---
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 character'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`

   ```text
   build_flags =
   ${esp32_base.build_flags}
   -D xxxxx
   -D OLED_{LANG_NAME}
   -I variants/xxxxx
   ```
