Example of native interface between EEZ Studio and LVGL when EEZ Flow is not used

User actions

In LVGL project without EEZ Flow you can still define user actions that can be attached to the event handlers. You are doing this in 3 steps:

Step 1: Add user actions

Go to User Actions tab, press + button, enter the name of user action and press OK:
Step 2: Create event handler and attach it to the user action

Select widget, for example Button, and in properties find Events section and press + button:

Now, select event and user action and press OK:
Step 3: Implement user action in C

You need to implement in C function called void action_<user action name>(lv_event_t * e). For example, if user action is called inc_counter you need to implement void action_inc_counter(lv_event_t * e);. Declaration of all user actions can be found in generated file actions.h. You can implement user actions in any C file or you can add actions.c file template in your project like this:

In LVGL project without EEZ Flow you can still define variables that can be used inside widget to add dynamic content. You are doing this in 3 steps:

Step 1: Add variable

Go to Variables tab, select Global, press + button, enter the name and type of variable and press OK:
Step 2: Use variable inside widget
Step 3: Implement get and set functions in C

You need to implement in C, for each variable, functions called <variable type> get_var_<variable name>() and void set_var_<variable name>(<variable_type> value). For example, if variable is called selected_item and type is integer you need to implement int32_t get_var_selected_item(); and void set_var_selected_item(int32_t value). Function declarations for all variables can be found in generated file vars.h. You can implement these functions in any C file or you can add vars.c file template in your project like this:

Downlad SDL (a graphics library to open a window and handle the mouse). On Linux:

Find the current version of SDL2: apt-cache search libsdl2 (e.g. libsdl2-2.0-0)
Install SDL2: sudo apt-get install libsdl2-2.0-0 (replace with the found version)
Install SDL2 development package: sudo apt-get install libsdl2-dev
If build essentials are not installed yet: sudo apt-get install build-essential

Download the Emscripten SDK and make sure it is in your PATH.