[SDL] SDL with Windows

[Doug]

In article <loom.20061005T001444-834 at post.gmane.org>, 
mrambhatla at phoenixworldwide.com says...
>
>Can I open multiple instances of SDL from the same application?

You can have multiple off-screen SDL surfaces in one instance of an app, but 
you can only really have one display SDL surface per process (which includes 
all threads within the main process).

[sidenote: trying to use SDL from different threads within the same process 
sometimes works (depending on what SDL features you use in the threads), but 
it's uber risky]

I got around this (in Windows only) by creating a SharedMemory class, which 
handles scheduling, interlocking, and synchronization.  Then I spawn these 
little mini-SDL rendering apps, which most of the time just 
WaitForSingleObject() on an appropriate rendering event.  When the event for 
a rendering mini-app is signaled, the little mini-app just gets the "data" it 
needs from the shared memory.

The main app does all "tough" work, but relies on the little mini-rendering 
apps to do the drawing.  In my case, I've got the main app managing 4 USB 
digital cameras.  When all the cameras are in viewfinder mode, they spit 
frames at me fast-and-furious.  I just route the frame data to the 
appropriate shared memory and then set the event for that rendering mini-app.

So far all four mini-apps are doing just fine, each rendering 320x240 30fps 
video, and none of the mini-apps nor the main app consume 100% CPU.  Also, 
the SDL gfx library works well as I use it to decompress the JPEG frames.

Doug.