Input and GLUTs Callbacks

1
Input and GLUTs Callbacks

• EECS 4530 Computer Graphics ISeptember 9, 2002

2
Characteristics

• All the GLUT supported I/O routines use callbacks
  to return information to the program.
• This type of input would be known as event mode
  input.
• Request mode wait at a given point in a program
  for input
• Sample mode Go out and get an input state at an
  instant in time dont wait for input.

3
Keyboard

• Register Callback withglutKeyboardFunc ( void
  (func) (unsigned char key, int x, int y))
• Routine receives
• key code (unsigned character) ASCII
• the x position of the mouse when the key was
  pressed
• the y position of the mouse when the key was
  pressed

4
Mouse/Locator Input

• glutMouseFunc attaches a callback to button
  press events.
• glutMotionFunc returns location information
  when a mouse is moved while the mouse button is
  down.
• glutPassiveMotionFunc returns location
  information when the mouse is moved with no
  buttons down.

5
Special keys

• glutSpecialFunc (void (func) (int key, int x,
  int y))
• Returns key information for special keys.
• GLUT_KEY_F1, GLUT_KEY_F2, GLUT_KEY_F3,
  GLUT_KEY_F4, GLUT_KEY_F5, GLUT_KEY_F6,GLUT_KEY_F7
  , GLUT_KEY_F8, GLUT_KEY_F9,GLUT_KEY_F10,
  GLUT_KEY_F11, GLUT_KEY_F12
• GLUT_KEY_UP, GLUT_KEY_DOWN, GLUT_KEY_RIGHT,
  GLUT_KEY_LEFT
• GLUT_KEY_HOME, GLUT_KEY_END, GLUT_KEY_PAGE_UP,
  GLUT_KEY_PAGE_DOWN

6
A Simple Example

• include "glut.h"
• include ltcmathgt
• include ltiostreamgt
• include ltstringgt
• using namespace std
• void getKey( unsigned char, int, int)
• void getButtonPress ( int, int, int, int)
• void getSpecialKey(int, int, int)
• void init (void)
• void display (void)

7
main

• int main (int argCount, char argValues)
• /
• Initialize the package (takes arguments from
  the command line
• /
• glutInit (argCount, argValues)
• /
• Initialize the display, and the window
  position
• /
• glutInitDisplayMode ( GLUT_SINGLE GLUT_RGB)
• glutInitWindowSize (400, 400)
• glutInitWindowPosition (100, 100)

8
main (contd)

• /
• Create the actual window
• /
• glutCreateWindow (argValues0)
• init()
• /
• hook up the display function to the GLUT
  package. You have
• one function you can hook up this way.
• /
• glutDisplayFunc (display)

9
main (contd)

• / Hook up the two functions for keyboard input
• /
• glutKeyboardFunc (getKey)
• glutSpecialFunc (getSpecialKey)
• /
• Add the mouse routine...
• /
• glutMouseFunc (getButtonPress)
• /
• Start responding to events.
• /
• glutMainLoop ( )
• return EXIT_SUCCESS

10
init

• void init()
• glClearColor(0.0, 0.0, 0.0, 0.0)/ background
  color/
• / Simple projection 6 by 6 by 20 cube
• /
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• glOrtho(-3.0, 3.0, -3.0, 3.0, -10.0, 10.0)
• / Return to drawing mode (modelview)
• /
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity()

11
getKey

• void getKey(unsigned char inChar, int xposition,
  int yposition)
• / Get the key press from the user. If you need
  to get a ctrl or alt key you will need
• glutGetModifiers to find the state of the
  keys. /
• if ( inChar 'q')
• cout ltlt "Exitting..." ltlt endl
• exit(0)
• else
• cout ltlt "Key " ltlt inChar ltlt " pressed " ltlt
  endl
• cout ltlt "\tThis occurred at position (" ltlt
  xposition ltlt " ," ltlt yposition ltlt ")" ltlt
  endl

12
getSpecialKey

• void getSpecialKey (int inKey, int xposition, int
  yposition)
• / Grab the special keys. If you need the
  modifiers
• you need to call glutGetModifiers()
• /
• if (inKey GLUT_KEY_F1)
• cout ltlt "F1 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F2)
• cout ltlt "F2 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F3)
• cout ltlt "F3 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F4)
• cout ltlt "F4 Key Pressed" ltlt endl

13
getSpecialKey (contd)

• else if (inKey GLUT_KEY_F5)
• cout ltlt "F5 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F6)
• cout ltlt "F6 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F7)
• cout ltlt "F7 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F8)
• cout ltlt "F8 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F9)
• cout ltlt "F9 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F10)
• cout ltlt "F10 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_F11)
• cout ltlt "F11 Key Pressed" ltlt endl

