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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/bindings/micropython.md
```
# Cpp
In progress: https://github.com/lvgl/lv_binding_cpp

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/bindings/index.md
```
# Bindings
```eval_rst
.. toctree::
:maxdepth: 2
micropython
cpp
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/bindings/micropython.md
```
# Micropython
## What is Micropython?
[Micropython](http://micropython.org/) is Python for microcontrollers.
Using Micropython, you can write Python3 code and run it even on a bare metal architecture with limited resources.
### Highlights of Micropython
- **Compact** - Fits and runs within just 256k of code space and 16k of RAM. No OS is needed, although you can also run it with an OS, if you want.
- **Compatible** - Strives to be as compatible as possible with normal Python (known as CPython).
- **Versatile** - Supports many architectures (x86, x86-64, ARM, ARM Thumb, Xtensa).
- **Interactive** - No need for the compile-flash-boot cycle. With the REPL (interactive prompt) you can type commands and execute them immediately, run scripts, etc.
- **Popular** - Many platforms are supported. The user base is growing bigger. Notable forks: [MicroPython](https://github.com/micropython/micropython), [CircuitPython](https://github.com/adafruit/circuitpython), [MicroPython_ESP32_psRAM_LoBo](https://github.com/loboris/MicroPython_ESP32_psRAM_LoBo)
- **Embedded Oriented** - Comes with modules specifically for embedded systems, such as the [machine module](https://docs.micropython.org/en/latest/library/machine.html#classes) for accessing low-level hardware (I/O pins, ADC, UART, SPI, I2C, RTC, Timers etc.)
---
## Why Micropython + LVGL?
Currently, Micropython [does not have a good high-level GUI library](https://forum.micropython.org/viewtopic.php?f=18&t=5543) by default. LVGL is an [Object-Oriented Component Based](https://blog.lvgl.io/2018-12-13/extend-lvgl-objects) high-level GUI library, which seems to be a natural candidate to map into a higher level language, such as Python. LVGL is implemented in C and its APIs are in C.
### Here are some advantages of using LVGL in Micropython:
- Develop GUI in Python, a very popular high level language. Use paradigms such as Object-Oriented Programming.
- Usually, GUI development requires multiple iterations to get things right. With C, each iteration consists of **`Change code` > `Build` > `Flash` > `Run`**.
In Micropython it's just **`Change code` > `Run`** ! You can even run commands interactively using the [REPL](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop) (the interactive prompt)
### Micropython + LVGL could be used for:
- Fast prototyping GUI.
- Shortening the cycle of changing and fine-tuning the GUI.
- Modelling the GUI in a more abstract way by defining reusable composite objects, taking advantage of Python's language features such as Inheritance, Closures, List Comprehension, Generators, Exception Handling, Arbitrary Precision Integers and others.
- Make LVGL accessible to a larger audience. No need to know C to create a nice GUI on an embedded system.
This goes well with [CircuitPython vision](https://learn.adafruit.com/welcome-to-circuitpython/what-is-circuitpython). CircuitPython was designed with education in mind, to make it easier for new or inexperienced users to get started with embedded development.
- Creating tools to work with LVGL at a higher level (e.g. drag-and-drop designer).
---
## So what does it look like?
> TL;DR:
> It's very much like the C API, but Object-Oriented for LVGL components.
Let's dive right into an example!
### A simple example
```python
import lvgl as lv
lv.init()
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")
lv.scr_load(scr)
```
## How can I use it?
### Online Simulator
If you want to experiment with LVGL + Micropython without downloading anything - you can use our online simulator!
It's a fully functional LVGL + Micropython that runs entirely in the browser and allows you to edit a python script and run it.
[Click here to experiment on the online simulator](https://sim.lvgl.io/)
[Hello World](https://sim.lvgl.io/v7/micropython/ports/javascript/bundle_out/index.html?script=https://gist.githubusercontent.com/amirgon/51299ce9b6448328a855826149482ae6/raw/0f235c6d40462fd2f0e55364b874f14fe3fd613c/lvgl_hello_world.py&script_startup=https://gist.githubusercontent.com/amirgon/7bf15a66ba6d959bbf90d10f3da571be/raw/8684b5fa55318c184b1310663b187aaab5c65be6/init_lv_mp_js.py)
Note: the online simulator is available for lvgl v6 and v7.
### PC Simulator
Micropython is ported to many platforms. One notable port is "unix", which allows you to build and run Micropython (+LVGL) on a Linux machine. (On a Windows machine you might need Virtual Box or WSL or MinGW or Cygwin etc.)
[Click here to know more information about building and running the unix port](https://github.com/lvgl/lv_micropython)
### Embedded platform
In the end, the goal is to run it all on an embedded platform.
Both Micropython and LVGL can be used on many embedded architectures, such as stm32, ESP32 etc.
You would also need display and input drivers. We have some sample drivers (ESP32+ILI9341, as well as some other examples), but chances are you would want to create your own input/display drivers for your specific hardware.
Drivers can be implemented either in C as a Micropython module, or in pure Micropython!
## Where can I find more information?
- In this [Blog Post](https://blog.lvgl.io/2019-02-20/micropython-bindings)
- `lv_micropython` [README](https://github.com/lvgl/lv_micropython)
- `lv_binding_micropython` [README](https://github.com/lvgl/lv_binding_micropython)
- The [LVGL micropython forum](https://forum.lvgl.io/c/micropython) (Feel free to ask anything!)
