From 274b7a0195d3378a490709c269f82b2965cdcdc5 Mon Sep 17 00:00:00 2001
From: Peter Nelson <peter1138@openttd.org>
Date: Thu, 6 Mar 2025 00:00:57 +0000
Subject: [PATCH] Fix #13645: "Follow vehicle" button not raised when following
 stopped. (#13746)

---
 src/vehicle_gui.cpp |  2 +-
 src/viewport.cpp    | 22 +++++++++++++++++++++-
 src/window.cpp      | 11 ++++++-----
 src/window_gui.h    |  2 ++
 4 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
index f1b275e328..9bfa5ecfb0 100644
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -3479,7 +3479,7 @@ void StopGlobalFollowVehicle(const Vehicle *v)
 	Window *w = GetMainWindow();
 	if (w->viewport->follow_vehicle == v->index) {
 		ScrollMainWindowTo(v->x_pos, v->y_pos, v->z_pos, true); // lock the main view on the vehicle's last position
-		w->viewport->follow_vehicle = VehicleID::Invalid();
+		w->viewport->CancelFollow(*w);
 	}
 }
 
diff --git a/src/viewport.cpp b/src/viewport.cpp
index 7405fce2d9..34b6245a05 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -94,6 +94,8 @@
 #include <forward_list>
 #include <stack>
 
+#include "widgets/vehicle_widget.h"
+
 #include "table/strings.h"
 #include "table/string_colours.h"
 
@@ -2530,7 +2532,7 @@ bool ScrollWindowTo(int x, int y, int z, Window *w, bool instant)
 	}
 
 	Point pt = MapXYZToViewport(w->viewport, x, y, z);
-	w->viewport->follow_vehicle = VehicleID::Invalid();
+	w->viewport->CancelFollow(*w);
 
 	if (w->viewport->dest_scrollpos_x == pt.x && w->viewport->dest_scrollpos_y == pt.y) return false;
 
@@ -3717,3 +3719,21 @@ void SetViewportCatchmentTown(const Town *t, bool sel)
 	}
 	if (_viewport_highlight_town != nullptr) SetWindowDirty(WC_TOWN_VIEW, _viewport_highlight_town->index);
 }
+
+/**
+ * Cancel viewport vehicle following, and raise follow location widget if needed.
+ * @param viewport_window Window of this viewport.
+ */
+void ViewportData::CancelFollow(const Window &viewport_window)
+{
+	if (this->follow_vehicle == VehicleID::Invalid()) return;
+
+	if (viewport_window.window_class == WC_MAIN_WINDOW) {
+		/* We're cancelling follow in the main viewport, so we need to check for a vehicle view window
+		 * to raise the location follow widget. */
+		Window *vehicle_window = FindWindowById(WC_VEHICLE_VIEW, this->follow_vehicle);
+		if (vehicle_window != nullptr) vehicle_window->RaiseWidgetWhenLowered(WID_VV_LOCATION);
+	}
+
+	this->follow_vehicle = VehicleID::Invalid();
+}
diff --git a/src/window.cpp b/src/window.cpp
index eb540dfe8a..4faa23342e 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -2697,17 +2697,17 @@ static void HandleAutoscroll()
 	/* If we succeed at scrolling in any direction, stop following a vehicle. */
 	static const int SCROLLSPEED = 3;
 	if (x - 15 < 0) {
-		w->viewport->follow_vehicle = VehicleID::Invalid();
+		w->viewport->CancelFollow(*w);
 		w->viewport->dest_scrollpos_x += ScaleByZoom((x - 15) * SCROLLSPEED, vp->zoom);
 	} else if (15 - (vp->width - x) > 0) {
-		w->viewport->follow_vehicle = VehicleID::Invalid();
+		w->viewport->CancelFollow(*w);
 		w->viewport->dest_scrollpos_x += ScaleByZoom((15 - (vp->width - x)) * SCROLLSPEED, vp->zoom);
 	}
 	if (y - 15 < 0) {
-		w->viewport->follow_vehicle = VehicleID::Invalid();
+		w->viewport->CancelFollow(*w);
 		w->viewport->dest_scrollpos_y += ScaleByZoom((y - 15) * SCROLLSPEED, vp->zoom);
 	} else if (15 - (vp->height - y) > 0) {
-		w->viewport->follow_vehicle = VehicleID::Invalid();
+		w->viewport->CancelFollow(*w);
 		w->viewport->dest_scrollpos_y += ScaleByZoom((15 - (vp->height - y)) * SCROLLSPEED, vp->zoom);
 	}
 }
@@ -2775,7 +2775,8 @@ static void HandleKeyScrolling()
 
 		if (_game_mode != GM_MENU && _game_mode != GM_BOOTSTRAP) {
 			/* Key scrolling stops following a vehicle. */
-			GetMainWindow()->viewport->follow_vehicle = VehicleID::Invalid();
+			Window *main_window = GetMainWindow();
+			main_window->viewport->CancelFollow(*main_window);
 		}
 
 		ScrollMainViewport(scrollamt[_dirkeys][0] * factor, scrollamt[_dirkeys][1] * factor);
diff --git a/src/window_gui.h b/src/window_gui.h
index 8d1718717b..9b27432192 100644
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -254,6 +254,8 @@ struct ViewportData : Viewport {
 	int32_t scrollpos_y;        ///< Currently shown y coordinate (virtual screen coordinate of topleft corner of the viewport).
 	int32_t dest_scrollpos_x;   ///< Current destination x coordinate to display (virtual screen coordinate of topleft corner of the viewport).
 	int32_t dest_scrollpos_y;   ///< Current destination y coordinate to display (virtual screen coordinate of topleft corner of the viewport).
+
+	void CancelFollow(const Window &viewport_window);
 };
 
 struct QueryString;