Francois.Bitz@SAM.CS.CMU.EDU (08/22/89)
Is there any X window manager that actually allows to have "transparent" windows; i.e the results for overlapping windows would be the same as 'blending' the colors found in each window (the background being transparent for example). In short I would like to create the same effect as would be created when superposing transparent (color) slides. According to Reiley's book there are ways to create overlays quite easily; however this requires reserving bit planes and is not pratical for a large number of windows. Also they require creating color entries that correspond to all the pixels used in these bit-planes. This effect would only work for a single window anyways. It seems to me that this kind of stuff should be done by the Server or Window manager, not the application. For example; if I want to superpose transparent windows (slides) containing arbitrary colors on top of another one with other arbitrary colors I would have to (considering a Pseudo Color display): 1/ Know what is in all windows (even from other applications). 2/ Know the color mapping between pixels numbers and colors 3/ For intersecting points compute a new color value from the colors composing the intersecting pixel... Step 2/ is obvious for a Direct Color display but otherwise requires Clients to know about each others colormaps. This process is quite tedious and requires a lot of traffic between server and client. Also another problem arises in the fact that it is not possible to 'read' portions of windows that are hidden by others. All these complications suggest to me that this could be done trough a window manager (or Server?). Anybody has done any work in this area? I have seen a Tektronik 'smalltalk' window system that does that and it was very cool. Thanks