Do I need to account for the width and height when orientation change

[Tahar]

Example

ApplicationWindow  {
	Rectangle{
		/// I need this to always be relative to the actual device width
		width: .1 * parent.width 
		/// I need this to always be relative to the actual device height
		height: .75 * parent.height
	}
}

Now if the device orientation changes, does the width becomes height, and height becomes width, and do I need to check which one is greater than the other?
And do I need to rotate my content or the content is automatically rotated?

I hope my question makes sense