1 files changed, 69 insertions, 450 deletions

diff --git a/src/mesa/drivers/dri/intel/intel_buffers.c b/src/mesa/drivers/dri/intel/intel_buffers.c
index 0fd2f16a8f..e7357e78c5 100644
--- a/src/mesa/drivers/dri/intel/intel_buffers.c
+++ b/src/mesa/drivers/dri/intel/intel_buffers.c
@@ -25,25 +25,14 @@
  * 
  **************************************************************************/
 
-#include "intel_screen.h"
 #include "intel_context.h"
-#include "intel_blit.h"
 #include "intel_buffers.h"
-#include "intel_chipset.h"
-#include "intel_depthstencil.h"
 #include "intel_fbo.h"
 #include "intel_regions.h"
 #include "intel_batchbuffer.h"
-#include "intel_reg.h"
-#include "main/context.h"
 #include "main/framebuffer.h"
-#include "swrast/swrast.h"
-#include "utils.h"
 #include "drirenderbuffer.h"
-#include "vblank.h"
-#include "i915_drm.h"
 
-#define FILE_DEBUG_FLAG DEBUG_BLIT
 
 /**
  * XXX move this into a new dri/common/cliprects.c file.
@@ -114,7 +103,6 @@ intel_get_cliprects(struct intel_context *intel,
 		    int *x_off, int *y_off)
 {
    __DRIdrawablePrivate *dPriv = intel->driDrawable;
-   struct intel_framebuffer *intel_fb = dPriv->driverPrivate;
 
    if (intel->constant_cliprect) {
       /* FBO or DRI2 rendering, which can just use the fb's size. */
@@ -143,399 +131,6 @@ intel_get_cliprects(struct intel_context *intel,
    }
 }
 
