Windows: fixed wrong layout in maximized frame after changing screen scale factor (issue #904)

Windows binaries built and signed locally in clean workspace

flatlaf-natives/flatlaf-natives-jna/src/main/java/com/formdev/flatlaf/natives/jna/windows/FlatWindowsNativeWindowBorder.java

@@ -309,6 +309,8 @@ public class FlatWindowsNativeWindowBorder
 			WM_ENTERSIZEMOVE = 0x0231,
 			WM_EXITSIZEMOVE = 0x0232,
 
+			WM_DPICHANGED = 0x02E0,
+
 			WM_DWMCOLORIZATIONCOLORCHANGED = 0x0320;
 
 		// WM_SIZE wParam
@@ -501,6 +503,22 @@ public class FlatWindowsNativeWindowBorder
 						isMoving = true;
 					break;
 
+				case WM_DPICHANGED:
+					LRESULT lResult = User32Ex.INSTANCE.CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+
+					// if window is maximized and DPI/scaling changed, then Windows
+					// does not send a subsequent WM_SIZE message and Java window bounds,
+					// which depend on scale factor, are not updated
+					boolean isMaximized = User32Ex.INSTANCE.IsZoomed( hwnd );
+					if( isMaximized ) {
+						MyRECT r = new MyRECT( new Pointer( lParam.longValue() ) );
+						int width = r.right - r.left;
+						int height = r.bottom - r.top;
+						User32Ex.INSTANCE.CallWindowProc( defaultWndProc, hwnd, WM_SIZE, new WPARAM( SIZE_MAXIMIZED ), MAKELPARAM( width, height ) );
+					}
+
+					return lResult;
+
 				case WM_ERASEBKGND:
 					// do not erase background while the user is moving the window,
 					// otherwise there may be rendering artifacts on HiDPI screens with Java 9+
@@ -818,6 +836,13 @@ public class FlatWindowsNativeWindowBorder
 			return (low & 0xffff) | ((high & 0xffff) << 16);
 		}
 
+		/**
+		 * Same implementation as MAKELPARAM(l, h) macro in winuser.h.
+		 */
+		private LPARAM MAKELPARAM( int low, int high ) {
+			return new LPARAM( MAKELONG( low, high ) );
+		}
+
 		/**
 		 * Same implementation as RGB(r,g,b) macro in wingdi.h.
 		 */
@@ -937,6 +962,23 @@ public class FlatWindowsNativeWindowBorder
 		}
 	}
 
+	//---- class MyRECT -------------------------------------------------------
+
+	@FieldOrder( { "left", "top", "right", "bottom" } )
+	public static class MyRECT
+		extends Structure
+	{
+		public int left;
+		public int top;
+		public int right;
+		public int bottom;
+
+		public MyRECT( Pointer pointer ) {
+			super( pointer );
+			read();
+		}
+	}
+
 	//---- class MENUITEMINFO -------------------------------------------------
 
 	@FieldOrder( { "cbSize", "fMask", "fType", "fState", "wID", "hSubMenu",

flatlaf-natives/flatlaf-natives-windows/README.md

@@ -19,3 +19,32 @@ The DLLs were built on a GitHub server with the help of GitHub Actions. See:
 [Native Libraries](https://github.com/JFormDesigner/FlatLaf/actions/workflows/natives.yml)
 workflow. Then the produced Artifacts ZIP was downloaded, signed DLLs with
 FormDev Software code signing certificate and committed the DLLs to Git.
+
+
+## Development
+
+To build the library on Windows using Gradle, (parts of)
+[Visual Studio Community
+2022](https://visualstudio.microsoft.com/downloads/)
+needs to be installed. After downloading and running `VisualStudioSetup.exe` the
+**Visual Studio Installer** is installed and started. Once running, it shows the
+**Workloads** tab that allows you to install additional packages. Either choose
+**Desktop development with C++**, or to save some disk space switch to the
+**Single Components** tab and choose following components (newest versions):
+
+- MSVC v143 - VS 2022 C++ x64/x86 Buildtools
+- MSVC v143 - VS 2022 C++ ARM64/ARM64EC Buildtools
+- Windows 11 SDK
+
+Note that the Visual Studio Installer shows many similar named components for
+MSVC. Make sure to choose exactly those components listed above.
+
+Using
+[Build Tools for Visual Studio 2022](https://visualstudio.microsoft.com/downloads/#remote-tools-for-visual-studio-2022)
+(installs only compiler and SDKs) instead of
+[Visual Studio Community
+2022](https://visualstudio.microsoft.com/downloads/)
+does not work with Gradle.
+
+[Visual Studio Code](https://code.visualstudio.com/) with **C/C++** extension
+can be used for C++ code editing.

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

@@ -288,6 +288,23 @@ LRESULT CALLBACK FlatWndProc::WindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, L
 				isMoving = true;
 			break;
 
+		case WM_DPICHANGED: {
+			LRESULT lResult = ::CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+
+			// if window is maximized and DPI/scaling changed, then Windows
+			// does not send a subsequent WM_SIZE message and Java window bounds,
+			// which depend on scale factor, are not updated
+			bool isMaximized = ::IsZoomed( hwnd );
+			if( isMaximized ) {
+				RECT* r = reinterpret_cast<RECT*>( lParam );
+				int width = r->right - r->left;
+				int height = r->bottom - r->top;
+				::CallWindowProc( defaultWndProc, hwnd, WM_SIZE, SIZE_MAXIMIZED, MAKELPARAM( width, height ) );
+			}
+
+			return lResult;
+		}
+
 		case WM_ERASEBKGND:
 			// do not erase background while the user is moving the window,
 			// otherwise there may be rendering artifacts on HiDPI screens with Java 9+