Bug 540674: [GTK4] Adapt to new drawing model changes

Implement basic drawing support in SWT-GTK4 as a proof of concept. With
patch, Snippet182 draws the Link widget correctly.

Change-Id: I256108677f7962207a8eb3d3934979566423650e
Signed-off-by: Eric Williams <ericwill@redhat.com>

12 files changed, 292 insertions, 10 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
index cbaa819dc1..0da9bed84c 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corporation and others. All rights reserved.
+ * Copyright (c) 2000, 2019 IBM Corporation and others. All rights reserved.
  * The contents of this file are made available under the terms
  * of the GNU Lesser General Public License (LGPL) Version 2.1 that
  * accompanies this distribution (lgpl-v21.txt).  The LGPL is also
@@ -8820,6 +8820,18 @@ JNIEXPORT jintLong JNICALL GTK_NATIVE(_1gtk_1settings_1get_1default)
 }
 #endif
 
+#ifndef NO__1gtk_1snapshot_1append_1cairo
+JNIEXPORT jintLong JNICALL GTK_NATIVE(_1gtk_1snapshot_1append_1cairo)
+	(JNIEnv *env, jclass that, jintLong arg0, jintLong arg1)
+{
+	jintLong rc = 0;
+	GTK_NATIVE_ENTER(env, that, _1gtk_1snapshot_1append_1cairo_FUNC);
+	rc = (jintLong)gtk_snapshot_append_cairo((GtkSnapshot *)arg0, (const graphene_rect_t *)arg1);
+	GTK_NATIVE_EXIT(env, that, _1gtk_1snapshot_1append_1cairo_FUNC);
+	return rc;
+}
+#endif
+
 #ifndef NO__1gtk_1socket_1get_1id
 JNIEXPORT jintLong JNICALL GTK_NATIVE(_1gtk_1socket_1get_1id)
 	(JNIEnv *env, jclass that, jintLong arg0)
@@ -13024,6 +13036,16 @@ fail:
 }
 #endif
 
+#ifndef NO__1gtk_1widget_1snapshot_1child
+JNIEXPORT void JNICALL GTK_NATIVE(_1gtk_1widget_1snapshot_1child)
+	(JNIEnv *env, jclass that, jintLong arg0, jintLong arg1, jintLong arg2)
+{
+	GTK_NATIVE_ENTER(env, that, _1gtk_1widget_1snapshot_1child_FUNC);
+	gtk_widget_snapshot_child((GtkWidget *)arg0, (GtkWidget *)arg1, (GtkSnapshot *)arg2);
+	GTK_NATIVE_EXIT(env, that, _1gtk_1widget_1snapshot_1child_FUNC);
+}
+#endif
+
 #if (!defined(NO__1gtk_1widget_1style_1get__I_3B_3II) && !defined(JNI64)) || (!defined(NO__1gtk_1widget_1style_1get__J_3B_3IJ) && defined(JNI64))
 #ifndef JNI64
 JNIEXPORT void JNICALL GTK_NATIVE(_1gtk_1widget_1style_1get__I_3B_3II)(JNIEnv *env, jclass that, jintLong arg0, jbyteArray arg1, jintArray arg2, jintLong arg3)
@@ -13526,6 +13548,44 @@ JNIEXPORT void JNICALL GTK_NATIVE(_1gtk_1window_1unmaximize)
 }
 #endif
 
