System File Chooser: Linux: cross-compile native library for ARM64 on x86_64 Linux

.github/workflows/natives.yml

@@ -40,6 +40,19 @@ jobs:
               if: matrix.os == 'ubuntu'
               run: sudo apt install libgtk-3-dev
 
+            - name: Download libgtk-3.so for arm64
+              if: matrix.os == 'ubuntu'
+              working-directory: flatlaf-natives/flatlaf-natives-linux/lib/aarch64
+              run: |
+                pwd
+                ls -l /usr/lib/x86_64-linux-gnu/libgtk*
+                wget --no-verbose https://ports.ubuntu.com/pool/main/g/gtk%2b3.0/libgtk-3-0_3.24.18-1ubuntu1_arm64.deb
+                ls -l
+                ar -x libgtk-3-0_3.24.18-1ubuntu1_arm64.deb data.tar.xz
+                tar -xvf data.tar.xz --wildcards --to-stdout "./usr/lib/aarch64-linux-gnu/libgtk-3.so.0.*" > libgtk-3.so
+                rm libgtk-3-0_3.24.18-1ubuntu1_arm64.deb data.tar.xz
+                ls -l
+
             - name: install g++-aarch64-linux-gnu
               if: matrix.os == 'ubuntu'
               run: sudo apt install g++-aarch64-linux-gnu

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

@@ -49,6 +49,9 @@ public class FlatNativeLinuxLibrary
 		return SystemInfo.isLinux && FlatNativeLibrary.isLoaded( API_VERSION_LINUX );
 	}
 
+
+	//---- X Window System ----------------------------------------------------
+
 	// direction for _NET_WM_MOVERESIZE message
 	// see https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html
 	static final int MOVE = 8;
@@ -118,6 +121,28 @@ public class FlatNativeLinuxLibrary
 	}
 
 
+	//---- GTK ----------------------------------------------------------------
+
+	private static Boolean isGtk3Available;
+
+	/**
+	 * Checks whether GTK 3 is available.
+	 * Use this before invoking any native method that uses GTK.
+	 * Otherwise the app may terminate immediately if GTK is not installed.
+	 * <p>
+	 * This works because Java uses {@code dlopen(RTLD_LAZY)} to load JNI libraries,
+	 * which only resolves symbols as the code that references them is executed.
+	 *
+	 * @since 3.6
+	 */
+	public static boolean isGtk3Available() {
+		if( isGtk3Available == null )
+			isGtk3Available = isLibAvailable( "libgtk-3.so.0" ) || isLibAvailable( "libgtk-3.so" );
+		return isGtk3Available;
+	}
+
+	private native static boolean isLibAvailable( String libname );
+
 	/**
 	 * https://docs.gtk.org/gtk3/iface.FileChooser.html#properties
 	 *

flatlaf-core/src/main/java/com/formdev/flatlaf/util/SystemFileChooser.java

@@ -49,8 +49,8 @@ import com.formdev.flatlaf.ui.FlatNativeWindowsLibrary;
  * If there are no compile errors, then there is a good chance that it works without further changes.
  * If there are compile errors, then you're using a feature that {@code SystemFileChooser} does not support.
  * <p>
- * Supported platforms are <b>Windows 10+</b>, <b>macOS 10.14+</b> and <b>Linux GTK 3</b>.
+ * Supported platforms are <b>Windows 10+</b>, <b>macOS 10.14+</b> and <b>Linux with GTK 3</b>.
- * {@code JFileChooser} is used on unsupported platforms.
+ * {@code JFileChooser} is used on unsupported platforms or if GTK 3 is not installed.
  * <p>
  * {@code SystemFileChooser} requires FlatLaf native libraries (usually contained in flatlaf.jar).
  * If not available or disabled (via {@link FlatSystemProperties#USE_NATIVE_LIBRARY}
@@ -421,7 +421,7 @@ public class SystemFileChooser
 			return new WindowsFileChooserProvider();
 		else if( SystemInfo.isMacOS && FlatNativeMacLibrary.isLoaded() )
 			return new MacFileChooserProvider();
-		else if( SystemInfo.isLinux && FlatNativeLinuxLibrary.isLoaded() )
+		else if( SystemInfo.isLinux && FlatNativeLinuxLibrary.isLoaded() && FlatNativeLinuxLibrary.isGtk3Available() )
 			return new LinuxFileChooserProvider();
 		else // unknown platform or FlatLaf native library not loaded
 			return new SwingFileChooserProvider();