14
getSpecialKey (contd)

• else if (inKey GLUT_KEY_F12)
• cout ltlt "F12 Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_LEFT)
• cout ltlt "Left arrow Key Pressed" ltlt endl
• else if (inKey GLUT_KEY_UP)
• cout ltlt "Up arrow key Pressed" ltlt endl
• else if (inKey GLUT_KEY_DOWN)
• cout ltlt "Down arrow key Pressed" ltlt endl
• else if (inKey GLUT_KEY_RIGHT)
• cout ltlt "Right arrow key pressed" ltlt endl
• cout ltlt "\tThis occurred at position (" ltlt
  xposition ltlt " ," ltlt yposition ltlt ")" ltlt endl

15
getButtonPress

• void getButtonPress (int buttonPressed, int
  state, int xposition, int yposition)
• / Handle a button press from the mouse...
• This routine doesn't do anything useful --
  just
• reports info. /
• string buttonState, buttonName
• if (buttonPressed GLUT_MIDDLE_BUTTON)
• buttonName "middle"
• else if (buttonPressed GLUT_LEFT_BUTTON)
• buttonName "left"
• else if (buttonPressed GLUT_RIGHT_BUTTON)
• buttonName "right"

16
getButtonPress (contd)

• if (state GLUT_UP)
• buttonState "released"
• else if (state GLUT_DOWN)
• buttonState "pressed"
• cout ltlt "The " ltlt buttonName ltlt " mouse button
  was " ltlt buttonState ltlt endl
• cout ltlt "\tThis occurred at position (" ltlt
  xposition ltlt " ," ltlt yposition ltlt ") ltlt
  endl

17
display

• void display ()
• /
• Simple display -- just output the teapot...
• /
• glClear(GL_COLOR_BUFFER_BIT)
• glutWireTeapot(1.0)
• glFlush()

18
Creating a Menu

• glutCreateMenu(void (func)(int value))
• glutAddMenuEntry ( char name, int value)
• glutAddSubMenu()
• glutAttachMenu(int button)
• glutDetachMenu(int button)
• glutRemoveMenuItem(int entry)

19
Menu Example 1

• include "glut.h"
• include ltcmathgt
• include ltiostreamgt
• using namespace std
• void display()
• void init()
• void menuHandler(int)

20
main

• int main (int argCount, char argValues)
• int menuID
• / Initialize the package /
• glutInit (argCount, argValues)
• / Initialize the display, and the window
  position /
• glutInitDisplayMode ( GLUT_SINGLE GLUT_RGB)
• glutInitWindowSize (400, 400)
• glutInitWindowPosition (100, 100)

21
main

• / Create the actual window
• /
• glutCreateWindow (argValues0)
• init()
• / Hook up the display function to the GLUT
• package.
• /
• glutDisplayFunc (display)

22
main (contd)

• / Build a simple menu /
• menuID glutCreateMenu(menuHandler)
• glutAddMenuEntry("Red", 1)
• glutAddMenuEntry("Green", 2)
• glutAddMenuEntry("Blue", 3)
• glutAddMenuEntry("White", 4)
• glutAddMenuEntry("Black", 5)
• glutAttachMenu (GLUT_RIGHT_BUTTON)
• / Start responding to events.
• /
• glutMainLoop ( )
• return EXIT_SUCCESS

23
init

• void init()
• glClearColor(0.0, 0.0, 0.0, 0.0)/ background
  color/
• / Simple projection -- 6 by 6 by 20 cube
• /
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• glOrtho(-3.0, 3.0, -3.0, 3.0, -10.0, 10.0)
• /
• Return to drawing mode (modelview)
• /
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity()

24
display

• void display ()
• /
• Simple display -- just output the teapot...
• /
• glClear(GL_COLOR_BUFFER_BIT)
• glutWireTeapot(1.0)
• glFlush()

25
menuHandler

• void menuHandler(int itemPicked)
• / Simple handler that changes color drawn
  with.
• /
• switch (itemPicked)
• case 1 / red /
• glColor3f(1.0, 0.0, 0.0)
• break
• case 2 / green /
• glColor3f(0.0, 1.0, 0.0)
• break
• case 3 / blue /
• glColor3f(0.0, 0.0, 1.0)
• break

26
menuHandler (contd)

• case 4 / white /
• glColor3f(1.0, 1.0, 1.0)
• break
• case 5 / black /
• glColor3f(0.0, 0.0, 0.0)
• break
• default
• cout ltlt "Unexpected Choice " ltlt itemPicked ltlt
  endl
• break
• glutPostRedisplay() // force a redraw