Responding to Mouse Events

OBJECTS

  typedef void (*mousefn)(control c, int buttons, point xy);

FUNCTIONS

  void setmousedown(control c, mousefn fn);
  void setmousemove(control c, mousefn fn);
  void setmousedrag(control c, mousefn fn);
  void setmouseup(control c, mousefn fn);
  void setmouserepeat(control c, mousefn fn);

CONSTANTS

  #define NoButton      0x0000
  #define LeftButton    0x0001
  #define MiddleButton  0x0002
  #define RightButton   0x0004

NOTES

The functions setmousedown, setmousemove, setmousedrag, setmouseup, setmouserepeat allow response to mouse events. They associate call-back functions with a control, so that when a certain kind of mouse events occurs, the relevent call-back function is called.

Each of the functions handles a different kind of mouse event:

• setmousedown handles when the mouse is clicked inside a control.
• setmousemove handles when the mouse is moved within a control, but no mouse buttons are held down.
• setmousedrag handles when the mouse is moved while one or more mouse buttons are held down simultaneously.
• setmouseup handles when all mouse buttons are released.
• setmouserepeat handles the situation that one or more mouse buttons are held down for more than a second.

Each of the call-backs are defined as mousefn. A mousefn has an integer argument buttons and a point xy. These refer to the mouse state.

If any of the mouse buttons are held down when the call-back is activated, the buttons parameter will be set to reflect the fact. It is a bit-field which is organised so that buttons&LeftButton is set when the left mouse button is down, buttons&MiddleButton corresponds to the middle mouse button and buttons&RightButton corresponds to the right mouse button. It will be zero if no buttons are held down. The point xy is the location of the mouse in local co-ordinates, relative to the control.