12. Keyboard & Mouse

Transcript

1. 12. Keyboard and mouse
   Tatsuya Yatagawa
   

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2. Keyboard events in GLFW
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   Register callback function
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   glfwSetKeyCallback
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   1st parameter: Window pointer (GLFWwindow*)
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   2nd parameter: Function pointer of callback
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   Code
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3. Callback function for keyboard event
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   Parameters of callback function
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   1st: Window pointer
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   2nd: Key type (ASCII code is stored)
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   3rd: Platform-dependent scan code (not used)
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   4th: Key is pressed or released?
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   5th: Status of special keys (Shift, Ctrl, Alt)
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   Code
   Computer Graphics Course @Waseda University
   (Simple key press and print its type and action)
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4. Identify key types
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   Key types in GLFW
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   GLFW_KEY_X is defined as an enumeration.
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   e.g.) “A” → GLFW_KEY_A, “1” → GLFW_KEY_1
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   GLFW_KEY_X is defined by ASCII codes(*1)
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   e.g.) GLFW_KEY_A → 0x41, GLFW_KEY_1 → 0x31
   Computer Graphics Course @Waseda University
   *1) ASCII - Wikipedia https://en.wikipedia.org/wiki/ASCII
   By converting to char type, it can be printed as a character.
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5. Identify event types
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   Type of keyboard events in GLFW
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   Any key is pressed → GLFW_PRESS
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   Any key is released → GLFW_RELEASE
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   When key is kept pressed, key-pressed event is repeatedly
   detected.
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6. Detect special key status
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   Special keys in GLFW
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   Shift key → GLFW_MOD_SHIFT (0x01)
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   Ctrl key → GLFW_MOD_CONTROL (0x02)
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   Alt key (Option in MacOS) → GLFW_MOD_ALT (0x04)
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   Super key → GLFW_MOD_SUPER (0x08)
   (Super key ＝ Windows key for Windows, Command key for MacOS)
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   Special key is defined as a bit mask.
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7. Mouse events in GLFW
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   Mouse press/release events
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   Set callback with glfwSetMouseButtonCallback
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   Parameters for callback function
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   1st: Window on which event is detected
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   2nd: Button type
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   3rd: Whether key is pressed or released
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   4th: Status of special keys
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   Mouse move events
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   Set callback with glfwSetCursorPosCallback
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   Parameters for callback function
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   1st: Window on which event is detected
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   2nd: X-coordinate to which mouse moved
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   3rd: Y-coordinate to which mouse moved
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8. Mouse press/release events
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   Callback parameters do not receive mouse position
   → glfwGetCursorPos provides the position
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9. Mouse move events
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   Event is detected when mouse is moved over window
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   Callback for move receives the mouse position
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10. How to achieve mouse drag?
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    Basic idea
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    Mouse drag = mouse press + mouse move (before mouse
    release)
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    Check mouse is keep pressed and then check it moves.
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    ToDo
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    Prepare a bool (global variable) to represent whether mouse
    button is pressed or not
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    If button is pressed, set the bool as “true”. If button is released,
    set the button as “false”.
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    If cursor position callback is called while the button is pressed,
    then the event is “drag”.
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11. Exercise 12-1
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    Implement mouse drag using mouse press/release and
    move callbacks. When mouse is dragged, output
    position and pressed keys.
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    Hint: To identify pressed/released mouse buttons, use:
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    GLFW_MOUSE_BUTTON_LEFT (left button)
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    GLFW_MOUSE_BUTTON_RIGHT (right button)
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    GLFW_MOUSE_BUTTON_MIDDLE (middle button)
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