Multimedia methods to use

With the more interactive programs using SplashKit there are now a whole range of methods that we can use to check for user inputs, and to help test different aspect of our game (such as time passing, and detecting collisions).

The methods we will need in this chapter include:

• Event loop methods:

  • Process Events - listens for actions that the user has performed such as keystrokes, mouse clicks, quitting, etc.
  • Quit Requested - returns true when the user has asked to close the program.

• Key input methods:

  • Key Down - allows you to test if a key is held down.

• Random number methods:

  • Rnd - Generate a random number.

• Time management methods:

  • Create Timer - create a timer to keep track of time.
  • Start Timer - start a timer ticking. You can then query it for how long has passed since it was started.
  • Timer Ticks - tells you how long has passed since the timer was started.

• Collision detection methods:

  • Circles Intersect - test if two circles intersect.
  • Triangle Rectangle Intersect - test if a triangle and rectangle intersect.
  • Rectangle From - create a rectangle from a given point, width, and height.
  • Triangle From - create a triangle from a given set of points.

These methods have the following declarations:

// These needs...
// using static SplashKitSDK.SplashKit;

// Event loop
public static void ProcessEvents();
public static bool QuitRequested();

// Key input
// This also requiers... to get access to the KeyCode details.
// using SplashKitSDK;
public static bool KeyDown(KeyCode key);

// Random numbers
public static float Rnd(); // 0 to 1
public static int Rnd(int ubound); // 0 to ubound - 1
public static int Rnd(int min, int max); // min to max


// Time tracking
public static Timer CreateTimer(string name);
public static void StartTimer(string name);
public static uint TimerTicks(string name);

// Collision detection
public static bool CirclesIntersect(double c1X, double c1Y, double c1Radius, double c2X, double c2Y, double c2Radius);
public static bool TriangleRectangleIntersect(Triangle tri, Rectangle rect);
public static Rectangle RectangleFrom(double x, double y, double width, double height);
public static Triangle TriangleFrom(double x1, double y1, double x2, double y2, double x3, double y3);

Key Codes

For the KeyDown method, you need to tell it which key you are wanting to check. SplashKit provides a list of key codes in a KeyCode type, which provides a list of values you can choose from. You should be able to see these in VS Code using its IntelliSense, just make sure you have using SplashKitSDK; so that you can see the KeyCode.

The main options include:

BackspaceKey	TabKey	ReturnKey	EscapeKey	SpaceKey
Num0Key	Num1Key	Num2Key	Num3Key	Num4Key
Num5Key	Num6Key	Num7Key	Num8Key	Num9Key
ColonKey	SemiColonKey	AKey	BKey	CKey
DKey	EKey	FKey	GKey	HKey
IKey	JKey	KKey	LKey	MKey
NKey	OKey	PKey	QKey	RKey
SKey	TKey	UKey	VKey	WKey
XKey	YKey	ZKey	DeleteKey	Keypad0
Keypad1	Keypad2	Keypad3	Keypad4	Keypad5
Keypad6	Keypad7	Keypad8	Keypad9	KeypadPeriod
KeypadDivide	KeypadMultiply	KeypadMinus	KeypadPlus	KeypadEnter
KeypadEquals	UpKey	DownKey	RightKey	LeftKey
InsertKey	HomeKey	EndKey	PageUpKey	PageDownKey
F1Key	F2Key	F3Key	F4Key	F5Key
F6Key	F7Key	F8Key	F9Key	F10Key
F11Key	F12Key	F13Key	F14Key	F15Key
RightShiftKey	LeftShiftKey	RightCtrlKey	LeftCtrlKey	RightAltKey
LeftAltKey	LeftSuperKey	RightSuperKey

You access these using KeyCode. and then the specific key value. For example, KeyCode.AKey for the “a” key or KeyCode.LeftKey for the left arrow. See the example code below for how to use this.

