Fix: Viewport drag tooltips not being removed when dragging over other windows

src/misc_gui.cpp

@@ -766,6 +766,12 @@ struct TooltipsWindow : public Window
 			case TCC_RIGHT_CLICK: if (!_right_button_down) delete this; break;
 			case TCC_HOVER: if (!_mouse_hovering) delete this; break;
 			case TCC_NONE: break;
+
+			case TCC_EXIT_VIEWPORT: {
+				Window *w = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);
+				if (w == nullptr || IsPtInWindowViewport(w, _cursor.pos.x, _cursor.pos.y) == nullptr) delete this;
+				break;
+			}
 		}
 	}
 };

src/viewport.cpp

@@ -2637,7 +2637,7 @@ void UpdateTileSelection()
  * @param params (optional) up to 5 pieces of additional information that may be added to a tooltip
  * @param close_cond Condition for closing this tooltip.
  */
-static inline void ShowMeasurementTooltips(StringID str, uint paramcount, const uint64 params[], TooltipCloseCondition close_cond = TCC_NONE)
+static inline void ShowMeasurementTooltips(StringID str, uint paramcount, const uint64 params[], TooltipCloseCondition close_cond = TCC_EXIT_VIEWPORT)
 {
 	if (!_settings_client.gui.measure_tooltip) return;
 	GuiShowTooltips(_thd.GetCallbackWnd(), str, paramcount, params, close_cond);

src/window_gui.h

@@ -268,6 +268,7 @@ enum TooltipCloseCondition {
 	TCC_RIGHT_CLICK,
 	TCC_HOVER,
 	TCC_NONE,
+	TCC_EXIT_VIEWPORT,
 };
 
 /**