Add minimal touch support for decision/cancel

Related: EasyRPG#634
This is a very naive implementation, as it only checks whether fingers
touch the screen and not where they touch and in which direction swipes
are done or if there are gestures, etc.

src/input_buttons_desktop.cpp

@@ -131,6 +131,11 @@ void Input::InitButtons() {
 	buttons[UP].push_back(Keys::JOY_AXIS_Y_UP);
 #endif
 
+#if defined(USE_TOUCH) && defined(SUPPORT_TOUCH)
+	buttons[DECISION].push_back(Keys::ONE_FINGER);
+	buttons[CANCEL].push_back(Keys::TWO_FINGERS);
+#endif
+
 	dir_buttons.resize(10);
 	dir_buttons[2].push_back(DOWN);
 	dir_buttons[4].push_back(LEFT);

src/keys.h

@@ -191,6 +191,11 @@ namespace Input {
 			JOY_AXIS_Y_UP,
 #endif
 
+#if defined(USE_TOUCH) && defined(SUPPORT_TOUCH)
+			ONE_FINGER,
+			TWO_FINGERS,
+#endif
+
 			KEYS_COUNT
 		};
 	}

src/options.h

@@ -90,6 +90,7 @@
 #define USE_JOYSTICK
 #define USE_JOYSTICK_HAT
 #define USE_JOYSTICK_AXIS
+#define USE_TOUCH
 
 //#define USE_FIXED_TIMESTEP_FPS
 

src/sdl_ui.cpp

@@ -672,11 +672,9 @@ void SdlUi::ProcessEvent(SDL_Event &evnt) {
 
 #if SDL_MAJOR_VERSION>1
 		case SDL_FINGERDOWN:
-			ProcessFingerDownEvent(evnt);
-			return;
-
 		case SDL_FINGERUP:
-			ProcessFingerUpEvent(evnt);
+		case SDL_FINGERMOTION:
+			ProcessFingerEvent(evnt);
 			return;
 #endif
 	}
@@ -941,17 +939,29 @@ void SdlUi::ProcessJoystickAxisEvent(SDL_Event &evnt) {
 }
 
 #if SDL_MAJOR_VERSION>1
-void SdlUi::ProcessFingerDownEvent(SDL_Event& evnt) {
-	ProcessFingerEvent(evnt, true);
-}
-
-void SdlUi::ProcessFingerUpEvent(SDL_Event& evnt) {
-	ProcessFingerEvent(evnt, false);
-}
-
-void SdlUi::ProcessFingerEvent(SDL_Event& evnt, bool finger_down) {
-	(void)finger_down;
-	(void)evnt;
+void SdlUi::ProcessFingerEvent(SDL_Event& evnt) {
+#if defined(USE_TOUCH) && defined(SUPPORT_TOUCH)
+	SDL_TouchID touchid;
+	int fingers = 0;
+
+	// We currently ignore swipe gestures
+	if (evnt.type != SDL_FINGERMOTION) {
+		/* FIXME: To simplify things, we lazily only get the current number of
+		   fingers touching the first device (hoping nobody actually uses
+		   multiple devices). This way we do not need to keep track on finger
+		   IDs and deal with the timing.
+		*/
+		touchid = SDL_GetTouchDevice(0);
+		if (touchid != 0)
+			fingers = SDL_GetNumTouchFingers(touchid);
+
+		keys[Input::Keys::ONE_FINGER] = fingers == 1;
+		keys[Input::Keys::TWO_FINGERS] = fingers == 2;
+	}
+#else
+	/* unused */
+	(void) evnt;
+#endif
 }
 
 void SdlUi::SetAppIcon() {

src/sdl_ui.h

@@ -112,10 +112,7 @@ class SdlUi : public BaseUi {
 	void ProcessJoystickAxisEvent(SDL_Event &evnt);
 #if SDL_MAJOR_VERSION>1
 	void ProcessMouseWheelEvent(SDL_Event &evnt);
-
-	void ProcessFingerDownEvent(SDL_Event & evnt);
-	void ProcessFingerUpEvent(SDL_Event & evnt);
-	void ProcessFingerEvent(SDL_Event & evnt, bool finger_down);
+	void ProcessFingerEvent(SDL_Event & evnt);
 
 	/** @} */
 

src/system.h

@@ -79,6 +79,11 @@
 #  if !defined(OPENDINGUX) && !defined(GEKKO)
 #    define SUPPORT_KEYBOARD
 #    define SUPPORT_MOUSE
+
+     // We have our own touch input solution on Android
+#    if !defined(__ANDROID__)
+#      define SUPPORT_TOUCH
+#    endif
 #  endif
 
 #  if !defined(OPENDINGUX)