Re: 8-bit vs. 24-bit on new Sun hardware.

Stephen J Turnbull writes: Stephen> This isn't true in theory; O'Reilly's Xlib Programmer's Guide claims Stephen> it wasn't true in practice (even as of the X11R4 edition). A server Stephen> can implement multiple hardware colormaps, and there will not Stephen> necessarily be any flashing when different window use different Stephen> colormaps. Yup. This is probably why Martin didn't notice any flashing. Stephen> you _can't_ have a private colormap with Truecolor (I think, or is Stephen> that directcolor?. The concept of "private" colormap is meaningless in the case of TrueColor. You can perfectly well create your own TrueColor colormap, but the color cells are Read Only, and have predefined values assigned by the server. On the other hand, a DirectColor colormap is like a TrueColor one, except that the cells are modifiable. Stephen> ? Those are orthogonal options, aren't they? Not completely. Stephen> If the server allows you to specify a visual, it has to provide a Stephen> compatible default colormap. Don't be so confident in X ;-) When you create an XWindow, you may assign it a particular visual and colormap. The obvious constraint is that the colormap must be of the same visual type as the window (this is why the options are not completely orthogonal). But the point is that by default, the colormap assigned to a newly created window inside the XWindowAttribute structure is CopyFromParent. Consequently, if for instance you create a TrueColor24 XWindow on a PseudoColor8 (by default) screen and don't explicitely give it a proper colormap, you'll get a BadMatch error. This brain damage in the conception is also visible with the Intrinsics widgets and Motif. A naive Motif application running under the same circumstances as described above will crash immediately when you try to open a menu. This is because the menus widgets (which inherits from Shell) inherits the visual and depth from their parent WIDGET, but the colormap from their parent WINDOW. Hence the BadMatch error. -- / / _ _ Didier Verna http://www.inf.enst.fr/~verna/ - / / - / / /_/ / E.N.S.T. INF C201.1 mailto:verna＠inf.enst.fr /_/ / /_/ / /__ / 46 rue Barrault Tel. (33) 01 45 81 73 46 75634 Paris cedex 13 Fax. (33) 01 45 81 31 19