-/**
- * This will be called whenever the currently bound window is moved/resized.
- * XXX: actually, it seems to NOT be called when the window is only moved (BP).
- */
-void
-intelWindowMoved(struct intel_context *intel)
-{
-   GLcontext *ctx = &intel->ctx;
-   __DRIdrawablePrivate *dPriv = intel->driDrawable;
-   struct intel_framebuffer *intel_fb = dPriv->driverPrivate;
-
-   if (!intel->intelScreen->driScrnPriv->dri2.enabled &&
-       intel->intelScreen->driScrnPriv->ddx_version.minor >= 7) {
-      volatile drm_i915_sarea_t *sarea = intel->sarea;
-      drm_clip_rect_t drw_rect = { .x1 = dPriv->x, .x2 = dPriv->x + dPriv->w,
-				   .y1 = dPriv->y, .y2 = dPriv->y + dPriv->h };
-      drm_clip_rect_t planeA_rect = { .x1 = sarea->planeA_x, .y1 = sarea->planeA_y,
-				     .x2 = sarea->planeA_x + sarea->planeA_w,
-				     .y2 = sarea->planeA_y + sarea->planeA_h };
-      drm_clip_rect_t planeB_rect = { .x1 = sarea->planeB_x, .y1 = sarea->planeB_y,
-				     .x2 = sarea->planeB_x + sarea->planeB_w,
-				     .y2 = sarea->planeB_y + sarea->planeB_h };
-      GLint areaA = driIntersectArea( drw_rect, planeA_rect );
-      GLint areaB = driIntersectArea( drw_rect, planeB_rect );
-      GLuint flags = dPriv->vblFlags;
-
-      /* Update vblank info
-       */
-      if (areaB > areaA || (areaA == areaB && areaB > 0)) {
-	 flags = dPriv->vblFlags | VBLANK_FLAG_SECONDARY;
-      } else {
-	 flags = dPriv->vblFlags & ~VBLANK_FLAG_SECONDARY;
-      }
-
-      /* Check to see if we changed pipes */
-      if (flags != dPriv->vblFlags && dPriv->vblFlags &&
-	  !(dPriv->vblFlags & VBLANK_FLAG_NO_IRQ)) {
-	 int64_t count;
-	 drmVBlank vbl;
-	 int i;
-
-	 /*
-	  * Deal with page flipping
-	  */
-	 vbl.request.type = DRM_VBLANK_ABSOLUTE;
-
-	 if ( dPriv->vblFlags & VBLANK_FLAG_SECONDARY ) {
-	    vbl.request.type |= DRM_VBLANK_SECONDARY;
-	 }
-
-	 for (i = 0; i < 2; i++) {
-	    if (!intel_fb->color_rb[i] ||
-		(intel_fb->vbl_waited - intel_fb->color_rb[i]->vbl_pending) <=
-		(1<<23))
-	       continue;
-
-	    vbl.request.sequence = intel_fb->color_rb[i]->vbl_pending;
-	    drmWaitVBlank(intel->driFd, &vbl);
-	 }
-
-	 /*
-	  * Update msc_base from old pipe
-	  */
-	 driDrawableGetMSC32(dPriv->driScreenPriv, dPriv, &count);
-	 dPriv->msc_base = count;
-	 /*
-	  * Then get new vblank_base and vblSeq values
-	  */
-	 dPriv->vblFlags = flags;
-	 driGetCurrentVBlank(dPriv);
-	 dPriv->vblank_base = dPriv->vblSeq;
-
-	 intel_fb->vbl_waited = dPriv->vblSeq;
-
-	 for (i = 0; i < 2; i++) {
-	    if (intel_fb->color_rb[i])
-	       intel_fb->color_rb[i]->vbl_pending = intel_fb->vbl_waited;
-	 }
-      }
-   } else {
-      dPriv->vblFlags &= ~VBLANK_FLAG_SECONDARY;
-   }
-
-   /* Update Mesa's notion of window size */
-   driUpdateFramebufferSize(ctx, dPriv);
-   intel_fb->Base.Initialized = GL_TRUE; /* XXX remove someday */
-
-   /* Update hardware scissor */
-   if (ctx->Driver.Scissor != NULL) {
