path: root/src/gallium/auxiliary/vl/vl_winsys_dri3.c

/**************************************************************************
 *
 * Copyright 2016 Advanced Micro Devices, Inc.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 **************************************************************************/

#include <fcntl.h>

#include <X11/Xlib-xcb.h>
#include <X11/xshmfence.h>
#include <xcb/dri3.h>
#include <xcb/present.h>
#include <xcb/xfixes.h>

#include "loader.h"

#include "pipe/p_screen.h"
#include "pipe/p_state.h"
#include "pipe-loader/pipe_loader.h"

#include "util/u_memory.h"
#include "util/u_inlines.h"

#include "vl/vl_compositor.h"
#include "vl/vl_winsys.h"

#define BACK_BUFFER_NUM 3

struct vl_dri3_buffer
{
   struct pipe_resource *texture;
   struct pipe_resource *linear_texture;

   uint32_t pixmap;
   uint32_t sync_fence;
   struct xshmfence *shm_fence;

   bool busy;
   uint32_t width, height, pitch;
};

struct vl_dri3_screen
{
   struct vl_screen base;
   xcb_connection_t *conn;
   xcb_drawable_t drawable;

   uint32_t width, height, depth;

   xcb_present_event_t eid;
   xcb_special_event_t *special_event;

   struct pipe_context *pipe;
   struct pipe_resource *output_texture;
   uint32_t clip_width, clip_height;

   struct vl_dri3_buffer *back_buffers[BACK_BUFFER_NUM];
   int cur_back;
   int next_back;

   struct u_rect dirty_areas[BACK_BUFFER_NUM];

   struct vl_dri3_buffer *front_buffer;
   bool is_pixmap;

   uint32_t send_msc_serial, recv_msc_serial;
   uint64_t send_sbc, recv_sbc;
   int64_t last_ust, ns_frame, last_msc, next_msc;

   bool flushed;
   bool is_different_gpu;
};

static void
dri3_free_front_buffer(struct vl_dri3_screen *scrn,
                        struct vl_dri3_buffer *buffer)
{
   xcb_sync_destroy_fence(scrn->conn, buffer->sync_fence);
   xshmfence_unmap_shm(buffer->shm_fence);
   pipe_resource_reference(&buffer->texture, NULL);
   FREE(buffer);
}

static void
dri3_free_back_buffer(struct vl_dri3_screen *scrn,
                        struct vl_dri3_buffer *buffer)
{
   xcb_free_pixmap(scrn->conn, buffer->pixmap);
   xcb_sync_destroy_fence(scrn->conn, buffer->sync_fence);
   xshmfence_unmap_shm(buffer->shm_fence);
   if (!scrn->output_texture)
      pipe_resource_reference(&buffer->texture, NULL);
   if (buffer->linear_texture)
       pipe_resource_reference(&buffer->linear_texture, NULL);
   FREE(buffer);
}

static void
dri3_handle_stamps(struct vl_dri3_screen *scrn, uint64_t ust, uint64_t msc)
{
   int64_t ust_ns =  ust * 1000;

   if (scrn->last_ust && (ust_ns > scrn->last_ust) &&
       scrn->last_msc && (msc > scrn->last_msc))
      scrn->ns_frame = (ust_ns - scrn->last_ust) / (msc - scrn->last_msc);

