Version 5.0 The LEDA User Manual

17.2 Windows ( window )
1. Definition
The data type window provides an interface for graphical input and output of basic twodimensional
geometric objects. Application programs using this data type have to be
linked with libW.a and (on UNIX systems) with the X11 base library libX11.a (cf. section
1.6):
CC prog.c -lW -lP -lG -lL -lX11 -lm
An instance W of type window is an iso-oriented rectangular window in the twodimensional
plane. The default representation of W on the screen is a square of maximal
possible edge length positioned in the upper right corner of the display.
In general, a window consists of two rectangular sections, a panel section in the upper
part and a drawing section in the rest of the window. The panel section contains panel
items such as sliders, choice fields, string items and buttons. They have to be created
before the window is opened by special panel operations described in section 17.2.
The drawing section can be used for the output of geometric objects such as points, lines,
segments, arrows, circles, polygons, graph, . . . and for the input of all these objects using
the mouse input device. All drawing and input operations in the drawing section use a
coordinate system that is defined by three parameters of type double: xmin, the minimal
x-coordinate, xmax, the maximal x-coordinate, and ymin, the minimal y-coordinate. The
two parameters xmin and xmax define the scaling factor scaling as w/(xmax − xmin),
where w is the width of the drawing section in pixels. The maximal y-coordinate ymax
of the drawing section is equal to ymin + h · scaling and depends on the actual shape of
the window on the screen. Here, h is the height of the drawing section in pixels.
A list of all window parameters:
1. The foreground color parameter (default black) defines the default color to be
used in all drawing operations. There are 18 predefined colors (enumeration in
): black, white, red, green, blue, yellow, violet,
orange, cyan, brown, pink, green2, blue2, grey1, grey2, grey3 ivory, and invisible.
Note that all drawing operations have an optional color argument that can be used
to override the default foreground color. On monochrome systems all colors different
from white are displayed as black. The color invisible can be used for invisible
(transparent) objects.
2. The background color parameter (default white) defines the default background color
(e.g. used by W .clear()).
3. The text font parameter defines the name of the font to be used in all text drawing
operations.