Initial prototype for taking screenshots with GTK4 #874

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/GDK.java

@@ -29,7 +29,7 @@ public class GDK extends Native {
 
 	static {
 		if (isGtk4()) {
-			GDK = SymbolLookup.libraryLookup("libgdk-4.so.0", Arena.ofAuto());
+			GDK = GTK.GTK;
 		} else {
 			GDK = SymbolLookup.libraryLookup("libgdk-3.so.0", Arena.ofAuto());
 		}

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/GObject.java

@@ -0,0 +1,22 @@
+package org.eclipse.wb.internal.os.linux;
+
+import java.lang.foreign.MemorySegment;
+
+/**
+ * The base type system and object class
+ */
+public class GObject {
+	private final MemorySegment segment;
+
+	protected GObject(long handle) {
+		this(handle == 0L ? MemorySegment.NULL : MemorySegment.ofAddress(handle));
+	}
+
+	protected GObject(MemorySegment segment) {
+		this.segment = segment;
+	}
+
+	public MemorySegment segment() {
+		return segment;
+	}
+}

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/GTK.java

@@ -26,7 +26,7 @@ public abstract class GTK extends Native {
 
 	static {
 		if (isGtk4()) {
-			GTK = SymbolLookup.libraryLookup("libgtk-4.so.0", Arena.ofAuto());
+			GTK = SymbolLookup.libraryLookup("libgtk-4.so.1", Arena.ofAuto());
 		} else {
 			GTK = SymbolLookup.libraryLookup("libgtk-3.so.0", Arena.ofAuto());
 		}

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/GtkWidget.java

@@ -16,33 +16,27 @@
 
 import org.eclipse.swt.widgets.Widget;
 
-import java.lang.foreign.MemorySegment;
 import java.util.Objects;
 
 /**
  * GtkWidget is the base class all widgets in GTK+ derive from. It manages the
  * widget lifecycle, states and style.
  */
-public class GtkWidget {
-	private final MemorySegment segment;
+public class GtkWidget extends GObject {
 
 	protected GtkWidget(long handle) {
-		segment = handle == 0L ? MemorySegment.NULL : MemorySegment.ofAddress(handle);
-	}
-
-	public MemorySegment segment() {
-		return segment;
+		super(handle);
 	}
 
 	@Override
 	public int hashCode() {
-		return Objects.hash(segment.address());
+		return Objects.hash(segment().address());
 	}
 
 	@Override
 	public boolean equals(Object o) {
 		if (o instanceof GtkWidget other) {
-			return segment.address() == other.segment.address();
+			return segment().address() == other.segment().address();
 		}
 		return false;
 	}

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/OS.java

@@ -0,0 +1,40 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Patrick Ziegler and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * https://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Patrick Ziegler - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.wb.internal.os.linux;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.SymbolLookup;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+
+/**
+ * This class contains native functions for various libraries.
+ */
+public class OS extends Native {
+
+	protected static final SymbolLookup GOBJECT;
+
+	static {
+		GOBJECT = SymbolLookup.libraryLookup("libgobject-2.0.so.0", Arena.ofAuto());
+	}
+
+	private static class InstanceHolder {
+		private static final MethodHandle g_object_unref = createHandle(GOBJECT, "g_object_unref",
+				FunctionDescriptor.ofVoid(ValueLayout.ADDRESS));
+	}
+
+	public static void g_object_unref(GObject object) {
+		runSafe(() -> InstanceHolder.g_object_unref.invoke(object.segment()));
+	}
+}

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/OSSupportLinux.java

@@ -17,6 +17,7 @@
 import org.eclipse.wb.internal.os.linux.gtk3.GTK3;
 import org.eclipse.wb.internal.os.linux.gtk3.GTK3ScreenshotMaker;
 import org.eclipse.wb.internal.os.linux.gtk3.GtkWindow;
+import org.eclipse.wb.internal.os.linux.gtk4.GTK4ScreenshotMaker;
 import org.eclipse.wb.internal.swt.VisualDataMockupProvider;
 import org.eclipse.wb.os.OSSupport;
 
@@ -44,7 +45,7 @@
 public final class OSSupportLinux extends OSSupport {
 	private static Version SWT_VERSION_3_126 = new Version(3, 126, 0);
 	private final VisualDataMockupProvider mockupProvider = new VisualDataMockupProvider();
-	private final ScreenshotMaker screenshotMaker = new GTK3ScreenshotMaker();
+	private final ScreenshotMaker screenshotMaker = GTK.isGtk4() ? new GTK4ScreenshotMaker() : new GTK3ScreenshotMaker();
 	private Shell m_eclipseShell;
 