   scrn->last_ust = ust_ns;
   scrn->last_msc = msc;
}

static void
dri3_handle_present_event(struct vl_dri3_screen *scrn,
                          xcb_present_generic_event_t *ge)
{
   switch (ge->evtype) {
   case XCB_PRESENT_CONFIGURE_NOTIFY: {
      xcb_present_configure_notify_event_t *ce = (void *) ge;
      scrn->width = ce->width;
      scrn->height = ce->height;
      break;
   }
   case XCB_PRESENT_COMPLETE_NOTIFY: {
      xcb_present_complete_notify_event_t *ce = (void *) ge;
      if (ce->kind == XCB_PRESENT_COMPLETE_KIND_PIXMAP) {
         scrn->recv_sbc = (scrn->send_sbc & 0xffffffff00000000LL) | ce->serial;
         if (scrn->recv_sbc > scrn->send_sbc)
            scrn->recv_sbc -= 0x100000000;
         dri3_handle_stamps(scrn, ce->ust, ce->msc);
      } else if (ce->kind == XCB_PRESENT_COMPLETE_KIND_NOTIFY_MSC) {
         scrn->recv_msc_serial = ce->serial;
         dri3_handle_stamps(scrn, ce->ust, ce->msc);
      }
      break;
   }
   case XCB_PRESENT_EVENT_IDLE_NOTIFY: {
      xcb_present_idle_notify_event_t *ie = (void *) ge;
      int b;
      for (b = 0; b < BACK_BUFFER_NUM; b++) {
         struct vl_dri3_buffer *buf = scrn->back_buffers[b];
         if (buf && buf->pixmap == ie->pixmap) {
            buf->busy = false;
            break;
         }
      }
      break;
   }
   }
   free(ge);
}

static void
dri3_flush_present_events(struct vl_dri3_screen *scrn)
{
   if (scrn->special_event) {
      xcb_generic_event_t *ev;
      while ((ev = xcb_poll_for_special_event(
                   scrn->conn, scrn->special_event)) != NULL)
         dri3_handle_present_event(scrn, (xcb_present_generic_event_t *)ev);
   }
}

static bool
dri3_wait_present_events(struct vl_dri3_screen *scrn)
{
   if (scrn->special_event) {
      xcb_generic_event_t *ev;
      ev = xcb_wait_for_special_event(scrn->conn, scrn->special_event);
      if (!ev)
         return false;
      dri3_handle_present_event(scrn, (xcb_present_generic_event_t *)ev);
      return true;
   }
   return false;
}

static int
dri3_find_back(struct vl_dri3_screen *scrn)
{
   int b;

   for (;;) {
      for (b = 0; b < BACK_BUFFER_NUM; b++) {
         int id = (b + scrn->cur_back) % BACK_BUFFER_NUM;
         struct vl_dri3_buffer *buffer = scrn->back_buffers[id];
         if (!buffer || !buffer->busy)
            return id;
      }
      xcb_flush(scrn->conn);
      if (!dri3_wait_present_events(scrn))
         return -1;
   }
}

static struct vl_dri3_buffer *
dri3_alloc_back_buffer(struct vl_dri3_screen *scrn)
{
   struct vl_dri3_buffer *buffer;
   xcb_pixmap_t pixmap;
   xcb_sync_fence_t sync_fence;
   struct xshmfence *shm_fence;
   int buffer_fd, fence_fd;
   struct pipe_resource templ, *pixmap_buffer_texture;
   struct winsys_handle whandle;
   unsigned usage;

   buffer = CALLOC_STRUCT(vl_dri3_buffer);
   if (!buffer)
      return NULL;

   fence_fd = xshmfence_alloc_shm();
   if (fence_fd < 0)
      goto free_buffer;

   shm_fence = xshmfence_map_shm(fence_fd);
   if (!shm_fence)
      goto close_fd;

   memset(&templ, 0, sizeof(templ));
   templ.bind = PIPE_BIND_RENDER_TARGET | PIPE_BIND_SAMPLER_VIEW;
   templ.format = vl_dri2_format_for_depth(&scrn->base, scrn->depth);
   templ.target = PIPE_TEXTURE_2D;
   templ.last_level = 0;
   templ.width0 = (scrn->output_texture) ?
                  scrn->output_texture->width0 : scrn->width;
   templ.height0 = (scrn->output_texture) ?
                   scrn->output_texture->height0 : scrn->height;
   templ.depth0 = 1;
   templ.array_size = 1;

   if (scrn->is_different_gpu) {
      buffer->texture = (scrn->output_texture) ? scrn->output_texture :
                        scrn->base.pscreen->resource_create(scrn->base.pscreen, &templ);
      if (!buffer->texture)
         goto unmap_shm;

      templ.bind |= PIPE_BIND_SCANOUT | PIPE_BIND_SHARED |
                    PIPE_BIND_LINEAR;
      buffer->linear_texture =
          scrn->base.pscreen->resource_create(scrn->base.pscreen, &templ);
      pixmap_buffer_texture = buffer->linear_texture;

