Update UI from EventDispatcher::schedule?

[qingxiang-jia]

Summary: updating UI from EventDispatcher doesn't seem to work (no UI is shown).

Short version: I created an EventDispatcher, attach it to instance's event loop. I call EventDispatcher::schedule with a lambda from a different thread, where I update the UI. Result: UI is not shown, but the UI update code inside lambda is called.

Longer version: I have two processes (A and B). A is an Fcitx engine, call it ImsEngine, it publishes key event to ZMQ and another process (B) listens. ImsEngine creates ImsServer and it receives candidates from another process B (via ZMQ). ImsServer has a pointer to the event dispatcher, and runs in another thread. Whenever ImsServer receives candidates from ZMQ, it uses the event dispatcher to schedule an UI update. However, while the UI update code runs, the UI isn't shown.

Thank you for the help!

[qingxiang-jia]

I am not sure if this is the right solution, but it does the work:

Use EvenDispatcher::schedule with a nullptr argument to wake up the event loop (the one from Instance when ImsEngine is initialized), and then do the UI update.

[wengxt]

What's the version for fcitx5 and what's your environment? Can you provide the output of fcitx5-diagnose

In some older version, there's indeed some bug that the xcb/wayland ui is not flushing the connection so Ui didn't really update.

[qingxiang-jia]

BTW, I am sure you know about this, but just in case. When putting UI update code in dispatcher's callback, the UI isn't really updated, because ClassicUI::update is not called. I don't know why it's the case, but hopefully this offers a bit more information.

[wengxt]

The key issue is the same, you're still not doing it fully in main thead.

For example, I noticed following backtrace:

ent&, fcitx::InputContext*&&, bool&) (this=0x556cdd6f3330) at /home/csslayer/Develop/fcitx5/src/lib/fcitx/inputcontext_p.h:45
#18 0x00007f1bd02e973b in fcitx::InputContext::updateUserInterface(fcitx::UserInterfaceComponent, bool)
    (this=0x556cdd746960, component=fcitx::UserInterfaceComponent::InputPanel, immediate=false) at /home/csslayer/Develop/fcitx5/src/lib/fcitx/inputcontext.cpp:468
#19 0x00007f1ba9686843 in QuweiEngine::uiUpdate() (this=0x556cde6530f0) at /home/csslayer/Develop/full-cloud-pinyin/fcp-fcitx5/fcitx5/src/quwei.cpp:371
#20 0x00007f1ba96864e5 in QuweiEngine::setCandidates(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >) (this=0x556cde6530f0, candidates=std::vector of length 161, capacity 161 = {...})
    at /home/csslayer/Develop/full-cloud-pinyin/fcp-fcitx5/fcitx5/src/quwei.cpp:349
#21 0x00007f1ba9684508 in set_candidates(int16_t**, size_t) (candidates=0x7f1b8c02fdf0, cnt=161) at /home/csslayer/Develop/full-cloud-pinyin/fcp-fcitx5/fcitx5/src/quwei.cpp:48
#22 0x00007f1ba969a966 in fcp::fcitx5::Fcitx5::ui_set_candidates (self=0x556cdd6c88b8, display_texts=...) at src/fcitx5.rs:25
#23 0x00007f1baa2c56bb in fcp::fcp::{impl#2}::on_key_press::{async_block#3} () at src/fcp.rs:447
#24 0x00007f1baa2def0c in core::future::from_generator::{impl#1}::poll<fcp::fcp::{impl#2}::on_key_press::{async_block_env#3}> (self=..., cx=0x7f1b97ffd408)

This is update not called from main thread. And you're triggering a systemd assertion and crash.

Please check and make sure all the relevant function are using the event dispatcher.

[qingxiang-jia]

Good morning and I am sorry for the confusion. You have been looking at a wrong place (but that's my fault, I didn't clearly state which directory you should look into, and the README is outdated, again I am sorry). Yes, what you said were all right, but that's old code (and I should have deleted to avoid the confusion), again, I apologize for letting you waste time on wrong place.

The code is at:
https://github.com/qingxiang-jia/full-cloud-pinyin/tree/main/fcp-zmq/ims (Fcitx5 part)
https://github.com/qingxiang-jia/full-cloud-pinyin/tree/main/fcp-zmq/fcp (Rust part)

To compile ims, you need ZMQ (if you are using Arch, the one in repository is good). I have a Makefile to simplify dev process. You can use:
make init to initialize cmake.
make build to build the code.
make install to install it to /usr/local (I have a debug build of fcitx5 and fctix5-gtk also in /usr/local)

For the Rust side, just run cargo run. For now, you need to run the Rust side after fcitx5 is running.

Also, I made a branch for you to check: https://github.com/qingxiang-jia/full-cloud-pinyin/tree/for-fcitx5-author-thank-you

[wengxt]

This branch has a very obvious bug, the cmd is a variable on stack and schedule lambda capture the pointer to it.

[qingxiang-jia]

Oh shoot, you are right 😭😭😭.