Some users may prefer viewing images with an alpha channel without a
background. Before D11629 this was the behaviour for SVGs, but is now
impossible for both SVGs and raster images. This patch adds this option,
effectively adding functionality for raster images, and getting back the
previous behaviour for SVGs.
For raster images, choosing {nav None} uses the main view background color
to draw the background on `mCurrentBuffer`.
For SVGs, this option doesn't draw anything, which was the beheviour before
D11629.
Depends on: D11629
Config option:
{F5764316}
Example (PNG on left, SVG on right):
{F5764317}