      if (!buffer->linear_texture)
         goto no_linear_texture;
   } else {
      templ.bind |= PIPE_BIND_SCANOUT | PIPE_BIND_SHARED;
      buffer->texture = (scrn->output_texture) ? scrn->output_texture :
                        scrn->base.pscreen->resource_create(scrn->base.pscreen, &templ);
      if (!buffer->texture)
         goto unmap_shm;
      pixmap_buffer_texture = buffer->texture;
   }
   memset(&whandle, 0, sizeof(whandle));
   whandle.type= WINSYS_HANDLE_TYPE_FD;
   usage = PIPE_HANDLE_USAGE_EXPLICIT_FLUSH;
   scrn->base.pscreen->resource_get_handle(scrn->base.pscreen, NULL,
                                           pixmap_buffer_texture, &whandle,
                                           usage);
   buffer_fd = whandle.handle;
   buffer->pitch = whandle.stride;
   buffer->width = templ.width0;
   buffer->height = templ.height0;

   xcb_dri3_pixmap_from_buffer(scrn->conn,
                               (pixmap = xcb_generate_id(scrn->conn)),
                               scrn->drawable,
                               0,
                               buffer->width, buffer->height, buffer->pitch,
                               scrn->depth, 32,
                               buffer_fd);
   xcb_dri3_fence_from_fd(scrn->conn,
                          pixmap,
                          (sync_fence = xcb_generate_id(scrn->conn)),
                          false,
                          fence_fd);

   buffer->pixmap = pixmap;
   buffer->sync_fence = sync_fence;
   buffer->shm_fence = shm_fence;

   xshmfence_trigger(buffer->shm_fence);

   return buffer;

no_linear_texture:
   pipe_resource_reference(&buffer->texture, NULL);
unmap_shm:
   xshmfence_unmap_shm(shm_fence);
close_fd:
   close(fence_fd);
free_buffer:
   FREE(buffer);
   return NULL;
}

static struct vl_dri3_buffer *
dri3_get_back_buffer(struct vl_dri3_screen *scrn)
{
   struct vl_dri3_buffer *buffer;
   struct pipe_resource *texture = NULL;
   bool allocate_new_buffer = false;
   int b, id;

   assert(scrn);

   scrn->cur_back = dri3_find_back(scrn);
   if (scrn->cur_back < 0)
      return NULL;
   buffer = scrn->back_buffers[scrn->cur_back];

   if (scrn->output_texture) {
      if (!buffer || buffer->width < scrn->width ||
          buffer->height < scrn->height)
         allocate_new_buffer = true;
      else if (scrn->is_different_gpu)
         /* In case of different gpu we can reuse the linear
          * texture so we only need to set the external
          * texture for copying
          */
         buffer->texture = scrn->output_texture;
      else {
         /* In case of a single gpu we search if the texture is
          * already present as buffer if not we get the
          * handle and pixmap for the texture that is set
          */
         for (b = 0; b < BACK_BUFFER_NUM; b++) {
            id = (b + scrn->cur_back) % BACK_BUFFER_NUM;
            buffer = scrn->back_buffers[id];
            if (buffer && !buffer->busy &&
                buffer->texture == scrn->output_texture) {
               scrn->cur_back = id;
               break;
            }
         }

         if (b == BACK_BUFFER_NUM) {
            allocate_new_buffer = true;
            scrn->cur_back = scrn->next_back;
            scrn->next_back = (scrn->next_back + 1) % BACK_BUFFER_NUM;
            buffer = scrn->back_buffers[scrn->cur_back];
         }
      }

   } else {
      if (!buffer || buffer->width != scrn->width ||
          buffer->height != scrn->height)
         allocate_new_buffer = true;
   }

   if (allocate_new_buffer) {
      struct vl_dri3_buffer *new_buffer;

      new_buffer = dri3_alloc_back_buffer(scrn);
      if (!new_buffer)
         return NULL;

      if (buffer)
         dri3_free_back_buffer(scrn, buffer);

      if (!scrn->output_texture)
         vl_compositor_reset_dirty_area(&scrn->dirty_areas[scrn->cur_back]);
      buffer = new_buffer;
      scrn->back_buffers[scrn->cur_back] = buffer;
   }