- At Micropython: [docs](http://docs.micropython.org/en/latest/) and [forum](https://forum.micropython.org/)

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/index.md
```
# Get started
There are several ways to get your feet wet with LVGL. Here is one recommended order of documents to read and things to play with when you are learning to use LVGL:
1. Check the [Online demos](https://lvgl.io/demos) to see LVGL in action (3 minutes)
2. Read the [Introduction](https://docs.lvgl.io/latest/en/html/intro/index.html) page of the documentation (5 minutes)
3. Read the [Quick overview](https://docs.lvgl.io/master/get-started/quick-overview.html) page of the documentation (15 minutes)
4. Set up a [Simulator](https://docs.lvgl.io/master/get-started/platforms/pc-simulator.html) (10 minutes)
5. Try out some [Examples](https://docs.lvgl.io/master/examples.html)
6. Check out the Platform-specific tutorials. (in this section below). (10 minutes)
7. Port LVGL to a board. See the [Porting](https://docs.lvgl.io/master/porting/index.html) guide or check the ready to use [Projects](https://github.com/lvgl?q=lv_port_&type=&language=)
8. Read the [Overview](https://docs.lvgl.io/master/overview/index.html) page to get a better understanding of the library. (2-3 hours)
9. Check the documentation of the [Widgets](https://docs.lvgl.io/master/widgets/index.html) to see their features and usage
10. If you have questions got to the [Forum](http://forum.lvgl.io/)
11. Read the [Contributing](https://docs.lvgl.io/master/CONTRIBUTING.html) guide to see how you can help to improve LVGL (15 minutes)
```eval_rst
.. toctree::
:maxdepth: 2
platforms/index
os/index
bindings/index
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/os/freertos.md
```
# FreeRTOS
TODO

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/os/index.md
```
# (RT)OS
```eval_rst
.. toctree::
:maxdepth: 2
nuttx
rt-thread
freertos
zephyr
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/os/nuttx.md
```
# NuttX RTOS
## What is NuttX?
[NuttX](https://nuttx.apache.org/) is a mature and secure real-time operating system (RTOS) with an emphasis on technical standards compliance and small size.
It is scalable from 8-bit to 64-bit microcontrollers and microprocessors and compliant with the Portable Operating System Interface (POSIX) and the American National Standards Institute (ANSI) standards and with many Linux-like subsystems.
The best way to think about NuttX is to think of it as a small Unix/Linux for microcontrollers.
### Highlights of NuttX
- **Small** - Fits and runs in microcontrollers as small as 32 kB Flash and 8 kB of RAM.
- **Compliant** - Strives to be as compatible as possible with POSIX and Linux.
- **Versatile** - Supports many architectures (ARM, ARM Thumb, AVR, MIPS, OpenRISC, RISC-V 32-bit and 64-bit, RX65N, x86-64, Xtensa, Z80/Z180, etc.).
- **Modular** - Its modular design allows developers to select only what really matters and use modules to include new features.
- **Popular** - NuttX is used by many companies around the world. Probably you already used a product with NuttX without knowing it was running NuttX.
- **Predictable** - NuttX is a preemptible Realtime kernel, so you can use it to create predictable applications for realtime control.
---
## Why NuttX + LVGL?
Although NuttX has its own graphic library called [NX](https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=139629474), LVGL is a good alternative because users could find more eye-candy demos and they can reuse code from previous projects.
LVGL is an [Object-Oriented Component Based](https://blog.lvgl.io/2018-12-13/extend-lvgl-objects) high-level GUI library, that could fit very well for a RTOS with advanced features like NuttX.
LVGL is implemented in C and its APIs are in C.
### Here are some advantages of using LVGL in NuttX
- Develop GUI in Linux first and when it is done just compile it for NuttX. Nothing more, no wasting of time.
- Usually, GUI development for low level RTOS requires multiple iterations to get things right, where each iteration consists of **`Change code` > `Build` > `Flash` > `Run`**.
Using LVGL, Linux and NuttX you can reduce this process and just test everything on your computer and when it is done, compile it on NuttX and that is it.
### NuttX + LVGL could be used for
- GUI demos to demonstrate your board graphics capacities.
- Fast prototyping GUI for MVP (Minimum Viable Product) presentation.
- visualize sensor data directly and easily on the board without using a computer.
- Final products with a GUI without a touchscreen (i.e. 3D Printer Interface using Rotary Encoder to Input data).
- Final products with a touchscreen (and all sorts of bells and whistles).
---
## How to get started with NuttX and LVGL?
There are many boards in the [NuttX mainline](https://github.com/apache/incubator-nuttx) with support for LVGL.
Let's use the [STM32F429IDISCOVERY](https://www.st.com/en/evaluation-tools/32f429idiscovery.html) as an example because it is a very popular board.
### First you need to install the pre-requisites on your system
Let's use the [Windows Subsystem for Linux](https://acassis.wordpress.com/2018/01/10/how-to-build-nuttx-on-windows-10/)
```shell
$ sudo apt-get install automake bison build-essential flex gcc-arm-none-eabi gperf git libncurses5-dev libtool libusb-dev libusb-1.0.0-dev pkg-config kconfig-frontends openocd
```
### Now let's create a workspace to save our files
```shell
$ mkdir ~/nuttxspace
$ cd ~/nuttxspace
```
### Clone the NuttX and Apps repositories:
```shell
$ git clone https://github.com/apache/incubator-nuttx nuttx
$ git clone https://github.com/apache/incubator-nuttx-apps apps
```
### Configure NuttX to use the stm32f429i-disco board and the LVGL Demo
```shell
$ ./tools/configure.sh stm32f429i-disco:lvgl
$ make
```
If everything went fine you should have now the file `nuttx.bin` to flash on your board:
```shell
$ ls -l nuttx.bin
-rwxrwxr-x 1 alan alan 287144 Jun 27 09:26 nuttx.bin
```
### Flashing the firmware in the board using OpenOCD:
```shell
$ sudo openocd -f interface/stlink-v2.cfg -f target/stm32f4x.cfg -c init -c "reset halt" -c "flash write_image erase nuttx.bin 0x08000000"
```
Reset the board and using the 'NSH>' terminal start the LVGL demo:
