Active keyboard and Language bar do not follow active window

ReactOS 0.4.12 does not allow multiple windows to have different keyboard layouts.

Steps to reproduce:

Install ReactOS with 2 keyboard layouts, US and Belgian French FR.

Open 2 sessions of notepad

In the first one, type "US" and <enter>.

In the second one, type "FR" and <enter>.

Select the notepad session with "US". Now go to language bar, and change the language multiple times (to enforce the change) with the "US" value to be the last selected one.

In the notepad window, on the line below "US", type the 6 chars next to the tab key. This should give you "qwerty". This is as expected.

Now select the other notepad session, where you entered "FR" before.

Again, change multiple times the language bar value, and select "FR" as the last one. Go back to your notepad session. Repeat the steps above, typing the 6 characters next to the tab key. This should give you "azerty". Again, this is the expected behaviour.

Now, switch back to the "US" notepad window, and type again the 6 keys next to the tab key. The result will be "azerty" whereas it should be "qwerty".

The notepad sessions should "memorize" their language setting, but they don't.

On Windows XP, using the above, any text entered in the "US" notepad session will use a qwerty input layout, just as the "FR" session will automatically use the azerty layout. The active window thus affects the active layout which also updates the language bar. A simple switch of focus will thus affect the selected language bar value.

On ReactOS, that does not happen: one can only select a language bar value, and that will be valid in ALL active windows.