sdl: disable touch input support by default

It looks like that the Android system gets confused when both a pointer
and an touch based input device are connected to the system. As touch
support is so far only used Ubports we can keep it disabled for the
snap version but provide a configuration switch to enable it again.

CMakeLists.txt

@@ -136,3 +136,8 @@ configure_file("${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
 add_custom_target(uninstall "${CMAKE_COMMAND}"
                   -P "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake")
 
+option(TOUCH_INPUT "Enable touch input support" OFF)
+if (TOUCH_INPUT)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DENABLE_TOUCH_INPUT")
+endif()
+

src/anbox/platform/sdl/platform.cpp

@@ -101,6 +101,7 @@ Platform::Platform(
   keyboard_->set_key_bit(BTN_MISC);
   keyboard_->set_key_bit(KEY_OK);
 
+#ifdef ENABLE_TOUCH_INPUT
   touch_ = input_manager->create_device();
   touch_->set_name("anbox-touch");
   touch_->set_driver_version(1);
@@ -122,6 +123,7 @@ Platform::Platform(
   touch_->set_abs_bit(ABS_MT_TRACKING_ID);
   touch_->set_abs_max(ABS_MT_TRACKING_ID, 10);
   touch_->set_prop_bit(INPUT_PROP_DIRECT);
+#endif
 
   event_thread_ = std::thread(&Platform::process_events, this);
 }
@@ -189,8 +191,10 @@ void Platform::process_input_event(const SDL_Event &event) {
   std::int32_t x = 0;
   std::int32_t y = 0;
 
+#ifdef ENABLE_TOUCH_INPUT
   std::int32_t rel_x = 0;
   std::int32_t rel_y = 0;
+#endif
 
   SDL_Window *window = nullptr;
 
@@ -251,6 +255,7 @@ void Platform::process_input_event(const SDL_Event &event) {
       keyboard_events.push_back({EV_KEY, code, 0});
       break;
     }
+#ifdef ENABLE_TOUCH_INPUT
     // Touch screen
     case SDL_FINGERDOWN: {
       touch_events.push_back({EV_ABS, ABS_MT_TRACKING_ID, static_cast<std::int32_t>(event.tfinger.fingerId)});
@@ -343,13 +348,21 @@ void Platform::process_input_event(const SDL_Event &event) {
       touch_events.push_back({EV_SYN, SYN_REPORT, 0});
       break;
     }
+#endif
     default:
       break;
   }
 
-  if (mouse_events.size() > 0) pointer_->send_events(mouse_events);
-  if (keyboard_events.size() > 0) keyboard_->send_events(keyboard_events);
-  if (touch_events.size() > 0) touch_->send_events(touch_events);
+  if (mouse_events.size() > 0)
+    pointer_->send_events(mouse_events);
+
+  if (keyboard_events.size() > 0)
+    keyboard_->send_events(keyboard_events);
+
+#ifdef ENABLE_TOUCH_INPUT
+  if (touch_events.size() > 0)
+    touch_->send_events(touch_events);
+#endif
 }
 
 Window::Id Platform::next_window_id() {