ref: 0.12.0
src/libs/lvgl/README.md
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<h1 align="center"> LittlevGL - Open-source Embedded GUI Library</h1> <p align="center"> <a href="https://github.com/littlevgl/lvgl/blob/master/LICENCE.txt"><img src="https://img.shields.io/badge/licence-MIT-blue.svg"></a> <a href="https://github.com/littlevgl/lvgl/releases/tag/v6.0"><img src="https://img.shields.io/badge/version-6.0-blue.svg"></a> </p> <p align="center"> <img src="https://littlevgl.com/github/cover_ori_reduced_2.gif"> </p> <p align="center"> LittlevGL provides everything you need to create a Graphical User Interface (GUI) on embedded systems with easy-to-use graphical elements, beautiful visual effects and low memory footprint. </p> <h4 align="center"> <a href="https://littlevgl.com">Website </a> · <a href="https://littlevgl.com/live-demo">Live demo</a> · <a href="https://docs.littlevgl.com/en/html/get-started/pc-simulator.html">Simulator</a> · <a href="https://forum.littlevgl.com">Forum</a> · <a href="https://docs.littlevgl.com/">Docs</a> · <a href="https://blog.littlevgl.com/">Blog</a> </h4> --- - [Features](#features) - [Supported devices](#supported-devices) - [Quick start in a simulator](#quick-start-in-a-simulator) - [Add LittlevGL to your project](#add-littlevgl-to-your-project) - [Learn the basics](#learn-the-basics) - [Examples](#examples) - [Contributing](#contributing) - [Donate](#donate) ## Features * **Powerful building blocks** buttons, charts, lists, sliders, images, etc. * **Advanced graphics** with animations, anti-aliasing, opacity, smooth scrolling * **Simultaneously use various input devices** touchscreen, mouse, keyboard, encoder, buttons, etc. * **Simultaneously use multiple displays** i.e. monochrome and color display * **Multi-language support** with UTF-8 encoding * **Fully customizable** graphical elements * **Hardware independent** to use with any microcontroller or display * **Scalable** to operate with little memory (64 kB Flash, 10 kB RAM) * **OS, External memory and GPU** supported but not required * **Single frame buffer** operation even with advances graphical effects * **Written in C** for maximal compatibility * **Micropython Binding** exposes [LittlevGL API in Micropython](https://blog.littlevgl.com/2019-02-20/micropython-bindings) * **Simulator** to develop on PC without embedded hardware * **Tutorials, examples, themes** for rapid development * **Documentation** and API references ## Supported devices Basically, every modern controller - which is able to drive a display - is suitable to run LittlevGL. The minimal requirements: - 16, 32 or 64 bit microcontroller or processor - > 16 MHz clock speed is recommended - Flash/ROM: > 64 kB for the very essential components (> 180 kB is recommended) - RAM: - Static RAM usage: ~8..16 kB depending on the used features and objects types - Stack: > 2kB (> 4 kB is recommended) - Dynamic data (heap): > 4 KB (> 16 kB is recommended if using several objects). Set by `LV_MEM_SIZE` in *lv_conf.h*. - Display buffer: > *"Horizontal resolution"* pixels (> 10 × *"Horizontal resolution"* is recommended) - C99 or newer compiler *Note that the memory usage might vary depending on the architecture, compiler and build options.* Just to mention some **platforms**: - STM32F1, STM32F3, [STM32F4](https://blog.littlevgl.com/2017-07-15/stm32f429_disco_port), [STM32F7](https://github.com/littlevgl/stm32f746_disco_no_os_sw4stm32) - Microchip dsPIC33, PIC24, PIC32MX, PIC32MZ - NXP Kinetis, LPC, iMX - [Linux frame buffer](https://blog.littlevgl.com/2018-01-03/linux_fb) (/dev/fb) - [Raspberry PI](http://www.vk3erw.com/index.php/16-software/63-raspberry-pi-official-7-touchscreen-and-littlevgl) - [Espressif ESP32](https://github.com/littlevgl/esp32_ili9431) - Nordic nrf52 - Quectell M66 ## Quick start in a simulator The easiest way to get started with LittlevGL is to run it in a simulator on your PC without any embedded hardware. Choose a project with your favourite IDE: | Eclipse | CodeBlocks | Visual Studio | PlatformIO | Qt Creator | |-------------|-------------|---------------|-----------|------------| | [](https://github.com/littlevgl/pc_simulator_sdl_eclipse) | [](https://github.com/littlevgl/pc_simulator_win_codeblocks) | [](https://github.com/littlevgl/visual_studio_2017_sdl_x64) | [](https://github.com/littlevgl/pc_simulator_sdl_platformio) | [](https://blog.littlevgl.com/2019-01-03/qt-creator) | | Cross-platform<br>with SDL<br>(Recommended on<br>Linux and Mac) | Native Windows | Windows<br>with SDL | Cross-platform<br>with SDL | Cross-platform<br>with SDL | ## Add LittlevGL to your project The steps below show how to setup LittlevGL on an embedded system with a display and a touchpad. You can use the [Simulators](https://docs.littlevgl.com/en/html/get-started/pc-simulator) to get ready to use projects which can be run on your PC. 1. [Download](https://littlevgl.com/download) or [Clone](https://github.com/littlevgl/lvgl) the library 2. Copy the `lvgl` folder into your project 3. Copy `lvgl/lv_conf_template.h` as `lv_conf.h` next to the `lvgl` folder and set at least `LV_HOR_RES_MAX`, `LV_VER_RES_MAX` and `LV_COLOR_DEPTH`. 4. Include `lvgl/lvgl.h` where you need to use LittlevGL related functions. 5. Call `lv_tick_inc(x)` every `x` milliseconds **in a Timer or Task** (`x` should be between 1 and 10). It is required for the internal timing of LittlevGL. 6. Call `lv_init()` 7. Create a display buffer for LittlevGL ```c static lv_disp_buf_t disp_buf; static lv_color_t buf[LV_HOR_RES_MAX * 10]; /*Declare a buffer for 10 lines*/ lv_disp_buf_init(&disp_buf, buf, NULL, LV_HOR_RES_MAX * 10); /*Initialize the display buffer*/ ``` 8. Implement and register a function which can **copy a pixel array** to an area of your display: ```c lv_disp_drv_t disp_drv; /*Descriptor of a display driver*/ lv_disp_drv_init(&disp_drv); /*Basic initialization*/ disp_drv.flush_cb = my_disp_flush; /*Set your driver function*/ disp_drv.buffer = &disp_buf; /*Assign the buffer to the display*/ lv_disp_drv_register(&disp_drv); /*Finally register the driver*/ void my_disp_flush(lv_disp_t * disp, const lv_area_t * area, lv_color_t * color_p) { int32_t x, y; for(y = area->y1; y <= area->y2; y++) { for(x = area->x1; x <= area->x2; x++) { set_pixel(x, y, *color_p); /* Put a pixel to the display.*/ color_p++; } } lv_disp_flush_ready(disp); /* Indicate you are ready with the flushing*/ } ``` 9. Implement and register a function which can **read an input device**. E.g. for a touch pad: ```c lv_indev_drv_init(&indev_drv); /*Descriptor of a input device driver*/ indev_drv.type = LV_INDEV_TYPE_POINTER; /*Touch pad is a pointer-like device*/ indev_drv.read_cb = my_touchpad_read; /*Set your driver function*/ lv_indev_drv_register(&indev_drv); /*Finally register the driver*/ bool my_touchpad_read(lv_indev_drv_t * indev_driver, lv_indev_data_t * data) { static lv_coord_t last_x = 0; static lv_coord_t last_y = 0; /*Save the state and save the pressed coordinate*/ data->state = touchpad_is_pressed() ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL; if(data->state == LV_INDEV_STATE_PR) touchpad_get_xy(&last_x, &last_y); /*Set the coordinates (if released use the last pressed coordinates)*/ data->point.x = last_x; data->point.y = last_y; return false; /*Return `false` because we are not buffering and no more data to read*/ } ``` 10. Call `lv_task_handler()` periodically every few milliseconds in the main `while(1)` loop, in Timer interrupt or in an Operation system task. It will redraw the screen if required, handle input devices etc. ## Learn the basics ### Objects (Widgets) The graphical elements like Buttons, Labels, Sliders, Charts etc are called objects in LittelvGL. Go to [Object types](https://docs.littlevgl.com/en/html/object-types/index) to see the full list of available types. Every object has a parent object. The child object moves with the parent and if you delete the parent the children will be deleted too. Children can be visible only on their parent. The *screen* are the "root" parents. To get the current screen call `lv_scr_act()`. You can create a new object with `lv_<type>_create(parent, obj_to_copy)`. It will return an `lv_obj_t *` variable which should be used as a reference to the object to set its parameters. The first parameter is the desired *parent*, te second parameters can be an object to copy (`NULL` is unused). For example: ```c lv_obj_t * slider1 = lv_slider_create(lv_scr_act(), NULL); ``` To set some basic attribute `lv_obj_set_<paramters_name>(obj, <value>)` function can be used. For example: ```c lv_obj_set_x(btn1, 30); lv_obj_set_y(btn1, 10); lv_obj_set_size(btn1, 200, 50); ``` The objects has type specific parameters too which can be set by `lv_<type>_set_<paramters_name>(obj, <value>)` functions. For example: ```c lv_slider_set_value(slider1, 70, LV_ANIM_ON); ``` To see the full API visit the documentation of the object types or the related header file (e.g. `lvgl/src/lv_objx/lv_slider.h`). ### Styles Styles can be assigned to the objects to changed their appearance. A style describes the appearance of rectangle-like objects (like a button or slider), texts, images and lines at once. You can create a new style like this: ```c static lv_style_t style1; /*Declare a new style. Should be `static`*/ lv_style_copy(&style1, &lv_style_plain); /*Copy a built-in style*/ style1.body.main_color = LV_COLOR_RED; /*Main color*/ style1.body.grad_color = lv_color_hex(0xffd83c) /*Gradient color (orange)*/ style1.body.radius = 3; style1.text.color = lv_color_hex3(0x0F0) /*Label color (green)*/ style1.text.font = &lv_font_dejavu_22; /*Change font*/ ... ``` To set a new style for an object use the `lv_<type>set_style(obj, LV_<TYPE>_STYLE_<NAME>, &my_style)` functions. For example: ```c lv_slider_set_style(slider1, LV_SLIDER_STYLE_BG, &slider_bg_style); lv_slider_set_style(slider1, LV_SLIDER_STYLE_INDIC, &slider_indic_style); lv_slider_set_style(slider1, LV_SLIDER_STYLE_KNOB, &slider_knob_style); ``` If an object's style is `NULL` then it will inherit its parent's style. For example, the labels' style are `NULL` by default. If you place them on a button then they will use the `style.text` properties from the button's style. Learn more in [Style overview](https://docs.littlevgl.com/en/html/overview/style) section. ### Events Events are used to inform the user if something has happened with an object. You can assign a callback to an object which will be called if the object is clicked, released, dragged, being deleted etc. It should look like this: ```c lv_obj_set_event_cb(btn, btn_event_cb); /*Assign a callback to the button*/ ... void btn_event_cb(lv_obj_t * btn, lv_event_t event) { if(event == LV_EVENT_CLICKED) { printf("Clicked\n"); } } ``` Learn more about the events in the [Event overview](https://docs.littlevgl.com/en/html/overview/event) section. ## Examples ### Button with label ```c lv_obj_t * btn = lv_btn_create(lv_scr_act(), NULL); /*Add a button the current screen*/ lv_obj_set_pos(btn, 10, 10); /*Set its position*/ lv_obj_set_size(btn, 100, 50); /*Set its size*/ lv_obj_set_event_cb(btn, btn_event_cb); /*Assign a callback to the button*/ lv_obj_t * label = lv_label_create(btn, NULL); /*Add a label to the button*/ lv_label_set_text(label, "Button"); /*Set the labels text*/ ... void btn_event_cb(lv_obj_t * btn, lv_event_t event) { if(event == LV_EVENT_CLICKED) { printf("Clicked\n"); } } ```  ### Button with styles Add styles to the previously button from the previous example ```c static lv_style_t style_btn_rel; /*A variable to store the released style*/ lv_style_copy(&style_btn_rel, &lv_style_plain); /*Initialize from a built-in style*/ style_btn_rel.body.border.color = lv_color_hex3(0x269); style_btn_rel.body.border.width = 1; style_btn_rel.body.main_color = lv_color_hex3(0xADF); style_btn_rel.body.grad_color = lv_color_hex3(0x46B); style_btn_rel.body.shadow.width = 4; style_btn_rel.body.shadow.type = LV_SHADOW_BOTTOM; style_btn_rel.body.radius = LV_RADIUS_CIRCLE; style_btn_rel.text.color = lv_color_hex3(0xDEF); static lv_style_t style_btn_pr; /*A variable to store the pressed style*/ lv_style_copy(&style_btn_pr, &style_btn_rel); /*Initialize from the released style*/ style_btn_pr.body.border.color = lv_color_hex3(0x46B); style_btn_pr.body.main_color = lv_color_hex3(0x8BD); style_btn_pr.body.grad_color = lv_color_hex3(0x24A); style_btn_pr.body.shadow.width = 2; style_btn_pr.text.color = lv_color_hex3(0xBCD); lv_btn_set_style(btn, LV_BTN_STYLE_REL, &style_btn_rel); /*Set the button's released style*/ lv_btn_set_style(btn, LV_BTN_STYLE_PR, &style_btn_pr); /*Set the button's pressed style*/ ```  ### Slider and object alignment ```c lv_obj_t * label; ... /* Create a slider in the center of the display */ lv_obj_t * slider = lv_slider_create(lv_scr_act(), NULL); lv_obj_set_width(slider, 200); /*Set the width*/ lv_obj_align(slider, NULL, LV_ALIGN_CENTER, 0, 0); /*Align to the center of the parent (screen)*/ lv_obj_set_event_cb(slider, slider_event_cb); /*Assign an event function*/ /* Create a label below the slider */ label = lv_label_create(lv_scr_act(), NULL); lv_label_set_text(label, "0"); lv_obj_set_auto_realign(slider, true); lv_obj_align(label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10); ... void slider_event_cb(lv_obj_t * slider, lv_event_t event) { if(event == LV_EVENT_VALUE_CHANGED) { static char buf[4]; /* max 3 bytes for number plus 1 null terminating byte */ snprintf(buf, 4, "%u", lv_slider_get_value(slider)); lv_label_set_text(slider_label, buf); /*Refresh the text*/ } } ```  ### List and themes ```c /*Texts of the list elements*/ const char * txts[] = {"First", "Second", "Third", "Forth", "Fifth", "Sixth", NULL}; /* Initialize and set a theme. `LV_THEME_NIGHT` needs to enabled in lv_conf.h. */ lv_theme_t * th = lv_theme_night_init(20, NULL); lv_theme_set_current(th); /*Create a list*/ lv_obj_t* list = lv_list_create(lv_scr_act(), NULL); lv_obj_set_size(list, 120, 180); lv_obj_set_pos(list, 10, 10); /*Add buttons*/ uint8_t i; for(i = 0; txts[i]; i++) { lv_obj_t * btn = lv_list_add_btn(list, LV_SYMBOL_FILE, txts[i]); lv_obj_set_event_cb(btn, list_event); /*Assign event function*/ lv_btn_set_toggle(btn, true); /*Enable on/off states*/ } /* Initialize and set an other theme. `LV_THEME_MATERIAL` needs to enabled in lv_conf.h. * If `LV_TEHE_LIVE_UPDATE 1` then the previous list's style will be updated too.*/ th = lv_theme_material_init(210, NULL); lv_theme_set_current(th); /*Create an other list*/ list = lv_list_create(lv_scr_act(), NULL); lv_obj_set_size(list, 120, 180); lv_obj_set_pos(list, 150, 10); /*Add buttons with the same texts*/ for(i = 0; txts[i]; i++) { lv_obj_t * btn = lv_list_add_btn(list, LV_SYMBOL_FILE, txts[i]); lv_obj_set_event_cb(btn, list_event); lv_btn_set_toggle(btn, true); } ... static void list_event(lv_obj_t * btn, lv_event_t e) { if(e == LV_EVENT_CLICKED) { printf("%s\n", lv_list_get_btn_text(btn)); } } ```  ### Use LittlevGL from Micropython Learn more about [Micropython](https://docs.littlevgl.com/en/html/get-started/micropython). ```python # Create a Button and a Label scr = lv.obj() btn = lv.btn(scr) btn.align(lv.scr_act(), lv.ALIGN.CENTER, 0, 0) label = lv.label(btn) label.set_text("Button") # Load the screen lv.scr_load(scr) ``` ## Contributing To ask questions please use the [Forum](https://forum.littlevgl.com). For development-related things (bug reports, feature suggestions) use [GitHub's Issue tracker](https://github.com/littlevgl/lvgl/issues). If you are interested in contributing to LittlevGL you can - **Help others** in the [Forum](https://forum.littlevgl.com). - **Inspire people** by speaking about your project in [My project](https://forum.littlevgl.com/c/my-projects) category in the Forum or add it to the [References](https://blog.littlevgl.com/2018-12-26/references) post - **Improve and/or translate the documentation.** Go to the [Documentation](https://github.com/littlevgl/docs) repository to learn more - **Write a blog post** about your experiences. See how to do it in the [Blog](https://github.com/littlevgl/blog) repository - **Report and/or fix bugs** in [GitHub's issue tracker](https://github.com/littlevgl/lvgl/issues) - **Help in the developement**. Check the [Open issues](https://github.com/littlevgl/lvgl/issues) especially the ones with [Help wanted](https://github.com/littlevgl/lvgl/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22) label and tell your ideas about a topic or implement a feature. It should be useful to read the - [Contributing guide](https://blog.littlevgl.com/2018-12-06/contributing) - [Coding style guide](https://github.com/littlevgl/lvgl/blob/master/docs/CODING_STYLE.md) ## Donate If you are pleased with the library, found it useful, or you are happy with the support you got, please help its further development: [](https://littlevgl.com/donate) |