-      ctx->Driver.Scissor(ctx, ctx->Scissor.X, ctx->Scissor.Y,
-			  ctx->Scissor.Width, ctx->Scissor.Height);
-   }
-
-   /* Re-calculate viewport related state */
-   if (ctx->Driver.DepthRange != NULL)
-      ctx->Driver.DepthRange( ctx, ctx->Viewport.Near, ctx->Viewport.Far );
-}
-
-
-
-/* A true meta version of this would be very simple and additionally
- * machine independent.  Maybe we'll get there one day.
- */
-static void
-intelClearWithTris(struct intel_context *intel, GLbitfield mask)
-{
-   GLcontext *ctx = &intel->ctx;
-   struct gl_framebuffer *fb = ctx->DrawBuffer;
-   GLuint buf;
-
-   intel->vtbl.install_meta_state(intel);
-
-   /* Back and stencil cliprects are the same.  Try and do both
-    * buffers at once:
-    */
-   if (mask & (BUFFER_BIT_BACK_LEFT | BUFFER_BIT_STENCIL | BUFFER_BIT_DEPTH)) {
-      struct intel_region *backRegion =
-	 intel_get_rb_region(fb, BUFFER_BACK_LEFT);
-      struct intel_region *depthRegion =
-	 intel_get_rb_region(fb, BUFFER_DEPTH);
-
-      intel->vtbl.meta_draw_region(intel, backRegion, depthRegion);
-
-      if (mask & BUFFER_BIT_BACK_LEFT)
-	 intel->vtbl.meta_color_mask(intel, GL_TRUE);
-      else
-	 intel->vtbl.meta_color_mask(intel, GL_FALSE);
-
-      if (mask & BUFFER_BIT_STENCIL)
-	 intel->vtbl.meta_stencil_replace(intel,
-					  intel->ctx.Stencil.WriteMask[0],
-					  intel->ctx.Stencil.Clear);
-      else
-	 intel->vtbl.meta_no_stencil_write(intel);
-
-      if (mask & BUFFER_BIT_DEPTH)
-	 intel->vtbl.meta_depth_replace(intel);
-      else
-	 intel->vtbl.meta_no_depth_write(intel);
-
-      intel->vtbl.meta_draw_quad(intel,
-				 fb->_Xmin,
-				 fb->_Xmax,
-				 fb->_Ymin,
-				 fb->_Ymax,
-				 intel->ctx.Depth.Clear,
-				 intel->ClearColor8888,
-				 0, 0, 0, 0);   /* texcoords */
-
-      mask &= ~(BUFFER_BIT_BACK_LEFT | BUFFER_BIT_STENCIL | BUFFER_BIT_DEPTH);
-   }
-
-   /* clear the remaining (color) renderbuffers */
-   for (buf = 0; buf < BUFFER_COUNT && mask; buf++) {
-      const GLuint bufBit = 1 << buf;
-      if (mask & bufBit) {
-	 struct intel_renderbuffer *irbColor =
-	    intel_renderbuffer(fb->Attachment[buf].Renderbuffer);
-
-	 ASSERT(irbColor);
-
-	 intel->vtbl.meta_no_depth_write(intel);
-	 intel->vtbl.meta_no_stencil_write(intel);
-	 intel->vtbl.meta_color_mask(intel, GL_TRUE);
-	 intel->vtbl.meta_draw_region(intel, irbColor->region, NULL);
-
-	 intel->vtbl.meta_draw_quad(intel,
-				    fb->_Xmin,
-				    fb->_Xmax,
-				    fb->_Ymin,
-				    fb->_Ymax,
-				    0, intel->ClearColor8888,
-				    0, 0, 0, 0);   /* texcoords */
-
-	 mask &= ~bufBit;
-      }
-   }
-
-   intel->vtbl.leave_meta_state(intel);
-}
-
-static const char *buffer_names[] = {
-   [BUFFER_FRONT_LEFT] = "front",
-   [BUFFER_BACK_LEFT] = "back",
-   [BUFFER_FRONT_RIGHT] = "front right",
-   [BUFFER_BACK_RIGHT] = "back right",
-   [BUFFER_AUX0] = "aux0",
-   [BUFFER_AUX1] = "aux1",
