Disable --auto-rotate in feh builds compiled wiht Imlib2 1.7.5+

Imlib2 v1.7.5 introduces automatic (and transparent) orientation adjustment
based on EXIF orientation tags. This makes feh's --auto-rotate function
both superfluous and erroneous: It doesn't know about Imlib2's adjustments,
so it rotates an image which is already correctly oriented, leading to
incorrect orientation.

I am not aware of a simple run-time check for detecting whethen running
Imlib2 < 1.7.5 or ≥ 1.7.5. For now, feh disables --auto-rotate entirely when
compiled on a system with Imlib2 1.7.5+ and outputs a warning when the
option is used.

Rationale: The Imlib2 version available at run-time should in most cases be
at least as recent as the Imlib2 version used at compile-time. So, while there
may be cases where feh was compiled with Imlib2 1.7.4 and exhibits erroneous
auto-rotate behaviour on an Imlib2 1.7.5 system, the inverse case
(a feh with disabled auto-rotate support running on Imlib2 1.7.4) should be
sufficiently rare. If it does occur, it can be remedied by compiling feh
from source locally.

Possible caveat: Imlib2 only adjusts for EXIF orientation when loading JPEG
and TIFF images. If there are additional EXIF-aware file formats supported by
feh, but not Imlib2, they lose auto-rotate support.

Reference: GitHub issue #642

1 files changed, 3 insertions, 0 deletions

diff --git a/man/feh.pre b/man/feh.pre
index d495254..340d6cd 100644
--- a/man/feh.pre
+++ b/man/feh.pre
@@ -261,9 +261,12 @@ Automatic reload is not supported in montage, index, or thumbnail mode.
 .It Cm --auto-rotate
 .
 .Pq optional feature, $MAN_EXIF$ in this build
+.Pq deprecated in favor of Imlib2's auto-orientation support
 Automatically rotate images based on EXIF data.
 Does not alter the image files.
 .
+.Pp
+.
 Note that Imlib2 version 1.7.5+ performs auto-rotation by itself, so this option is obsolete on systems with Imlib2 version 1.7.5 or later.
 .Nm
 currently cannot detect this at runtime.