[Dri-devel] SGI_make_current_read for MGA

[Ian Romanick]

Here is a patch that enables SGI_make_current_read for the MGA driver. 
I have only tested this with progs/xdemos/wincopy, and it works as 
expected.  It should be fairly trivial for people to make similar 
patches for the other drivers.  Drivers that support pageflipping will 
be a bit more tricky, but that shouldn't be a significant problem.

Assuming everyone likes this patch, I'll commit it tomorrow.

HOWEVER, the wincopy demo runs about as fast with this patch as with 
indirect, software rasterization.  The software path for glCopyPixels is 
*death*.  Could people who are working on drivers *please* implement 
screen-to-screen blits for at least the common, easy cases of 
glCopyPixels?  I understand that glCopyPixels isn't a common performance 
critical path, but the a lot of the code used to accelerate that should 
be re-usable for accelerating glCopyTexImage and some other pbuffer 
related functionality when the time comes.

Index: lib/GL/mesa/src/drv/mga/mga_xmesa.c
===================================================================
RCS file: /cvs/dri/xc/xc/lib/GL/mesa/src/drv/mga/mga_xmesa.c,v
retrieving revision 1.62
diff -u -d -r1.62 mga_xmesa.c
--- lib/GL/mesa/src/drv/mga/mga_xmesa.c 25 Oct 2003 16:11:46 -0000      1.62
+++ lib/GL/mesa/src/drv/mga/mga_xmesa.c 29 Oct 2003 18:40:09 -0000
@@ -129,6 +129,7 @@
            (*glx_enable_extension)( psc, "GLX_MESA_swap_control" );
         }
 
+        (*glx_enable_extension)( psc, "GLX_SGI_make_current_read" );
         (*glx_enable_extension)( psc, "GLX_MESA_swap_frame_usage" );
       }
    }
@@ -377,7 +378,6 @@
    mmesa->mgaScreen = mgaScreen;
    mmesa->driScreen = sPriv;
    mmesa->sarea = (void *)saPriv;
-   mmesa->glBuffer = NULL;
 
    /* Parse configuration files */
    driParseConfigFiles (&mmesa->optionCache, &mgaScreen->optionCache,
@@ -655,6 +655,8 @@
         mmesa->dirty_cliprects = (MGA_FRONT|MGA_BACK); 
       }
 
+      mmesa->driReadable = driReadPriv;
+
       _mesa_make_current2(mmesa->glCtx,
                           (GLframebuffer *) driDrawPriv->driverPrivate,
                           (GLframebuffer *) driReadPriv->driverPrivate);
Index: lib/GL/mesa/src/drv/mga/mgacontext.h
===================================================================
RCS file: /cvs/dri/xc/xc/lib/GL/mesa/src/drv/mga/mgacontext.h,v
retrieving revision 1.30
diff -u -d -r1.30 mgacontext.h
--- lib/GL/mesa/src/drv/mga/mgacontext.h        25 Oct 2003 16:11:46 -0000      1.30
+++ lib/GL/mesa/src/drv/mga/mgacontext.h        29 Oct 2003 18:40:09 -0000
@@ -298,11 +298,19 @@
 
    /* Mirrors of some DRI state.
     */
-   GLframebuffer *glBuffer;
    drmContext hHWContext;
    drmLock *driHwLock;
    int driFd;
    __DRIdrawablePrivate *driDrawable;
+   __DRIdrawablePrivate *driReadable;
+
+   /**
+    * Drawable used by Mesa for software fallbacks for reading and
+    * writing.  It is set by Mesa's \c SetBuffer callback, and will always be
+    * either \c mga_context_t::driDrawable or \c mga_context_t::driReadable.
+    */
+   __DRIdrawablePrivate *mesa_drawable;
+
    __DRIscreenPrivate *driScreen;
    struct mga_screen_private_s *mgaScreen;
    MGASAREAPrivPtr sarea;
Index: lib/GL/mesa/src/drv/mga/mgaspan.c
===================================================================
RCS file: /cvs/dri/xc/xc/lib/GL/mesa/src/drv/mga/mgaspan.c,v
retrieving revision 1.31
diff -u -d -r1.31 mgaspan.c
--- lib/GL/mesa/src/drv/mga/mgaspan.c   30 Apr 2003 01:50:42 -0000      1.31
+++ lib/GL/mesa/src/drv/mga/mgaspan.c   29 Oct 2003 18:40:09 -0000
@@ -37,7 +37,7 @@
 
 
 #define LOCAL_VARS                                     \
-   __DRIdrawablePrivate *dPriv = mmesa->driDrawable;   \
+   __DRIdrawablePrivate *dPriv = mmesa->mesa_drawable; \
    mgaScreenPrivate *mgaScreen = mmesa->mgaScreen;     \
    __DRIscreenPrivate *sPriv = mmesa->driScreen;       \
    GLuint pitch = mgaScreen->frontPitch;               \
@@ -56,7 +56,7 @@
 
 
 #define LOCAL_DEPTH_VARS                                               \
-   __DRIdrawablePrivate *dPriv = mmesa->driDrawable;                   \
+   __DRIdrawablePrivate *dPriv = mmesa->mesa_drawable;                 \
    mgaScreenPrivate *mgaScreen = mmesa->mgaScreen;                     \
    __DRIscreenPrivate *sPriv = mmesa->driScreen;                       \
    GLuint pitch = mgaScreen->frontPitch;                               \
@@ -242,20 +242,22 @@
                            GLuint bufferBit)
 {
    mgaContextPtr mmesa = MGA_CONTEXT(ctx);
+   unsigned int   offset;
 
-   if (bufferBit == FRONT_LEFT_BIT) 
-   {
-      mmesa->drawOffset = mmesa->mgaScreen->frontOffset;
-      mmesa->readOffset = mmesa->mgaScreen->frontOffset;
-   } 
-   else if (bufferBit == BACK_LEFT_BIT)
-   {
-      mmesa->drawOffset = mmesa->mgaScreen->backOffset;
-      mmesa->readOffset = mmesa->mgaScreen->backOffset;
-   }
-   else {
-      assert(0);
-   }
+   assert( (bufferBit == FRONT_LEFT_BIT) || (bufferBit == BACK_LEFT_BIT) );
+
+   offset = (bufferBit == FRONT_LEFT_BIT)
+       ? mmesa->mgaScreen->frontOffset
+       : mmesa->mgaScreen->backOffset;
+
+   mmesa->drawOffset = offset;
+   mmesa->readOffset = offset;
+
+   assert( (buffer == mmesa->driDrawable->driverPrivate)
+          || (buffer == mmesa->driReadable->driverPrivate) );
+
+   mmesa->mesa_drawable = (buffer == mmesa->driDrawable->driverPrivate)
+       ? mmesa->driDrawable : mmesa->driReadable;
 }
 
 void mgaDDInitSpanFuncs( GLcontext *ctx )