Index: src/transparency_gui.cpp
===================================================================
--- src/transparency_gui.cpp	(revision 10002)
+++ src/transparency_gui.cpp	(working copy)
@@ -46,13 +46,29 @@
 				SetWindowWidgetLoweredState(w, i, HASBIT(_transparent_opt, i - TTW_WIDGET_SIGNS));
 			}
 			DrawWindowWidgets(w);
+			
+			//draw an X over the widget which tells wether the "invisible trees" patch is actived
+			if (_patches.invisible_trees) {
+				DrawString(w->widget[TTW_WIDGET_TREES].left+1, w->widget[TTW_WIDGET_TREES].top+1, STR_00C5, 0);
+			}
 			break;
 
 		case WE_CLICK:
-			if (e->we.click.widget >= TTW_WIDGET_SIGNS) {
-				Transparent_Click(e->we.click.widget - TTW_WIDGET_SIGNS);
-				MarkWholeScreenDirty();
+			/* check for the CTRL key pressed, if so and we click on a widget which support it, we toggle the invisibility */
+			if (_ctrl_pressed) {
+				switch (e->we.click.widget) {
+					case TTW_WIDGET_TREES:
+						_patches.invisible_trees ^= 1;
+						break;
+				}
 			}
+			else {
+				/* else we toggle the transparency */
+				if (e->we.click.widget >= TTW_WIDGET_SIGNS) {
+					Transparent_Click(e->we.click.widget - TTW_WIDGET_SIGNS);
+				}
+			}
+			MarkWholeScreenDirty();
 			break;
 	}
 }