+#ifndef Graphene_NATIVE
+#define Graphene_NATIVE(func) Java_org_eclipse_swt_internal_gtk_Graphene_##func
+#endif
+
+#ifndef NO__1graphene_1rect_1alloc
+JNIEXPORT jintLong JNICALL Graphene_NATIVE(_1graphene_1rect_1alloc)
+	(JNIEnv *env, jclass that)
+{
+	jintLong rc = 0;
+	Graphene_NATIVE_ENTER(env, that, _1graphene_1rect_1alloc_FUNC);
+	rc = (jintLong)graphene_rect_alloc();
+	Graphene_NATIVE_EXIT(env, that, _1graphene_1rect_1alloc_FUNC);
+	return rc;
+}
+#endif
+
+#ifndef NO__1graphene_1rect_1free
+JNIEXPORT void JNICALL Graphene_NATIVE(_1graphene_1rect_1free)
+	(JNIEnv *env, jclass that, jintLong arg0)
+{
+	Graphene_NATIVE_ENTER(env, that, _1graphene_1rect_1free_FUNC);
+	graphene_rect_free((graphene_rect_t *)arg0);
+	Graphene_NATIVE_EXIT(env, that, _1graphene_1rect_1free_FUNC);
+}
+#endif
+
+#ifndef NO__1graphene_1rect_1init
+JNIEXPORT jintLong JNICALL Graphene_NATIVE(_1graphene_1rect_1init)
+	(JNIEnv *env, jclass that, jintLong arg0, jfloat arg1, jfloat arg2, jfloat arg3, jfloat arg4)
+{
+	jintLong rc = 0;
+	Graphene_NATIVE_ENTER(env, that, _1graphene_1rect_1init_FUNC);
+	rc = (jintLong)graphene_rect_init((graphene_rect_t *)arg0, arg1, arg2, arg3, arg4);
+	Graphene_NATIVE_EXIT(env, that, _1graphene_1rect_1init_FUNC);
+	return rc;
+}
+#endif
+
 #ifndef OS_NATIVE
 #define OS_NATIVE(func) Java_org_eclipse_swt_internal_gtk_OS_##func
 #endif
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.h b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.h
index 2676362c5c..c0c30a13a9 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.h
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.h
@@ -429,6 +429,15 @@
 #define NO__1gdk_1surface_1get_1root_1origin
 #define NO__1gdk_1surface_1invalidate_1region
 
+// No GtkSnapshot on GTK3
+#define NO__1gtk_1snapshot_1append_1cairo
+#define NO__1gtk_1widget_1snapshot_1child
+
+// No Graphene library on GTK3
+#define NO__1graphene_1rect_1alloc
+#define NO__1graphene_1rect_1free
+#define NO__1graphene_1rect_1init
+
 // Miscellaneous functions not present on GTK3
 #define NO__1gdk_1device_1warp__III
 #define NO__1gdk_1device_1warp__JII
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_custom.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_custom.c
index d46a299e88..1ca440b5b5 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_custom.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_custom.c
@@ -749,7 +749,6 @@ enum {
 static void swt_fixed_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
 static void swt_fixed_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
 static void swt_fixed_finalize (GObject *object);
-static void swt_fixed_realize (GtkWidget *widget);
 static void swt_fixed_map (GtkWidget *widget);
 static AtkObject *swt_fixed_get_accessible (GtkWidget *widget);
 static void swt_fixed_measure (GtkWidget *widget, GtkOrientation  orientation, int for_size, int *minimum,
@@ -920,6 +919,7 @@ static void swt_fixed_set_property (GObject *object, guint prop_id, const GValue
     }
 }
 
+/*
 static void swt_fixed_realize (GtkWidget *widget) {
 	GtkAllocation allocation;
 	GdkSurface *surface;
@@ -935,7 +935,7 @@ static void swt_fixed_realize (GtkWidget *widget) {
 	gtk_widget_set_surface(widget, surface);
 	gdk_surface_set_user_data (surface, widget);
 	return GTK_WIDGET_CLASS (swt_fixed_parent_class)->realize (widget);
-}
+}*/
 
