Fix #1173 - bad UI on MacOS merge viewer

Implement ContentMergeViewer.computeSize

team/bundles/org.eclipse.compare/compare/org/eclipse/compare/contentmergeviewer/ContentMergeViewer.java

@@ -78,6 +78,7 @@
 import org.eclipse.swt.graphics.Rectangle;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Layout;
 import org.eclipse.swt.widgets.Sash;
 import org.eclipse.swt.widgets.Shell;
@@ -126,8 +127,15 @@ public abstract class ContentMergeViewer extends ContentViewer
 
 	private class ContentMergeViewerLayout extends Layout {
 		@Override
-		public Point computeSize(Composite c, int w, int h, boolean force) {
-			return new Point(100, 100);
+		public Point computeSize(Composite composite, int wHint, int hHint, boolean force) {
+			if (hHint > SWT.DEFAULT && wHint > SWT.DEFAULT) {
+				return new Point(wHint, hHint);
+			}
+
+			Rectangle r = composite.getClientArea();
+
+
+			return new Point(r.width, r.height);
 		}
 
 		@Override
@@ -797,8 +805,12 @@ private void internalRefresh(Object input) {
 				ToolBarManager tbm = (ToolBarManager) getToolBarManager(fComposite.getParent());
 				if (tbm != null ) {
 					updateToolItems();
-					tbm.update(true);
-					tbm.getControl().getParent().layout(true);
+					Display.getDefault().asyncExec(() -> {
+						// relayout in next tick
+						tbm.update(true);
+						tbm.getControl().getParent().setRedraw(true);
+					});
+
 				}
 			}
 		}