Linux: use X11 window manager events to move window and to show window menu (right-click on window title bar), if custom window decorations are enabled (issue #482)

flatlaf-natives/flatlaf-natives-linux/README.md

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+FlatLaf Linux Native Library
+============================
+
+This sub-project contains the source code for the FlatLaf Linux native library.
+
+The native library can be built only on Linux and requires a C++ compiler.
+
+To be able to build FlatLaf on any platform, and without C++ compiler, the
+pre-built native library is checked into Git at
+[flatlaf-core/src/main/resources/com/formdev/flatlaf/natives/](https://github.com/JFormDesigner/FlatLaf/tree/main/flatlaf-core/src/main/resources/com/formdev/flatlaf/natives).
+
+The native library was 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 and the native library
+checked into Git.
+
+
+## Development
+
+To build the library on Linux, some packages needs to be installed.
+
+
+### Ubuntu
+
+`build-essential` contains GCC and development tools. `libxt-dev` contains the
+X11 toolkit development headers.
+
+~~~
+sudo apt update
+sudo apt install build-essential libxt-dev
+~~~
+
+
+### CentOS
+
+~~~
+sudo yum install libXt-devel
+~~~

flatlaf-natives/flatlaf-natives-linux/build.gradle.kts

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+/*
+ * Copyright 2022 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.
+ */
+
+plugins {
+	`cpp-library`
+	`flatlaf-cpp-library`
+	`flatlaf-jni-headers`
+}
+
+flatlafJniHeaders {
+	headers = listOf( "com_formdev_flatlaf_ui_FlatNativeLinuxLibrary.h" )
+}
+
+library {
+	targetMachines.set( listOf( machines.linux.x86_64 ) )
+}
+
+var javaHome = System.getProperty( "java.home" )
+if( javaHome.endsWith( "jre" ) )
+	javaHome += "/.."
+
+tasks {
+	register( "build-natives" ) {
+		group = "build"
+		description = "Builds natives"
+
+		if( org.gradle.internal.os.OperatingSystem.current().isLinux )
+			dependsOn( "linkRelease" )
+	}
+
+	withType<CppCompile>().configureEach {
+		onlyIf { name.contains( "Release" ) }
+
+		// generate and copy needed JNI headers
+		dependsOn( "jni-headers" )
+
+		includes.from(
+			"${javaHome}/include",
+			"${javaHome}/include/linux"
+		)
+
+		compilerArgs.addAll( toolChain.map {
+			when( it ) {
+				is Gcc, is Clang -> listOf()
+				else -> emptyList()
+			}
+		} )
+	}
+
+	withType<LinkSharedLibrary>().configureEach {
+		onlyIf { name.contains( "Release" ) }
+
+		val nativesDir = project( ":flatlaf-core" ).projectDir.resolve( "src/main/resources/com/formdev/flatlaf/natives" )
+		val libraryName = "libflatlaf-linux-x86_64.so"
+		val jawt = "jawt"
+		var jawtPath = "${javaHome}/lib"
+		if( JavaVersion.current() == JavaVersion.VERSION_1_8 )
+			jawtPath += "/amd64"
+
+		linkerArgs.addAll( toolChain.map {
+			when( it ) {
+				is Gcc, is Clang -> listOf( "-L${jawtPath}", "-l${jawt}" )
+				else -> emptyList()
+			}
+		} )
+
+		doLast {
+			// copy shared library to flatlaf-core resources
+			copy {
+				from( linkedFile )
+				into( nativesDir )
+				rename( "libflatlaf-natives-linux.so", libraryName )
+			}
+		}
+	}
+}