   pipe_resource_reference(&texture, buffer->texture);
   xcb_flush(scrn->conn);
   xshmfence_await(buffer->shm_fence);

   return buffer;
}

static bool
dri3_set_drawable(struct vl_dri3_screen *scrn, Drawable drawable)
{
   xcb_get_geometry_cookie_t geom_cookie;
   xcb_get_geometry_reply_t *geom_reply;
   xcb_void_cookie_t cookie;
   xcb_generic_error_t *error;
   bool ret = true;

   assert(drawable);

   if (scrn->drawable == drawable)
      return true;

   scrn->drawable = drawable;

   geom_cookie = xcb_get_geometry(scrn->conn, scrn->drawable);
   geom_reply = xcb_get_geometry_reply(scrn->conn, geom_cookie, NULL);
   if (!geom_reply)
      return false;

   scrn->width = geom_reply->width;
   scrn->height = geom_reply->height;
   scrn->depth = geom_reply->depth;
   free(geom_reply);

   if (scrn->special_event) {
      xcb_unregister_for_special_event(scrn->conn, scrn->special_event);
      scrn->special_event = NULL;
      cookie = xcb_present_select_input_checked(scrn->conn, scrn->eid,
                                                scrn->drawable,
                                                XCB_PRESENT_EVENT_MASK_NO_EVENT);
      xcb_discard_reply(scrn->conn, cookie.sequence);
   }

   scrn->is_pixmap = false;
   scrn->eid = xcb_generate_id(scrn->conn);
   cookie =
      xcb_present_select_input_checked(scrn->conn, scrn->eid, scrn->drawable,
                      XCB_PRESENT_EVENT_MASK_CONFIGURE_NOTIFY |
                      XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY |
                      XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY);

   error = xcb_request_check(scrn->conn, cookie);
   if (error) {
      if (error->error_code != BadWindow)
         ret = false;
      else {
         scrn->is_pixmap = true;
         if (scrn->front_buffer) {
            dri3_free_front_buffer(scrn, scrn->front_buffer);
            scrn->front_buffer = NULL;
         }
      }
      free(error);
   } else
      scrn->special_event =
         xcb_register_for_special_xge(scrn->conn, &xcb_present_id, scrn->eid, 0);

   dri3_flush_present_events(scrn);

   return ret;
}

static struct vl_dri3_buffer *
dri3_get_front_buffer(struct vl_dri3_screen *scrn)
{
   xcb_dri3_buffer_from_pixmap_cookie_t bp_cookie;
   xcb_dri3_buffer_from_pixmap_reply_t *bp_reply;
   xcb_sync_fence_t sync_fence;
   struct xshmfence *shm_fence;
   int fence_fd, *fds;
   struct winsys_handle whandle;
   struct pipe_resource templ, *texture = NULL;

   if (scrn->front_buffer) {
      pipe_resource_reference(&texture, scrn->front_buffer->texture);
      return scrn->front_buffer;
   }

   scrn->front_buffer = CALLOC_STRUCT(vl_dri3_buffer);
   if (!scrn->front_buffer)
      return NULL;

   fence_fd = xshmfence_alloc_shm();
   if (fence_fd < 0)
      goto free_buffer;

   shm_fence = xshmfence_map_shm(fence_fd);
   if (!shm_fence)
      goto close_fd;

   bp_cookie = xcb_dri3_buffer_from_pixmap(scrn->conn, scrn->drawable);
   bp_reply = xcb_dri3_buffer_from_pixmap_reply(scrn->conn, bp_cookie, NULL);
   if (!bp_reply)
      goto unmap_shm;

   fds = xcb_dri3_buffer_from_pixmap_reply_fds(scrn->conn, bp_reply);
   if (fds[0] < 0)
      goto free_reply;

