more fixes for mesa's fbo handling (fixes tests/fbotest1/2)

src/mesa/main/buffers.c

@@ -557,9 +557,8 @@ _mesa_ReadBuffer(GLenum buffer)
       }
    }
 
-   if (fb->Name == 0) {
-      ctx->Pixel.ReadBuffer = buffer;
-   }
+   ctx->Pixel.ReadBuffer = buffer;
+
    fb->ColorReadBuffer = buffer;
    fb->_ColorReadBufferIndex = srcBuffer;
 

src/mesa/main/context.c

@@ -1499,6 +1499,11 @@ _mesa_make_current( GLcontext *newCtx, GLframebuffer *drawBuffer,
             if the DRIdrawable changes, and someone may rely on them.
           */
             /* What a mess!?! */
+            /* XXX this is still not quite correct. Imagine a user-created fbo
+               bound on a context. Now rebind with a completely new drawable.
+               Upon rebinding to the window-framebuffer, we have no idea what
+               the read and write buffers should be (front, back, ...) - that
+               information was only available in the previously used drawable... */
             int i;
             GLenum buffers[MAX_DRAW_BUFFERS];
             for(i = 0; i < newCtx->Const.MaxDrawBuffers; i++) {

src/mesa/main/fbobject.c

@@ -1003,13 +1003,20 @@ _mesa_BindFramebufferEXT(GLenum target, GLuint framebuffer)
 
    if (bindReadBuf) {
       _mesa_reference_framebuffer(&ctx->ReadBuffer, newFbread);
+      /* set context value */
+      ctx->Pixel.ReadBuffer = newFbread->ColorReadBuffer;
    }
 
    if (bindDrawBuf) {
+      GLuint i;
       /* check if old FB had any texture attachments */
       check_end_texture_render(ctx, ctx->DrawBuffer);
       /* check if time to delete this framebuffer */
       _mesa_reference_framebuffer(&ctx->DrawBuffer, newFb);
+      /* set context value */
+      for (i = 0; i < ctx->Const.MaxDrawBuffers; i++) {
+	 ctx->Color.DrawBuffer[i] = newFb->ColorDrawBuffer[i];
+      }
       if (newFb->Name != 0) {
          /* check if newly bound framebuffer has any texture attachments */
          check_begin_texture_render(ctx, newFb);