Merge branch 'master' into jgrpp

# Conflicts:
#	.github/workflows/ci-build.yml
#	src/ai/ai_gui.cpp
#	src/blitter/32bpp_optimized.cpp
#	src/blitter/32bpp_simple.cpp
#	src/blitter/32bpp_sse2.cpp
#	src/blitter/8bpp_optimized.cpp
#	src/blitter/8bpp_simple.cpp
#	src/blitter/null.cpp
#	src/blitter/null.hpp
#	src/company_gui.cpp
#	src/game/game_gui.cpp
#	src/genworld_gui.cpp
#	src/gfx.cpp
#	src/gfx_func.h
#	src/graph_gui.cpp
#	src/industry_gui.cpp
#	src/linkgraph/linkgraphjob.cpp
#	src/network/network_gui.cpp
#	src/newgrf_debug_gui.cpp
#	src/openttd.cpp
#	src/pathfinder/npf/aystar.h
#	src/road_gui.cpp
#	src/saveload/order_sl.cpp
#	src/saveload/saveload.cpp
#	src/saveload/saveload.h
#	src/script/api/script_log.cpp
#	src/script/api/script_town.cpp
#	src/script/script_gui.cpp
#	src/settings.cpp
#	src/settings_gui.cpp
#	src/settings_table.cpp
#	src/settings_type.h
#	src/smallmap_gui.cpp
#	src/sortlist_type.h
#	src/spritecache.cpp
#	src/spriteloader/grf.cpp
#	src/spriteloader/grf.hpp
#	src/spriteloader/spriteloader.hpp
#	src/station_cmd.cpp
#	src/station_cmd.h
#	src/station_gui.cpp
#	src/strings.cpp
#	src/toolbar_gui.cpp
#	src/town_cmd.cpp
#	src/town_gui.cpp
#	src/vehicle_gui.cpp
#	src/vehicle_gui_base.h
#	src/video/opengl.cpp
#	src/video/opengl.h
#	src/widgets/dropdown.cpp
#	src/widgets/dropdown_type.h
#	src/window_gui.h

src/widget_type.h

@@ -39,6 +39,12 @@ enum ArrowWidgetValues {
 	AWV_RIGHT,    ///< Force the arrow to the right
 };
 
+/** WidgetData values for a resize box widget. */
+enum ResizeWidgetValues {
+	RWV_SHOW_BEVEL, ///< Bevel of resize box is shown.
+	RWV_HIDE_BEVEL, ///< Bevel of resize box is hidden.
+};
+
 /**
  * Window widget types, nested widget types, and nested widget part types.
  */
@@ -482,7 +488,7 @@ public:
 	NWidgetCore *GetWidgetFromPos(int x, int y) override;
 	void FillDirtyWidgets(std::vector<NWidgetBase *> &dirty_widgets) override;
 
-	void SetDisplayedPlane(int plane);
+	bool SetDisplayedPlane(int plane);
 
 	int shown_plane; ///< Plane being displayed (for #NWID_SELECTION only).
 	int index;       ///< If non-negative, index in the #Window::nested_array.