Page 92 Table of Contents Index Page 94
Chapters
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30
A, B, C, D, E




Chapter 12

Graphics

12.1 Overview of Graphics

The CLIM graphic drawing model is an idealized model of graphical pictures. The model provides
the language that application programs use to describe the intended visual appearance of textual
and graphical output. Usually not all of the contents of the screen are described using the graphic
drawing model. For example, menus and scroll bars might be described in higher-level terms.

An important aspect of the CLIM graphic drawing model is its extreme device independence.
The model describes ideal graphical images and ignores limitations of actual graphics devices.
One consequence of this is that the actual visual appearance of the screen can only be an
approximation of the appearance specified by the model. Another consequence of this is that
the model is highly portable.

CLIM separates output into two layers, a text/graphics layer in which one specifies the desired
visual appearance independent of device resolution and characteristics, and a rendering layer in
which some approximation of the desired visual appearance is created on the device. Of course
application programs can inquire about the device resolution and characteristics if they wish and
modify their desired visual appearance on that basis. (There is also a third layer above these
two layers, the adaptive toolkit layer where one specifies the desired functionality rather than
the desired visual appearance.)

Major issue: There are still no functions to ask about device resolution and characteristics.
What characteristics do we need to be able to get to besides the obvious ones of resolution and
"color depth". Also, do we really need to refer to the adaptive toolkit layer here? | SWM

CLIM's drawing functions provide convenient ways to draw several commonly-used shapes.

The interaction between graphics and output recording will be described in Chapter 16.

Page 92 Table of Contents Index Page 94
Chapters
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30
A, B, C, D, E