[GEF] New fix for SWTException "Widget is disposed" when displaying a…

… Tooltip

- The fix in 42f4319 caused a regression on Linux Wayland
- See #1076
- See eclipse/gef-classic#469

org.eclipse.draw2d/src/org/eclipse/draw2d/PopUpHelper.java

@@ -84,14 +84,7 @@ protected LightweightSystem createLightweightSystem() {
      * @since 2.0
      */
     protected Shell createShell() {
-        // Phillipus changed this.
-        // If a workbench part is detached and a tooltip is initially displayed, when the part is re-attached
-        // the parent Shell is disposed which in turn disposes of the PopupHelper's Shell.
-        // This will lead to an SWT Error when the Shell is accessed again.
-        // To fix this, create the PopupHelper Shell with the Control's Display instead of its Shell.
-
-        //return new Shell(control.getShell(), shellStyle);
-        return new Shell(control.getDisplay(), shellStyle);
+        return new Shell(control.getShell(), shellStyle);
     }
 
     /**

org.eclipse.draw2d/src/org/eclipse/draw2d/SWTEventDispatcher.java

@@ -335,8 +335,18 @@ protected IFigure getCursorTarget() {
      * @return the ToolTipHelper
      */
     protected ToolTipHelper getToolTipHelper() {
-        if (toolTipHelper == null)
+        // Phillipus changed this.
+        // If a workbench part is detached and a tooltip is initially displayed, when the part is re-attached
+        // the parent Shell is disposed which in turn disposes of the PopupHelper's Shell.
+        // This will lead to an SWT Error when the Shell is accessed again.
+        // To fix this, if the ToolTipHelper's shell is disposed return a new one
+
+        //if (toolTipHelper == null)
+        //    toolTipHelper = new ToolTipHelper(control);
+
+        if(toolTipHelper == null || toolTipHelper.getShell().isDisposed()) {
             toolTipHelper = new ToolTipHelper(control);
+        }
         return toolTipHelper;
     }