-   [BUFFER_AUX2] = "aux2",
-   [BUFFER_AUX3] = "aux3",
-   [BUFFER_DEPTH] = "depth",
-   [BUFFER_STENCIL] = "stencil",
-   [BUFFER_ACCUM] = "accum",
-   [BUFFER_COLOR0] = "color0",
-   [BUFFER_COLOR1] = "color1",
-   [BUFFER_COLOR2] = "color2",
-   [BUFFER_COLOR3] = "color3",
-   [BUFFER_COLOR4] = "color4",
-   [BUFFER_COLOR5] = "color5",
-   [BUFFER_COLOR6] = "color6",
-   [BUFFER_COLOR7] = "color7",
-};
-
-/**
- * Called by ctx->Driver.Clear.
- */
-static void
-intelClear(GLcontext *ctx, GLbitfield mask)
-{
-   struct intel_context *intel = intel_context(ctx);
-   const GLuint colorMask = *((GLuint *) & ctx->Color.ColorMask);
-   GLbitfield tri_mask = 0;
-   GLbitfield blit_mask = 0;
-   GLbitfield swrast_mask = 0;
-   struct gl_framebuffer *fb = ctx->DrawBuffer;
-   GLuint i;
-
-   if (0)
-      fprintf(stderr, "%s\n", __FUNCTION__);
-
-   /* HW color buffers (front, back, aux, generic FBO, etc) */
-   if (colorMask == ~0) {
-      /* clear all R,G,B,A */
-      /* XXX FBO: need to check if colorbuffers are software RBOs! */
-      blit_mask |= (mask & BUFFER_BITS_COLOR);
-   }
-   else {
-      /* glColorMask in effect */
-      tri_mask |= (mask & BUFFER_BITS_COLOR);
-   }
-
-   /* HW stencil */
-   if (mask & BUFFER_BIT_STENCIL) {
-      const struct intel_region *stencilRegion
-         = intel_get_rb_region(fb, BUFFER_STENCIL);
-      if (stencilRegion) {
-         /* have hw stencil */
-         if (IS_965(intel->intelScreen->deviceID) ||
-	     (ctx->Stencil.WriteMask[0] & 0xff) != 0xff) {
-	    /* We have to use the 3D engine if we're clearing a partial mask
-	     * of the stencil buffer, or if we're on a 965 which has a tiled
-	     * depth/stencil buffer in a layout we can't blit to.
-	     */
-            tri_mask |= BUFFER_BIT_STENCIL;
-         }
-         else {
-            /* clearing all stencil bits, use blitting */
-            blit_mask |= BUFFER_BIT_STENCIL;
-         }
-      }
-   }
-
-   /* HW depth */
-   if (mask & BUFFER_BIT_DEPTH) {
-      /* clear depth with whatever method is used for stencil (see above) */
-      if (IS_965(intel->intelScreen->deviceID) ||
-	  tri_mask & BUFFER_BIT_STENCIL)
-         tri_mask |= BUFFER_BIT_DEPTH;
-      else
-         blit_mask |= BUFFER_BIT_DEPTH;
-   }
-
-   /* SW fallback clearing */
-   swrast_mask = mask & ~tri_mask & ~blit_mask;
-
-   for (i = 0; i < BUFFER_COUNT; i++) {
-      GLuint bufBit = 1 << i;
-      if ((blit_mask | tri_mask) & bufBit) {
-         if (!fb->Attachment[i].Renderbuffer->ClassID) {
-            blit_mask &= ~bufBit;
-            tri_mask &= ~bufBit;
-            swrast_mask |= bufBit;
-         }
-      }
-   }
-
-   if (blit_mask) {
-      if (INTEL_DEBUG & DEBUG_BLIT) {
-	 DBG("blit clear:");
-	 for (i = 0; i < BUFFER_COUNT; i++) {
-	    if (blit_mask & (1 << i))
-	       DBG(" %s", buffer_names[i]);
-	 }
-	 DBG("\n");
-      }
-      intelClearWithBlit(ctx, blit_mask);
-   }
