2

I've been trying to animate in a C program using Xlib and I wanna do something when an event occurs, otherwise I wanna keep animating. Here's an example code snippet of what I am doing currently:

while( 1 ) 
{
 //  If an event occurs, stop and do whatever is needed. 
 // If no event occurs, skip this if statement.
    if ( XEventsQueued( display, QueuedAlready ) > 0 ) 
 {
        XNextEvent( display, &event )
        switch ( event.type ) 
  {
   // Don't do anything
   case Expose:
    while ( event.xexpose.count != 0 )
    break;

   // Do something, when a button is pressed
   case ButtonPress:
    ...
    break;

   // Do something, when a key is pressed
   case KeyPress:
    ...
    break;
        }
 }
    animate(); // Do animation step i.e. change any drawings...
    repaint(); // Paint again with the new changes from animation...
}

So basically, I wanna keep looping if the user hasn't clicked the mouse OR pressed a key in the keyboard yet. When the user presses a key OR clicks the mouse, I wanna stop and do a specific action. The problem in my above code is that, it doesnt stop whenever I do an action. If I remove the if statement, the animation blocks until an event occurs, however I do not want this. It's a simple problem, but I'm kinda new to Xlib/animations so any help would be highly appreciated. Thanks.

4

1 回答 1

2

ConnectionNumber(display)使用with返回的文件描述符select()并使用 timeout 参数。如果select()返回 0，则再画一些帧。XSync()请记住在您之前致电，select()以便 X 服务器获取您的更新。

int fd,r;
struct timeval tv;
FD_SET rfds;

fd=ConnectionNumber(display);
FD_ZERO(&rfds);
FD_SET(fd,&rfds);
memset(&tv,0,sizeof(tv));
tv.tv_usec = 100000; /* delay in microseconds */
r=select(fd+1,&rfds,0,0,&tv);
if(r == 0) { /* draw frame */ }
else if (r < 0) { /* error; try again if errno=EINTR */ }
else { /* pull events out */ }
于 2010-05-22T19:18:45.197 回答