   memset(&whandle, 0, sizeof(whandle));
   whandle.type = WINSYS_HANDLE_TYPE_FD;
   whandle.handle = (unsigned)fds[0];
   whandle.stride = bp_reply->stride;
   memset(&templ, 0, sizeof(templ));
   templ.bind = PIPE_BIND_RENDER_TARGET | PIPE_BIND_SAMPLER_VIEW;
   templ.format = vl_dri2_format_for_depth(&scrn->base, bp_reply->depth);
   templ.target = PIPE_TEXTURE_2D;
   templ.last_level = 0;
   templ.width0 = bp_reply->width;
   templ.height0 = bp_reply->height;
   templ.depth0 = 1;
   templ.array_size = 1;
   scrn->front_buffer->texture =
      scrn->base.pscreen->resource_from_handle(scrn->base.pscreen,
                                               &templ, &whandle,
                                               PIPE_HANDLE_USAGE_FRAMEBUFFER_WRITE);
   close(fds[0]);
   if (!scrn->front_buffer->texture)
      goto free_reply;

   xcb_dri3_fence_from_fd(scrn->conn,
                          scrn->drawable,
                          (sync_fence = xcb_generate_id(scrn->conn)),
                          false,
                          fence_fd);

   pipe_resource_reference(&texture, scrn->front_buffer->texture);
   scrn->front_buffer->pixmap = scrn->drawable;
   scrn->front_buffer->width = bp_reply->width;
   scrn->front_buffer->height = bp_reply->height;
   scrn->front_buffer->shm_fence = shm_fence;
   scrn->front_buffer->sync_fence = sync_fence;
   free(bp_reply);

   return scrn->front_buffer;

free_reply:
   free(bp_reply);
unmap_shm:
   xshmfence_unmap_shm(shm_fence);
close_fd:
   close(fence_fd);
free_buffer:
   FREE(scrn->front_buffer);
   return NULL;
}

static xcb_screen_t *
dri3_get_screen_for_root(xcb_connection_t *conn, xcb_window_t root)
{
   xcb_screen_iterator_t screen_iter =
   xcb_setup_roots_iterator(xcb_get_setup(conn));

   for (; screen_iter.rem; xcb_screen_next (&screen_iter)) {
      if (screen_iter.data->root == root)
         return screen_iter.data;
   }

   return NULL;
}

static void
vl_dri3_flush_frontbuffer(struct pipe_screen *screen,
                          struct pipe_resource *resource,
                          unsigned level, unsigned layer,
                          void *context_private, struct pipe_box *sub_box)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)context_private;
   uint32_t options = XCB_PRESENT_OPTION_NONE;
   struct vl_dri3_buffer *back;
   struct pipe_box src_box;
   xcb_xfixes_region_t region;
   xcb_rectangle_t rectangle;

   back = scrn->back_buffers[scrn->cur_back];
   if (!back)
       return;

   if (scrn->flushed) {
      while (scrn->special_event && scrn->recv_sbc < scrn->send_sbc)
         if (!dri3_wait_present_events(scrn))
            return;
   }

   rectangle.x = 0;
   rectangle.y = 0;
   rectangle.width = (scrn->output_texture) ? scrn->clip_width : scrn->width;
   rectangle.height = (scrn->output_texture) ? scrn->clip_height : scrn->height;

   region = xcb_generate_id(scrn->conn);
   xcb_xfixes_create_region(scrn->conn, region, 2, &rectangle);

   if (scrn->is_different_gpu) {
      u_box_origin_2d(back->width, back->height, &src_box);
      scrn->pipe->resource_copy_region(scrn->pipe,
                                       back->linear_texture,
                                       0, 0, 0, 0,
                                       back->texture,
                                       0, &src_box);

      scrn->pipe->flush(scrn->pipe, NULL, 0);
   }
   xshmfence_reset(back->shm_fence);
   back->busy = true;

   xcb_present_pixmap(scrn->conn,
                      scrn->drawable,
                      back->pixmap,
                      (uint32_t)(++scrn->send_sbc),
                      0, region, 0, 0,
                      None, None,
                      back->sync_fence,
                      options,
                      scrn->next_msc,
                      0, 0, 0, NULL);

   xcb_flush(scrn->conn);

   scrn->flushed = true;

   return;
}

static struct pipe_resource *
vl_dri3_screen_texture_from_drawable(struct vl_screen *vscreen, void *drawable)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;
   struct vl_dri3_buffer *buffer;

   assert(scrn);

   if (!dri3_set_drawable(scrn, (Drawable)drawable))
      return NULL;

