[Controller] improve character joystick movement (#8449)

Source/controls/controller_motion.cpp

@@ -207,17 +207,48 @@ void ProcessControllerMotion(const SDL_Event &event)
 	}
 }
 
-AxisDirection GetLeftStickOrDpadDirection(bool usePadmapper)
+AxisDirection GetAnalogStickDirection(float stickX, float stickY)
 {
-	const float stickX = leftStickX;
-	const float stickY = leftStickY;
-
+	// avoid sqrt() by comparing squared magnitudes
+	const float magnitudeSquared = stickX * stickX + stickY * stickY;
+	const float thresholdSquared = StickDirectionThreshold * StickDirectionThreshold;
+	if (magnitudeSquared < thresholdSquared)
+		return { AxisDirectionX_NONE, AxisDirectionY_NONE };
+
+	const float absX = std::fabs(stickX);
+	const float absY = std::fabs(stickY);
 	AxisDirection result { AxisDirectionX_NONE, AxisDirectionY_NONE };
 
-	bool isUpPressed = stickY >= 0.5;
-	bool isDownPressed = stickY <= -0.5;
-	bool isLeftPressed = stickX <= -0.5;
-	bool isRightPressed = stickX >= 0.5;
+	// 8-way sectoring with 22.5° cutoffs
+	constexpr float DiagonalCutoff = 0.41421356F; // tan(22.5°)
+	if (absX == 0.0F) {
+		result.y = stickY > 0 ? AxisDirectionY_UP : AxisDirectionY_DOWN;
+		return result;
+	}
+
+	const float ratio = absY / absX;
+	if (ratio <= DiagonalCutoff) {
+		result.x = stickX > 0 ? AxisDirectionX_RIGHT : AxisDirectionX_LEFT;
+		return result;
+	}
+	if (ratio >= 1.0F / DiagonalCutoff) {
+		result.y = stickY > 0 ? AxisDirectionY_UP : AxisDirectionY_DOWN;
+		return result;
+	}
+
+	result.x = stickX > 0 ? AxisDirectionX_RIGHT : AxisDirectionX_LEFT;
+	result.y = stickY > 0 ? AxisDirectionY_UP : AxisDirectionY_DOWN;
+	return result;
+}
+
+AxisDirection GetLeftStickOrDpadDirection(bool usePadmapper)
+{
+	AxisDirection result = GetAnalogStickDirection(leftStickX, leftStickY);
+
+	bool isUpPressed = false;
+	bool isDownPressed = false;
+	bool isLeftPressed = false;
+	bool isRightPressed = false;
 
 	if (usePadmapper) {
 		isUpPressed |= PadmapperIsActionActive("MoveUp");

Source/controls/controller_motion.h

@@ -25,6 +25,9 @@ extern float leftStickX, leftStickY, rightStickX, rightStickY;
 // Whether stick positions have been updated and need rescaling.
 extern bool leftStickNeedsScaling, rightStickNeedsScaling;
 
+// Minimum scaled stick magnitude to register a direction.
+constexpr float StickDirectionThreshold = 0.4F;
+
 // Updates motion state for mouse and joystick sticks.
 void ProcessControllerMotion(const SDL_Event &event);
 

Source/controls/plrctrls.cpp

@@ -1594,8 +1594,11 @@ struct RightStickAccumulator {
 
 bool IsStickMovementSignificant()
 {
-	return leftStickX >= 0.5 || leftStickX <= -0.5
-	    || leftStickY >= 0.5 || leftStickY <= -0.5
+	// avoid sqrt() by comparing squared magnitudes
+	const float leftStickMagnitudeSquared = leftStickX * leftStickX + leftStickY * leftStickY;
+	const float thresholdSquared = StickDirectionThreshold * StickDirectionThreshold;
+
+	return leftStickMagnitudeSquared >= thresholdSquared
 	    || rightStickX != 0 || rightStickY != 0;
 }