LVGL 9 support

[nicklasb]

Checklist

• Checked the issue tracker for similar issues to ensure this is not a duplicate.
• Described the feature in detail and justified the reason for the request.
• Provided specific use cases and examples.

Feature description

LVGL9 has been out a year now, it would be great if esp-brookesia moved to it before it has a lot of users.

I see no reason for a really new library like esp-brookesia to move to an old LVGL version as it is unlikely that old projects would move directly to esp-brookesia anyway.

(Note also that Squareline support LVGL 9, and also that LVGL are building an open generator themselves)

Use cases

People not having to move from LVGL 8 to 9 as one of the first things they will have to do if they start using esp-brookesia in a year when LVGL8 naturally goes out of focus for the LVGL project (8.x is soon to be 4 years old, a really long time in LVGL-time).

Alternatives

No response

Additional context

No response

[Lzw655]

Hi @nicklasb,

Thank you very much for your feedback! I completely agree with your point of view. The migration from LVGL 8 to 9 should not be too difficult, with the main work likely involving re-exporting images and other resource files. It looks like it's time to put this into the plan.

Additionally, I’ve been considering implementing a C++ layer for GUI abstraction based on LVGL and enabling a dynamic UI generation approach similar to LVGL 9’s XML-based system. This would better align with modern UI design practices.

[espzav]

re-exporting images

Hi @Lzw655,
the LVGL port supports automatic generating images for LVGL8/LVGL9. Here is the example: https://github.com/espressif/esp-bsp/blob/35a10dc3ff6435776e456648af6b915bea1af01f/examples/display/main/CMakeLists.txt#L4

[nicklasb]

Ok, sounds promising. When will this happen?
Because I just made my framework LVGL 9 only, so I am kind of incompatible with this library currently.

[nicklasb]

@Lzw655 So I sat down and put down a few hours to port esp-brookesia it to LVGL 9, and as expected, most was pretty obvious (lv_img_dsc_t, lv_obj_send_event and so on), but after a while I got really into the weeds as I ended up getting issues like this, code I risked breaking without being able to understand how to fix it. For example, I realize that the gesture is in the user data, but I feel like I venture into areas where I am unsure of intents makes to many changes where I assume:

..../components/esp-brookesia/src/widgets/gesture/esp_brookesia_gesture.cpp: In static member function 'static void ESP_Brookesia_Gesture::onTouchDetectTimerCallback(lv_timer_t*)':
..../components/esp-brookesia/src/widgets/gesture/esp_brookesia_gesture.cpp:502:64: error: invalid use of incomplete type 'struct lv_timer_t'
  502 |     ESP_Brookesia_Gesture *gesture = (ESP_Brookesia_Gesture *)t->user_data;

Actually I think I didn't have much left to do had I understood the code, you'd probably be able to do it much quicker.

[Lzw655]

re-exporting images

Hi @Lzw655, the LVGL port supports automatic generating images for LVGL8/LVGL9. Here is the example: https://github.com/espressif/esp-bsp/blob/35a10dc3ff6435776e456648af6b915bea1af01f/examples/display/main/CMakeLists.txt#L4

Hi @espzav,

Awesome! This is much more convenient than manually using a web tool to convert images. Thank you for sharing!

[Lzw655]

Ok, sounds promising. When will this happen? Because I just made my framework LVGL 9 only, so I am kind of incompatible with this library currently.

I think the earliest will be mid-March.

[Lzw655]

@Lzw655 So I sat down and put down a few hours to port esp-brookesia it to LVGL 9, and as expected, most was pretty obvious (lv_img_dsc_t, lv_obj_send_event and so on), but after a while I got really into the weeds as I ended up getting issues like this, code I risked breaking without being able to understand how to fix it. For example, I realize that the gesture is in the user data, but I feel like I venture into areas where I am unsure of intents makes to many changes where I assume:

..../components/esp-brookesia/src/widgets/gesture/esp_brookesia_gesture.cpp: In static member function 'static void ESP_Brookesia_Gesture::onTouchDetectTimerCallback(lv_timer_t*)':
..../components/esp-brookesia/src/widgets/gesture/esp_brookesia_gesture.cpp:502:64: error: invalid use of incomplete type 'struct lv_timer_t'
  502 |     ESP_Brookesia_Gesture *gesture = (ESP_Brookesia_Gesture *)t->user_data;

Actually I think I didn't have much left to do had I understood the code, you'd probably be able to do it much quicker.

You are right, the code structure of esp-brookesia still needs optimization.

I think the issue in the example you provided is due to LVGL9 hiding many element structures in lvgl_private.h, which is not included by default. For example, _lv_timer_t is located in lv_timer_private.h. I believe including lvgl_private.h in the source file should resolve this issue.