The os::System::setTranslateDeadKeys() function is used by Aseprite to indicate when we are inside a input field. For example, if we are outside a input field, setTranslateDeadKeys(false) is called, so dead keys are not received, we need only keyboard shortcuts as they are. When we focus a text input field, then setTranslateDeadKeys(true) is called to start receiving dead keys/special unicode chars.

There is a comment in this member function:

Probably we could just refactor setTranslateDeadKeys() to something like:

class System {
...
  virtual void setTextInput(bool state, const gfx::Point& screenCaretPos = {}) = 0;
...
};

@dacap It seems much easier than I thought to check if user is inputting with IME. Please have a look:
https://learn.microsoft.com/en-us/windows/win32/learnwin32/keyboard-input
https://learn.microsoft.com/en-us/windows/win32/api/imm/nf-imm-immgetvirtualkey

The key point is to handle messages with virtual key value of VK_PROCESSKEY. Should I still work on exposing an API to indicate if we are inside an input field or not?

Should I still work on exposing an API to indicate if we are inside an input field or not?

I think the main thing is that the app (not laf) is the only one that can tell us if we are inside a text field or not, which means what we should do with this VK_PROCESSKEY. For example, if we are not in a text field, we should ignore VK_PROCESSKEY.

@dacap I’ve finished making the requested changes. Please take a look whenever it’s convenient.

Thanks a lot for this PR @Cerallin, so far it's a good starting point to integrate in laf. I'll merge as it is and make some minor adjustments and more testing in a near future. I think we could start compiling some beta version of Aseprite with LAF_WITH_IME=ON in a near future.