CS 450: COMPUTER GRAPHICS GLUT INPUT FUNCTIONS SPRING 2015 DR. MICHAEL J. REALE

INTRODUCTION Apart from creating the window, GLUT also allows accessing the mouse and keyboard as well as creating popup menus.

MOUSE COORDINATES: UP IS DOWN All mouse coordinates in GLUT are in SCREEN COORDINATES with Y INVERTED (so up is down) Relative to TOP-LEFT window corner! If storing, do something like this: currentYMouse = windowHeight – yMouse;

MOUSE BUTTONS glutMouseFunc(mouseFunction); void mouseFunction(GLint button, GLint action, GLint xMouse, GLint yMouse) Called when a mouse button is FIRST PRESSED or RELEASED Mouse click = two events (a press and release) GLint button  can be GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON, or GLUT_RIGHT_BUTTON GLint action  either GLUT_DOWN or GLUT_UP GLint xMouse, yMouse  mouse coordinates at time of event

MOUSE MOVING If the MOUSE is MOVING and ANY MOUSE BUTTON is DOWN: glutMotionFunc(mouseMovingButton); void mouseMovingButton(GLint xMouse, GLint yMouse) If the MOUSE is MOVING and NO MOUSE BUTTONS are DOWN: glutPassiveMotionFunc(mouseMovingNoButton); void mouseMovingNoButton(GLint xMouse, GLint yMouse) Usually means you have to keep track of what mouse buttons are down with your glutMouseFunc() callback E.g., have a global called “leftMouseDown” and set it in mouseFunction()

KEYBOARD: REGULAR KEYS glutKeyboardFunc(keyboard) void keyboard(GLubyte key, GLint xMouse, GLint yMouse) Function called when the user PRESSES a key. NOTE: It will CONTINUE to be called if the user keeps holding the key down! GLubyte key = character value or ASCII code for key pressed GLint xMouse, yMouse = mouse coordinates at time of key press

KEYBOARD: SPECIAL KEYS glutSpecialFunc(specialKeyboard) Void specialKeyboard(GLint specialKey, GLint xMouse, GLint yMouse) Uses for special-purpose keys like the function keys (F1, F2, etc.) and arrow keys GLint specialKey = integer-valued GLUT symbolic constant Examples: GLUT_KEY_F1, GLUT_KEY_UP, GLUT_KEY_HOME, etc. GLint xMouse, yMouse = mouse coordinates at time of key press

POPUP MENUS GLUT also allows you to create popup menus and submenus These are generally set up in the same place where you register the GLUT callback functions However, you can also add/remove items in other parts of your code

CREATING, SETTING, AND DESTROY A MENU GLuint menuID = glutCreateMenu(menuFunction) void menuFunction(GLint menuItemNumber) Called when a menu item is clicked on GLint menuItemNumber = index of menu item In function, decide what to do for each menu item glutSetMenu(menuID) Sets menu as current menu for display window glutDestroyMenu(menuID) Destroys menu If menu happens to be the current menu for the display window  window now has no menu assigned

GETTING CURRENT MENU ID currentMenuID = glutGetMenu() Returns current menu attached to display window (or 0 if no menu is attached)

ADDING MENU ENTRIES glutAddMenuEntry(charString, menuItemNumber) Add a menu item to current menu (determined by either last call to glutCreateMenu() or by glutSetMenu()) charString = text for menu entry menuItemNumber = menu item number NOTE: Order you add them in determines order of display ALSO NOTE: ID does NOT have to follow order of display (e.g., first item could have an ID of 500) FURTHER NOTE: Two or more items can have the SAME ID

ATTACHING A MOUSE BUTTON We also need to determine which mouse button will be used to open the menu: glutAttachMenu(button) button = can be GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON, or GLUT_RIGHT_BUTTON

CREATING SUBMENUS Just create another menu: GLuint submenuID = glutCreateMenu(subMenuFunction); glutAddMenuEntry(“First submenu item”, 1); … Then, add menu to main menu: glutCreateMenu(menuFunction); … glutAddSubMenu(“Submenu Option”, submenuID);

CHANGING THE MENU MOUSE BUTTON To change the mouse button used to open menus, first detach it: glutDetachMenu(mouseButton); Then attach the button you want

DELETING MENU ITEMS glutRemoveMenuItem(itemNumber) Removes itemNumber from the current menu If multiple items have the same number, will delete one of them