 static void swt_fixed_map (GtkWidget *widget) {
 	SwtFixed *fixed = SWT_FIXED (widget);
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
index 42f35e0a5d..35bad2edca 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corporation and others. All rights reserved.
+ * Copyright (c) 2000, 2019 IBM Corporation and others. All rights reserved.
  * The contents of this file are made available under the terms
  * of the GNU Lesser General Public License (LGPL) Version 2.1 that
  * accompanies this distribution (lgpl-v21.txt).  The LGPL is also
@@ -793,6 +793,7 @@ char * GTK_nativeFunctionNames[] = {
 	"_1gtk_1separator_1tool_1item_1new",
 	"_1gtk_1separator_1tool_1item_1set_1draw",
 	"_1gtk_1settings_1get_1default",
+	"_1gtk_1snapshot_1append_1cairo",
 	"_1gtk_1socket_1get_1id",
 	"_1gtk_1socket_1new",
 	"_1gtk_1spin_1button_1configure",
@@ -1173,6 +1174,7 @@ char * GTK_nativeFunctionNames[] = {
 #else
 	"_1gtk_1widget_1size_1allocate__JLorg_eclipse_swt_internal_gtk_GtkAllocation_2I",
 #endif
+	"_1gtk_1widget_1snapshot_1child",
 #ifndef JNI64
 	"_1gtk_1widget_1style_1get__I_3B_3II",
 #else
@@ -1249,6 +1251,38 @@ JNIEXPORT jint JNICALL STATS_NATIVE(GTK_1GetFunctionCallCount)
 #endif
 #ifdef NATIVE_STATS
 
+char * Graphene_nativeFunctionNames[] = {
+	"_1graphene_1rect_1alloc",
+	"_1graphene_1rect_1free",
+	"_1graphene_1rect_1init",
+};
+#define NATIVE_FUNCTION_COUNT sizeof(Graphene_nativeFunctionNames) / sizeof(char*)
+int Graphene_nativeFunctionCount = NATIVE_FUNCTION_COUNT;
+int Graphene_nativeFunctionCallCount[NATIVE_FUNCTION_COUNT];
+
+#define STATS_NATIVE(func) Java_org_eclipse_swt_tools_internal_NativeStats_##func
+
+JNIEXPORT jint JNICALL STATS_NATIVE(Graphene_1GetFunctionCount)
+	(JNIEnv *env, jclass that)
+{
+	return Graphene_nativeFunctionCount;
+}
+
+JNIEXPORT jstring JNICALL STATS_NATIVE(Graphene_1GetFunctionName)
+	(JNIEnv *env, jclass that, jint index)
+{
+	return (*env)->NewStringUTF(env, Graphene_nativeFunctionNames[index]);
+}
+
+JNIEXPORT jint JNICALL STATS_NATIVE(Graphene_1GetFunctionCallCount)
+	(JNIEnv *env, jclass that, jint index)
+{
+	return Graphene_nativeFunctionCallCount[index];
+}
+
+#endif
+#ifdef NATIVE_STATS
+
 char * OS_nativeFunctionNames[] = {
 #ifndef JNI64
 	"Call__IIII",
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
index c0f9f3d9b5..47b18611bc 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corporation and others. All rights reserved.
+ * Copyright (c) 2000, 2019 IBM Corporation and others. All rights reserved.
  * The contents of this file are made available under the terms
  * of the GNU Lesser General Public License (LGPL) Version 2.1 that
  * accompanies this distribution (lgpl-v21.txt).  The LGPL is also
@@ -791,6 +791,7 @@ typedef enum {
 	_1gtk_1separator_1tool_1item_1new_FUNC,
 	_1gtk_1separator_1tool_1item_1set_1draw_FUNC,
 	_1gtk_1settings_1get_1default_FUNC,
+	_1gtk_1snapshot_1append_1cairo_FUNC,
 	_1gtk_1socket_1get_1id_FUNC,
 	_1gtk_1socket_1new_FUNC,
 	_1gtk_1spin_1button_1configure_FUNC,
@@ -1171,6 +1172,7 @@ typedef enum {
 #else
 	_1gtk_1widget_1size_1allocate__JLorg_eclipse_swt_internal_gtk_GtkAllocation_2I_FUNC,
 #endif
+	_1gtk_1widget_1snapshot_1child_FUNC,
 #ifndef JNI64
 	_1gtk_1widget_1style_1get__I_3B_3II_FUNC,
 #else
@@ -1221,6 +1223,26 @@ typedef enum {
 	_1gtk_1window_1unmaximize_FUNC,
 } GTK_FUNCS;
 #ifdef NATIVE_STATS
+extern int Graphene_nativeFunctionCount;
+extern int Graphene_nativeFunctionCallCount[];
+extern char* Graphene_nativeFunctionNames[];
+#define Graphene_NATIVE_ENTER(env, that, func) Graphene_nativeFunctionCallCount[func]++;
+#define Graphene_NATIVE_EXIT(env, that, func) 
+#else
+#ifndef Graphene_NATIVE_ENTER
+#define Graphene_NATIVE_ENTER(env, that, func) 
+#endif
+#ifndef Graphene_NATIVE_EXIT
+#define Graphene_NATIVE_EXIT(env, that, func) 
+#endif
+#endif
+
+typedef enum {
+	_1graphene_1rect_1alloc_FUNC,
+	_1graphene_1rect_1free_FUNC,
+	_1graphene_1rect_1init_FUNC,
+} Graphene_FUNCS;
+#ifdef NATIVE_STATS
 extern int OS_nativeFunctionCount;
 extern int OS_nativeFunctionCallCount[];
 extern char* OS_nativeFunctionNames[];
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_structs.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_structs.c
index 98a4547ba1..7ab62ec7d3 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_structs.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_structs.c
@@ -1171,7 +1171,7 @@ void setGtkTargetEntryFields(JNIEnv *env, jobject lpObject, GtkTargetEntry *lpSt
 typedef struct GtkWidgetClass_FID_CACHE {
 	int cached;
 	jclass clazz;
-	jfieldID map, size_allocate;
+	jfieldID map, size_allocate, snapshot;
 } GtkWidgetClass_FID_CACHE;
 
