.. _style_themes:

====== Themes

Overview

A Theme is a collection of styles with the knowledge of which subset of styles are applied to which types of Widgets. If there is an active theme LVGL applies it to every newly-created widget. This will give a default appearance to the UI which can then be modified by adding further styles.

Every display can have a different theme. For example, you could have a colorful theme on a TFT and monochrome theme on a secondary monochrome display.

To set a theme for a display, two steps are required:

Initialize the theme.
Assign the initialized theme to the display.

Theme initialization functions can have different prototypes. This example shows how to set the "default" theme:

.. code-block:: c

lv_theme_t * th = lv_theme_default_init(display, /* Use DPI, size, etc. from this display / LV_COLOR_PALETTE_BLUE, / Primary and secondary palette / LV_COLOR_PALETTE_CYAN, false, / Dark theme? False = light theme. / &lv_font_montserrat_10, / Small, normal, large fonts */ &lv_font_montserrat_14, &lv_font_montserrat_18);

lv_display_set_theme(display, th); /* Assign theme to display */

The included themes are enabled in lv_conf.h. If the default theme is enabled by :c:macro:LV_USE_THEME_DEFAULT LVGL automatically initializes and sets it when a display is created.

Extending themes

Built-in themes can be extended. If a custom theme is created, a parent theme can be selected. The parent theme's styles will be added before the custom theme's styles. Any number of themes can be chained this way. E.g. default theme -> custom theme -> dark theme.

:cpp:expr:lv_theme_set_parent(new_theme, base_theme) extends the base_theme with the new_theme.

There is an example of this among the :ref:Style examples <style_examples>.