X11 Display/Inputs driver

Overview

The X11 display/input driver offers support for simulating the LVGL display and keyboard/mouse inputs in an X11 desktop window.

It is an alternative to Wayland, XCB, SDL or Qt.

The main purpose for this driver is for testing/debugging the LVGL application in a Linux simulation window.

Prerequisites

The X11 driver uses XLib to access the linux window manager.

1. Install XLib: sudo apt-get install libx11-6 (should be installed already)

2. Install XLib development package: sudo apt-get install libx11-dev

Configure X11 driver

1. Enable the X11 driver support in lv_conf.h, by cmake compiler define or by KConfig

   #define LV_USE_X11  1
   

2. Optional configuration options:

   • Direct Exit

     #define LV_X11_DIRECT_EXIT  1 /*preferred default - ends the application automatically if last window has been closed*/
     // or
     #define LV_X11_DIRECT_EXIT  0 /*application is responsible for ending the application (e.g. by own LV_EVENT_DELETE handler*/
     

   • Double buffering

     #define LV_X11_DOUBLE_BUFFER  1 /*preferred default*/
     // or
     #define LV_X11_DOUBLE_BUFFER  0 /*not recommended*/
     

   • Render mode

     #define LV_X11_RENDER_MODE_PARTIAL 1  /*LV_DISPLAY_RENDER_MODE_PARTIAL, preferred default*/
     // or
     #define LV_X11_RENDER_MODE_DIRECT  1  /*LV_DISPLAY_RENDER_MODE_DIRECT, not recommended for X11 driver*/
     // or
     #define LV_X11_RENDER_MODE_DULL    1  /*LV_DISPLAY_RENDER_MODE_FULL, not recommended for X11 driver*/
     

Usage

The minimal initialisation opening a window and enabling keyboard/mouse support

(e.g. in main.c, LV_X11_DIRECT_EXIT must be 1):

int main(int argc, char ** argv)
{
    ...

    /* initialize X11 display driver */
    lv_disp_t * disp = lv_x11_window_create("LVGL X11 Simulation", monitor_hor_res, monitor_ver_res);

    /* initialize X11 input drivers (for keyboard, mouse & mousewheel) */
    lv_x11_inputs_create(disp, NULL);

    ...

    while(true)
    {
        ...

        /* Periodically call the lv_task handler */
        lv_task_handler();
    }
}

Full initialisation with mouse pointer symbol and own application exit handling

(dependent on LV_X11_DIRECT_EXIT (can be 1 or 0))

bool terminated = false;

#if !LV_X11_DIRECT_EXIT
static void on_close_cb(lv_event_t * e)
{
    ...

    terminate = true;
}
#endif

int main(int argc, char ** argv)
{
    ...

    /* initialize X11 display driver */
    lv_disp_t * disp = lv_x11_window_create("LVGL X11 Simulation", monitor_hor_res, monitor_ver_res);
    lv_display_add_event_cb(disp, on_close_cb, LV_EVENT_DELETE, disp);

    /* initialize X11 input drivers (for keyboard, mouse & mousewheel) */
    LV_IMG_DECLARE(my_mouse_cursor_icon);
    lv_x11_inputs_create(disp, &my_mouse_cursor_icon);

    #if !LV_X11_DIRECT_EXIT
    /* set optional window close callback to enable application cleanup and exit */
    lv_x11_window_set_close_cb(disp, on_close_cb, disp);
    #endif

    ...

    while(!terminated)
    {
        ...

        /* Periodically call the lv_task handler */
        lv_task_handler();
    }
}