Add relative output transform

This commit enhances the output transform
command with options for a relative transform,
i.e. the provided transform will be applied as
an offset to the current transform. Append
`clockwise` to rotate clockwise from the current
rotation, or `anticlockwise` to rotate in the
opposite direction.

For example, if the output LVDS-1 is rotated
90 degrees clockwise, the command
`output LVDS-1 transform 90 clockwise`
will rotate the display to 180 degrees.
All transform options are supported,
including flipped transforms.

Relative transforms can only be applied to
a single output and cannot be used with
a wildcard (*) output specifier.

1 files changed, 5 insertions, 2 deletions

diff --git a/sway/sway-output.5.scd b/sway/sway-output.5.scd
index 1b456008..37b7108b 100644
--- a/sway/sway-output.5.scd
+++ b/sway/sway-output.5.scd
@@ -59,10 +59,13 @@ must be separated by one space. For example:
         Sets the background of the given output to the specified color. _color_
         should be specified as _#RRGGBB_. Alpha is not supported.
 
-*output* <name> transform <transform>
+*output* <name> transform <transform> [clockwise|anticlockwise]
         Sets the background transform to the given value. Can be one of "90", "180",
         "270" for rotation; or "flipped", "flipped-90", "flipped-180", "flipped-270"
-        to apply a rotation and flip, or "normal" to apply no transform.
+        to apply a rotation and flip, or "normal" to apply no transform. If a single
+        output is chosen and a rotation direction is specified 
+        (_clockwise_ or _anticlockwise_) then the transform is added or 
+        subtracted from the current tranform.
 
 *output* <name> disable|enable
         Enables or disables the specified output (all outputs are enabled by