Fix memory management (take 2)

src/gui/touchscreengui.cpp

@@ -271,7 +271,7 @@ AutoHideButtonBar::AutoHideButtonBar(IrrlichtDevice *device, ISimpleTextureSourc
 	load_button_texture(starter_gui_button, starter_img, starter_rect,
 			m_texturesource, m_driver);
 
-	m_starter.grab(starter_gui_button);
+	m_starter = grab_gui_element<IGUIButton>(starter_gui_button);
 	m_dir = dir;
 }
 
@@ -325,7 +325,7 @@ void AutoHideButtonBar::addButton(touch_gui_button_id id, const std::string &ima
 
 	button_info btn{};
 	btn.keycode = id_to_keycode(id);
-	btn.gui_button.grab(btn_gui_button);
+	btn.gui_button = grab_gui_element<IGUIButton>(btn_gui_button);
 	m_buttons.push_back(btn);
 }
 
@@ -437,26 +437,26 @@ TouchScreenGUI::TouchScreenGUI(IrrlichtDevice *device, ISimpleTextureSource *tsr
 	// Initialize joystick display "button".
 	// Joystick is placed on the bottom left of screen.
 	if (m_fixed_joystick) {
-		m_joystick_btn_off.grab(makeJoystickButton(joystick_off_id,
+		m_joystick_btn_off = grab_gui_element<IGUIButton>(makeJoystickButton(joystick_off_id,
 				recti(m_button_size,
 						m_screensize.Y - m_button_size * 4,
 						m_button_size * 4,
 						m_screensize.Y - m_button_size), true));
 	} else {
-		m_joystick_btn_off.grab(makeJoystickButton(joystick_off_id,
+		m_joystick_btn_off = grab_gui_element<IGUIButton>(makeJoystickButton(joystick_off_id,
 				recti(m_button_size,
 						m_screensize.Y - m_button_size * 3,
 						m_button_size * 3,
 						m_screensize.Y - m_button_size), true));
 	}
 
-	m_joystick_btn_bg.grab(makeJoystickButton(joystick_bg_id,
+	m_joystick_btn_bg = grab_gui_element<IGUIButton>(makeJoystickButton(joystick_bg_id,
 			recti(m_button_size,
 					m_screensize.Y - m_button_size * 4,
 					m_button_size * 4,
 					m_screensize.Y - m_button_size), false));
 
-	m_joystick_btn_center.grab(makeJoystickButton(joystick_center_id,
+	m_joystick_btn_center = grab_gui_element<IGUIButton>(makeJoystickButton(joystick_center_id,
 			recti(0, 0, m_button_size, m_button_size), false));
 
 	// init jump button
@@ -539,7 +539,7 @@ void TouchScreenGUI::addButton(touch_gui_button_id id, const std::string &image,
 
 	button_info &btn = m_buttons.emplace_back();
 	btn.keycode = id_to_keycode(id);
-	btn.gui_button.grab(btn_gui_button);
+	btn.gui_button = grab_gui_element<IGUIButton>(btn_gui_button);
 }
 
 IGUIButton *TouchScreenGUI::makeJoystickButton(touch_gui_button_id id,

src/gui/touchscreengui.h

@@ -20,7 +20,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #pragma once
 
-#include "irr_ptr.h"
 #include "irrlichttypes.h"
 #include <IEventReceiver.h>
 #include <IGUIButton.h>
@@ -39,6 +38,29 @@ using namespace irr;
 using namespace irr::core;
 using namespace irr::gui;
 
+
+// We cannot use irr_ptr for Irrlicht GUI elements we own.
+// Option 1: Pass IGUIElement* returned by IGUIEnvironment::add* into irr_ptr
+//           constructor.
+//           -> We steal the reference owned by IGUIEnvironment and drop it later,
+//           causing the IGUIElement to be deleted while IGUIEnvironment still
+//           references it.
+// Option 2: Pass IGUIElement* returned by IGUIEnvironment::add* into irr_ptr::grab.
+//           -> We add another reference and drop it later, but since IGUIEnvironment
+//           still references the IGUIElement, it is never deleted.
+// To make IGUIEnvironment drop its reference to the IGUIElement, we have to call
+// IGUIElement::remove, so that's what we'll do.
+template <typename T>
+std::shared_ptr<T> grab_gui_element(T *element)
+{
+	static_assert(std::is_base_of_v<IGUIElement, T>,
+			"grab_gui_element only works for IGUIElement");
+	return std::shared_ptr<T>(element, [](T *e) {
+		e->remove();
+	});
+}
+
+
 enum class TapState
 {
 	None,
@@ -101,7 +123,7 @@ struct button_info
 	float repeat_counter;
 	EKEY_CODE keycode;
 	std::vector<size_t> pointer_ids;
-	irr_ptr<IGUIButton> gui_button = nullptr;
+	std::shared_ptr<IGUIButton> gui_button = nullptr;
 
 	enum {
 		NOT_TOGGLEABLE,
@@ -144,7 +166,7 @@ private:
 	IGUIEnvironment *m_guienv = nullptr;
 	IEventReceiver *m_receiver = nullptr;
 	ISimpleTextureSource *m_texturesource = nullptr;
-	irr_ptr<IGUIButton> m_starter;
+	std::shared_ptr<IGUIButton> m_starter;
 	std::vector<button_info> m_buttons;
 
 	v2s32 m_upper_left;
@@ -244,9 +266,9 @@ private:
 	bool m_fixed_joystick = false;
 	bool m_joystick_triggers_aux1 = false;
 	bool m_draw_crosshair = false;
-	irr_ptr<IGUIButton> m_joystick_btn_off;
-	irr_ptr<IGUIButton> m_joystick_btn_bg;
-	irr_ptr<IGUIButton> m_joystick_btn_center;
+	std::shared_ptr<IGUIButton> m_joystick_btn_off;
+	std::shared_ptr<IGUIButton> m_joystick_btn_bg;
+	std::shared_ptr<IGUIButton> m_joystick_btn_center;
 
 	std::vector<button_info> m_buttons;