 GtkWidgetClass_FID_CACHE GtkWidgetClassFc;
@@ -1183,6 +1183,7 @@ void cacheGtkWidgetClassFields(JNIEnv *env, jobject lpObject)
 	GtkWidgetClassFc.clazz = (*env)->GetObjectClass(env, lpObject);
 	GtkWidgetClassFc.map = (*env)->GetFieldID(env, GtkWidgetClassFc.clazz, "map", I_J);
 	GtkWidgetClassFc.size_allocate = (*env)->GetFieldID(env, GtkWidgetClassFc.clazz, "size_allocate", I_J);
+	GtkWidgetClassFc.snapshot = (*env)->GetFieldID(env, GtkWidgetClassFc.clazz, "snapshot", I_J);
 	GtkWidgetClassFc.cached = 1;
 }
 
@@ -1192,6 +1193,9 @@ GtkWidgetClass *getGtkWidgetClassFields(JNIEnv *env, jobject lpObject, GtkWidget
 	getGObjectClassFields(env, lpObject, (GObjectClass *)lpStruct);
 	lpStruct->map = (void(*)())(*env)->GetIntLongField(env, lpObject, GtkWidgetClassFc.map);
 	lpStruct->size_allocate = (void(*)())(*env)->GetIntLongField(env, lpObject, GtkWidgetClassFc.size_allocate);
+#ifdef GTK4
+	lpStruct->snapshot = (void(*)())(*env)->GetIntLongField(env, lpObject, GtkWidgetClassFc.snapshot);
+#endif
 	return lpStruct;
 }
 
