Handle modifier keys differently to avoid Apple flagging us as wishing to monitor input from other applications

Fixes #291

src/tools/SConscript

@@ -5,6 +5,7 @@ tools = Split("""
 	undo.cpp
 	framerate_limiter.cpp
 	drawable_manager.cpp
+	keymods.cpp
 	../location.cpp
 	../mathutil.cpp
 	../porting.cpp

src/tools/keymods.cpp

@@ -0,0 +1,93 @@
+//
+//  keymods.cpp
+//  Common
+//
+//  Created by Celtic Minstrel on 2023-01-12.
+//
+
+#include "keymods.hpp"
+#include <SFML/Window/Keyboard.hpp>
+
+keymods_t kb;
+
+bool keymods_t::isAltPressed() const {
+	return alt;
+}
+
+bool keymods_t::isCtrlPressed() const {
+	return ctrl;
+}
+
+bool keymods_t::isShiftPressed() const {
+	return shift;
+}
+
+bool keymods_t::isMetaPressed() const {
+	return meta;
+}
+
+bool keymods_t::isSystemPressed() const {
+#ifdef __APPLE__
+	return meta;
+#else
+	return ctrl;
+#endif
+}
+
+bool keymods_t::isUpPressed() const {
+	return up;
+}
+
+bool keymods_t::isDownPressed() const {
+	return down;
+}
+
+bool keymods_t::isLeftPressed() const {
+	return left;
+}
+
+bool keymods_t::isRightPressed() const {
+	return right;
+}
+
+bool keymods_t::handleModifier(const sf::Event& evt) {
+	if(evt.type != sf::Event::KeyPressed && evt.type != sf::Event::KeyReleased) {
+		return false;
+	}
+	using Key = sf::Keyboard::Key;
+	bool newState = evt.type == sf::Event::KeyPressed;
+	switch(evt.key.code) {
+		case Key::LShift:
+		case Key::RShift:
+			shift = newState;
+			break;
+		case Key::LAlt:
+		case Key::RAlt:
+			alt = newState;
+			break;
+		case Key::LControl:
+		case Key::RControl:
+			ctrl = newState;
+			break;
+		case Key::LSystem:
+		case Key::RSystem:
+			meta = newState;
+			break;
+		
+		case Key::Left:
+			left = newState;
+			break;
+		case Key::Right:
+			right = newState;
+			break;
+		case Key::Up:
+			up = newState;
+			break;
+		case Key::Down:
+			down = newState;
+			break;
+			
+		default: return false;
+	}
+	return true;
+}

src/tools/keymods.hpp

@@ -0,0 +1,33 @@
+//
+//  keymods.hpp
+//  Common
+//
+//  Created by Celtic Minstrel on 2023-01-12.
+//
+
+#ifndef BOE_keymods_hpp
+#define BOE_keymods_hpp
+
+#include <SFML/Window/Event.hpp>
+
+class keymods_t {
+	bool alt = false, ctrl = false, shift = false, meta = false;
+	bool up = false, down = false, left = false, right = false;
+public:
+	bool isAltPressed() const;
+	bool isCtrlPressed() const;
+	bool isShiftPressed() const;
+	// Windows key, Command key, Meta key, etc
+	bool isMetaPressed() const;
+	// System is a special pseudo-key - it's Command on Mac and Control on other systems
+	bool isSystemPressed() const;
+	bool isUpPressed() const;
+	bool isDownPressed() const;
+	bool isLeftPressed() const;
+	bool isRightPressed() const;
+	bool handleModifier(const sf::Event& evt);
+};
+
+extern keymods_t kb;
+
+#endif /* keymods_hpp */