---
id: oled-guide
title: OLED Localization Guide
sidebar_label: OLED Localization
---

1. Create an extended ASCII custom font. Use a glyph editor to create a new font file. The easiest way is to use the online [glyph editor](https://rawgit.com/ThingPulse/esp8266-oled-ssd1306/master/resources/glyphEditor.html) from the OLED library. ([glyph editor source code](https://github.com/ThingPulse/esp8266-oled-ssd1306/tree/master/resources)) 
    1. Copy and paste the existing font.
    2. Modify it according desired codepage and save the new font file in `graphics/font` folder.
  Please note that the used font file format differs from common Adafruit GFX.
2. Update the `customFontTableLookup` function in `Screen.h`
    1. To map the double-byte UTF-8 code to the corresponding extended ASCII character of the desired codepage update the `customFontTableLookup` function in the `Screen.h` file.
    2. Modify the `switch (last)` statement: use left byte from UTF-8 code in the `case` label to map charachter's right byte to its extended ASCII code by specifying an offset.
3. Define language and font in `Screen.cpp`
  ```c
  #ifdef OLED_{LANG_NAME}
  #include "fonts/OLEDDisplayFonts{LANG_NAME}.h"
  #endif

  ...

  #ifdef OLED_{LANG_NAME}
  #define FONT_SMALL ArialMT_Plain_10_{LANG_NAME}
  #else
  #define FONT_SMALL ArialMT_Plain_10
  #endif
  ```
4. Define language in `variant/*/platformio.ini`
  ```
  build_flags =
    ${esp32_base.build_flags}
    -D xxxxx
    -D OLED_{LANG_NAME}
    -I variants/xxxxx
  ```