Fix a front/back CopyPixels glitch.

src/mesa/drivers/x11/xm_dd.c

@@ -930,7 +930,9 @@ xmesa_CopyPixels( GLcontext *ctx,
    ASSERT(dpy);
    ASSERT(gc);
 
-   if (drawBuffer &&  /* buffer != 0 means it's a Window or Pixmap */
+   if (ctx->Color.DrawBuffer == GL_FRONT &&
+       ctx->Pixel.ReadBuffer == GL_FRONT &&
+       drawBuffer &&  /* buffer != 0 means it's a Window or Pixmap */
        readBuffer &&
        type == GL_COLOR &&
        (swrast->_RasterMask & ~CLIP_BIT) == 0 && /* no blend, z-test, etc */
@@ -1120,7 +1122,7 @@ void xmesa_init_pointers( GLcontext *ctx )
    ctx->Driver.DrawPixels = _swrast_DrawPixels;
    ctx->Driver.CopyPixels = _swrast_CopyPixels;
 #else
-   ctx->Driver.CopyPixels = xmesa_CopyPixels;
+   ctx->Driver.CopyPixels = /*_swrast_CopyPixels;*/xmesa_CopyPixels;
    if (xmesa->xm_visual->undithered_pf == PF_8R8G8B &&
        xmesa->xm_visual->dithered_pf == PF_8R8G8B) {
       ctx->Driver.DrawPixels = xmesa_DrawPixels_8R8G8B;

src/mesa/swrast/s_copypix.c

@@ -310,8 +310,13 @@ copy_rgba_pixels(GLcontext *ctx, GLint srcx, GLint srcy,
       stepy = 1;
    }
 
-   overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
-                                 ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   if (ctx->DrawBuffer == ctx->ReadBuffer) {
+      overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
+                                    ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   }
+   else {
+      overlapping = GL_FALSE;
+   }
 
    if (ctx->Depth.Test)
       _swrast_span_default_z(ctx, &span);
@@ -521,8 +526,13 @@ copy_ci_pixels( GLcontext *ctx, GLint srcx, GLint srcy,
       stepy = 1;
    }
 
-   overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
-                                 ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   if (ctx->DrawBuffer == ctx->ReadBuffer) {
+      overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
+                                    ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   }
+   else {
+      overlapping = GL_FALSE;
+   }
 
    if (ctx->Depth.Test)
       _swrast_span_default_z(ctx, &span);
@@ -636,8 +646,13 @@ copy_depth_pixels( GLcontext *ctx, GLint srcx, GLint srcy,
       stepy = 1;
    }
 
-   overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
-                                 ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   if (ctx->DrawBuffer == ctx->ReadBuffer) {
+      overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
+                                    ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   }
+   else {
+      overlapping = GL_FALSE;
+   }
 
    _swrast_span_default_color(ctx, &span);
    if (ctx->Fog.Enabled)
@@ -736,8 +751,13 @@ copy_stencil_pixels( GLcontext *ctx, GLint srcx, GLint srcy,
       stepy = 1;
    }
 
-   overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
-                                 ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   if (ctx->DrawBuffer == ctx->ReadBuffer) {
+      overlapping = regions_overlap(srcx, srcy, destx, desty, width, height,
+                                    ctx->Pixel.ZoomX, ctx->Pixel.ZoomY);
+   }
+   else {
+      overlapping = GL_FALSE;
+   }
 
    if (overlapping) {
       GLint ssy = sy;