Change button color when pressed

This actually serves a practical purpose as it provides visual
indication that the button has been pressed and makes the game more
playable (for me, at least).

src/sdl/video.c

@@ -738,6 +738,7 @@ static void FingerDown(SDL_TouchFingerEvent *ev)
 
 	b = GetTouchButton(ev);
 	pressed_buttons[ev->fingerId] = b;
+	Vid_TouchButtonPress(b, true);
 	if (b == NULL) {
 		return;
 	}
@@ -777,6 +778,7 @@ static void FingerUp(SDL_TouchFingerEvent *ev)
 		break;
 	}
 	pressed_buttons[ev->fingerId] = NULL;
+	Vid_TouchButtonPress(b, false);
 }
 
 static void FingerMove(SDL_TouchFingerEvent *ev)

src/touch_area.c

@@ -71,12 +71,14 @@ static void DrawTouchArea(const struct touch_button *buttons)
 			swcolor(3);
 		} else {
 			int x, y;
+			bool pressed = i < arrlen(button_pressed)
+			            && button_pressed[i];
 			GetButtonPos(b, &x, &y);
 			Vid_Box(x, SCR_HGHT - y,
 			        BUTTON_WIDTH, BUTTON_HEIGHT, 3);
 			Vid_Box(x + 1, SCR_HGHT - y - 1,
 			        BUTTON_WIDTH - 2, BUTTON_HEIGHT - 2,
-			        b->type == TOUCH_BUTTON_CLOSE ? 2 : 1);
+			        pressed ? 2 : 1);
 			swcolor(0);
 		}
 
@@ -103,6 +105,14 @@ const struct touch_button *Vid_GetTouchButton(int x, int y)
 	return NULL;
 }
 
+void Vid_TouchButtonPress(const struct touch_button *b, bool pressed)
+{
+	int idx = b - game_buttons;
+	if (idx >= 0 && idx < arrlen(button_pressed)) {
+		button_pressed[idx] = pressed;
+	}
+}
+
 void Vid_DrawTouchControls(void)
 {
 	DrawTouchArea(game_buttons);

src/video.h

@@ -129,5 +129,6 @@ struct touch_button {
 
 extern void Vid_DrawTouchControls(void);
 extern const struct touch_button *Vid_GetTouchButton(int x, int y);
+extern void Vid_TouchButtonPress(const struct touch_button *b, bool pressed);
 
 #endif