This implementation is nearly identical to Sway's, except that
it also reloads the configuration, to spur on reloading the
server-side decorations.
v2: Fix style.
v3: Add a reset to the magnifier.
v4: Oops, restructure reset handler a bit.
v5: Commit the magnifier reset immediately, before freeing the
lost allocator and renderer.
v6: Also check for failed render pass, which may return NULL.
v7: Add a second NULL test, just in case.
Gamma changes take another code path and thus did not
render the magnifier. This patch consalidates both
code paths and therefore also renders the magnifier on
gamma changes.
Fixes: #1905
This adds a screen magnifier which can be controlled with the
`ZoomIn` / `ZoomOut` and `ToggleMagnify` actions.
It scales up part of the rendered framebuffer so the magnification
may end up looking blurry depending on the magnification scale.
PR #1774
