Solaris X Window System Developer's Guide

Rendering to a Transparent Overlay Window

Once a transparent overlay window is created, you can use all the standard Xlib primitive rendering routines, such as XDrawLines and XFillRectangles, to draw into the window. When drawing to transparent overlay windows, the paint type attribute of the GC is used to control the quality of the pixels rendered. The paint type attribute applies to both the foreground and background GC attributes. To set the paint type, use the XSolarisOvlSetPaintType routine; for information on this routine, see Setting the Paint Type of a Graphics Context.

The paint type of the GC also controls the type of pixels rendered with XPutImage. If the paint type of the argument GC is XSolarisOvlPaintOpaque, the color information from the source image is used and the pixels are rendered with opaque paint. However, if the paint type is XSolarisOvlPaintTransparent, the source color information is ignored, and the pixels are rendered with transparent paint.

If a GC with a paint type of XSolarisOvlPaintTransparent is used to render to a drawable other than a transparent overlay window, such as an underlay window or pixmap, the GC paint type is ignored, and the pixels are rendered with opaque paint.