```shell
nsh> lvgldemo
```
## Where can I find more information?
- This blog post: [LVGL on LPCXpresso54628](https://acassis.wordpress.com/2018/07/19/running-nuttx-on-lpcxpresso54628-om13098/)
- NuttX mailing list: [Apache NuttX Mailing List](http://nuttx.incubator.apache.org/community/)

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/os/rt-thread.md
```
# RT-Thread RTOS
<img src="https://raw.githubusercontent.com/RT-Thread/rt-thread/master/documentation/figures/logo.png" width=40% style="float: center;" >
## What is RT-Thread?
[Introduce about RT-Thread and how to run LVGL on RT-Thread in simulators](https://www.youtube.com/watch?v=k7QYk6hSwnc)
[**RT-Thread**](https://www.rt-thread.io/) is an [open source](https://github.com/RT-Thread/rt-thread), neutral, and community-based real-time operating system (RTOS). RT-Thread has **Standard version** and **Nano version**. For resource-constrained microcontroller (MCU) systems, the Nano version that requires only 3 KB Flash and 1.2 KB RAM memory resources can be tailored with easy-to-use tools. For resource-rich IoT devices, RT-Thread can use the **online software package** management tool, together with system configuration tools, to achieve intuitive and rapid modular cutting, seamlessly import rich software packages; thus, achieving complex functions like Android's graphical interface and touch sliding effects, smart voice interaction effects, and so on.
### Key features
- Designed for resource-constrained devices, the minimum kernel requires only 1.2KB of RAM and 3 KB of Flash.
- A variety of standard interfaces, such as POSIX, CMSIS, C++ application environment.
- Has rich components and a prosperous and fast growing <a href="https://packages.rt-thread.org/en/">package ecosystem</a>
- Elegant code style, easy to use, read and master.
- High Scalability. RT-Thread has high-quality scalable software architecture, loose coupling, modularity, is easy to tailor and expand.
- Supports high-performance applications.
- Supports all mainstream compiling tools such as GCC, Keil and IAR.
- Supports a wide range of <a href="https://www.rt-thread.io/board.html">architectures and chips</a>.
## How to run LVGL on RT-Thread?
[中文文档](https://www.rt-thread.org/document/site/#/rt-thread-version/rt-thread-standard/packages-manual/lvgl-docs/introduction)
LVGL has registered as a [software package](https://packages.rt-thread.org/en/detail.html?package=LVGL) of RT-Thread. By using [Env tool](https://www.rt-thread.io/download.html?download=Env) or [RT-Thread Studio IDE](https://www.rt-thread.io/download.html?download=Studio), RT-Thread users can easily download LVGL source code and combine with RT-Thread project. RT-Thread community has port LVGL to several BSPs:
| BSP | Note |
| ------------------------------------------------------------ | ---- |
| [QEMU simulator](https://github.com/RT-Thread/rt-thread/tree/master/bsp/qemu-vexpress-a9/applications/lvgl) | |
| [Visual Studio simulator](https://github.com/RT-Thread/rt-thread/tree/master/bsp/simulator/applications/lvgl) | |
| [Nuvoton numaker-iot-m487](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/numaker-iot-m487/applications/lvgl) | |
| [Nuvoton numaker-pfm-m487](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/numaker-pfm-m487/applications/lvgl) | |
| [Nuvoton nk-980iot](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/nk-980iot/applications/lvgl) | |
| [Nuvoton numaker-m2354](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/numaker-m2354/applications/lvgl) | |
| [Nuvoton nk-n9h30](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/nk-n9h30/applications/lvgl) | |
| [Nuvoton numaker-m032ki](https://github.com/RT-Thread/rt-thread/tree/master/bsp/nuvoton/numaker-m032ki/applications/lvgl) | |
| [NXP imxrt1060-evk](https://github.com/RT-Thread/rt-thread/tree/master/bsp/imxrt/imxrt1060-nxp-evk/applications/lvgl) | |
| [STM32L475 pandora](https://github.com/RT-Thread/rt-thread/tree/master/bsp/stm32/stm32l475-atk-pandora/applications/lvgl) | |
| [STM32F407 explorer](https://github.com/RT-Thread/rt-thread/tree/master/bsp/stm32/stm32f407-atk-explorer/applications/lvgl) | |
| [STM32F469 Discovery](https://github.com/RT-Thread/rt-thread/tree/master/bsp/stm32/stm32f469-st-disco/applications/lvgl) | |
| [Raspberry PICO](https://github.com/RT-Thread/rt-thread/tree/master/bsp/raspberry-pico/applications/lvgl) | |

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/os/zephyr.md
```
# Zephyr
TODO

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/arduino.md
```
# Arduino
The [LVGL library](https://github.com/lvgl/lvgl) is directly available as Arduino libraries.
Note that you need to choose a board powerful enough to run LVGL and your GUI. See the [requirements of LVGL](https://docs.lvgl.io/master/intro/index.html#requirements).
For example ESP32 is a good candidate to create UI's with LVGL.
## Get the LVGL Arduino library
LVGL can be installed via the Arduino IDE Library Manager or as a .ZIP library.
You can [Download](https://github.com/lvgl/lvgl/archive/refs/heads/master.zip) the latest version of LVGL from GitHub and simply copy it to Arduino's library folder.
## Set up drivers
To get started it's recommended to use [TFT_eSPI](https://github.com/Bodmer/TFT_eSPI) library as a TFT driver to simplify testing.
To make it work, setup `TFT_eSPI` according to your TFT display type via editing either
- `User_Setup.h`
- or by selecting a configuration in the `User_Setup_Select.h`
Both files are located in `TFT_eSPI` library's folder.
## Configure LVGL
LVGL has its own configuration file called `lv_conf.h`. When LVGL is installed, follow these configuration steps:
1. Go to the directory of the installed Arduino libraries
2. Go to `lvgl` and copy `lv_conf_template.h` as `lv_conf.h` into the Arduino Libraries directory next to the `lvgl` library folder.