   if (scrn->flushed) {
      while (scrn->special_event && scrn->recv_sbc < scrn->send_sbc)
         if (!dri3_wait_present_events(scrn))
            return NULL;
   }
   scrn->flushed = false;

   buffer = (scrn->is_pixmap) ?
            dri3_get_front_buffer(scrn) :
            dri3_get_back_buffer(scrn);
   if (!buffer)
      return NULL;

   return buffer->texture;
}

static struct u_rect *
vl_dri3_screen_get_dirty_area(struct vl_screen *vscreen)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;

   assert(scrn);

   return &scrn->dirty_areas[scrn->cur_back];
}

static uint64_t
vl_dri3_screen_get_timestamp(struct vl_screen *vscreen, void *drawable)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;

   assert(scrn);

   if (!dri3_set_drawable(scrn, (Drawable)drawable))
      return 0;

   if (!scrn->last_ust) {
      xcb_present_notify_msc(scrn->conn,
                             scrn->drawable,
                             ++scrn->send_msc_serial,
                             0, 0, 0);
      xcb_flush(scrn->conn);

      while (scrn->special_event &&
             scrn->send_msc_serial > scrn->recv_msc_serial) {
         if (!dri3_wait_present_events(scrn))
            return 0;
      }
   }

   return scrn->last_ust;
}

static void
vl_dri3_screen_set_next_timestamp(struct vl_screen *vscreen, uint64_t stamp)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;

   assert(scrn);

   if (stamp && scrn->last_ust && scrn->ns_frame && scrn->last_msc)
      scrn->next_msc = ((int64_t)stamp - scrn->last_ust + scrn->ns_frame/2) /
                       scrn->ns_frame + scrn->last_msc;
   else
      scrn->next_msc = 0;
}

static void *
vl_dri3_screen_get_private(struct vl_screen *vscreen)
{
   return vscreen;
}

static void
vl_dri3_screen_set_back_texture_from_output(struct vl_screen *vscreen,
                                            struct pipe_resource *buffer,
                                            uint32_t width, uint32_t height)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;

   assert(scrn);

   scrn->output_texture = buffer;
   scrn->clip_width = (width) ? width : scrn->width;
   scrn->clip_height = (height) ? height : scrn->height;
}

static void
vl_dri3_screen_destroy(struct vl_screen *vscreen)
{
   struct vl_dri3_screen *scrn = (struct vl_dri3_screen *)vscreen;
   int i;

   assert(vscreen);

   dri3_flush_present_events(scrn);

   if (scrn->front_buffer) {
      dri3_free_front_buffer(scrn, scrn->front_buffer);
      scrn->front_buffer = NULL;
   }

   for (i = 0; i < BACK_BUFFER_NUM; ++i) {
      if (scrn->back_buffers[i]) {
         dri3_free_back_buffer(scrn, scrn->back_buffers[i]);
         scrn->back_buffers[i] = NULL;
      }
   }

   if (scrn->special_event) {
      xcb_void_cookie_t cookie =
         xcb_present_select_input_checked(scrn->conn, scrn->eid,
                                          scrn->drawable,
                                          XCB_PRESENT_EVENT_MASK_NO_EVENT);

      xcb_discard_reply(scrn->conn, cookie.sequence);
      xcb_unregister_for_special_event(scrn->conn, scrn->special_event);
   }
   scrn->pipe->destroy(scrn->pipe);
   scrn->base.pscreen->destroy(scrn->base.pscreen);
   pipe_loader_release(&scrn->base.dev, 1);
   FREE(scrn);

   return;
}

struct vl_screen *
vl_dri3_screen_create(Display *display, int screen)
{
   struct vl_dri3_screen *scrn;
   const xcb_query_extension_reply_t *extension;
   xcb_dri3_open_cookie_t open_cookie;
   xcb_dri3_open_reply_t *open_reply;
   xcb_get_geometry_cookie_t geom_cookie;
   xcb_get_geometry_reply_t *geom_reply;
   xcb_xfixes_query_version_cookie_t xfixes_cookie;
   xcb_xfixes_query_version_reply_t *xfixes_reply;
   xcb_generic_error_t *error;
   int fd;

   assert(display);

   scrn = CALLOC_STRUCT(vl_dri3_screen);
   if (!scrn)
      return NULL;

