rom/graphics/qblit.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Queue a Blit
   6     Lang: english
   7 */
   8
   9 #include <proto/exec.h>
  10 #include <hardware/blit.h>
  11 #include <graphics/gfxbase.h>
  12
  13 /*****************************************************************************
  14
  15     NAME */
  16 #include <proto/graphics.h>
  17
  18         AROS_LH1(void, QBlit,
  19
  20 /*  SYNOPSIS */
  21         AROS_LHA(struct bltnode *, bn, A1),
  22
  23 /*  LOCATION */
  24         struct GfxBase *, GfxBase, 46, Graphics)
  25
  26 /*  FUNCTION
  27         Queues a request for a blit. This request is queued at the end
  28         of the list.
  29
  30     INPUTS
  31         bn - pointer to blitnode structure
  32
  33     RESULT
  34         The routine that function in the bltnode is pointing to is
  35         called when the blitter is ready for work. No other task will
  36         be able to access the blitter while you're doing the blit.
  37         Queued blits have precedence over a task that tries to own the
  38         blitter via OwnBlitter(). So all queued blitter requests will
  39         be done first until the task that attempts a OwnBlitter can
  40         actually access the blitter.
  41
  42     NOTES
  43         Not all hardware has a blitter. On hardware where there is no
  44         blitter, a blitter is simulated. Therefore all code that will
  45         be executed in the function that is called must not contain
  46         code that is hacking the blitter's register but should contain
  47         calls to graphics functions instead.
  48
  49     EXAMPLE
  50
  51     BUGS
  52
  53     SEE ALSO
  54         QBSBlit(), OwnBlitter(), DisownBlitter(), hardware/blit.h
  55
  56     INTERNALS
  57
  58     HISTORY
  59
  60 ******************************************************************************/
  61 {
  62   AROS_LIBFUNC_INIT
  63
  64   /* this function uses the simple FIFO queue blthd (blttl) */
  65
  66   /* I am accessing a public structure and there's no semaphore...*/
  67   Forbid();
  68
  69   if (NULL == GfxBase->blthd)
  70   {
  71     /* it's the first one in the list */
  72     GfxBase->blthd = bn;
  73     GfxBase->blttl = bn;
  74
  75     /* In this case the following also has to happen:
  76        It is my understanding that at the end of every blit an interrupt
  77        occurs that can take care of any blits in this queue or allow
  78        a taks to wake up when it was blocked due to a call to OwnBlitter.
  79        But in this case there might not be such an interrupt for a long
  80        time if no calls to blitterfunctions are made. Therefore this
  81        blit might be queued forever. To avoid this I have to cause
  82        a Blitter interrupt, if no task owns the blitter right now.
  83        (BlitOwner)
  84     */
  85     /*
  86       !!! missing code here!! See explanation above!
  87     */
  88   }
  89   else
  90   {
  91     /* queue it at the end */
  92     GfxBase->blttl->n = bn;
  93     GfxBase->blttl    = bn;
  94   }
  95
  96   Permit();
  97
  98   AROS_LIBFUNC_EXIT
  99 } /* QBlit */