Fit to width with files containing pages having different formats

[gtache]

The Fit to width option (and others maybe) behaves incorrectly when a pdf file contains pages with different sizes.
It probably considers only the width of the current page, but if there are pages which are wider, there will be an horizontal scrollbar at the bottom and the current page won't be centered in the viewport.
Fit to width should consider the widest page in the document to adapt the view.