Native window decorations: initial implementation in C++ using JNI

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

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2021 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.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <windows.h>
+
+/**
+ * @author Karl Tauber
+ */
+class FlatWndProc
+{
+public:
+	static HWND install( JNIEnv *env, jobject obj, jobject window );
+	static void uninstall( JNIEnv *env, jobject obj, HWND hwnd );
+
+private:
+	static int initialized;
+	static jmethodID onNcHitTestMID;
+	static jmethodID isFullscreenMID;
+	static jmethodID fireStateChangedLaterOnceMID;
+
+	static std::map<HWND, FlatWndProc*> hwndMap;
+
+	JavaVM* jvm;
+	JNIEnv* env; // attached to AWT-Windows/Win32 thread
+	jobject obj;
+	HWND hwnd;
+	WNDPROC defaultWndProc;
+
+	FlatWndProc();
+	static void initIDs( JNIEnv *env, jobject obj );
+	void updateFrame();
+
+	static LRESULT CALLBACK StaticWindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT CALLBACK WindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmDestroy( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmNcCalcSize( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmNcHitTest( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+
+	int getResizeHandleHeight();
+	bool hasAutohideTaskbar( UINT edge, RECT rcMonitor );
+	BOOL isFullscreen();
+	int onNcHitTest( int x, int y, boolean isOnResizeBorder );
+	void fireStateChangedLaterOnce();
+	JNIEnv* getEnv();
+
+	void openSystemMenu( HWND hwnd, int x, int y );
+	void setMenuItemState( HMENU systemMenu, int item, bool enabled );
+
+	static HWND getWindowHandle( JNIEnv* env, jobject window );
+};