App:Library:LVGL:docs:Get started

https://docs.lvgl.io/8.2/get-started/index.html

Quick overview

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Here you can learn the most important things about LVGL. You should read this first to get a general impression and read the detailed Porting and Overview sections after that.

Get started in a simulator

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Instead of porting LVGL to embedded hardware straight away, it's highly recommended to get started in a simulator first. LVGL is ported to many IDEs to be sure you will find your favorite one. Go to the Simulators section to get ready-to-use projects that can be run on your PC. This way you can save the time of porting for now and get some experience with LVGL immediately.

Add LVGL into your project

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If you would rather try LVGL on your own project follow these steps: Download or clone the library from GitHub with git clone https://github.com/lvgl/lvgl.git. Copy the lvgl folder into your project. Copy lvgl/lv_conf_template.h as lv_conf.h next to the lvgl folder, change the first #if 0 to 1 to enable the file's content and set the LV_COLOR_DEPTH defines. Include lvgl/lvgl.h in files where you need to use LVGL related functions. 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 LVGL. Alternatively, configure LV_TICK_CUSTOM (see lv_conf.h) so that LVGL can retrieve the current time directly. Call lv_init() Create a draw buffer: LVGL will render the graphics here first, and send the rendered image to the display. The buffer size can be set freely but 1/10 screen size is a good starting point. static lv_disp_draw_buf_t draw_buf; static lv_color_t buf1[DISP_HOR_RES * DISP_VER_RES / 10]; /*Declare a buffer for 1/10 screen size*/ lv_disp_draw_buf_init(&draw_buf, buf1, NULL, MY_DISP_HOR_RES * MY_DISP_VER_SER / 10); /*Initialize the display buffer.*/ Implement and register a function which can copy the rendered image to an area of your display: static 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.draw_buf = &draw_buf; /*Assign the buffer to the display*/ disp_drv.hor_res = MY_DISP_HOR_RES; /*Set the horizontal resolution of the display*/ disp_drv.ver_res = MY_DISP_VER_RES; /*Set the vertical resolution of the display*/ lv_disp_drv_register(&disp_drv); /*Finally register the driver*/ void my_disp_flush(lv_disp_drv_t * disp, const lv_area_t * area, lv_color_t * color_p) { int32_t x, y; /*It's a very slow but simple implementation. *`set_pixel` needs to be written by you to a set pixel on the screen*/ for(y = area->y1; y <= area->y2; y++) { for(x = area->x1; x <= area->x2; x++) { set_pixel(x, y, *color_p); color_p++; } } lv_disp_flush_ready(disp); /* Indicate you are ready with the flushing*/ } Implement and register a function which can read an input device. E.g. for a touchpad: static lv_indev_drv_t indev_drv; /*Descriptor of a input device driver*/ lv_indev_drv_init(&indev_drv); /*Basic initialization*/ 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*/ void my_touchpad_read(lv_indev_t * indev, lv_indev_data_t * data) { /*`touchpad_is_pressed` and `touchpad_get_xy` needs to be implemented by you*/ if(touchpad_is_pressed()) { data->state = LV_INDEV_STATE_PRESSED; touchpad_get_xy(&data->point.x, &data->point.y); } else { data->state = LV_INDEV_STATE_RELEASED; } } Call lv_timer_handler() periodically every few milliseconds in the main while(1) loop or in an operating system task. It will redraw the screen if required, handle input devices, animation etc. For a more detailed guide go to the Porting section.

Learn the basics

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Widgets The graphical elements like Buttons, Labels, Sliders, Charts etc. are called objects or widgets. Go to Widgets to see the full list of available widgets. Every object has a parent object where it is created. For example, if a label is created on a button, the button is the parent of label. The child object moves with the parent and if the parent is deleted the children will be deleted too. Children can be visible only within their parent's bounding area. In other words, the parts of the children outside the parent are clipped. A Screen is the "root" parent. You can have any number of screens. To get the current screen call lv_scr_act(), and to load a screen use lv_scr_load(scr1). You can create a new object with lv_<type>_create(parent). It will return an lv_obj_t * variable that can be used as a reference to the object to set its parameters. For example: lv_obj_t * slider1 = lv_slider_create(lv_scr_act()); To set some basic attributes lv_obj_set_<parameter_name>(obj, <value>) functions can be used. For example: lv_obj_set_x(btn1, 30); lv_obj_set_y(btn1, 10); lv_obj_set_size(btn1, 200, 50); Along with the basic attributes, widgets can have type specific parameters which are set by lv_<widget_type>_set_<parameter_name>(obj, <value>) functions. For example: lv_slider_set_value(slider1, 70, LV_ANIM_ON); To see the full API visit the documentation of the widgets or the related header file (e.g. lvgl/src/widgets/lv_slider.h).

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