1865779 - [wayland] input method window position lags behind

Status: UNCONFIRMED

(Core :: Widget: Gtk, defect, P2)

Description

[lilydjwg]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:121.0) Gecko/20100101 Firefox/121.0

Steps to reproduce:

use fcitx5 on KDE Wayland to input Chinese.

Actual results:

With preedit on, the input window position lags behind by about one frame, causing a bit flickering. The position gets updated on preedit text update, not on text committed or cursor moved.

With preedit off (press Ctrl-Alt-P once), the input window position isn't update during inputting.

Expected results:

The input method window should follow the cursor swiftly.

In widget/gtk/IMContextWrapper.cpp:

  if (IsComposing()) {
    SetCursorPosition(GetActiveContext());
  } else {
    // If not composing, candidate window position is updated before key
    // down
    mSetCursorPositionOnKeyEvent = true;
  }

It assumes that Firefox will receive a later key down event, which isn't true as (in wayland) fcitx5 grabs key events and processes them before sending to Firefox.

Note that a GTK issue may cause another lag after the set_cursor_location call.