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

@@ -43,6 +43,16 @@ Only on x86_64 Linux for cross-compiling for arm64 architecture:
 sudo apt install g++-aarch64-linux-gnu
 ~~~
 
+Download `libgtk-3.so` for arm64 architecture:
+
+~~~
+cd flatlaf-natives/flatlaf-natives-linux/lib/aarch64
+wget --no-verbose https://ports.ubuntu.com/pool/main/g/gtk%2b3.0/libgtk-3-0_3.24.18-1ubuntu1_arm64.deb
+ar -x libgtk-3-0_3.24.18-1ubuntu1_arm64.deb data.tar.xz
+tar -xvf data.tar.xz --wildcards --to-stdout "./usr/lib/aarch64-linux-gnu/libgtk-3.so.0.*" > libgtk-3.so
+rm libgtk-3-0_3.24.18-1ubuntu1_arm64.deb data.tar.xz
+~~~
+
 
 ### Fedora
 

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

@@ -149,7 +149,20 @@ tasks {
 				"-I", "${javaHome}/include/linux",
 				"-I", "$include",
 
+				// for GTK
+				"-I", "/usr/include/gtk-3.0",
+				"-I", "/usr/include/glib-2.0",
+				"-I", "/usr/lib/x86_64-linux-gnu/glib-2.0/include",
+				"-I", "/usr/include/gdk-pixbuf-2.0",
+				"-I", "/usr/include/atk-1.0",
+				"-I", "/usr/include/cairo",
+				"-I", "/usr/include/pango-1.0",
+				"-I", "/usr/include/harfbuzz",
+
 				"$src/ApiVersion.cpp",
+				"$src/GtkFileChooser.cpp",
+				"$src/GtkMessageDialog.cpp",
+				"$src/JNIUtils.cpp",
 				"$src/X11WmUtils.cpp",
 			)
 		}
@@ -173,10 +186,14 @@ tasks {
 				"-o", "$outDir/$libraryName",
 
 				"$objDir/ApiVersion.o",
+				"$objDir/GtkFileChooser.o",
+				"$objDir/GtkMessageDialog.o",
+				"$objDir/JNIUtils.o",
 				"$objDir/X11WmUtils.o",
 
 				"-L${layout.projectDirectory}/lib/aarch64",
 				"-ljawt",
+				"-lgtk-3",
 			)
 
 			doLast {

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

@@ -17,6 +17,7 @@
 // avoid inlining of printf()
 #define _NO_CRT_STDIO_INLINE
 
+#include <dlfcn.h>
 #include "JNIUtils.h"
 
 /**
@@ -35,3 +36,19 @@ AutoReleaseStringUTF8::~AutoReleaseStringUTF8() {
 	if( chars != NULL )
 		env->ReleaseStringUTFChars( javaString, chars );
 }
+
+//---- JNI methods ------------------------------------------------------------
+
+extern "C"
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_isLibAvailable
+	( JNIEnv* env, jclass cls, jstring libname )
+{
+	AutoReleaseStringUTF8 clibname( env, libname );
+
+	void* lib = dlopen( clibname, RTLD_LAZY );
+	if( lib == NULL )
+		return false;
+
+	dlclose( lib );
+	return true;
+}

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

@@ -37,6 +37,14 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xM
 JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_xShowWindowMenu
   (JNIEnv *, jclass, jobject, jint, jint);
 
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
+ * Method:    isLibAvailable
+ * Signature: (Ljava/lang/String;)Z
+ */
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_isLibAvailable
+  (JNIEnv *, jclass, jstring);
+
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
  * Method:    showFileChooser

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

@@ -49,7 +49,7 @@ public class FlatSystemFileChooserLinuxTest
 			}
 
 			FlatTestFrame frame = FlatTestFrame.create( args, "FlatSystemFileChooserLinuxTest" );
-			addListeners( frame );
+//			addListeners( frame );
 			frame.showFrame( FlatSystemFileChooserLinuxTest::new );
 		} );
 	}
@@ -134,6 +134,8 @@ public class FlatSystemFileChooserLinuxTest
 			return true;
 		};
 
+		System.out.println( FlatNativeLinuxLibrary.isGtk3Available() );
+
 		if( direct ) {
 			String[] files = FlatNativeLinuxLibrary.showFileChooser( owner, open,
 				title, okButtonLabel, currentName, currentFolder,