Yes, that's what I need to do.
So, you say that I don't even need Qt for that? That is, can I do it with LCL's native widgets?
Switching between keyboard layouts should not be a problem.
But one more question: when you have mixed text on the same line (as in the example you gave, which seems to be perfectly fine), and you move the cursor along the line (right and left arrow keys), how does the cursor behave, while moving from one end to the other of the line? Does it behave normally, i.e. as if it was normal text from the same language? Or by keeping pressed the same arrow key, the direction of the cursor suddenly changes when it reaches the text in the other language?