3. Open `lv_conf.h` and change the first `#if 0` to `#if 1` to enable the content of the file
4. Set the color depth of you display in `LV_COLOR_DEPTH`
5. Set `LV_TICK_CUSTOM 1`
Finally the layout with `lv_conf.h` should look like this:
```
arduino
|-libraries
|-lvgl
|-other_lib_1
|-other_lib_2
|-lv_conf.h
```
## Initialize and run LVGL
Take a look at [LVGL_Arduino.ino](https://github.com/lvgl/lvgl/blob/master/examples/arduino/LVGL_Arduino/LVGL_Arduino.ino) to see how to initialize LVGL.
`TFT_eSPI` is used as the display driver.
In the INO file you can see how to register a display and a touchpad for LVGL and call an example.
## Use the examples and demos
Note that, there is no dedicated INO file for every example. Instead, you can load an example by calling an `lv_example_...` function. For example `lv_example_btn_1()`.
**IMPORTANT**
Due to some the limitations of Arduino's build system you need to copy `lvgl/examples` to `lvgl/src/examples`. Similarly for the demos `lvgl/demos` to `lvgl/src/demos`.
## Debugging and logging
LVGL can display debug information in case of trouble.
In the `LVGL_Arduino.ino` example there is a `my_print` method, which sends this debug information to the serial interface.
To enable this feature you have to edit the `lv_conf.h` file and enable logging in the section `log settings`:
```c
/*Log settings*/
#define USE_LV_LOG 1 /*Enable/disable the log module*/
#if LV_USE_LOG
/* How important log should be added:
* LV_LOG_LEVEL_TRACE A lot of logs to give detailed information
* LV_LOG_LEVEL_INFO Log important events
* LV_LOG_LEVEL_WARN Log if something unwanted happened but didn't cause a problem
* LV_LOG_LEVEL_ERROR Only critical issue, when the system may fail
* LV_LOG_LEVEL_NONE Do not log anything
*/
# define LV_LOG_LEVEL LV_LOG_LEVEL_WARN
```
After enabling the log module and setting LV_LOG_LEVEL accordingly, the output log is sent to the `Serial` port @ 115200 bps.

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/cmake.md
```
# CMake
LVGL supports integrating with [CMake](https://cmake.org/). It comes with preconfigured targets for:
- [Espressif (ESP32)](https://docs.espressif.com/projects/esp-idf/en/v3.3/get-started-cmake/index.html)
- [MicroPython](https://docs.micropython.org/en/v1.15/develop/cmodules.html)
- [Zephyr](https://docs.zephyrproject.org/latest/guides/zephyr_cmake_package.html)
On top of the preconfigured targets you can also use "plain" CMake to integrate LVGL into any custom C/C++ project.
### Prerequisites
- CMake ( >= 3.12.4 )
- Compatible build tool e.g.
- [Make](https://www.gnu.org/software/make/)
- [Ninja](https://ninja-build.org/)
## Building LVGL with CMake
There are many ways to include external CMake projects into your own. A modern one also used in this example is the CMake [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html) module. This module conveniently allows us to download dependencies directly at configure time from e.g. [GitHub](https://github.com/). Here is an example how we might include LVGL into our own project.
```cmake
cmake_minimum_required(VERSION 3.14)
include(FetchContent)
project(MyProject LANGUAGES C CXX)
# Build an executable called "MyFirmware"
add_executable(MyFirmware src/main.c)
# Specify path to own LVGL config header
set(LV_CONF_PATH
${CMAKE_CURRENT_SOURCE_DIR}/src/lv_conf.h
CACHE STRING "" FORCE)
# Fetch LVGL from GitHub
FetchContent_Declare(lvgl URL https://github.com/lvgl/lvgl.git)
FetchContent_MakeAvailable(lvgl)
# The target "MyFirmware" depends on LVGL
target_link_libraries(MyFirmware PRIVATE lvgl::lvgl)
```
This configuration declares a dependency between the two targets **MyFirmware** and **lvgl**. Upon building the target **MyFirmware** this dependency will be resolved and **lvgl** will be built and linked with it. Since LVGL requires a config header called [lv_conf.h](https://github.com/lvgl/lvgl/blob/master/lv_conf_template.h) to be includable by its sources we also set the option `LV_CONF_PATH` to point to our own copy of it.
### Additional CMake options
Besides `LV_CONF_PATH` there are two additional CMake options to specify include paths.
`LV_LVGL_H_INCLUDE_SIMPLE` which specifies whether to `#include "lvgl.h"` absolut or relative
| ON (default) | OFF |
| ------------ | -------------- |
| "lvgl.h" | "../../lvgl.h" |
`LV_CONF_INCLUDE_SIMPLE` which specifies whether to `#include "lv_conf.h"` and `"lv_drv_conf.h"` absolut or relative
| ON (default) | OFF |
| --------------- | --------------------- |
| "lv_conf.h" | "../../lv_conf.h" |
| "lv_drv_conf.h" | "../../lv_drv_conf.h" |
I do not recommend disabling those options unless your folder layout makes it absolutely necessary.
## Building LVGL examples with CMake
LVGL [examples](https://docs.lvgl.io/master/examples.html) have their own CMake target. If you want to build the examples simply add them to your dependencies.
```cmake
# The target "MyFirmware" depends on LVGL and examples
target_link_libraries(MyFirmware PRIVATE lvgl::lvgl lvgl::examples)
```
## Building LVGL drivers and demos with CMake
Exactly the same goes for the [drivers](https://github.com/lvgl/lv_drivers) and the [demos](https://github.com/lvgl/lvgl/demos).
