When requesting an icon size that cannot be served, the pixmap is centered in the requested size.
By using the original pixmap's device pixel ratio we ensure the padded pixmap is painted correctly.

BUG: 396990

There's still various issues in Dolphin's view engine when using fractional scaling, such as icons being too small, or preview icons larger then file icons, etc but at least icons aren't cut-off and misaligned anymore.

There is also a bug in caching and restoring from cache the icon. Initally the icon is fine, then it's cached to disk but when it is restored the icon doesn't match the requested size anymore and is instead padded.
Probably us writing "icon@2x" to cache, then restoring it as "icon@1.4" and then there's a mismatch..

• deleted icon cache in ~/.cache, ran QT_SCREEN_SCALE_FACTORS=1.4 dolphin, no longer have icons rendered out of bounds