Add axis control for camera move

This is simple linear control.

It needs some more tuning of the sensitivity, but works ok.

src/js/core/input_distributor.js

@@ -220,6 +220,24 @@ export class InputDistributor {
         }
     }
 
+    getGamepadAxes() {
+        if (this.connectedGamepadIndex === null) {
+            return {
+                x: 0,
+                y: 0,
+            };
+        }
+
+        const gamepad = navigator.getGamepads()[this.connectedGamepadIndex];
+
+        // Threshold 0.25 as the joysticks never return to exact 0
+        // power to 9 function to decrease the sensitivity, to be ~0.25 at 85%
+        return {
+            x: Math.abs(gamepad.axes[0]) < 0.25 ? 0 : gamepad.axes[0],
+            y: Math.abs(gamepad.axes[1]) < 0.25 ? 0 : gamepad.axes[1],
+        };
+    }
+
     /**
      * @param {Event} event
      */

src/js/game/camera.js

@@ -778,6 +778,7 @@ export class Camera extends BasicSerializableObject {
             this.internalUpdateCentering(now, physicsStepSizeMs);
             this.internalUpdateShake(now, physicsStepSizeMs);
             this.internalUpdateKeyboardForce(now, physicsStepSizeMs);
+            this.internalUpdateGamepadForce(now, physicsStepSizeMs);
         }
         this.clampZoomLevel();
     }
@@ -1008,4 +1009,24 @@ export class Camera extends BasicSerializableObject {
             this.center.y += moveAmount * forceY * movementSpeed;
         }
     }
+
+    /**
+     * Updates the gamepad axis forces
+     * @param {number} now
+     * @param {number} dt Delta time
+     */
+    internalUpdateGamepadForce(now, dt) {
+        const inputMgr = this.root.app.inputMgr;
+
+        if (inputMgr.connectedGamepadIndex !== null && !this.currentlyMoving && this.desiredCenter == null) {
+            const limitingDimension = Math.min(this.root.gameWidth, this.root.gameHeight);
+
+            const moveAmount = ((limitingDimension / 2048) * dt) / this.zoomLevel;
+
+            let { x, y } = inputMgr.getGamepadAxes();
+
+            this.center.x += moveAmount * x * 2;
+            this.center.y += moveAmount * y * 2;
+        }
+    }
 }