```cmake
FetchContent_Declare(lv_drivers
GIT_REPOSITORY https://github.com/lvgl/lv_drivers)
FetchContent_MakeAvailable(lv_drivers)
# The target "MyFirmware" depends on LVGL, drivers and demos
target_link_libraries(MyFirmware PRIVATE lvgl::lvgl lvgl::drivers lvgl::examples)
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/espressif.md
```
# Espressif (ESP32 chip series)
LVGL can be used and configured as a standard [ESP-IDF](https://github.com/espressif/esp-idf) component.
More information about ESP-IDF build system can be found [here](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/build-system.html).
## LVGL demo project for ESP32
We've created [lv_port_esp32](https://github.com/lvgl/lv_port_esp32), a project using ESP-IDF and LVGL to show one of the demos from [demos](https://github.com/lvgl/lvgl/demos).
You can configure the project to use one of the many supported display controllers and targets (chips).
See [lvgl_esp32_drivers](https://github.com/lvgl/lvgl_esp32_drivers) repository for a complete list
of supported display and indev (touch) controllers and targets.
## Using LVGL in your ESP-IDF project
### Prerequisites
* ESP-IDF v4.1 and above
* ESP evaluation board with a display
### Obtaining LVGL
__Option 1:__ git submodule
Simply clone LVGL into your `project_root/components` directory and it will be automatically integrated into the project.
If the project is a git repository you can include LVGL as a git submodule:
```sh
git submodule add https://github.com/lvgl/lvgl.git components/lvgl
```
The above command will clone LVGL's main repository into the `components/lvgl` directory. LVGL includes a `CMakeLists.txt` file that sets some configuration options so you can use LVGL right away.
__Option 2:__ IDF Component Manager
LVGL is also distributed through [IDF Component Manager](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/tools/idf-component-manager.html).
It allows users to seamlessly integrate [LVGL component](https://components.espressif.com/component/lvgl/lvgl) into their project with following command:
```sh
idf.py add-dependency lvgl/lvgl>=8.*
```
During next project build, LVGL component will be fetched from the component registry and added to project build.
### Configuration
When you are ready to configure LVGL, launch the configuration menu with `idf.py menuconfig` in your project root directory, go to `Component config` and then `LVGL configuration`.
## Using lvgl_esp32_drivers in ESP-IDF project
You can also add `lvgl_esp32_drivers` as a "component". This component should be located inside a directory named "components" in your project root directory.
When your project is a git repository you can include `lvgl_esp32_drivers` as a git submodule:
```sh
git submodule add https://github.com/lvgl/lvgl_esp32_drivers.git components/lvgl_esp32_drivers
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/index.md
```
# Platforms
```eval_rst
.. toctree::
:maxdepth: 2
pc-simulator
nxp
stm32
espressif
arduino
tasmota-berry
cmake
```

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/nxp.md
```
# NXP
NXP has integrated LVGL into the MCUXpresso SDK packages for several of their general
purpose and crossover microcontrollers, allowing easy evaluation and migration into your
product design. [Download an SDK for a supported board](https://www.nxp.com/design/software/embedded-software/littlevgl-open-source-graphics-library:LITTLEVGL-OPEN-SOURCE-GRAPHICS-LIBRARY?&tid=vanLITTLEVGL-OPEN-SOURCE-GRAPHICS-LIBRARY)
today and get started with your next GUI application.
## Creating new project with LVGL
Downloading the MCU SDK example project is recommended as a starting point. It comes fully
configured with LVGL (and with PXP support if module is present), no additional integration
work is required.
## Adding HW acceleration for NXP iMX RT platforms using PXP (PiXel Pipeline) engine for existing projects
Several drawing features in LVGL can be offloaded to the PXP engine. The CPU is available for other operations while the PXP is running. An RTOS is required to block the LVGL drawing thread and switch to another task or suspend the CPU for power savings.
#### Features supported:
- RGB565 color format
- Area fill + optional transparency
- BLIT (BLock Image Transfer) + optional transparency
- Color keying + optional transparency
- Recoloring (color tint) + optional transparency
- RTOS integration layer
- Default FreeRTOS and bare metal code provided
#### Basic configuration:
- Select NXP PXP engine in lv_conf.h: Set `LV_USE_GPU_NXP_PXP` to 1
- Enable default implementation for interrupt handling, PXP start function and automatic initialization: Set `LV_USE_GPU_NXP_PXP_AUTO_INIT` to 1
- If `FSL_RTOS_FREE_RTOS` symbol is defined, FreeRTOS implementation will be used, otherwise bare metal code will be included
#### Basic initialization:
- If `LV_USE_GPU_NXP_PXP_AUTO_INIT` is enabled, no user code is required; PXP is initialized automatically in `lv_init()`
- For manual PXP initialization, default configuration structure for callbacks can be used. Initialize PXP before calling `lv_init()`
```c
#if LV_USE_GPU_NXP_PXP
#include "lv_gpu/lv_gpu_nxp_pxp.h"
#include "lv_gpu/lv_gpu_nxp_pxp_osa.h"
#endif
. . .
#if LV_USE_GPU_NXP_PXP
if (lv_gpu_nxp_pxp_init(&pxp_default_cfg) != LV_RES_OK) {
PRINTF("PXP init error. STOP.\n");
for ( ; ; ) ;
}
#endif
```
#### Project setup:
- Add PXP related files to project:
- lv_gpu/lv_gpu_nxp.c, lv_gpu/lv_gpu_nxp.h: low level drawing calls for LVGL
- lv_gpu/lv_gpu_nxp_osa.c, lv_gpu/lv_gpu_osa.h: default implementation of OS-specific functions (bare metal and FreeRTOS only)
- optional, required only if `LV_USE_GPU_NXP_PXP_AUTO_INIT` is set to 1
- PXP related code depends on two drivers provided by MCU SDK. These drivers need to be added to project:
- fsl_pxp.c, fsl_pxp.h: PXP driver
- fsl_cache.c, fsl_cache.h: CPU cache handling functions
#### Advanced configuration:
- Implementation depends on multiple OS-specific functions. The struct `lv_nxp_pxp_cfg_t` with callback pointers is used
as a parameter for the `lv_gpu_nxp_pxp_init()` function. Default implementation for FreeRTOS and baremetal is provided in lv_gpu_nxp_osa.c
- `pxp_interrupt_init()`: Initialize PXP interrupt (HW setup, OS setup)
- `pxp_interrupt_deinit()`: Deinitialize PXP interrupt (HW setup, OS setup)
- `pxp_run()`: Start PXP job. Use OS-specific mechanism to block drawing thread. PXP must finish drawing before leaving this function.