 	////////////////////////////////////////////////////////////////////////////

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/ScreenshotMaker.java

@@ -26,6 +26,7 @@
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Widget;
 
 import java.lang.foreign.MemorySegment;
 import java.util.HashMap;
@@ -148,7 +149,30 @@ private void makeShots0(final Shell shell) {
 	 *                 model. Can be <code>null</code>.
 	 * @return the GdkPixmap* or cairo_surface_t* of {@link Shell}.
 	 */
-	protected abstract Image makeShot(Shell shell, BiConsumer<GtkWidget, Image> callback);
+	protected final Image makeShot(Shell shell, BiConsumer<GtkWidget, Image> callback) {
+		return traverse(shell, callback);
+	}
+
+	private Image traverse(Widget widget, BiConsumer<GtkWidget, Image> callback) {
+		Image image = getImageSurface(GtkWidget.from(widget), callback);
+		if (image == null) {
+			return null;
+		}
+		if (widget instanceof Composite composite) {
+			for (Control childWidget : composite.getChildren()) {
+				Image childImage = traverse(childWidget, callback);
+				if (childImage == null) {
+					continue;
+				}
+				if (callback == null) {
+					childImage.dispose();
+				}
+			}
+		}
+		return image;
+	}
+
+	protected abstract Image getImageSurface(GtkWidget widget, BiConsumer<GtkWidget, Image> callback);
 
 	private boolean bindImage(final Control control, final Image image) {
 		if (control.getData(OSSupport.WBP_NEED_IMAGE) != null && control.getData(OSSupport.WBP_IMAGE) == null) {

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/cairo/CairoContext.java

@@ -12,6 +12,10 @@
  *******************************************************************************/
 package org.eclipse.wb.internal.os.linux.cairo;
 
+import org.eclipse.wb.internal.core.utils.reflect.ReflectionUtils;
+
+import org.eclipse.swt.graphics.GC;
+
 import java.lang.foreign.MemorySegment;
 
 /**
@@ -22,5 +26,18 @@
  * and all drawing with cairo is always done to a cairo_t object.
  */
 public record CairoContext(MemorySegment segment) {
+	/**
+	 * Creates a new CairoContext instance associated with the GC object.
+	 *
+	 * @param gc The context to paint on.
+	 * @return The Cairo context backed by the given GC.
+	 */
+	public static CairoContext from(GC gc) {
+		long handle = getHandleValue(gc, "handle");
+		return new CairoContext(MemorySegment.ofAddress(handle));
+	}
 
+	private static long getHandleValue(GC gc, String fieldName) {
+		return ReflectionUtils.getFieldLong(gc, fieldName);
+	}
 }

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/gtk3/GTK3ScreenshotMaker.java

@@ -27,10 +27,6 @@
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Device;
 import org.eclipse.swt.graphics.Image;
-import org.eclipse.swt.widgets.Composite;
-import org.eclipse.swt.widgets.Control;
-import org.eclipse.swt.widgets.Shell;
-import org.eclipse.swt.widgets.Widget;
 
 import java.util.function.BiConsumer;
 
@@ -40,29 +36,6 @@
 public class GTK3ScreenshotMaker extends ScreenshotMaker {
 
 	@Override
-	protected Image makeShot(Shell shell, BiConsumer<GtkWidget, Image> callback) {
-		return traverse(shell, callback);
-	}
-
-	private Image traverse(Widget widget, BiConsumer<GtkWidget, Image> callback) {
-		Image image = getImageSurface(GtkWidget.from(widget), callback);
-		if (image == null) {
-			return null;
-		}
-		if (widget instanceof Composite composite) {
-			for (Control childWidget : composite.getChildren()) {
-				Image childImage = traverse(childWidget, callback);
-				if (childImage == null) {
-					continue;
-				}
-				if (callback == null) {
-					childImage.dispose();
-				}
-			}
-		}
-		return image;
-	}
-
 	protected Image getImageSurface(GtkWidget widget, BiConsumer<GtkWidget, Image> callback) {
 		GdkWindow window = GTK3.gtk_widget_get_window(widget);
 		if (!GDK3.gdk_window_is_visible(window)) {

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/gtk3/GdkWindow.java

@@ -12,11 +12,15 @@
  *******************************************************************************/
 package org.eclipse.wb.internal.os.linux.gtk3;
 
+import org.eclipse.wb.internal.os.linux.GObject;
+
 import java.lang.foreign.MemorySegment;
 
 /**
  * A GDK window.
  */
-public record GdkWindow(MemorySegment segment) {
-
+public class GdkWindow extends GObject {
+	protected GdkWindow(MemorySegment segment) {
+		super(segment);
+	}
 }

org.eclipse.wb.os.linux/src_java24/org/eclipse/wb/internal/os/linux/gtk4/GTK4.java

