How do PC based X servers handle colours?
Thanks to Wojtek Jarosz of Attachmate Canada Inc. for this information. PC based X servers usually use the MS Windows palette to handle colours. As far as I know this is how all the servers I have heard of work: eXceed, Xoftware, XVision, PCXware and EXTRA! X. This imposes some restrictions on what can be done with colormaps on such servers; in particular it is not possible to overwrite cells 0 and 255 which Windows reserves for black and white respectively. Because some applications require to have the ability to write over these reserved cells, some servers actually pretend to the application that the write is successful while in reality no colour changes occur. As far as I know this is e.g. what the eXceed server does and also XVision (which has an explicit configuration option to enable this feature – I am currently in the process of getting more information on this). Related to this is the so-called “white pixel option” which some servers posses and which defines black and white a