- There are configurable area thresholds which are used to decide whether the area will be processed by CPU, or by PXP. Areas smaller than a
defined value will be processed by CPU and those bigger than the threshold will be processed by PXP. These thresholds may be defined as
preprocessor variables. Default values are defined lv_gpu/lv_gpu_nxp_pxp.h
- `GPU_NXP_PXP_BLIT_SIZE_LIMIT`: size threshold for image BLIT, BLIT with color keying, and BLIT with recolor (OPA > LV_OPA_MAX)
- `GPU_NXP_PXP_BLIT_OPA_SIZE_LIMIT`: size threshold for image BLIT and BLIT with color keying with transparency (OPA < LV_OPA_MAX)
- `GPU_NXP_PXP_FILL_SIZE_LIMIT`: size threshold for fill operation (OPA > LV_OPA_MAX)
- `GPU_NXP_PXP_FILL_OPA_SIZE_LIMIT`: size threshold for fill operation with transparency (OPA < LV_OPA_MAX)

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platoforms/simulator.md
```
# Simulator on PC
You can try out LVGL **using only your PC** (i.e. without any development boards). LVGL will run on a simulator environment on the PC where anyone can write and experiment with real LVGL applications.
Using the simulator on a PC has the following advantages:
- Hardware independent - Write code, run it on the PC and see the result on a monitor.
- Cross-platform - Any Windows, Linux or macOS system can run the PC simulator.
- Portability - The written code is portable, which means you can simply copy it when migrating to embedded hardware.
- Easy Validation - The simulator is also very useful to report bugs because it provides a common platform for every user. So it's a good idea to reproduce a bug in the simulator and use that code snippet in the [Forum](https://forum.lvgl.io).
## Select an IDE
The simulator is ported to various IDEs (Integrated Development Environments). Choose your favorite IDE, read its README on GitHub, download the project, and load it to the IDE.
- [Eclipse with SDL driver](https://github.com/lvgl/lv_sim_eclipse_sdl): Recommended on Linux and Mac
- [CodeBlocks](https://github.com/lvgl/lv_sim_codeblocks_win): Recommended on Windows
- [VisualStudio with SDL driver](https://github.com/lvgl/lv_sim_visual_studio_sdl): For Windows
- [VSCode with SDL driver](https://github.com/lvgl/lv_sim_vscode_sdl): Recommended on Linux and Mac
- [PlatformIO with SDL driver](https://github.com/lvgl/lv_platformio): Recommended on Linux and Mac
You can use any IDE for development but, for simplicity, the configuration for Eclipse CDT is what we'll focus on in this tutorial.
The following section describes the set-up guide of Eclipse CDT in more detail.
**Note: If you are on Windows, it's usually better to use the Visual Studio or CodeBlocks projects instead. They work out of the box without requiring extra steps.**
## Set-up Eclipse CDT
### Install Eclipse CDT
[Eclipse CDT](https://eclipse.org/cdt/) is a C/C++ IDE.
Eclipse is a Java-based tool so be sure **Java Runtime Environment** is installed on your system.
On Debian-based distros (e.g. Ubuntu): `sudo apt-get install default-jre`
Note: If you are using other distros, then please install a 'Java Runtime Environment' suitable to your distro.
Note: If you are using macOS and get a "Failed to create the Java Virtual Machine" error, uninstall any other Java JDK installs and install Java JDK 8u. This should fix the problem.
You can download Eclipse's CDT from: [https://www.eclipse.org/cdt/downloads.php](https://www.eclipse.org/cdt/downloads.php). Start the installer and choose *Eclipse CDT* from the list.
### Install SDL 2
The PC simulator uses the [SDL 2](https://www.libsdl.org/download-2.0.php) cross-platform library to simulate a TFT display and a touchpad.
#### Linux
On **Linux** you can easily install SDL2 using a terminal:
1. Find the current version of SDL2: `apt-cache search libsdl2 (e.g. libsdl2-2.0-0)`
2. Install SDL2: `sudo apt-get install libsdl2-2.0-0` (replace with the found version)
3. Install SDL2 development package: `sudo apt-get install libsdl2-dev`
4. If build essentials are not installed yet: `sudo apt-get install build-essential`
#### Windows
If you are using **Windows** firstly you need to install MinGW ([64 bit version](http://mingw-w64.org/doku.php/download)). After installing MinGW, do the following steps to add SDL2:
1. Download the development libraries of SDL.
Go to [https://www.libsdl.org/download-2.0.php](https://www.libsdl.org/download-2.0.php) and download _Development Libraries: SDL2-devel-2.0.5-mingw.tar.gz_
2. Decompress the file and go to _x86_64-w64-mingw32_ directory (for 64 bit MinGW) or to _i686-w64-mingw32_ (for 32 bit MinGW)
3. Copy _..._mingw32/include/SDL2_ folder to _C:/MinGW/.../x86_64-w64-mingw32/include_
4. Copy _..._mingw32/lib/_ content to _C:/MinGW/.../x86_64-w64-mingw32/lib_
5. Copy _..._mingw32/bin/SDL2.dll_ to _{eclipse_workspace}/pc_simulator/Debug/_. Do it later when Eclipse is installed.
Note: If you are using **Microsoft Visual Studio** instead of Eclipse then you don't have to install MinGW.
