=== modified file 'src/widget.cpp'
--- src/widget.cpp	2008-07-15 12:55:36 +0000
+++ src/widget.cpp	2008-07-15 13:27:58 +0000
@@ -603,3 +603,17 @@
 	int offset = this->IsWidgetLowered(widget) ? 1 : 0;
 	DoDrawString(state == SBS_DOWN ? DOWNARROW : UPARROW, this->widget[widget].right - 11 + offset, this->widget[widget].top + 1 + offset, TC_BLACK);
 }
+
+
+/** Mark widget as dirty (in need of repaint)
+ * @param w  Window that the widget belongs to
+ */
+void Widget::SetDirty(const Window *w) const
+{
+	/* Don't redraw if the widget is invisible or of no-type */
+	if (type == WWT_EMPTY || IsHidden()) return;
+
+	/* Mark area covered by the widget dirty */
+	SetDirtyBlocks(w->left + left, w->top + top, w->left + right + 1, w->top + bottom + 1);
+}
+

=== modified file 'src/window.cpp'
--- src/window.cpp	2008-07-15 12:55:36 +0000
+++ src/window.cpp	2008-07-15 13:27:58 +0000
@@ -102,14 +102,15 @@
 	}
 }
 
+/**
+ * Mark widget of a window as invalid. Specified widget is marked as dirty to
+ * have it repainted by the video system.
+ * @param widget_index  Number of the widget to invalidate
+ */
 void Window::InvalidateWidget(byte widget_index) const
 {
 	const Widget *wi = &this->widget[widget_index];
-
-	/* Don't redraw the window if the widget is invisible or of no-type */
-	if (wi->type == WWT_EMPTY || wi->IsHidden()) return;
-
-	SetDirtyBlocks(this->left + wi->left, this->top + wi->top, this->left + wi->right + 1, this->top + wi->bottom + 1);
+	wi->SetDirty(this);
 }
 
 void Window::HandleButtonClick(byte widget)

=== modified file 'src/window_gui.h'
--- src/window_gui.h	2008-07-15 12:55:36 +0000
+++ src/window_gui.h	2008-07-15 13:27:58 +0000
@@ -86,6 +86,8 @@
 	uint16 data;                      ///< The String/Image or special code (list-matrixes) of a widget
 	StringID tooltips;                ///< Tooltips that are shown when rightclicking on a widget
 
+	void SetDirty(const Window *w) const;
+
 	void SetDisabledState(bool disab_stat);
 	void Disable();
 	void Enable();