   scrn->conn = XGetXCBConnection(display);
   if (!scrn->conn)
      goto free_screen;

   xcb_prefetch_extension_data(scrn->conn , &xcb_dri3_id);
   xcb_prefetch_extension_data(scrn->conn, &xcb_present_id);
   xcb_prefetch_extension_data (scrn->conn, &xcb_xfixes_id);
   extension = xcb_get_extension_data(scrn->conn, &xcb_dri3_id);
   if (!(extension && extension->present))
      goto free_screen;
   extension = xcb_get_extension_data(scrn->conn, &xcb_present_id);
   if (!(extension && extension->present))
      goto free_screen;
   extension = xcb_get_extension_data(scrn->conn, &xcb_xfixes_id);
   if (!(extension && extension->present))
      goto free_screen;

   xfixes_cookie = xcb_xfixes_query_version(scrn->conn, XCB_XFIXES_MAJOR_VERSION,
                                            XCB_XFIXES_MINOR_VERSION);
   xfixes_reply = xcb_xfixes_query_version_reply(scrn->conn, xfixes_cookie, &error);
   if (!xfixes_reply || error || xfixes_reply->major_version < 2) {
      free(error);
      free(xfixes_reply);
      goto free_screen;
   }
   free(xfixes_reply);

   open_cookie = xcb_dri3_open(scrn->conn, RootWindow(display, screen), None);
   open_reply = xcb_dri3_open_reply(scrn->conn, open_cookie, NULL);
   if (!open_reply)
      goto free_screen;
   if (open_reply->nfd != 1) {
      free(open_reply);
      goto free_screen;
   }

   fd = xcb_dri3_open_reply_fds(scrn->conn, open_reply)[0];
   if (fd < 0) {
      free(open_reply);
      goto free_screen;
   }
   fcntl(fd, F_SETFD, FD_CLOEXEC);
   free(open_reply);

   fd = loader_get_user_preferred_fd(fd, &scrn->is_different_gpu);

   geom_cookie = xcb_get_geometry(scrn->conn, RootWindow(display, screen));
   geom_reply = xcb_get_geometry_reply(scrn->conn, geom_cookie, NULL);
   if (!geom_reply)
      goto close_fd;

   scrn->base.xcb_screen = dri3_get_screen_for_root(scrn->conn, geom_reply->root);
   if (!scrn->base.xcb_screen) {
      free(geom_reply);
      goto close_fd;
   }

   /* TODO support depth other than 24 or 30 */
   if (geom_reply->depth != 24 && geom_reply->depth != 30) {
      free(geom_reply);
      goto close_fd;
   }
   scrn->base.color_depth = geom_reply->depth;
   free(geom_reply);

   if (pipe_loader_drm_probe_fd(&scrn->base.dev, fd))
      scrn->base.pscreen = pipe_loader_create_screen(scrn->base.dev);

   if (!scrn->base.pscreen)
      goto release_pipe;

   scrn->pipe = scrn->base.pscreen->context_create(scrn->base.pscreen,
                                                   NULL, 0);
   if (!scrn->pipe)
       goto no_context;

   scrn->base.destroy = vl_dri3_screen_destroy;
   scrn->base.texture_from_drawable = vl_dri3_screen_texture_from_drawable;
   scrn->base.get_dirty_area = vl_dri3_screen_get_dirty_area;
   scrn->base.get_timestamp = vl_dri3_screen_get_timestamp;
   scrn->base.set_next_timestamp = vl_dri3_screen_set_next_timestamp;
   scrn->base.get_private = vl_dri3_screen_get_private;
   scrn->base.pscreen->flush_frontbuffer = vl_dri3_flush_frontbuffer;
   scrn->base.set_back_texture_from_output = vl_dri3_screen_set_back_texture_from_output;

   scrn->next_back = 1;
   return &scrn->base;

no_context:
   scrn->base.pscreen->destroy(scrn->base.pscreen);
release_pipe:
   if (scrn->base.dev) {
      pipe_loader_release(&scrn->base.dev, 1);
      fd = -1;
   }
close_fd:
   if (fd != -1)
      close(fd);
free_screen:
   FREE(scrn);
   return NULL;
}