-
-   if (tri_mask) {
-      if (INTEL_DEBUG & DEBUG_BLIT) {
-	 DBG("tri clear:");
-	 for (i = 0; i < BUFFER_COUNT; i++) {
-	    if (tri_mask & (1 << i))
-	       DBG(" %s", buffer_names[i]);
-	 }
-	 DBG("\n");
-      }
-      intelClearWithTris(intel, tri_mask);
-   }
-
-   if (swrast_mask) {
-      if (INTEL_DEBUG & DEBUG_BLIT) {
-	 DBG("swrast clear:");
-	 for (i = 0; i < BUFFER_COUNT; i++) {
-	    if (swrast_mask & (1 << i))
-	       DBG(" %s", buffer_names[i]);
-	 }
-	 DBG("\n");
-      }
-      _swrast_Clear(ctx, swrast_mask);
-   }
-}
-
-void
-intelSwapBuffers(__DRIdrawablePrivate * dPriv)
-{
-   __DRIscreenPrivate *psp = dPriv->driScreenPriv;
-
-   if (dPriv->driContextPriv && dPriv->driContextPriv->driverPrivate) {
-      GET_CURRENT_CONTEXT(ctx);
-      struct intel_context *intel;
-
-      if (ctx == NULL)
-	 return;
-
-      intel = intel_context(ctx);
-
-      if (ctx->Visual.doubleBufferMode) {
-	 GLboolean missed_target;
-	 struct intel_framebuffer *intel_fb = dPriv->driverPrivate;
-	 int64_t ust;
-         
-	 _mesa_notifySwapBuffers(ctx);  /* flush pending rendering comands */
-
-	/*
-	 * The old swapping ioctl was incredibly racy, just wait for vblank
-	 * and do the swap ourselves.
-	 */
-	 driWaitForVBlank(dPriv, &missed_target);
-
-	 /*
-	  * Update each buffer's vbl_pending so we don't get too out of
-	  * sync
-	  */
-	 intel_get_renderbuffer(&intel_fb->Base,
-		   		BUFFER_BACK_LEFT)->vbl_pending = dPriv->vblSeq;
-         intel_get_renderbuffer(&intel_fb->Base,
-		   		BUFFER_FRONT_LEFT)->vbl_pending = dPriv->vblSeq;
-
-	 intelCopyBuffer(dPriv, NULL);
-
-	 intel_fb->swap_count++;
-	 (*psp->systemTime->getUST) (&ust);
-	 if (missed_target) {
-	    intel_fb->swap_missed_count++;
-	    intel_fb->swap_missed_ust = ust - intel_fb->swap_ust;
-	 }
-
-	 intel_fb->swap_ust = ust;
-      }
-      drmCommandNone(intel->driFd, DRM_I915_GEM_THROTTLE);
-
-   }
-   else {
-      /* XXX this shouldn't be an error but we can't handle it for now */
-      fprintf(stderr, "%s: drawable has no context!\n", __FUNCTION__);
-   }
-}
-
-void
-intelCopySubBuffer(__DRIdrawablePrivate * dPriv, int x, int y, int w, int h)
-{
-   if (dPriv->driContextPriv && dPriv->driContextPriv->driverPrivate) {
-      struct intel_context *intel =
-         (struct intel_context *) dPriv->driContextPriv->driverPrivate;
-      GLcontext *ctx = &intel->ctx;
-
-      if (ctx->Visual.doubleBufferMode) {
-         drm_clip_rect_t rect;
-         rect.x1 = x + dPriv->x;
-         rect.y1 = (dPriv->h - y - h) + dPriv->y;
-         rect.x2 = rect.x1 + w;
-         rect.y2 = rect.y1 + h;
-         _mesa_notifySwapBuffers(ctx);  /* flush pending rendering comands */
-         intelCopyBuffer(dPriv, &rect);
-      }
-   }
-   else {
-      /* XXX this shouldn't be an error but we can't handle it for now */
-      fprintf(stderr, "%s: drawable has no context!\n", __FUNCTION__);
-   }
-}
-
 
