPane", new FormLayoutManager( class javax.swing.JScrollPane ) ) {
+						name: "messageScrollPane"
+						add( new FormComponent( "javax.swing.JTextArea" ) {
+							name: "messageField"
+							"columns": 40
+							"rows": 4
+						} )
+					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+						"value": "cell 1 0"
+					} )
+					add( new FormComponent( "javax.swing.JLabel" ) {
+						name: "buttonsLabel"
+						"text": "Buttons:"
+					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+						"value": "cell 0 1"
+					} )
+					add( new FormComponent( "javax.swing.JTextField" ) {
+						name: "buttonsField"
+					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+						"value": "cell 1 1"
+					} )
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 0 8 3 1,grow"
+				} )
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
-				"value": "cell 2 1 1 10,aligny top,growy 0"
+				"value": "cell 2 1 1 10,growy"
 			} )
 			add( new FormComponent( "javax.swing.JLabel" ) {
 				name: "okButtonLabelLabel"
@@ -344,11 +381,30 @@ new FormModel {
 				"value": "cell 0 11 3 1"
 			} )
 			add( new FormComponent( "javax.swing.JCheckBox" ) {
-				name: "showMessageDialogsOnOKCheckBox"
+				name: "showMessageDialogOnOKCheckBox"
 				"text": "show message dialog on OK"
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 0 11 3 1"
 			} )
+			add( new FormComponent( "com.jformdesigner.designer.wrapper.HSpacer" ) {
+				name: "hSpacer1"
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 11 3 1,growx"
+			} )
+			add( new FormComponent( "javax.swing.JButton" ) {
+				name: "messageDialogButton"
+				"text": "MessageDialog..."
+				addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "messageDialog", false ) )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 11 3 1,alignx right,growx 0"
+			} )
+			add( new FormComponent( "javax.swing.JButton" ) {
+				name: "messageBoxButton"
+				"text": "MessageBox..."
+				addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "messageBox", false ) )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 11 3 1"
+			} )
 			add( new FormContainer( "javax.swing.JScrollPane", new FormLayoutManager( class javax.swing.JScrollPane ) ) {
 				name: "filesScrollPane"
 				add( new FormComponent( "javax.swing.JTextArea" ) {
@@ -360,7 +416,7 @@ new FormModel {
 			} )
 		}, new FormLayoutConstraints( null ) {
 			"location": new java.awt.Point( 0, 0 )
-			"size": new java.awt.Dimension( 845, 630 )
+			"size": new java.awt.Dimension( 890, 630 )
 		} )
 		add( new FormNonVisual( "javax.swing.ButtonGroup" ) {
 			name: "ownerButtonGroup"