Add analog stick gamepad controls

src/sdl_input.c

@@ -117,6 +117,34 @@ static int sdl_input_update(nes_Input_Reader* reader,
                 }
             }
 
+        } else if (SDL_CONTROLLERAXISMOTION == event.type) {
+            const uint8_t axis = event.caxis.axis;
+            const int16_t value = event.caxis.value;
+            uint8_t mask_set = 0;
+            uint8_t mask_clear = 0;
+
+            if (SDL_CONTROLLER_AXIS_LEFTX == axis) {
+                mask_clear = (1 << Button_Left) |
+                             (1 << Button_Right);
+                if (value <= -8192) {
+                    mask_set = (1 << Button_Left);
+                } else if (value >= 8192) {
+                    mask_set = (1 << Button_Right);
+                }
+
+            } else if (SDL_CONTROLLER_AXIS_LEFTY == axis) {
+                mask_clear = (1 << Button_Down) |
+                             (1 << Button_Up);
+                if (value <= -8192) {
+                    mask_set = (1 << Button_Up);
+                } else if (value >= 8192) {
+                    mask_set = (1 << Button_Down);
+                }
+            }
+
+            input->controllers[0].buttons &= ~mask_clear;
+            input->controllers[0].buttons |= mask_set;
+
         } else if (SDL_CONTROLLERDEVICEADDED == event.type) {
             if (NULL == reader->data) {
                 reader->data = sdl_find_gamepad();