Integer scaling is achieved (after aspect expansion) by "lying" to the
stretching code about the window's size, telling it that it's always an
integer multiple of the viewport so that it only gets stretched to an
integer factor.
This approach works with all stretch and aspect modes and doesn't
require handling for each, only requiring to "loosen up" some
self-excluding conditions (in other words, replacing some `else if`s
with just `if`s) regarding viewport offset and margin calculation (black
bars).
Includes a tiny usability change that adds a range hint for the content
scale factor between 0.5 to 8.0.
Co-Authored-By: Hugo Locurcio <hugo.locurcio@hugo.pro>
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