Alternate CopyPixels path based on get/put_tile().

For some drivers (like Xlib) it's not possible to treat the front/back color
buffers as pipe_regions.  So pipe->region_copy() won't work.  Added a new
state tracker field indicating if we can use regions for colorbuffer accesses.
This should probably be re-considered someday...

src/mesa/drivers/x11/xm_api.c

@@ -1603,6 +1603,8 @@ XMesaContext XMesaCreateContext( XMesaVisual v, XMesaContext share_list )
    mesaCtx->st->pipe->surface_alloc = xmesa_surface_alloc;
    mesaCtx->st->pipe->supported_formats = xmesa_supported_formats;
 
+   mesaCtx->st->haveFramebufferRegions = GL_FALSE;
+
    /* special pipe->clear function */
    mesaCtx->st->pipe->clear = xmesa_clear;
 

src/mesa/state_tracker/st_cb_drawpixels.c

@@ -1219,6 +1219,11 @@ st_CopyPixels(GLcontext *ctx, GLint srcx, GLint srcy,
       srcy = ctx->DrawBuffer->Height - srcy - height;
    }
 
+   /* For some drivers (like Xlib) it's not possible to treat the
+    * front/back color buffers as regions (they're XImages and Pixmaps).
+    * So, this var tells us if we can use region_copy here...
+    */
+   if (st->haveFramebufferRegions) {
       /* copy source framebuffer region into mipmap/texture */
       pipe->region_copy(pipe,
                         mt->region, /* dest */
@@ -1227,6 +1232,27 @@ st_CopyPixels(GLcontext *ctx, GLint srcx, GLint srcy,
                         psRead->region,
                         0, /* src_offset */
                         srcx, srcy, width, height);
+   }
+   else {
+      /* alternate path using get/put_tile() */
+      struct pipe_surface *psTex;
+      GLfloat *buf = (GLfloat *) malloc(width * height * 4 * sizeof(GLfloat));
+
+      psTex = pipe->get_tex_surface(pipe, mt, 0, 0, 0);
+
+      (void) pipe->region_map(pipe, psRead->region);
+      (void) pipe->region_map(pipe, psTex->region);
+
+      psRead->get_tile(psRead, srcx, srcy, width, height, buf);
+      psTex->put_tile(psTex, 0, 0, width, height, buf);
+
+      pipe->region_unmap(pipe, psRead->region);
+      pipe->region_unmap(pipe, psTex->region);
+
+      pipe_surface_reference(&psTex, NULL);
+
+      free(buf);
+   }
 
 
    /* draw textured quad */

src/mesa/state_tracker/st_context.c

@@ -90,6 +90,7 @@ struct st_context *st_create_context( GLcontext *ctx,
 
    st->ctx->VertexProgram._MaintainTnlProgram = GL_TRUE;
 
+   st->haveFramebufferRegions = GL_TRUE;
 
 #if 0
    st_init_cb_clear( st );

src/mesa/state_tracker/st_context.h

@@ -111,6 +111,12 @@ struct st_context
    char vendor[100];
    char renderer[100];
 
+   /** Can we access the front/back color buffers as pipe_regions?
+    * We can't with the Xlib driver...
+    * This is a hack that should be fixed someday.
+    */
+   GLboolean haveFramebufferRegions;
+
    /* State to be validated:
     */
    struct st_tracked_state **atoms;