Bug 545403: [GTK3] MouseWheel event only reports GDK.GDK_SCROLL_UP

gdk_event_get_scroll_direction() will return false if GDK_SMOOTH is
enabled. The fix is to check if this function returns false, and then
call gdk_event_get_scroll_deltas() to get the scroll delta.

Change-Id: I27bb15b61d9da4c5e749e71d6bb27bbcfc63b879
Signed-off-by: Eric Williams <ericwill@redhat.com>

3 files changed, 64 insertions, 24 deletions

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 9d202ecfcc..8ae4bbbdb5 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
@@ -4131,6 +4131,7 @@ long /*int*/ gtk_realize (long /*int*/ widget) {
 
 @Override
 long /*int*/ gtk_scroll_event (long /*int*/ widget, long /*int*/ eventPtr) {
+	long /*int*/ result = 0;
 	double [] eventX = new double[1];
 	double [] eventY = new double[1];
 	GDK.gdk_event_get_coords(eventPtr, eventX, eventY);
@@ -4143,31 +4144,31 @@ long /*int*/ gtk_scroll_event (long /*int*/ widget, long /*int*/ eventPtr) {
 	lastInput.x = (int) eventX[0];
 	lastInput.y = (int) eventY[0];
 	int [] direction = new int[1];
-	GDK.gdk_event_get_scroll_direction(eventPtr, direction);
+	boolean fetched = GDK.gdk_event_get_scroll_direction(eventPtr, direction);
 	if (containedInRegion(lastInput.x, lastInput.y)) return 0;
-	switch (direction[0]) {
-		case GDK.GDK_SCROLL_UP:
-			return sendMouseEvent (SWT.MouseWheel, 0, 3, SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
-		case GDK.GDK_SCROLL_DOWN:
-			return sendMouseEvent (SWT.MouseWheel, 0, -3, SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
-		case GDK.GDK_SCROLL_LEFT:
-			return sendMouseEvent (SWT.MouseHorizontalWheel, 0, 3, 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
-		case GDK.GDK_SCROLL_RIGHT:
-			return sendMouseEvent (SWT.MouseHorizontalWheel, 0, -3, 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
-		case GDK.GDK_SCROLL_SMOOTH:
-			long /*int*/ result = 0;
-			double[] delta_x = new double[1], delta_y = new double [1];
-			if (GDK.gdk_event_get_scroll_deltas (eventPtr, delta_x, delta_y)) {
-				if (delta_x [0] != 0) {
-					result = (sendMouseEvent (SWT.MouseHorizontalWheel, 0, (int)(-3 * delta_x [0]), 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1);
-				}
-				if (delta_y [0] != 0) {
-					result = (sendMouseEvent (SWT.MouseWheel, 0, (int)(-3 * delta_y [0]), SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1);
-				}
+	if (fetched) {
+		switch (direction[0]) {
+			case GDK.GDK_SCROLL_UP:
+				return sendMouseEvent (SWT.MouseWheel, 0, 3, SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
+			case GDK.GDK_SCROLL_DOWN:
+				return sendMouseEvent (SWT.MouseWheel, 0, -3, SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
+			case GDK.GDK_SCROLL_LEFT:
+				return sendMouseEvent (SWT.MouseHorizontalWheel, 0, 3, 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
+			case GDK.GDK_SCROLL_RIGHT:
+				return sendMouseEvent (SWT.MouseHorizontalWheel, 0, -3, 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1;
+		}
+	} else {
+		double[] delta_x = new double[1], delta_y = new double [1];
+		if (GDK.gdk_event_get_scroll_deltas (eventPtr, delta_x, delta_y)) {
+			if (delta_x [0] != 0) {
+				result = (sendMouseEvent (SWT.MouseHorizontalWheel, 0, (int)(-3 * delta_x [0]), 0, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1);
 			}
-			return result;
+			if (delta_y [0] != 0) {
+				result = (sendMouseEvent (SWT.MouseWheel, 0, (int)(-3 * delta_y [0]), SWT.SCROLL_LINE, true, time, eventRX[0], eventRY[0], false, state[0]) ? 0 : 1);
+			}
+		}
 	}
-	return 0;
+	return result;
 }
 
 @Override
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Scrollable.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Scrollable.java
index c8c10beccb..1c9054a060 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Scrollable.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Scrollable.java
@@ -315,8 +315,8 @@ long /*int*/ gtk_scroll_event (long /*int*/ widget, long /*int*/ eventPtr) {
 	if ((state & CANVAS) != 0) {
 		ScrollBar scrollBar;
 		int [] direction = new int[1];
-		GDK.gdk_event_get_scroll_direction(eventPtr, direction);
-		if (direction[0] == GDK.GDK_SCROLL_SMOOTH) {
+		boolean fetched = GDK.gdk_event_get_scroll_direction(eventPtr, direction);
+		if (!fetched) {
 			double[] delta_x = new double[1], delta_y = new double [1];
 			if (GDK.gdk_event_get_scroll_deltas (eventPtr, delta_x, delta_y)) {
 				if (delta_x [0] != 0) {
diff --git a/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug545403_ScrollDirection.java b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug545403_ScrollDirection.java
new file mode 100644
index 0000000000..718ead0126
--- /dev/null
+++ b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug545403_ScrollDirection.java
@@ -0,0 +1,39 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Red Hat and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Red Hat - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.tests.gtk.snippets;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+
+public class Bug545403_ScrollDirection {
+
+	public static void main(String[] args) {
+		final Display display = new Display();
+
+		final Shell shell = new Shell(display);
+		shell.addListener(SWT.MouseWheel, event -> System.out.println(event.count));
+
+		shell.setSize(300, 200);
+		shell.open();
+
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+
+		display.dispose();
+	}
+}
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