On Tue, Jul 17, 2007 at 06:19:13PM -0500, Spencer Janssen wrote:
It is possible, but annoying. It requires a magic version of nextEvent that doesn't block inside foreign calls. Thankfully, this isn't so hard to write with threadWaitRead and XPending. With this magic nextEvent, we can use asynchronous exceptions to interrupt the thread with a timer. I've sent you a patch that implements this.
Just a marginal note. I'm thinking about writing a tutorial about X programming for the Haskell.org wiki. I think, indeed, that some documentation for writing an X application, such as a status bar, in Haskell could be useful. My major problem, indeed, is that I could not find code examples, and I presume I'm not the only one that can grasp Haskell but have quite some problems in reading C. I was lucky because there is this XMonad project going on, with you guys, real X and/or Haskell experts. Since I'm sure I'm going to forget everything in a couple of months, if I write it down all the information that thanks to your help I was able to gather won't get lost. This is basically the possible outline of such a tutorial: 1. the process of windows creation and mapping - (with the Hello World example) 2. writing to windows (creating a pixmap, writing to it and copying it to the window, drawing strings, selecting fonts, colors, calculating string length, etc.) 3. handling events I think the example code could be a simple splash screen that reads a text file, and displays each row at every mouse bottom press. And what about mixing events and time driven updates? After studying Spencer's code I have the impression that his solution is the Haskell way of doing this kind of stuff, if I read correctly the documentation.[1] But I don't now whether I should cover it or not. I'm afraid it could be confusing and too complicated. On the other side, since there seems to exist no other Haskell examples of such a case probably it should be covered and solved with asynchronous exceptions. What do you think? Thanks, Andrea [1] http://haskell.org/ghc/docs/latest/html/libraries/base/Control-Exception.htm...