68 lines
2.0 KiB
Markdown
68 lines
2.0 KiB
Markdown
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All display operations based on [u8g2](https://github.com/olikraus/u8g2) library.
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API available as `ValueComposer`.
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Driver call render callback and pass API contains u8g2 functions, instance and fonts:
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```C
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typedef struct {
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u8g2_t* display;
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void (*u8g2_SetFont)(u8g2_t *u8g2, const uint8_t *font);
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void (*u8g2_SetDrawColor)(u8g2_t *u8g2, uint8_t color);
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void (*u8g2_SetFontMode)(u8g2_t *u8g2, uint8_t is_transparent);
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u8g2_uint_t (*u8g2_DrawStr)(u8g2_t *u8g2, u8g2_uint_t x, u8g2_uint_t y, const char *str);
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Fonts fonts;
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} DisplayApi;
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typedef struct {
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const uint8_t* u8g2_font_6x10_mf;
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} Fonts;
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```
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First of all you can open display API instance by calling `open_display`
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```C
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/// Get display instance and API
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inline Display* open_display(const char* name) {
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return (Display*)furi_open(name);
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}
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```
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Default display name is `/dev/display`.
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For draw something to display you need to register new layer in display composer:
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```C
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typedef void (RenderCallback*)(void* ctx, DisplayApi* api);
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inline ValueComposerHandle* init_display_composer(
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Display* api, RenderCallback render, void* ctx, uint32_t layer) {
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return add_compose_layer(api->composer, (ValueComposerCallback)render, ctx, layer);
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}
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```
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And then call `request_compose` every time you need to redraw your image.
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## Usage example
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```C
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void example_render(void* ctx, DisplayApi* api) {
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api->u8g2_SetFont(api->display, display_api->fonts.u8g2_font_6x10_mf);
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api->u8g2_SetDrawColor(api->display, 1);
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api->u8g2_SetFontMode(api->display, 1);
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api->u8g2_DrawStr(api->display, 2, 12, (char*)ctx); // ctx contains some static text
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}
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void u8g2_example(void* p) {
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Display* display_api = open_display("/dev/display");
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if(display_api == NULL) return; // display not available, critical error
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ValueComposerHandle display_handler = init_display_composer(
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display_api, example_render, (void*)"Hello world", UiLayerBelowNotify);
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request_compose(display_handler);
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}
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```
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