Make default hide delay for tooltip configurable (#364)

The hide delay for tooltips in Draw2d is currently fixed to 5 seconds.
The value can only be changed for a speific `ToolTipHelper`, which in
turn is tied to a specific control. There is option to configure this
delay globally.

With this change, the default value for the hide delay can globally be
changed on the `ToolTipHelper` class, such that subsequent tooltip
creations will use this value as default.

org.eclipse.draw2d/src/org/eclipse/draw2d/ToolTipHelper.java

@@ -32,9 +32,11 @@
  */
 public class ToolTipHelper extends PopUpHelper {
 
+	private static int defaultHideDelay = 5000;
+
 	private Timer timer;
 	private IFigure currentTipSource;
-	private int hideDelay = 5000;
+	private int hideDelay;
 
 	/**
 	 * Constructs a ToolTipHelper to be associated with Control <i>c</i>.
@@ -46,6 +48,7 @@ public ToolTipHelper(org.eclipse.swt.widgets.Control c) {
 		super(c, SWT.TOOL | SWT.ON_TOP);
 		getShell().setBackground(ColorConstants.tooltipBackground);
 		getShell().setForeground(ColorConstants.tooltipForeground);
+		hideDelay = defaultHideDelay;
 	}
 
 	/*
@@ -82,6 +85,18 @@ public void setHideDelay(int hideDelay) {
 		this.hideDelay = hideDelay;
 	}
 
+	/**
+	 * Sets the default tooltip hide delay, which is the number in ms after which
+	 * the tooltip will disappear again if not overwritten using
+	 * {@link #setHideDelay(int)}.
+	 *
+	 * @param defaultHideDelay the delay in ms after which the tooltip is hidden
+	 * @since 3.15
+	 */
+	public static void setDefaultHideDelay(int defaultHideDelay) {
+		ToolTipHelper.defaultHideDelay = defaultHideDelay;
+	}
+
 	/**
 	 * Sets the LightWeightSystem's contents to the passed tooltip, and displays the
 	 * tip. The tip will be displayed only if the tip source is different than the