Mouse Buttons and Methods

SplashKit also includes a number of methods for working with the mouse. These include the following:

// These methods need
// using static SplashKitSDK.SplashKit;

// Was a given button on the mouse clicked?
public static bool MouseClicked(MouseButton button);
// Is a given button in the mouse current held down?
public static bool MouseDown(MouseButton button);

// Where is the mouse - relative to the left side of the window?
public static float MouseX();
// Where is the mouse - relative to the top of the window?
public static float MouseY();

For these you will need to use the MouseButton data. As with the KeyCode data, make sure you have using SplashKitSDK; so that you can see the MouseButton type.

There are the following mouse button values:

• LeftButton for the left mouse button
• MiddleButton for the middle mouse button
• RightButton for the right mouse button
• MouseX1Button for the x1 mouse button
• MouseX2Button for the x2 mouse button

As with the KeyCode data, you access this using MouseButton. and the button name, MouseButton.LeftButton for example. See the example code below to see how this may work.

Example Multimedia Code

Here is some example multimedia code that creates a program where the user is able to move a shape around on the screen.

using static SplashKitSDK.SplashKit;
using SplashKitSDK;

const int MOVE_SPEED = 3;

OpenWindow("Movement", 800, 600);

// Event loop
double x = 400;
Color clr = ColorBlack();

while( !QuitRequested() )
{
  ProcessEvents();

  if (KeyDown(KeyCode.RightKey))
  {
    x += MOVE_SPEED;
  }

  if (KeyDown(KeyCode.LeftKey))
  {
    x -= MOVE_SPEED;
  }

  if (KeyTyped(KeyCode.SpaceKey))
  {
    clr = RandomColor();
  }

  ClearScreen(ColorWhite());
  FillCircle(clr, x, 300, 50);
  RefreshScreen(60);
}

The following code shows an example of using the mouse, and its position as part of a program. This uses the distance from the player to the mouse to set the direction of a ball which is thrown when the mouse is clicked.

using static SplashKitSDK.SplashKit;
using SplashKitSDK;

const int BALL_RADIUS = 5;
const int PLAYER_RADIUS = 20;

// Used to calculate distance from player - mouse for
// Ball speed. speed = distance / DIST_TO_SPEED_RATIO.
const double DIST_TO_SPEED_RATIO = 30;
// as above for the line drawn to show direction of shot
const double DIST_LINE_RATIO = 10;

OpenWindow("Ball Throw", 800, 600);

bool ballFired = false;

double playerX = 400, playerY = 300;
double ballX = playerX;
double ballY = playerY;
double ballXSpeed = 0;
double ballYSpeed = 0;

while (!QuitRequested())
{
  ProcessEvents();

  if (MouseClicked(MouseButton.LeftButton) && !ballFired)
  {
    ballFired = true;

    // calculate velocity for the BALL
    ballXSpeed = (MouseX() - playerX) / DIST_TO_SPEED_RATIO;
    ballYSpeed = (MouseY() - playerY) / DIST_TO_SPEED_RATIO;
  }

  if (ballFired)
  {
    // Move the projective by its x and y speed
    ballX += ballXSpeed;
    ballY += ballYSpeed;

    // check if off screen
    if (ballX + BALL_RADIUS < 0 || // off left
        ballX - BALL_RADIUS > ScreenWidth() || // off right
        ballY + BALL_RADIUS < 0 || // off top
        ballY - BALL_RADIUS > ScreenHeight()
        ) // off bottom
    {
      ballFired = false;
      ballX = playerX;
      ballY = playerY;
    }
  }

  ClearScreen(ColorWhite());
  FillCircle(ColorLightGreen(), playerX, playerY, PLAYER_RADIUS);
  FillCircle(ColorBlack(), ballX, ballY, BALL_RADIUS);

  if ( ! ballFired )
  {
    // Show direction of travel
    DrawLine(ColorBlack(),
      playerX, playerY,
      playerX + (MouseX() - playerX) / DIST_LINE_RATIO,
      playerY + (MouseY() - playerY) / DIST_LINE_RATIO
    );
  }

  RefreshScreen(60);
}