flatlaf-natives/flatlaf-natives-linux/src/main/cpp/X11WmUtils.cpp

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+/*
+ * Copyright 2022 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 <jawt.h>
+#include <linux/jawt_md.h>
+#include <X11/Xatom.h>
+#include "com_formdev_flatlaf_ui_FlatNativeLinuxLibrary.h"
+
+/**
+ * @author Karl Tauber
+ * @since 2.5
+ */
+
+
+bool sendEvent( JNIEnv *env, jobject window, const char *atom_name,
+	long data0, long data1, long data2, long data3, long data4 );
+bool isWMHintSupported( Display* display, Window rootWindow, Atom atom );
+Window getWindowHandle( JNIEnv* env, JAWT* awt, jobject window, Display** display_return );
+
+
+//---- JNI methods ------------------------------------------------------------
+
+/**
+ * Send _NET_WM_MOVERESIZE to window to initiate moving or resizing.
+ *
+ * https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#idm45446104441728
+ * https://gitlab.gnome.org/GNOME/gtk/-/blob/main/gdk/x11/gdksurface-x11.c#L3841-3881
+ */
+extern "C"
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xMoveOrResizeWindow
+	( JNIEnv *env, jclass cls, jobject window, jint x, jint y, jint direction )
+{
+	return sendEvent( env, window,
+		"_NET_WM_MOVERESIZE",
+		x,
+		y,
+		direction,
+		Button1,		// left mouse button
+		1 );			// source indication
+}
+
+/**
+ * Send _GTK_SHOW_WINDOW_MENU to window to show system window menu.
+ *
+ * https://docs.gtk.org/gdk3/method.Window.show_window_menu.html
+ * https://gitlab.gnome.org/GNOME/gtk/-/blob/main/gdk/x11/gdksurface-x11.c#L4751-4801
+ */
+extern "C"
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xShowWindowMenu
+	( JNIEnv *env, jclass cls, jobject window, jint x, jint y )
+{
+	// TODO pass useful value for (input?) devide id ?
+	//
+	// not used in Mutter and Metacity window manager (but maybe in other WMs?): 
+	//     https://github.com/GNOME/mutter/blob/5e5480e620ed5b307902d913f89f5937cc01a28f/src/x11/window-x11.c#L3437
+	//     https://github.com/GNOME/metacity/blob/7c1cc3ca1d8131499b9cf2ef50b295602ffd6112/src/core/window.c#L5699
+	// not used in KWin:
+	//     https://github.com/KDE/kwin/blob/7e1617c2808b7c9b23a8c786327fc88212e10b32/src/netinfo.cpp#L222
+
+	return sendEvent( env, window,
+		"_GTK_SHOW_WINDOW_MENU",
+		0,				//TODO device id
+		x,
+		y,
+		0,
+		0 );
+}
+
+bool sendEvent( JNIEnv *env, jobject window, const char *atom_name,
+	long data0, long data1, long data2, long data3, long data4 )
+{
+	// get the AWT
+	JAWT awt;
+	awt.version = JAWT_VERSION_1_4;
+	if( !JAWT_GetAWT( env, &awt ) )
+		return false;
+
+	// get Xlib window and display from AWT window
+	Display* display;
+	Window w = getWindowHandle( env, &awt, window, &display );
+	if( w == 0 )
+		return false;
+
+	awt.Lock( env );
+
+	Window rootWindow = XDefaultRootWindow( display );
+
+	// check whether window manager supports message
+	Atom atom = XInternAtom( display, atom_name, false );
+	if( !isWMHintSupported( display, rootWindow, atom ) ) {
+		awt.Unlock( env );
+		return false;
+	}
+
+	// ungrab (mouse) pointer and keyboard to allow the window manager to grab them
+	XUngrabPointer( display, CurrentTime );
+	XUngrabKeyboard( display, CurrentTime );
+
+	// build event structure
+	XClientMessageEvent xclient = { 0 };
+	xclient.type = ClientMessage;
+	xclient.window = w;
+	xclient.message_type = atom;
+	xclient.format = 32;
+	xclient.data.l[0] = data0;
+	xclient.data.l[1] = data1;
+	xclient.data.l[2] = data2;
+	xclient.data.l[3] = data3;
+	xclient.data.l[4] = data4;
+
+	// send event
+	XSendEvent( display, rootWindow, False,
+		SubstructureRedirectMask | SubstructureNotifyMask,
+		(XEvent*) &xclient );
+
+	awt.Unlock( env );
+	return true;
+}
+
+
+bool isWMHintSupported( Display* display, Window rootWindow, Atom atom ) {
+	Atom type;
+	int format;
+	unsigned long n_atoms;
+	unsigned long bytes_after;
+	Atom* atoms;
+
+	// get all supported hints
+	XGetWindowProperty( display, rootWindow,
+		XInternAtom( display, "_NET_SUPPORTED", false ),
+		0, 0xffff, False, XA_ATOM,
+		&type, &format, &n_atoms, &bytes_after, (unsigned char**) &atoms );
+
+	if( atoms == NULL )
+		return false;
+
+	if( type != XA_ATOM ) {
+		XFree( atoms );
+		return false;
+	}
+
+	bool supported = false;
+	for( int i = 0; i < n_atoms; i++ ) {
+		if( atoms[i] == atom ) {
+			supported = true;
+			break;
+		}
+	}
+
+	XFree( atoms );
+	return supported;
+}
+
+Window getWindowHandle( JNIEnv* env, JAWT* awt, jobject window, Display** display_return ) {
+	jawt_DrawingSurface* ds = awt->GetDrawingSurface( env, window );
+	if( ds == NULL )
+		return 0;
+
+	jint lock = ds->Lock( ds );
+	if( (lock & JAWT_LOCK_ERROR) != 0 ) {
+		awt->FreeDrawingSurface( ds );
+		return 0;
+	}
+
+	JAWT_DrawingSurfaceInfo* dsi = ds->GetDrawingSurfaceInfo( ds );
+	JAWT_X11DrawingSurfaceInfo* xdsi = (JAWT_X11DrawingSurfaceInfo*) dsi->platformInfo;
+
+	Window handle = xdsi->drawable;
+	*display_return = xdsi->display;
+
+	ds->FreeDrawingSurfaceInfo( dsi );
+	ds->Unlock( ds );
+	awt->FreeDrawingSurface( ds );
+
+	return handle;
+}

flatlaf-natives/flatlaf-natives-linux/src/main/headers/com_formdev_flatlaf_ui_FlatNativeLinuxLibrary.h

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+/* DO NOT EDIT THIS FILE - it is machine generated */
+#include <jni.h>
+/* Header for class com_formdev_flatlaf_ui_FlatNativeLinuxLibrary */
+
+#ifndef _Included_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
+#define _Included_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
+#ifdef __cplusplus
+extern "C" {
+#endif
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_MOVE
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_MOVE 8L
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
+ * Method:    xMoveOrResizeWindow
+ * Signature: (Ljava/awt/Window;III)Z
+ */
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xMoveOrResizeWindow
+  (JNIEnv *, jclass, jobject, jint, jint, jint);
+
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
+ * Method:    xShowWindowMenu
+ * Signature: (Ljava/awt/Window;II)Z
+ */
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xShowWindowMenu
+  (JNIEnv *, jclass, jobject, jint, jint);
+
+#ifdef __cplusplus
+}
+#endif
+#endif