What is the ruling on wearing pants and short skirts in front of the husband's father, and who is in the right regarding this matter?

The husband's father is a mahram to the wife, so she is not obliged to observe hijab in front of him. However, he is not permitted to see any part of her body except what is commonly apparent from the extremities, such as the head, arms, and feet. Therefore, wearing a short skirt in front of him is not permissible, but wearing loose or wide trousers is permissible. It is incumbent upon a woman to strive for the pleasure of Allah before the pleasure of anyone else.