Volume 7A: XView Programming Manual

21.7 Canvases and Colormaps

When the colormap segment associated with a canvas is changed, the contents of the canvas

must be repainted to reflect the new colors. If the boolean attribute CANVAS_CMS_REPAINT is

set to TRUE, the library automatically calls the canvas’s repaint procedure each time a new

colormap segment is set on the canvas. The damage list passed to the routine contains the

dimensions of the entire paint window.

Note that the application itself must track any changes in the contents of a colormap segment.

CANVAS_CMS_REPAINT enables the library to generate a synthetic repaint event only when

the actual colormap segment is switched.

For dynamic colormap segments, when a color changes, the pixel value remains the same but

the color represented by the index into the colormap segment changes. Therefore, the repaint

routine is not called and the window’s appearance changes automatically. This method of

colormap manipulation is commonly used to implement color animation.

21.8 Multi-visual Support

XView allows you to create windows and colormap segments using arbitrary visuals (See

Chapter 7 of Volume One, Xlib Programming Manual for a description of visuals in X11).

You can use this functionality to access any visual that the X11 server supports. The attri-

butes described in this section allow you to indicate visuals you want associated with your

windows and colormap segments.

The attribute

XV_VISUAL specifies the exact visual that will be used in the creation of a win-

dow or colormap