@@ -1201,6 +1205,9 @@ void setGtkWidgetClassFields(JNIEnv *env, jobject lpObject, GtkWidgetClass *lpSt
 	setGObjectClassFields(env, lpObject, (GObjectClass *)lpStruct);
 	(*env)->SetIntLongField(env, lpObject, GtkWidgetClassFc.map, (jintLong)lpStruct->map);
 	(*env)->SetIntLongField(env, lpObject, GtkWidgetClassFc.size_allocate, (jintLong)lpStruct->size_allocate);
+#ifdef GTK4
+	(*env)->SetIntLongField(env, lpObject, GtkWidgetClassFc.snapshot, (jintLong)lpStruct->snapshot);
+#endif
 }
 #endif
 
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GTK.java b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GTK.java
index 06ee6453d3..628c5fd7b0 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GTK.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GTK.java
@@ -5748,6 +5748,20 @@ public class GTK extends OS {
 		}
 	}
 	/**
+	 * @param snapshot cast=(GtkSnapshot *)
+	 * @param rect cast=(const graphene_rect_t *)
+	 */
+	public static final native long /*int*/ _gtk_snapshot_append_cairo(long /*int*/ snapshot, long /*int*/ rect);
+	/** [GTK4 only, if-def'd in os.h] */
+	public static final long /*int*/ gtk_snapshot_append_cairo(long /*int*/ snapshot, long /*int*/ rect) {
+		lock.lock();
+		try {
+			 return _gtk_snapshot_append_cairo(snapshot, rect);
+		} finally {
+			lock.unlock();
+		}
+	}
+	/**
 	 * @param handle cast=(GtkStatusIcon*)
 	 * @param screen cast=(GdkScreen**)
 	 * @param area cast=(GdkRectangle*)
@@ -9505,4 +9519,19 @@ public class GTK extends OS {
 			lock.unlock();
 		}
 	}
+	/**
+	 * @param widget cast=(GtkWidget *)
+	 * @param child cast=(GtkWidget *)
+	 * @param snapshot cast=(GtkSnapshot *)
+	 */
+	public static final native void _gtk_widget_snapshot_child(long /*int*/ widget, long /*int*/ child, long /*int*/ snapshot);
+	/** [GTK4 only, if-def'd in os.h] */
+	public static final void gtk_widget_snapshot_child(long /*int*/ widget, long /*int*/ child, long /*int*/ snapshot) {
+		lock.lock();
+		try {
+			_gtk_widget_snapshot_child(widget,child,snapshot);
+		} finally {
+			lock.unlock();
+		}
+	}
 }
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/Graphene.java b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/Graphene.java
new file mode 100644
index 0000000000..276b1d66de
--- /dev/null
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/Graphene.java
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Red Hat Inc. and others. All rights reserved.
+ * The contents of this file are made available under the terms
+ * of the GNU Lesser General Public License (LGPL) Version 2.1 that
+ * accompanies this distribution (lgpl-v21.txt).  The LGPL is also
+ * available at http://www.gnu.org/licenses/lgpl.html.  If the version
+ * of the LGPL at http://www.gnu.org is different to the version of
+ * the LGPL accompanying this distribution and there is any conflict
+ * between the two license versions, the terms of the LGPL accompanying
+ * this distribution shall govern.
+ *
+ * Contributors:
+ *     Red Hat Inc. - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.internal.gtk;