@@ -0,0 +1,119 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Patrick Ziegler and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * https://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Patrick Ziegler - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.wb.internal.os.linux.gtk4;
+
+import org.eclipse.wb.internal.os.linux.GTK;
+import org.eclipse.wb.internal.os.linux.GtkWidget;
+import org.eclipse.wb.internal.os.linux.cairo.CairoContext;
+
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+
+/**
+ * The GTK toolkit compatible with GTK 4.x
+ */
+public class GTK4 extends GTK {
+
+	private static class InstanceHolder {
+		private static final MethodHandle gtk_widget_get_height = createHandle(GTK, "gtk_widget_get_height",
+				FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS));
+
+		private static final MethodHandle gtk_widget_get_width = createHandle(GTK, "gtk_widget_get_width",
+				FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS));
+
+		private static final MethodHandle gtk_widget_paintable_new = createHandle(GTK, "gtk_widget_paintable_new",
+				FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.ADDRESS));
+
+		private static final MethodHandle gtk_snapshot_new = createHandle(GTK, "gtk_snapshot_new",
+				FunctionDescriptor.of(ValueLayout.ADDRESS));
+
+		private static final MethodHandle gtk_snapshot_free_to_node = createHandle(GTK, "gtk_snapshot_free_to_node",
+				FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.ADDRESS));
+
+		private static final MethodHandle gsk_render_node_draw = createHandle(GTK, "gsk_render_node_draw",
+				FunctionDescriptor.ofVoid(ValueLayout.ADDRESS, ValueLayout.ADDRESS));
+
+		private static final MethodHandle gsk_render_node_unref = createHandle(GTK, "gsk_render_node_unref",
+				FunctionDescriptor.ofVoid(ValueLayout.ADDRESS));
+
+		private static final MethodHandle gdk_paintable_snapshot = createHandle(GTK, "gdk_paintable_snapshot",
+				FunctionDescriptor.ofVoid(ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.JAVA_DOUBLE, ValueLayout.JAVA_DOUBLE));
+	}
+
+	/**
+	 * Returns the content height of the widget. This function returns the height
+	 * passed to its size-allocate implementation, which is the height you should be
+	 * using in <a href=
+	 * "https://docs.gtk.org/gtk4/vfunc.Widget.snapshot.html">Gtk.WidgetClass.snapshot</a>.
+	 *
+	 * For pointer events, see <a href=
+	 * "https://docs.gtk.org/gtk4/method.Widget.contains.html">gtk_widget_contains()</a>.
+	 *
+	 * To learn more about widget sizes, see the coordinate system <a
+	 * href="https://docs.gtk.org/gtk4/coordinates.html" overview</a>.
+	 *
+	 * @param widget
+	 * @return The height of {@code widget}.
+	 */
+	public static int gtk_widget_get_height(GtkWidget widget) {
+		return (int) callSafe(() -> InstanceHolder.gtk_widget_get_height.invoke(widget.segment()));
+	}
+
+	/**
+	 * Returns the content width of the widget. This function returns the width
+	 * passed to its size-allocate implementation, which is the width you should be
+	 * using in <a href=
+	 * "https://docs.gtk.org/gtk4/vfunc.Widget.snapshot.html">Gtk.WidgetClass.snapshot</a>.
+	 *
+	 * For pointer events, see <a href=
+	 * "https://docs.gtk.org/gtk4/method.Widget.contains.html">gtk_widget_contains()</a>.
+	 *
+	 * To learn more about widget sizes, see the coordinate system <a
+	 * href="https://docs.gtk.org/gtk4/coordinates.html" overview</a>.
+	 *
+	 * @param widget
+	 * @return The width of {@code widget}.
+	 */
+	public static int gtk_widget_get_width(GtkWidget widget) {
+		return (int) callSafe(() -> InstanceHolder.gtk_widget_get_width.invoke(widget.segment()));
+	}
+
+	public static GtkPaintable gtk_widget_paintable_new(GtkWidget widget) {
+		MemorySegment segment = (MemorySegment) callSafe(() -> InstanceHolder.gtk_widget_paintable_new.invoke(widget.segment()));
+		return new GtkPaintable(segment);
+	}
+
+	public static GtkSnapshot gtk_snapshot_new() {
+		MemorySegment segment = (MemorySegment) callSafe(() -> InstanceHolder.gtk_snapshot_new.invoke());
+		return new GtkSnapshot(segment);
+	}
+
+	public static GskRenderNode gtk_snapshot_free_to_node(GtkSnapshot snapshot) {
+		MemorySegment segment = (MemorySegment) callSafe(() -> InstanceHolder.gtk_snapshot_free_to_node.invoke(snapshot.segment()));
+		return new GskRenderNode(segment);
+	}
+
+	public static void gsk_render_node_draw(GskRenderNode node, CairoContext cr) {
+		runSafe(() -> InstanceHolder.gsk_render_node_draw.invoke(node.segment(), cr.segment()));
+	}
+
+	public static void gsk_render_node_unref(GskRenderNode node) {
+		runSafe(() -> InstanceHolder.gsk_render_node_unref.invoke(node.segment()));
+	}
+
+	public static void gdk_paintable_snapshot(GdkPaintable paintable, GdkSnapshot snapshot, double width, double height) {
+		runSafe(() -> InstanceHolder.gdk_paintable_snapshot.invoke(paintable.segment(), snapshot.segment(), width, height));
+	}
+}