Version 5.0 The LEDA User Manual

3.5 Input
The main input operation for reading positions, mouse clicks, and buttons from a window
W is the operation W .read mouse(). This operation is blocking, i.e., waits for a button to
be pressed which is either a “real” button on the mouse device pressed inside the drawing
area of W or a button in the panel section of W . In both cases, the number of the selected
button is returned. Mouse buttons have pre-defined numbers MOUSE BUTTON(1) for
the left button, MOUSE BUTTON(2) for the middle button, and MOUSE BUTTON(3)
for the right button. The numbers of the panel buttons can be defined by the user. If the
selected button has an associated action function or sub-window this function/window is
executed/opened (cf. 17.2 for details).
There is also a non-blocking version W .get mouse() which returns the constant
NO BUTTON if no button was pressed.
The window data type also provides two more general input operations W .read event()
and W .get event() for reading events. They return the event type (enumeration in
), the value of the event, the position of the event in
the drawing section, and a time stamp of the event.
3.5.1 Read Mouse
int W.read mouse( ) waits until a mouse button is pressed inside of the drawing
area or until a button of the panel section is selected. In
both cases, the number n of the button is returned which
is one of the predefined constants MOUSE BUTTON(i)
with i ∈ {1, 2, 3} for mouse buttons and a user defined
value (defined when adding the button with W .button())
for panel buttons. If the button has an associated action
function this function is called with parameter n. If
the button has an associated window M it is opened and
M.read mouse() is returned.
int W.read mouse(double& x, double& y)
int W.read mouse(point& p)
If a button is pressed inside the drawing area the current
position of the cursor is assigned to (x, y). The operation
returns the number of the pressed button (see
W .read mouse().)
as above, the current position is assigned to point p.
int W.read mouse seg(double x 0 , double y 0 , double& x, double& y)
displays a line segment from (x 0 , y 0 ) to the current cursor
position until a mouse button is pressed inside the drawing
section of W . When a button is pressed the current position
is assigned to (x, y) and the number of the pressed
button is returned.