 /**
  * Update the hardware state for drawing into a window or framebuffer object.
@@ -559,10 +154,10 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
       return;
    }
 
-   /* Do this here, note core Mesa, since this function is called from
+   /* Do this here, not core Mesa, since this function is called from
     * many places within the driver.
     */
-   if (ctx->NewState & (_NEW_BUFFERS | _NEW_COLOR | _NEW_PIXEL)) {
+   if (ctx->NewState & _NEW_BUFFERS) {
       /* this updates the DrawBuffer->_NumColorDrawBuffers fields, etc */
       _mesa_update_framebuffer(ctx);
       /* this updates the DrawBuffer's Width/Height if it's a FBO */
@@ -577,9 +172,6 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
       return;
    }
 
-   if (fb->Name)
-      intel_validate_paired_depth_stencil(ctx, fb);
-
    /*
     * How many color buffers are we drawing into?
     */
@@ -587,7 +179,8 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
       /* writing to 0  */
       colorRegions[0] = NULL;
       intel->constant_cliprect = GL_TRUE;
-   } else if (fb->_NumColorDrawBuffers > 1) {
+   }
+   else if (fb->_NumColorDrawBuffers > 1) {
        int i;
        struct intel_renderbuffer *irb;
 
@@ -609,6 +202,8 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
 	       intel_batchbuffer_flush(intel->batch);
 	    intel->front_cliprects = GL_TRUE;
 	    colorRegions[0] = intel_get_rb_region(fb, BUFFER_FRONT_LEFT);
+
+	    intel->front_buffer_dirty = GL_TRUE;
 	 }
 	 else {
 	    if (!intel->constant_cliprect && intel->front_cliprects)
@@ -626,14 +221,6 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
       }
    }
 
-   /* Update culling direction which changes depending on the
-    * orientation of the buffer:
-    */
-   if (ctx->Driver.FrontFace)
-      ctx->Driver.FrontFace(ctx, ctx->Polygon.FrontFace);
-   else
-      ctx->NewState |= _NEW_POLYGON;
-
    if (!colorRegions[0]) {
       FALLBACK(intel, INTEL_FALLBACK_DRAW_BUFFER, GL_TRUE);
    }
@@ -665,59 +252,50 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
    /***
     *** Stencil buffer
     *** This can only be hardware accelerated if we're using a
-    *** combined DEPTH_STENCIL buffer (for now anyway).
+    *** combined DEPTH_STENCIL buffer.
     ***/
    if (fb->_StencilBuffer && fb->_StencilBuffer->Wrapped) {
       irbStencil = intel_renderbuffer(fb->_StencilBuffer->Wrapped);
       if (irbStencil && irbStencil->region) {
          ASSERT(irbStencil->Base._ActualFormat == GL_DEPTH24_STENCIL8_EXT);
          FALLBACK(intel, INTEL_FALLBACK_STENCIL_BUFFER, GL_FALSE);
-         /* need to re-compute stencil hw state */
-	 if (ctx->Driver.Enable != NULL)
-	    ctx->Driver.Enable(ctx, GL_STENCIL_TEST, ctx->Stencil.Enabled);
-	 else
-	    ctx->NewState |= _NEW_STENCIL;
-         if (!depthRegion)
-            depthRegion = irbStencil->region;
       }
       else {
          FALLBACK(intel, INTEL_FALLBACK_STENCIL_BUFFER, GL_TRUE);
       }
    }
    else {
-      /* XXX FBO: instead of FALSE, pass ctx->Stencil.Enabled ??? */
+      /* XXX FBO: instead of FALSE, pass ctx->Stencil._Enabled ??? */
       FALLBACK(intel, INTEL_FALLBACK_STENCIL_BUFFER, GL_FALSE);
-      /* need to re-compute stencil hw state */
-      if (ctx->Driver.Enable != NULL)
-	 ctx->Driver.Enable(ctx, GL_STENCIL_TEST, ctx->Stencil.Enabled);
-      else
-	 ctx->NewState |= _NEW_STENCIL;
    }
 
    /*
-    * Update depth test state
+    * Update depth and stencil test state
     */
    if (ctx->Driver.Enable) {
-      if (ctx->Depth.Test && fb->Visual.depthBits > 0) {
-	 ctx->Driver.Enable(ctx, GL_DEPTH_TEST, GL_TRUE);
-      } else {
-	 ctx->Driver.Enable(ctx, GL_DEPTH_TEST, GL_FALSE);
-      }
-   } else {
-      ctx->NewState |= _NEW_DEPTH;
+      ctx->Driver.Enable(ctx, GL_DEPTH_TEST,
+                         (ctx->Depth.Test && fb->Visual.depthBits > 0));
+      ctx->Driver.Enable(ctx, GL_STENCIL_TEST,
+                         (ctx->Stencil.Enabled && fb->Visual.stencilBits > 0));
+   }
+   else {
+      /* Mesa's Stencil._Enabled field is updated when
+       * _NEW_BUFFERS | _NEW_STENCIL, but i965 code assumes that the value
+       * only changes with _NEW_STENCIL (which seems sensible).  So flag it
+       * here since this is the _NEW_BUFFERS path.
+       */
+      ctx->NewState |= (_NEW_DEPTH | _NEW_STENCIL);
    }
 
    intel->vtbl.set_draw_region(intel, colorRegions, depthRegion, 
-	fb->_NumColorDrawBuffers);
+                               fb->_NumColorDrawBuffers);
 