+
+/**
+ * This class contains Graphene specific native functions. Please note this library is only relevant
+ * for GTK4 and above.
+ *
+ * In contrast to OS.java, dynamic functions are automatically linked, no need to add os_custom.h entries.
+ */
+public class Graphene extends OS {
+
+	public static final native long /*int*/ _graphene_rect_alloc();
+	/** [GTK4 only, if-def'd in os.h] */
+	public static final long /*int*/ graphene_rect_alloc() {
+		lock.lock();
+		try {
+			return _graphene_rect_alloc();
+		} finally {
+			lock.unlock();
+		}
+	}
+	/**
+	 * @param rectangle cast=(graphene_rect_t *)
+	 */
+	public static final native void _graphene_rect_free(long /*int*/ rectangle);
+	/** [GTK4 only, if-def'd in os.h] */
+	public static final void graphene_rect_free(long /*int*/ rectangle) {
+		lock.lock();
+		try {
+			_graphene_rect_free(rectangle);
+		} finally {
+			lock.unlock();
+		}
+	}
+	/**
+	 * @param rectangle cast=(graphene_rect_t *)
+	 */
+	public static final native long /*int*/ _graphene_rect_init(long /*int*/ rectangle, float x, float y, float width, float height);
+	/** [GTK4 only, if-def'd in os.h] */
+	public static final long /*int*/ graphene_rect_init(long /*int*/ rectangle, float x, float y, float width, float height) {
+		lock.lock();
+		try {
+			return _graphene_rect_init(rectangle, x, y, width, height);
+		} finally {
+			lock.unlock();
+		}
+	}
+}
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GtkWidgetClass.java b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GtkWidgetClass.java
index 51e04b41f0..64b25b6dab 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GtkWidgetClass.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GtkWidgetClass.java
@@ -20,4 +20,6 @@ public class GtkWidgetClass extends GObjectClass {
 	public long /*int*/ map;
 	/** @field cast=(void(*)()) */
 	public long /*int*/ size_allocate;
+	/** @field cast=(void(*)()),exclude=#ifdef GTK4 */
+	public long /*int*/ snapshot;
 }
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
index 799ee5e0c7..9f265d8c97 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
@@ -163,11 +163,18 @@ public Control (Composite parent, int style) {
 void connectPaint () {
 	long /*int*/ paintHandle = paintHandle ();
 	int paintMask = GDK.GDK_EXPOSURE_MASK;
-	if (!GTK.GTK4) GTK.gtk_widget_add_events (paintHandle, paintMask);
-
-	OS.g_signal_connect_closure_by_id (paintHandle, display.signalIds [DRAW], 0, display.getClosure (EXPOSE_EVENT_INVERSE), false);
+	if (GTK.GTK4 && (hooksPaint() || drawRegion)) {
+		long /*int*/ widgetClass = GTK.GTK_WIDGET_GET_CLASS(paintHandle);
+		GtkWidgetClass widgetClassStruct = new GtkWidgetClass ();
+		OS.memmove(widgetClassStruct, widgetClass);
+		widgetClassStruct.snapshot = display.snapshotDrawProc;
+		OS.memmove(widgetClass, widgetClassStruct);
+	} else {
+		GTK.gtk_widget_add_events (paintHandle, paintMask);
+		OS.g_signal_connect_closure_by_id (paintHandle, display.signalIds [DRAW], 0, display.getClosure (EXPOSE_EVENT_INVERSE), false);
 
