diff -r 000000000000 -r 88d965579617 components/u8g2/csrc/u8g2_buffer.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/components/u8g2/csrc/u8g2_buffer.c	Tue Oct 08 12:00:31 2019 +0200
@@ -0,0 +1,181 @@
+/* 
+
+  u8g2_buffer.c 
+
+  Universal 8bit Graphics Library (https://github.com/olikraus/u8g2/)
+
+  Copyright (c) 2016, olikraus@gmail.com
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without modification, 
+  are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright notice, this list 
+    of conditions and the following disclaimer.
+    
+  * Redistributions in binary form must reproduce the above copyright notice, this 
+    list of conditions and the following disclaimer in the documentation and/or other 
+    materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
+  CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
+  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
+  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
+  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
+  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
+  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
+  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
+
+*/
+
+#include "u8g2.h"
+#include <string.h>
+
+/*============================================*/
+void u8g2_ClearBuffer(u8g2_t *u8g2)
+{
+  size_t cnt;
+  cnt = u8g2_GetU8x8(u8g2)->display_info->tile_width;
+  cnt *= u8g2->tile_buf_height;
+  cnt *= 8;
+  memset(u8g2->tile_buf_ptr, 0, cnt);
+}
+
+/*============================================*/
+
+static void u8g2_send_tile_row(u8g2_t *u8g2, uint8_t src_tile_row, uint8_t dest_tile_row)
+{
+  uint8_t *ptr;
+  uint16_t offset;
+  uint8_t w;
+  
+  w = u8g2_GetU8x8(u8g2)->display_info->tile_width;
+  offset = src_tile_row;
+  ptr = u8g2->tile_buf_ptr;
+  offset *= w;
+  offset *= 8;
+  ptr += offset;
+  u8x8_DrawTile(u8g2_GetU8x8(u8g2), 0, dest_tile_row, w, ptr);
+}
+
+/* 
+  write the buffer to the display RAM. 
+  For most displays, this will make the content visible to the user.
+  Some displays (like the SSD1606) require a u8x8_RefreshDisplay()
+*/
+static void u8g2_send_buffer(u8g2_t *u8g2) U8X8_NOINLINE;
+static void u8g2_send_buffer(u8g2_t *u8g2)
+{
+  uint8_t src_row;
+  uint8_t src_max;
+  uint8_t dest_row;
+  uint8_t dest_max;
+
+  src_row = 0;
+  src_max = u8g2->tile_buf_height;
+  dest_row = u8g2->tile_curr_row;
+  dest_max = u8g2_GetU8x8(u8g2)->display_info->tile_height;
+  
+  do
+  {
+    u8g2_send_tile_row(u8g2, src_row, dest_row);
+    src_row++;
+    dest_row++;
+  } while( src_row < src_max && dest_row < dest_max );
+}
+
+/* same as u8g2_send_buffer but also send the DISPLAY_REFRESH message (used by SSD1606) */
+void u8g2_SendBuffer(u8g2_t *u8g2)
+{
+  u8g2_send_buffer(u8g2);
+  u8x8_RefreshDisplay( u8g2_GetU8x8(u8g2) );  
+}
+
+/*============================================*/
+void u8g2_SetBufferCurrTileRow(u8g2_t *u8g2, uint8_t row)
+{
+  u8g2->tile_curr_row = row;
+  u8g2->cb->update_dimension(u8g2);
+  u8g2->cb->update_page_win(u8g2);
+}
+
+void u8g2_FirstPage(u8g2_t *u8g2)
+{
+  if ( u8g2->is_auto_page_clear )
+  {
+    u8g2_ClearBuffer(u8g2);
+  }
+  u8g2_SetBufferCurrTileRow(u8g2, 0);
+}
+
+uint8_t u8g2_NextPage(u8g2_t *u8g2)
+{
+  uint8_t row;
+  u8g2_send_buffer(u8g2);
+  row = u8g2->tile_curr_row;
+  row += u8g2->tile_buf_height;
+  if ( row >= u8g2_GetU8x8(u8g2)->display_info->tile_height )
+  {
+    u8x8_RefreshDisplay( u8g2_GetU8x8(u8g2) );
+    return 0;
+  }
+  if ( u8g2->is_auto_page_clear )
+  {
+    u8g2_ClearBuffer(u8g2);
+  }
+  u8g2_SetBufferCurrTileRow(u8g2, row);
+  return 1;
+}
+
+
+
+/*============================================*/
+/*
+  Description:
+    Update a sub area of the display, given by tile position, width and height.
+    The arguments are "tile" coordinates. Any u8g2 rotation is ignored.
+    This procedure only checks whether full buffer mode is active.
+    There is no error checking for the arguments: It is the responsibility of the
+    user to ensure, that the provided arguments are correct.
+
+  Limitations:
+    - Only available in full buffer mode (will not do anything in page mode)
+    - Tile positions and sizes (pixel position divided by 8)
+    - Any display rotation/mirror is ignored
+    - Only works with displays, which support U8x8 API
+    - Will not send the e-paper refresh message (will probably not work with e-paper devices)
+*/
+void u8g2_UpdateDisplayArea(u8g2_t *u8g2, uint8_t  tx, uint8_t ty, uint8_t tw, uint8_t th)
+{
+  uint16_t page_size;
+  uint8_t *ptr;
+  
+  /* check, whether we are in full buffer mode */
+  if ( u8g2->tile_buf_height != u8g2_GetU8x8(u8g2)->display_info->tile_height )
+    return; /* not in full buffer mode, do nothing */
+
+  page_size = u8g2->pixel_buf_width;  /* 8*u8g2->u8g2_GetU8x8(u8g2)->display_info->tile_width */
+    
+  ptr = u8g2_GetBufferPtr(u8g2);
+  ptr += tx*8;
+  ptr += page_size*ty;
+  
+  while( th > 0 )
+  {
+    u8x8_DrawTile( u8g2_GetU8x8(u8g2), tx, ty, tw, ptr );
+    ptr += page_size;
+    ty++;
+    th--;
+  }  
+}
+
+/* same as sendBuffer, but does not send the ePaper refresh message */
+void u8g2_UpdateDisplay(u8g2_t *u8g2)
+{
+  u8g2_send_buffer(u8g2);
+}