If for some reason gdk_pixmap_new() fails (e.g. CreateDIBSection() fails), we end up g_object_unref()-ing the temporary GdkPixmap we created and this triggers an assert in GdkDrawable's finalize:

Gdk:ERROR:gdkdrawable-win32.c:2047:_gdk_win32_drawable_finish: assertion failed: (impl->hdc_count == 0)

Easily reproducible, just by doing:

  /* Invalid sizes for pixmap, and depth=16 to
   * trigger CreateDIBSection() */
  pixmap = gdk_pixmap_new (NULL, -1, -1, 16);