-	OS.g_signal_connect_closure_by_id (paintHandle, display.signalIds [DRAW], 0, display.getClosure (DRAW), true);
+		OS.g_signal_connect_closure_by_id (paintHandle, display.signalIds [DRAW], 0, display.getClosure (DRAW), true);
+	}
 }
 
 Font defaultFont () {
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
index 32a101c4ea..1d5dc12a09 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
@@ -126,7 +126,9 @@ public class Display extends Device {
 	int [] max_priority = new int [1], timeout = new int [1];
 	Callback eventCallback;
 	long /*int*/ eventProc, windowProc2, windowProc3, windowProc4, windowProc5, windowProc6;
+	long /*int*/ snapshotDrawProc;
 	Callback windowCallback2, windowCallback3, windowCallback4, windowCallback5, windowCallback6;
+	Callback snapshotDraw;
 	EventTable eventTable, filterTable;
 	static String APP_NAME = "SWT"; //$NON-NLS-1$
 	static String APP_VERSION = ""; //$NON-NLS-1$
@@ -1474,6 +1476,13 @@ static long /*int*/ rendererClassInitProc (long /*int*/ g_class, long /*int*/ cl
 	return 0;
 }
 
+static long /*int*/ snapshotDrawProc (long /*int*/ handle, long /*int*/ snapshot) {
+	Display display = getCurrent ();
+	Widget widget = display.getWidget (handle);
+	widget.snapshotToDraw(handle, snapshot);
+	return 0;
+}
+
 static long /*int*/ rendererGetPreferredWidthProc (long /*int*/ cell, long /*int*/ handle, long /*int*/ minimun_size, long /*int*/ natural_size) {
 	Display display = getCurrent ();
 	Widget widget = display.getWidget (handle);
@@ -3577,6 +3586,12 @@ void initializeCallbacks () {
 	signalIds [Widget.UNREALIZE] = OS.g_signal_lookup (OS.realize, GTK.GTK_TYPE_WIDGET ());
 	signalIds [Widget.WINDOW_STATE_EVENT] = OS.g_signal_lookup (OS.window_state_event, GTK.GTK_TYPE_WIDGET ());
 
+	if (GTK.GTK4) {
+		snapshotDraw = new Callback (getClass (), "snapshotDrawProc", 2); //$NON-NLS-1$
+		snapshotDrawProc = snapshotDraw.getAddress ();
+		if (snapshotDrawProc == 0) error (SWT.ERROR_NO_MORE_CALLBACKS);
+	}
+
 	windowCallback2 = new Callback (this, "windowProc", 2); //$NON-NLS-1$
 	windowProc2 = windowCallback2.getAddress ();
 	if (windowProc2 == 0) error (SWT.ERROR_NO_MORE_CALLBACKS);
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Widget.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Widget.java
index d424355e8a..1e17cd3a2d 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Widget.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Widget.java
@@ -1197,6 +1197,19 @@ void postEvent (int eventType, Event event) {
 	sendEvent (eventType, event, false);
 }
 
+void propagateSnapshot (long /*int*/ widget, long /*int*/ snapshot) {
+	long /*int*/ list = GTK.gtk_container_get_children (widget);
+	long /*int*/ temp = list;
+	while (temp != 0) {
+		long /*int*/ child = OS.g_list_data (temp);
+		if (child != 0) {
+			GTK.gtk_widget_snapshot_child(widget, child, snapshot);
+		}
+		temp = OS.g_list_next (temp);
+	}
+	OS.g_list_free (list);
+}
+
 void register () {
 	if (handle == 0) return;
 	if ((state & HANDLE) != 0) display.addWidget (handle, this);
@@ -1785,6 +1798,29 @@ long /*int*/ sizeRequestProc (long /*int*/ handle, long /*int*/ arg0, long /*int
 	return 0;
 }
 
+/**
+ * Converts an incoming snapshot into a gtk_draw() call, complete with
+ * a Cairo context.
+ *
+ * @param handle the widget receiving the snapshot
+ * @param snapshot the actual GtkSnapshot
+ */
+void snapshotToDraw (long /*int*/ handle, long /*int*/ snapshot) {
+	GtkAllocation allocation = new GtkAllocation ();
+	GTK.gtk_widget_get_allocation(handle, allocation);
+	long /*int*/ rect = Graphene.graphene_rect_alloc();
+	Graphene.graphene_rect_init(rect, 0, 0, allocation.width, allocation.height);
+	long /*int*/ cairo = GTK.gtk_snapshot_append_cairo(snapshot, rect);
+	gtk_draw(handle, cairo);
+	Graphene.graphene_rect_free(rect);
+	// Propagates the snapshot down the widget hierarchy so that other widgets
+	// will draw.
+	if (GTK.GTK_IS_CONTAINER(handle)) {
+		propagateSnapshot(handle, snapshot);
+	}
+	return;
+}
+
 long /*int*/ gtk_widget_get_window (long /*int*/ widget){
 	GTK.gtk_widget_realize(widget);
 	return GTK.gtk_widget_get_window (widget);