    /* update viewport since it depends on window size */
-   if (ctx->Driver.Viewport) {
-      ctx->Driver.Viewport(ctx, ctx->Viewport.X, ctx->Viewport.Y,
-			   ctx->Viewport.Width, ctx->Viewport.Height);
-   } else {
-      ctx->NewState |= _NEW_VIEWPORT;
-   }
-
+#ifdef I915
+   intelCalcViewport(ctx);
+#else
+   ctx->NewState |= _NEW_VIEWPORT;
+#endif
    /* Set state we know depends on drawable parameters:
     */
    if (ctx->Driver.Scissor)
@@ -729,12 +307,37 @@ intel_draw_buffer(GLcontext * ctx, struct gl_framebuffer *fb)
       ctx->Driver.DepthRange(ctx,
 			     ctx->Viewport.Near,
 			     ctx->Viewport.Far);
+
+   /* Update culling direction which changes depending on the
+    * orientation of the buffer:
+    */
+   if (ctx->Driver.FrontFace)
+      ctx->Driver.FrontFace(ctx, ctx->Polygon.FrontFace);
+   else
+      ctx->NewState |= _NEW_POLYGON;
 }
 
 
 static void
 intelDrawBuffer(GLcontext * ctx, GLenum mode)
 {
+   if ((ctx->DrawBuffer != NULL) && (ctx->DrawBuffer->Name == 0)) {
+      struct intel_context *const intel = intel_context(ctx);
+      const GLboolean was_front_buffer_rendering =
+	intel->is_front_buffer_rendering;
+
+      intel->is_front_buffer_rendering = (mode == GL_FRONT_LEFT)
+	|| (mode == GL_FRONT);
+
+      /* If we weren't front-buffer rendering before but we are now, make sure
+       * that the front-buffer has actually been allocated.
+       */
+      if (!was_front_buffer_rendering && intel->is_front_buffer_rendering) {
+	 intel_update_renderbuffers(intel->driContext,
+				    intel->driContext->driDrawablePriv);
+      }
+   }
+
    intel_draw_buffer(ctx, ctx->DrawBuffer);
 }
 
@@ -742,6 +345,23 @@ intelDrawBuffer(GLcontext * ctx, GLenum mode)
 static void
 intelReadBuffer(GLcontext * ctx, GLenum mode)
 {
+   if ((ctx->DrawBuffer != NULL) && (ctx->DrawBuffer->Name == 0)) {
+      struct intel_context *const intel = intel_context(ctx);
+      const GLboolean was_front_buffer_reading =
+	intel->is_front_buffer_reading;
+
+      intel->is_front_buffer_reading = (mode == GL_FRONT_LEFT)
+	|| (mode == GL_FRONT);
+
+      /* If we weren't front-buffer reading before but we are now, make sure
+       * that the front-buffer has actually been allocated.
+       */
+      if (!was_front_buffer_reading && intel->is_front_buffer_reading) {
+	 intel_update_renderbuffers(intel->driContext,
+				    intel->driContext->driDrawablePriv);
+      }
+   }
+
    if (ctx->ReadBuffer == ctx->DrawBuffer) {
       /* This will update FBO completeness status.
        * A framebuffer will be incomplete if the GL_READ_BUFFER setting
@@ -759,7 +379,6 @@ intelReadBuffer(GLcontext * ctx, GLenum mode)
 void
 intelInitBufferFuncs(struct dd_function_table *functions)
 {
-   functions->Clear = intelClear;
    functions->DrawBuffer = intelDrawBuffer;
    functions->ReadBuffer = intelReadBuffer;
 }