T-DeckLoader/lib/lvgl/docs/porting/project.md

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Set up a project

Get the library

LVGL is available on GitHub: https://github.com/lvgl/lvgl.

You can clone it or Download the latest version of the library from GitHub.

Add lvgl to your project

The graphics library itself is the lvgl directory. It contains a couple of folders but to use lvgl you only need .c and .h files from the src folder.

Automatically add files

If your IDE automatically adds the files from the folders copied to the project folder (as Eclipse or VSCode does), you can simply copy the lvgl folder as it is into your project.

Make and CMake

LVGL also supports make and CMake build systems out of the box. To add LVGL to your Makefile based build system add these lines to your main Makefile:

LVGL_DIR_NAME ?= lvgl     #The name of the lvgl folder (change this if you have renamed it)
LVGL_DIR ?= ${shell pwd}  #The path where the lvgl folder is
include $(LVGL_DIR)/$(LVGL_DIR_NAME)/lvgl.mk

For integration with CMake take a look this section of the Documentation.

Other platforms and tools

The Get started section contains many platform specific descriptions e.g. for ESP32, Arduino, NXP, RT-Thread, NuttX, etc.

Demos and Examples

The lvgl folder also contains an examples and a demos folder. If you needed to add the source files manually to your project, you can do the same with the source files of these two folders too. make and CMake handles the examples and demos, so no extra action required in these cases.

Configuration file

There is a configuration header file for LVGL called lv_conf.h. You modify this header to set the library's basic behavior, disable unused modules and features, adjust the size of memory buffers in compile-time, etc.

To get lv_conf.h copy lvgl/lv_conf_template.h next to the lvgl directory and rename it to lv_conf.h. Open the file and change the #if 0 at the beginning to #if 1 to enable its content. So the layout of the files should look like this:

|-lvgl
|-lv_conf.h
|-other files and folders

Comments in the config file explain the meaning of the options. Be sure to set at least LV_COLOR_DEPTH according to your display's color depth. Note that, the examples and demos explicitly need to be enabled in lv_conf.h.

Alternatively, lv_conf.h can be copied to another place but then you should add the LV_CONF_INCLUDE_SIMPLE define to your compiler options (e.g. -DLV_CONF_INCLUDE_SIMPLE for GCC compiler) and set the include path manually (e.g. -I../include/gui). In this case LVGL will attempt to include lv_conf.h simply with #include "lv_conf.h".

You can even use a different name for lv_conf.h. The custom path can be set via the LV_CONF_PATH define. For example -DLV_CONF_PATH="/home/joe/my_project/my_custom_conf.h"

If LV_CONF_SKIP is defined, LVGL will not try to include lv_conf.h. Instead you can pass the config defines using build options. For example "-DLV_COLOR_DEPTH=32 -DLV_USE_BTN=1". The unset options will get a default value which is the same as the ones in lv_conf_template.h.

LVGL also can be used via Kconfig and menuconfig.  You can use lv_conf.h together with Kconfig, but keep in mind that the value from lv_conf.h or build settings (-D...) overwrite the values set in Kconfig. To ignore the configs from lv_conf.h simply remove its content, or define LV_CONF_SKIP. 

Initialization

To use the graphics library you have to initialize it and setup required components. The order of the initialization is:

1. Call lv_init().
2. Initialize your drivers.
3. Register the display and input devices drivers in LVGL. Learn more about Display and Input device registration.
4. Call lv_tick_inc(x) every x milliseconds in an interrupt to report the elapsed time to LVGL. Learn more.
5. Call lv_timer_handler() every few milliseconds to handle LVGL related tasks. Learn more.