#### OSX
On **OSX** you can easily install SDL2 with brew: `brew install sdl2`
If something is not working, then please refer [this tutorial](http://lazyfoo.net/tutorials/SDL/01_hello_SDL/index.php) to get started with SDL.
### Pre-configured project
A pre-configured graphics library project (based on the latest release) is always available to get started easily.
You can find the latest one on [GitHub](https://github.com/lvgl/lv_sim_eclipse_sdl).
(Please note that, the project is configured for Eclipse CDT).
### Add the pre-configured project to Eclipse CDT
Run Eclipse CDT. It will show a dialogue about the **workspace path**. Before accepting the path, check that path and copy (and unzip) the downloaded pre-configured project there. After that, you can accept the workspace path. Of course you can modify this path but in that case copy the project to the corresponding location.
Close the start-up window and go to **File-&gt;Import** and choose **General-&gt;Existing project into Workspace**. **Browse the root directory** of the project and click **Finish**
On **Windows** you have to do two additional things:
- Copy the **SDL2.dll** into the project's Debug folder
- Right-click on the project -&gt; Project properties -&gt; C/C++ Build -&gt; Settings -&gt; Libraries -&gt; Add ... and add _mingw32_ above SDLmain and SDL. (The order is important: mingw32, SDLmain, SDL)
### Compile and Run
Now you are ready to run LVGL on your PC. Click on the Hammer Icon on the top menu bar to Build the project. If you have done everything right, then you will not get any errors. Note that on some systems additional steps might be required to "see" SDL 2 from Eclipse but in most cases the configuration in the downloaded project is enough.
After a successful build, click on the Play button on the top menu bar to run the project. Now a window should appear in the middle of your screen.
Now you are ready to use LVGL and begin development on your PC.

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/stm32.md
```
# STM32
TODO

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/platforms/tasmota-berry.md
```
# Tasmota and berry
## What is Tasmota?
[Tasmota](https://github.com/arendst/Tasmota) is a widely used open-source firmware for ESP8266 and EPS32 based devices. It supports a wide variety of devices, sensors and integrations to Home Automation and Cloud services. Tasmota firmware is downloaded more than 200,000 times each month, and has an active and growing community.
Tasmota provides access to hundreds of supported devices, full support of MQTT, HTTP(S), integration with major Home Automation systems, myriad of sensors, IR, RF, Zigbee, Bluetooth, AWS IoT, Azure IoT, Alexa and many more.
## What is Berry?
[Berry](https://github.com/berry-lang/berry) is a ultra-lightweight dynamically typed embedded scripting language. It is designed for lower-performance embedded devices. The interpreter of Berry include a one-pass compiler and register-based VM, all the code is written in ANSI C99. Berry offers a syntax very similar to Python, and is inspired from LUA VM. It is fully integrated in Tasmota
### Highlights of Berry
Berry has the following advantages:
- Lightweight: A well-optimized interpreter with very little resources. Ideal for use in microprocessors.
- Fast: optimized one-pass bytecode compiler and register-based virtual machine.
- Powerful: supports imperative programming, object-oriented programming, functional programming.
- Flexible: Berry is a dynamic type script, and it's intended for embedding in applications. It can provide good dynamic scalability for the host system.
- Simple: simple and natural syntax, support garbage collection, and easy to use FFI (foreign function interface).
- RAM saving: With compile-time object construction, most of the constant objects are stored in read-only code data segments, so the RAM usage of the interpreter is very low when it starts.
All features are detailed in the [Berry Reference Manual](https://github.com/berry-lang/berry/wiki/Reference)
---
## Why LVGL + Tasmota + Berry?
In 2021, Tasmota added full support of LVGL for ESP32 based devices. It also introduced the Berry scripting language, a small-footprint language similar to Python and fully integrated in Tasmota.
A comprehensive mapping of LVGL in Berry language is now available, similar to the mapping of Micropython. It allows to use +98% of all LVGL features. It is also possible to write custom widgets in Berry.
Versions supported: LVGL v8.0.2, LodePNG v20201017, Freetype 2.10.4
### Tasmota + Berry + LVGL could be used for:
- Fast prototyping GUI.
- Shortening the cycle of changing and fine-tuning the GUI.
- Modelling the GUI in a more abstract way by defining reusable composite objects, taking advantage of Berry's language features such as Inheritance, Closures, Exception Handling...
- Make LVGL accessible to a larger audience. No need to know C to create a nice GUI on an embedded system.
A higher level interface compatible with [OpenHASP](https://github.com/HASwitchPlate/openHASP) is also under development.
---
## So what does it look like?
> TL;DR:
> Similar to MicroPython, it's very much like the C API, but Object-Oriented for LVGL components.
Let's dive right into an example!
### A simple example
```python
lv.start() # start LVGL
scr = lv.scr_act() # get default screen
btn = lv.btn(scr) # create button
btn.center()
label = lv.label(btn) # create a label in the button
label.set_text("Button") # set a label to the button
```
## How can I use it?
You can start in less than 10 minutes on a M5Stack or equivalent device in less than 10 minutes in this [short tutorial](https://tasmota.github.io/docs/LVGL_in_10_minutes/)
## Where can I find more information?
- [Tasmota Documentation](https://tasmota.github.io/docs/)
- [Berry Documentation](https://github.com/berry-lang/berry/wiki/Reference)
- [Tasmota LVGL Berry documentation](https://tasmota.github.io/docs/LVGL/)

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```eval_rst
.. include:: /header.rst
:github_url: |github_link_base|/get-started/quick-overview.md
```
# Quick overview
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](/porting/index) and [Overview](/overview/index) sections after that.
