Font Manager

The font manager is a secondary encapsulation of the LVGL font engine, which facilitates the use and management of fonts for applications.

The font manager is a secondary encapsulation of the LVGL font engine, which facilitates the use and management of fonts for applications. The font management functions currently provided include:

• Font resource reference counting (reduces repeated creation of font resources).
• Font resource concatenation (font fallback).
• Font resource recycling mechanism (buffers recently deleted font resources to reduce the time overhead of repeated creation).

Usage

Enable FreeType and Font Manager in lv_conf.h by setting the LV_USE_FONT_MANAGER macros to non-zero values, and configure LV_FONT_MANAGER_NAME_MAX_LEN to set the maximum length of the font name.

Initialize Font Manager

Use lv_font_manager_create to create a font manager, where the recycle_cache_size parameter is used to set the number of font recycling caches, which can improve font creation efficiency.

Use lv_font_manager_add_src_static to add a mapping between font names and font resources to tell the font manager how to access the font resources. Note that if the font resource description structure is not statically allocated (for example, allocated from a local variable), use lv_font_manager_add_src to add the resource. This function will copy the contents of the structure itself.

Use lv_font_manager_remove_src to remove the font resource mapping.

It should be noted that the src parameter must strictly correspond to class_p. class_p will affect the way the font manager interprets src. If an incompatible parameter is passed, the program may fail. For currently supported font classes, please refer to the example code.

static lv_font_manager_t * g_font_manager = NULL;

void font_manager_init(void)
{
   /* Create font manager, with 8 fonts recycling buffers */
   g_font_manager = lv_font_manager_create(8);

   /* Add font path mapping to font manager */
   lv_font_manager_add_src_static(g_font_manager, "Lato-Regular", "./lvgl/examples/libs/freetype/Lato-Regular.ttf", &lv_freetype_font_class);

   char path[] = "/path/to/myfont.ttf";
   lv_font_manager_add_src(g_font_manager, "MyFont", path, &lv_freetype_font_class);
}

Create Font from Font Manager

The parameters will be passed to the font creation function of the font backend, such as lv_freetype_font_create and lv_tiny_ttf_create_file. The font backend will select the supported parameters by itself and ignore the unsupported parameters.

The font_family parameter can be filled with the names of multiple fonts (separated by ,) to achieve font concatenation (when the corresponding glyph is not found in a font file, it will automatically search from the next concatenated font).

static lv_font_t * g_font = NULL;

/* Create font from font manager */
lv_font_t * g_font = lv_font_manager_create_font(g_font_manager,
                                                 "Lato-Regular,MyFont",
                                                 LV_FREETYPE_FONT_RENDER_MODE_BITMAP,
                                                 24,
                                                 LV_FREETYPE_FONT_STYLE_NORMAL,
                                                 LV_FONT_KERNING_NONE);

/* Handle error case */
if(g_font == NULL) {
   g_font = (lv_font_t *)LV_FONT_DEFAULT;
}

/* Create label with the font */
lv_obj_t * label = lv_label_create(lv_screen_active());
lv_obj_set_style_text_font(label, g_font, 0);
lv_label_set_text(label, "Hello World!");

Delete Font

Use lv_font_manager_delete_font to delete the font when it is no longer needed. The font manager will mark the font resource as a recyclable font so that it has the possibility of being more quickly created next time.

Note that you need to delete any Widgets that used the font first, and then delete the font to avoid accessing wild pointers.

/* Delete label and font */
lv_obj_delete(label);
lv_font_manager_delete_font(g_font_manager, g_font);
g_font = NULL;

Delete Font Manager

Use lv_font_manager_delete to destroy the entire font manager. It should be noted that before destruction, it is necessary to ensure that the application has deleted all fonts using lv_font_manager_delete_font. The font manager will check the reference status of all allocated fonts. If there are still fonts being referenced, the font manager will fail to be destroyed and the function will return false.

Example

Create FreeType Font

Create Font Family

Create Custom Image Font

API