CompuServe Messages

>> I don't remember getting a message about Windows handling code. I'll >> be on the lookout… Weird but that's what I thought when I didn't get any replies. At any rate, here it goes again… —————————————————————————– This is very simple. Well, it is once you know things that aren't readily documented. I will give you some directions without going into excruciating details. Let you guys go over it and if you have any problems let me know. I have a couple of systems permanently set to do this sort of debugging so it fairly simple for me to recreate all kinds of scenarios. This is breakfast stuff for me. I love it. Yeah, I know… I'm warped… First of all, you issue a 2Fh 1600h to find out if Windows is up and about. Then you call the VDD (Virtual Display Driver) and tell it you want to take care of the video state from now on. Do this by issuing a 2Fh with 4000h. This function has no parameters. It does, however, return the video modes the VDD can safely save and restore. Not much of use for the type of display devices you support but good to know. It may be that you don't need to do anything depending the Windows Display Device Driver present at the moment. The returned values are: 01h – No modes virtualized in background 02h – Only text modes virtualized in background 03h – Only text and single-plane graphics modes virtualized 04h – Only text, single-plane, and VGA multiplane modes virtualized 0FFh – All supported video modes virtualized (I never saw such driver) When you call this function, the VDD disables I/O trapping of unreadable registers. It will, therefore, call you when it needs to save and restore register state (functions 4005h and 4006h below). You should hook yourself into the int 2Fh chain. You will be looking for some types of call: AX 4001h – Notify Background Switch. Windows will issue this call whenever it's putting your VM in the background. You can do anything you want as long as it doesn't take longer than 1000ms. After that Windows will switch you out. Note that the 3D Studio VM will continue to run in the background as long as you don't touch the video (memory or ports). If you do, the VDD will pull the plug on you. With some work in your driver, you could set a global flag indicating that you're in the background and no video access should be performed. This would allow 3D Studio to continue working (rendering, whatever). 4002h – Notify Foreground Switch. This is the opposite. The VDD will call this when your are about to go to the foreground again. Use this to enable you "in foreground" flag allowing the video functions to access the video. 4005h – Save Video Registers. If you did the 4000h call, the VDD will call this whenever it need to save the video register state. It's up to you to save it but do it within 1000ms, after which the VDD will go ahead and do it. 4006h – Restore Video Registers. The opposite of above. It's up to you to restore the video registers. A couple of other necessary calls. 4007h – Disable these services. Issue this call when leaving if you had issued the 4000h. 4003h – Enter critical section. Use this when you're doing something that can't be stopped by a "Save/Restore Video Register" call above. If the VDD decides to call you, it will postpone its call for up to 1000ms (the magic number) before doing it itself. 4004h – Leave critical section. Disables the above. Note that none of these calls expect parameters or return values (unless otherwise noted). Let me know if you get in trouble… P.S. This should have been put in the hardware section, but, so what… Now, only if I could get an answer for my quartenians nightmares… <g> Another crazy idea… Has anybody ever thought the idea of implementing a driver that would switch the video requests to the Windows GDI? You get a request from 3D Studio, if you are in DOS, go ahead and do what you do. If under Windows (and provided a special interface driver got loaded along with it) you would call this driver and transfer the request over to it. This is a the fastest and simplest way to have 3D Studio as a Windows application without changing a single line of code. Scary but why not…