1. CS 134
Alternate Inputs

2. Today in Video Games

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4. Alternate Inputs Other input methods are similar via polling Mouse
XInput
Joystick
Other inputs that must be done with events
Touchscreen

5. Alternate Inputs
Gesture recognition is much more important with other inputs
Mouse
Click vs Drag
Joystick
Light vs Heavy press

6. Alternate Inputs
Each input has a different way of getting the actual input state
May require setup / cleanup code
But we usually don't care about cleanup, the OS will do that for us!

7. Keyboard

8. Keyboard No setup or cleanup code C API – Polling
SDL_GetKeyboardState()
Returns the state of each key on the keyboard
Java API – Events (converted to Polling)
KeyListener.keyPressed, .keyReleased
Store current state in kbState
Gestures
Keep the last state of the keyboard around to know if it was just pressed or just released

9. Mouse

10. Mouse No setup or cleanup code C API – Polling SDL_GetMouseState()
SDL_GetRelativeMouseState()
SDL_SetRelativeMouseMode()
Java API – Events (converted to polling)
MouseListener.mouseMoved, .mouseClicked, .mouseDragged, etc.
Gestures
Click, double click, drag

11. Mouse SDL_GetMouseState(int* x, int* y)
SDL_GetRelativeMouseState(int* x, int* y)
Fill out X, Y with the pixel position / change of the mouse.
Returns the current state of the mouse buttons
Bitand (&) with each button to see its state
SDL_BUTTON_LMASK for left
SDL_BUTTON_MMASK for middle
SDL_BUTTON_RMASK for right

12. Mouse // globals int mouseX, mouseY, mouseDeltaX, mouseDeltaY;
Uint32 mouseButtons;
// game loop
while (!shouldExit) {
lastFrameMs = currentFrameMs;
memcpy(kbPrevState, kbState, sizeof(kbPrevState));
SDL_Event event;
while (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_QUIT:
shouldExit = 1; }
currentFrameMs = SDL_GetTicks();
float deltaTime = (currentFrameMs - lastFrameMs) / f;
mouseButtons = SDL_GetMouseState(&mouseX, &mouseY);
SDL_GetRelativeMouseState(&mouseDeltaX, &mouseDeltaY);
/* Rest of the game loop goes here */
SDL_GL_SwapWindow(window);

13. Mouse MouseListener.mouseMoved(MouseEvent e)
Also mouseDragged, mousePressed, etc.
e.getX(), e.getY()
Get X, Y of mouse when event happened.
e.getButton()
Get button event happened for.
No way to get only relative motion.

14. Mouse // fields public static int mouseX, mouseY;
public static boolean mouseButton[] = new boolean[3];
// initializiation
window.addKeyListener(new KeyListener() {...});
window.addMouseListener(new MouseListener() {
private void updateMousePos(MouseEvent ev) {
mouseX = ev.getX();
mouseY = ev.getY(); }
private void updateMouseButtons(MouseEvent ev) {
int idx = mouseEvent.getButton() - 1;
if (idx >= 0 && idx < mouseButtons.length) {
mouseButtons[idx] = true;
public void mouseEntered(MouseEvent ev) { updateMousePos(ev); }
public void mouseMoved(MouseEvent ev) { updateMousePos(ev); }
public void mouseDragged(MouseEvent ev) { updateMousePos(ev); }
public void mouseExited(MouseEvent ev) { updateMousePos(ev); }
public void mousePressed(MouseEvent ev) { updateMouseButtons(ev); }
public void mouseReleased(MouseEvent ev) { updateMouseButtons(ev); }
public void mouseClicked(MouseEvent ev) {}
public void mouseWheelMoved(MouseEvent ev){}
});

15. Mouse SDL_SetRelativeMouseMode(bool)
If set, the mouse will disappear and freeze. Relative motion will still work
Useful for cameras!
For RTS: Enable when dragging starts, disable when dragging ends
For FPS: Enable when in gameplay, disable leaving gameplay
No corresponding method for Java.

16. Mouse
Using the mouse, you may want to distinguish between different gestures:
Click / Double Click / Drag
All you can detect is the low level operations
Mouse Button Is Down / Mouse Button Is Up
Unlike the keyboard, these gestures have a time component to them

17. Mouse
What is a click?
What is a double click?
What is a drag?

18. Mouse What is a click? A down followed by an up within .1 sec
Minimal mouse movement
What is a double click?
Two clicks within .3 seconds
Note that this will ALSO include the clicks!
What is a drag?
Mouse held down for more than .1 sec
-OR- significant movement with mouse down

19. Mouse
To detect these you will need to keep track of when and where the mouse went down last!
int lastMouseDownX, lastMouseDownY
int lastMouseDownTime
Then a click is when all of the following are true
Left button is just down
currentFrameTime - lastMouseDownTime < .1 sec
abs(mouseX - lastMouseDownX) < 5
abs(mouseY - lastMouseDownY) < 5

20. Mouse
Similar checks for Drag, Double click:

21. Mouse
Questions?

22. Joysticks

23. Joysticks APIs for Joysticks XInput JInput
XInput is significantly easier to use, but only works for Xbox 360-style controllers
And only on Windows
With Java bindings too!

24. Joysticks No setup or cleanup code C API – Polling XInputGetState()
struct XINPUT_STATE
Java API – Polling
XInputDevice.poll(), .getComponents().getAxes(), .getComponents().getButtons()
Gestures
Deadzone for sticks

25. Joysticks XInputGetState(int i, XINPUT_STATE* state)
Returns ERROR_SUCCESS if a gamepad is connected
i is 0 – 3, for each of the gamepads
Fills out state with all the different parts of a gamepad

26. Joysticks struct XINPUT_STATE .Gamepad.wButtons
Bitand with values to see the state of the DPAD, face buttons, bumpers, and click sticks
XINPUT_GAMEPAD_DPAD_UP, etc.
.Gamepad.bLeftTrigger, bRightTrigger
0 – 255 values for each trigger
.Gamepad.sThumbLX, sThumbLY
– values for the axis
sThumbRX, sThumbRY for right stick

27. Joysticks XInputDevice.isAvailable()
Returns true if XInput is available and library is loaded
XInputDevice.getAllDevices()
Returns an array of four XInputDevice objects, one for each player.
Player 1’s controller is in arr[0], Player 2’s in arr[1], etc.

28. Joysticks XInputDevice.poll()
Updates the state of all buttons and axes based on the current state of the controller.
Returns true if that controller is plugged in.
Call this every frame on every device!
XInputDevice.getComponents().getButtons()
Get the current state of all the buttons as an XinputButtons object.
Has public fields .a, .b, .x, .y, .up, .down, etc.

29. Joysticks XInputDevice.getComponents().getAxes()
Get the current state of all the axes as an XinputAxes object.
Has public fields .lx, .ly, .rx, .ry, .lt, .rt, and raw copies of each
Axes range from -1 to +1 for left and right sticks and 0 to 1 for triggers
Raw values have the underlying integer values, which range from to for sticks and 0 to 255 for triggers.

30. Joysticks XInputDevice.getLastComponents()
Gets the previous state for axes and buttons.
Think “prevKb” but for the input device!

31. Joysticks
Players are very bad at holding the sticks perfectly stationary.
Need to create a “dead zone” where even if the stick is moving, it is treated as being at zero
I suggest values from -500 to +500
(-0.02 to +0.02)
Not an issue with triggers!

32. Joysticks
Questions?