flipperzero-firmware/wiki/fw/api/API-Display.md

All display operations based on u8g2 library.

API available as struct, contains u8g2 functions, instance and fonts:

typedef struct {
    ValueManager* display; /// ValueManager<u8g2_t*>
    void (*u8g2_SetFont)(u8g2_t *u8g2, const uint8_t  *font);
    void (*u8g2_SetDrawColor)(u8g2_t *u8g2, uint8_t color);
    void (*u8g2_SetFontMode)(u8g2_t *u8g2, uint8_t is_transparent);
    u8g2_uint_t (*u8g2_DrawStr)(u8g2_t *u8g2, u8g2_uint_t x, u8g2_uint_t y, const char *str);

    Fonts fonts;
} Display;

typedef struct {
    const uint8_t* u8g2_font_6x10_mf;
} Fonts;

First of all you can open display API instance by calling open_display

/// Get display instance and API
inline Display* open_display(const char* name) {
    return (Display*)furi_open(name);
}

Default display name is /dev/display.

For draw something to display you can get display instance pointer by calling take_display, do something and commit your changes by calling commit_display:

/// return pointer in case off success, NULL otherwise
inline u8g2_t* take_display(Display* api, uint32_t timeout) {
    return (u8g2_t*)take_mutex(api->display->value, timeout);
}

inline void commit_display(Display* api, u8g2_t* display) {
    commit_valuemanager(api->display, display);
}

Usage example

void u8g2_example(void* p) {
    Display* display_api = open_display("/dev/display");
    if(display_api == NULL) return; // display not available, critical error

    u8g2_t* display = take_display(display_api);
    if(display != NULL) {
        display_api->u8g2_SetFont(display, display_api->fonts.u8g2_font_6x10_mf);
        display_api->u8g2_SetDrawColor(display, 1);
        display_api->u8g2_SetFontMode(display, 1);
        display_api->u8g2_DrawStr(display, 2, 12, "hello world!");
    }
    commit_display(display_api, display);
}