Tiny TTF font engine（微小的TTF字体引擎）
Usage（用法）
显示原文
Allow using TrueType fonts in LVGL.
Detailed introduction: https://github.com/nothings/stb
When enabled in lv_conf.h with LV_USE_TINY_TTF
lv_tiny_ttf_create_data(data, data_size, font_size) can be used to
create a TTF font instance at the specified line height. You can then
use that font anywhere lv_font_t is accepted.
By default, the TTF or OTF file must be embedded as an array, either in a header, or loaded into RAM in order to function.
However, if LV_TINY_TTF_FILE_SUPPORT is enabled,
lv_tiny_ttf_create_file(path, font_size) will also be available,
allowing tiny_ttf to stream from a file. The file must remain open the
entire time the font is being used.
After a font is created, you can change the font size in pixels by using lv_tiny_ttf_set_size(font, font_size).
By default, a font will cache data for upto 256 glyphs elements to speed up rendering. This maximum can be changed by using lv_tiny_ttf_create_data_ex(data, data_size, font_size, kerning, cache_size) or lv_tiny_ttf_create_file_ex(path, font_size, kerning, cache_size) (when available). The cache size is indicated in number of entries. Kerning is whether to allow if supported, or disable.
允许在 LVGL 中使用 TrueType 字体。
详细介绍：<https://github.com/nothings/stb>
在 lv_conf.h 中启用 LV_USE_TINY_TTF 后，可以使用 lv_tiny_ttf_create_data(data, data_size, font_size) 创建一个指定行高的 TTF 字体实例。随后可以在任何接受 lv_font_t 的地方使用该字体。
默认情况下，TTF 或 OTF 文件必须作为数组嵌入到头文件中，或者加载到 RAM 中才能正常工作。
然而，如果启用了 LV_TINY_TTF_FILE_SUPPORT，还可以使用 lv_tiny_ttf_create_file(path, font_size)，允许 tiny_ttf 从文件中流式加载。文件在字体使用期间必须保持打开状态。
创建字体后，可以通过 lv_tiny_ttf_set_size(font, font_size) 按像素更改字体大小。
默认情况下，字体将缓存最多 256 个字形元素以加速渲染。可以通过使用 lv_tiny_ttf_create_data_ex(data, data_size, font_size, kerning, cache_size) 或 :cpp:expr:`lv_tiny_ttf_create_file_ex(path, font_size, kerning, cache_size)`（如果可用）更改此最大值。缓存大小以条目数表示。Kerning 参数用于指定是否启用字距调整（如果支持），或禁用。
Example
Open a font with Tiny TTF from data array
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_TINY_TTF && LV_BUILD_EXAMPLES
/**
* Load a font with Tiny_TTF
*/
void lv_example_tiny_ttf_1(void)
{
extern const uint8_t ubuntu_font[];
extern const int ubuntu_font_size;
/*Create style with the new font*/
static lv_style_t style;
lv_style_init(&style);
lv_font_t * font = lv_tiny_ttf_create_data(ubuntu_font, ubuntu_font_size, 30);
lv_style_set_text_font(&style, font);
lv_style_set_text_align(&style, LV_TEXT_ALIGN_CENTER);
/*Create a label with the new style*/
lv_obj_t * label = lv_label_create(lv_screen_active());
lv_obj_add_style(label, &style, 0);
lv_label_set_text(label, "Hello world\nI'm a font\ncreated\nwith Tiny TTF");
lv_obj_center(label);
}
#endif
Load a font with Tiny_TTF from file
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_TINY_TTF && LV_TINY_TTF_FILE_SUPPORT && LV_BUILD_EXAMPLES
/**
* Load a font with Tiny_TTF from file
*/
void lv_example_tiny_ttf_2(void)
{
/*Create style with the new font*/
static lv_style_t style;
lv_style_init(&style);
lv_font_t * font = lv_tiny_ttf_create_file("A:lvgl/examples/libs/tiny_ttf/Ubuntu-Medium.ttf", 30);
lv_style_set_text_font(&style, font);
lv_style_set_text_align(&style, LV_TEXT_ALIGN_CENTER);
/*Create a label with the new style*/
lv_obj_t * label = lv_label_create(lv_screen_active());
lv_obj_add_style(label, &style, 0);
lv_label_set_text(label, "Hello world\nI'm a font\ncreated\nwith Tiny TTF");
lv_obj_center(label);
}
#endif
Change font size with Tiny_TTF
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_TINY_TTF && LV_BUILD_EXAMPLES && LV_USE_OBSERVER
static void font_size_observer_cb(lv_observer_t * observer, lv_subject_t * subject);
static lv_subject_t subject_font;
/**
* Change font size with Tiny_TTF
*/
void lv_example_tiny_ttf_3(void)
{
extern const uint8_t ubuntu_font[];
extern const int ubuntu_font_size;
lv_subject_init_int(&subject_font, 25);
/*Create style with the new font*/
static lv_style_t style;
lv_style_init(&style);
lv_font_t * font = lv_tiny_ttf_create_data(ubuntu_font, ubuntu_font_size, 25);
lv_style_set_text_font(&style, font);
lv_style_set_text_align(&style, LV_TEXT_ALIGN_CENTER);
lv_obj_t * slider = lv_slider_create(lv_screen_active());
lv_obj_center(slider);
lv_slider_set_range(slider, 5, 50);
lv_obj_align(slider, LV_ALIGN_BOTTOM_MID, 0, -50);
lv_slider_bind_value(slider, &subject_font);
lv_obj_t * slider_label = lv_label_create(lv_screen_active());
lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
lv_label_bind_text(slider_label, &subject_font, "%d");
/*Create a label with the new style*/
lv_obj_t * label = lv_label_create(lv_screen_active());
lv_obj_add_style(label, &style, 0);
lv_obj_set_size(label, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
lv_label_set_text(label, "Hello world!");
lv_obj_center(label);
lv_subject_add_observer(&subject_font, font_size_observer_cb, &style);
}
static void font_size_observer_cb(lv_observer_t * observer, lv_subject_t * subject)
{
lv_style_t * style = lv_observer_get_user_data(observer);
lv_style_value_t v;
lv_style_get_prop(style, LV_STYLE_TEXT_FONT, &v);
lv_font_t * font = (lv_font_t *) v.ptr;
int32_t size = lv_subject_get_int(subject);
lv_tiny_ttf_set_size(font, size);
lv_obj_report_style_change(style);
}
#endif