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NiLuJe · 06-09-2020, 06:59 PM

Linux FB rotation is expressed in terms of 90° clockwise turns. So +1 or -1 from Portrait is always going to be Landscape.

Don't trust the actual absolute values, as eInk panels are only extremely rarely mounted Upright/Portrait, and some of them respond in weird ways to rotation events (see mirroring, which may not apply to every rotation state).

fbdepth -o returns the current rotation (as would reading /sys/class/graphics/fb0/rotate), and the actual range of valid constants is 0 to 3, so the & 3 gets us a wraparound at 3 (as would % 4, if you're more comfortable with divisions).

06-09-2020, 06:59 PM	#9
NiLuJe BLAM! Posts: 13,506 Karma: 26047202 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	Linux FB rotation is expressed in terms of 90° clockwise turns. So +1 or -1 from Portrait is always going to be Landscape. Don't trust the actual absolute values, as eInk panels are only extremely rarely mounted Upright/Portrait, and some of them respond in weird ways to rotation events (see mirroring, which may not apply to every rotation state). fbdepth -o returns the current rotation (as would reading /sys/class/graphics/fb0/rotate), and the actual range of valid constants is 0 to 3, so the & 3 gets us a wraparound at 3 (as would % 4, if you're more comfortable with divisions). Last edited by NiLuJe; 06-09-2020 at 07:02 PM.