Support both mouse and touch input in GUIs in a single binary (#14146)

src/gui/modalMenu.h

@@ -23,6 +23,11 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "irr_ptr.h"
 #include "util/string.h"
 
+enum class PointerType {
+	Mouse,
+	Touch,
+};
+
 class GUIModalMenu;
 
 class IMenuManager
@@ -58,6 +63,8 @@ class GUIModalMenu : public gui::IGUIElement
 	bool hasAndroidUIInput();
 #endif
 
+	PointerType getPointerType() { return m_pointer_type; };
+
 protected:
 	virtual std::wstring getLabelByID(s32 id) = 0;
 	virtual std::string getNameByID(s32 id) = 0;
@@ -69,18 +76,25 @@ class GUIModalMenu : public gui::IGUIElement
 	 */
 	bool DoubleClickDetection(const SEvent &event);
 
+	// Stores the last known pointer type.
+	PointerType m_pointer_type = PointerType::Mouse;
+	// Stores the last known pointer position.
+	// If the last input event was a mouse event, it's the cursor position.
+	// If the last input event was a touch event, it's the finger position.
 	v2s32 m_pointer;
 	v2s32 m_old_pointer;  // Mouse position after previous mouse event
+
 	v2u32 m_screensize_old;
 	float m_gui_scale;
 #ifdef __ANDROID__
 	std::string m_jni_field_name;
 #endif
-#ifdef HAVE_TOUCHSCREENGUI
+
 	// This is set to true if the menu is currently processing a second-touch event.
 	bool m_second_touch = false;
-	bool m_touchscreen_visible = true;
-#endif
+	// This is set to true if the menu is currently processing a mouse event
+	// that was synthesized by the menu itself from a touch event.
+	bool m_simulated_mouse = false;
 
 private:
 	struct clickpos
@@ -102,11 +116,11 @@ class GUIModalMenu : public gui::IGUIElement
 	// wants to launch other menus
 	bool m_allow_focus_removal = false;
 
-#ifdef HAVE_TOUCHSCREENGUI
-	irr_ptr<gui::IGUIElement> m_hovered;
+	// Stuff related to touchscreen input
+
+	irr_ptr<gui::IGUIElement> m_touch_hovered;
 
 	bool simulateMouseEvent(gui::IGUIElement *target, ETOUCH_INPUT_EVENT touch_event);
 	void enter(gui::IGUIElement *element);
 	void leave();
-#endif
 };