Codechange: Implement OnTooltip event for custom window tooltips.

This avoids windows from needing to know or care about tooltip delay settings.

src/window_gui.h

@@ -265,6 +265,13 @@ struct ViewportData : ViewPort {
 
 struct QueryString;
 
+/* misc_gui.cpp */
+enum TooltipCloseCondition {
+	TCC_RIGHT_CLICK,
+	TCC_HOVER,
+	TCC_NONE,
+};
+
 /**
  * Data structure for an opened window
  */
@@ -629,12 +636,20 @@ public:
 	virtual bool OnRightClick(Point pt, int widget) { return false; }
 
 	/**
-	 * The mouse is hovering over a widget in the window, perform an action for it, like opening a custom tooltip.
+	 * The mouse is hovering over a widget in the window, perform an action for it.
 	 * @param pt     The point where the mouse is hovering.
 	 * @param widget The widget where the mouse is hovering.
 	 */
 	virtual void OnHover(Point pt, int widget) {}
 
+	/**
+	 * Event to display a custom tooltip.
+	 * @param pt     The point where the mouse is located.
+	 * @param widget The widget where the mouse is located.
+	 * @return True if the event is handled, false if it is ignored.
+	 */
+	virtual bool OnTooltip(Point pt, int widget, TooltipCloseCondition close_cond) { return false; }
+
 	/**
 	 * An 'object' is being dragged at the provided position, highlight the target if possible.
 	 * @param pt     The point inside the window that the mouse hovers over.
@@ -870,13 +885,6 @@ Wcls *AllocateWindowDescFront(WindowDesc *desc, int window_number, bool return_e
 
 void RelocateAllWindows(int neww, int newh);
 
-/* misc_gui.cpp */
-enum TooltipCloseCondition {
-	TCC_RIGHT_CLICK,
-	TCC_HOVER,
-	TCC_NONE,
-};
-
 void GuiShowTooltips(Window *parent, StringID str, uint paramcount = 0, const uint64 params[] = NULL, TooltipCloseCondition close_tooltip = TCC_HOVER);
 
 /* widget.cpp */