Touchscreen: Allow mods to swap the meaning of short and long taps (punch with single tap) (#14087)

This works through a new field "touch_interaction" in item definitions.
The two most important use cases are:
 - Punching players/entities with short tap instead of long tap (enabled by default)
 - Making items usable that require holding the place button (e.g. bows and shields in MC-like games)

src/itemdef.h

@@ -31,6 +31,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 class IGameDef;
 class Client;
 struct ToolCapabilities;
+struct PointedThing;
 #ifndef SERVER
 #include "client/tile.h"
 struct ItemMesh;
@@ -50,6 +51,25 @@ enum ItemType : u8
 	ItemType_END // Dummy for validity check
 };
 
+enum TouchInteractionMode : u8
+{
+	LONG_DIG_SHORT_PLACE,
+	SHORT_DIG_LONG_PLACE,
+	TouchInteractionMode_END, // Dummy for validity check
+};
+
+struct TouchInteraction
+{
+	TouchInteractionMode pointed_nothing;
+	TouchInteractionMode pointed_node;
+	TouchInteractionMode pointed_object;
+
+	TouchInteraction();
+	TouchInteractionMode getMode(const PointedThing &pointed) const;
+	void serialize(std::ostream &os) const;
+	void deSerialize(std::istream &is);
+};
+
 struct ItemDefinition
 {
 	/*
@@ -92,6 +112,8 @@ struct ItemDefinition
 	std::optional<u8> place_param2;
 	bool wallmounted_rotate_vertical;
 
+	TouchInteraction touch_interaction;
+
 	/*
 		Some helpful methods
 	*/