## Get started in a simulator
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](/get-started/pc-simulator) 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
If you would rather try LVGL on your own project follow these steps:
- [Download](https://github.com/lvgl/lvgl/archive/master.zip) 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.
```c
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:
```c
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:
```c
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](/porting/index) section.
## Learn the basics
### Widgets
The graphical elements like Buttons, Labels, Sliders, Charts etc. are called objects or widgets. Go to [Widgets](/widgets/index) 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:
```c
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:
```c
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:
```c
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](https://github.com/lvgl/lvgl/blob/master/src/widgets/lv_slider.h)).
### Events
Events are used to inform the user that something has happened with an object.
You can assign one or more callbacks to an object which will be called if the object is clicked, released, dragged, being deleted, etc.
A callback is assigned like this:
```c
lv_obj_add_event_cb(btn, btn_event_cb, LV_EVENT_CLICKED, NULL); /*Assign a callback to the button*/
...
void btn_event_cb(lv_event_t * e)
{
printf("Clicked\n");
}
```
`LV_EVENT_ALL` can be used instead of `LV_EVENT_CLICKED` to invoke the callback for any event.
From `lv_event_t * e` the current event code can be retrieved with:
```c
lv_event_code_t code = lv_event_get_code(e);
```
The object that triggered the event can be retrieved with:
```c
lv_obj_t * obj = lv_event_get_target(e);
```
To learn all features of the events go to the [Event overview](/overview/event) section.
### Parts
Widgets might be built from one or more *parts*. For example, a button has only one part called `LV_PART_MAIN`.
However, a [Slider](/widgets/core/slider) has `LV_PART_MAIN`, `LV_PART_INDICATOR` and `LV_PART_KNOB`.
By using parts you can apply different styles to sub-elements of a widget. (See below)
Read the widgets' documentation to learn which parts each uses.
### States
LVGL objects can be in a combination of the following states:
- `LV_STATE_DEFAULT` Normal, released state
- `LV_STATE_CHECKED` Toggled or checked state
- `LV_STATE_FOCUSED` Focused via keypad or encoder or clicked via touchpad/mouse
- `LV_STATE_FOCUS_KEY` Focused via keypad or encoder but not via touchpad/mouse
- `LV_STATE_EDITED` Edit by an encoder
- `LV_STATE_HOVERED` Hovered by mouse (not supported now)
- `LV_STATE_PRESSED` Being pressed
- `LV_STATE_SCROLLED` Being scrolled
- `LV_STATE_DISABLED` Disabled
For example, if you press an object it will automatically go to the `LV_STATE_FOCUSED` and `LV_STATE_PRESSED` states and when you release it the `LV_STATE_PRESSED` state will be removed while focus remains active.
To check if an object is in a given state use `lv_obj_has_state(obj, LV_STATE_...)`. It will return `true` if the object is currently in that state.
To manually add or remove states use:
```c
lv_obj_add_state(obj, LV_STATE_...);
lv_obj_clear_state(obj, LV_STATE_...);
```
### Styles
A style instance contains properties such as background color, border width, font, etc. that describe the appearance of objects.
Styles are represented with `lv_style_t` variables. Only their pointer is saved in the objects so they need to be defined as static or global.
Before using a style it needs to be initialized with `lv_style_init(&style1)`. After that, properties can be added to configure the style. For example:
```
static lv_style_t style1;
lv_style_init(&style1);
lv_style_set_bg_color(&style1, lv_color_hex(0xa03080))
lv_style_set_border_width(&style1, 2))
```
See the full list of properties [here](/overview/style.html#properties).
Styles are assigned using the ORed combination of an object's part and state. For example to use this style on the slider's indicator when the slider is pressed:
```c
lv_obj_add_style(slider1, &style1, LV_PART_INDICATOR | LV_STATE_PRESSED);
```
If the *part* is `LV_PART_MAIN` it can be omitted:
```c
lv_obj_add_style(btn1, &style1, LV_STATE_PRESSED); /*Equal to LV_PART_MAIN | LV_STATE_PRESSED*/
```
Similarly, `LV_STATE_DEFAULT` can be omitted too:
```c
lv_obj_add_style(slider1, &style1, LV_PART_INDICATOR); /*Equal to LV_PART_INDICATOR | LV_STATE_DEFAULT*/
```
For `LV_STATE_DEFAULT` and `LV_PART_MAIN` simply write `0`:
```c
lv_obj_add_style(btn1, &style1, 0); /*Equal to LV_PART_MAIN | LV_STATE_DEFAULT*/
```
Styles can be cascaded (similarly to CSS). It means you can add more styles to a part of an object.
For example `style_btn` can set a default button appearance, and `style_btn_red` can overwrite the background color to make the button red:
```c
lv_obj_add_style(btn1, &style_btn, 0);
lv_obj_add_style(btn1, &style1_btn_red, 0);
```
If a property is not set on for the current state, the style with `LV_STATE_DEFAULT` will be used. A default value is used if the property is not defined in the default state.
Some properties (typically the text-related ones) can be inherited. This means if a property is not set in an object it will be searched for in its parents too.
For example, you can set the font once in the screen's style and all text on that screen will inherit it by default.
Local style properties also can be added to objects. This creates a style which resides inside the object and is used only by the object:
```c
lv_obj_set_style_bg_color(slider1, lv_color_hex(0x2080bb), LV_PART_INDICATOR | LV_STATE_PRESSED);
```
To learn all the features of styles see the [Style overview](/overview/style) section.
### Themes
Themes are the default styles for objects. Styles from a theme are applied automatically when objects are created.
The theme for your application is a compile time configuration set in `lv_conf.h`.
## Examples
```eval_rst
.. include:: ../../examples/get_started/index.rst
```
## Micropython
Learn more about [Micropython](/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)
```