A fully functional implementation of layered windows
Peter Daifuku · 1993
Incorporating layered windows into the X server is a nontrivial task, which has been attempted repeatedly in the past, with varying lack of success. We present our criteria for the proper behavior of layered windows. We show that the assumptions built into the DIX windowing code prevent the proper implementation of layered windows, proving that the current windowing code is inherently device-dependent. We propose a restructuring of the sample server, moving much of the windowing code to DDX. We show how the sample windowing model can be extended to clip layered windows, and what changes are required to other parts of the server which depend in part on knowledge of the current window tree. Introduction Many hardware vendors support overlays as a performance enhancement. However, the sample server does not address the issue of overlays, or of other framebuffer layers. In the past, there have been a number of attempts to incorporate overlays into the X server. Most recently, in the 1992...