I just discovered a behavior (in 5.01) I wasn’t aware of. Open Darktable and open an image in darkroom. Right click in the image and drag the cursor a bit and then release. The image rotates! And I haven’t selected the ‘rotate and perspective’.
Is this expected? I would have expected that you would need to open the ‘rotate and perspective’ module before this would happen.
Cheers!
This is expected, it was introduced a while ago
Ah, good to know, thanks!
Right click, drag (and draw a green line) along the line that you want to vertical or horizontal. Darktable will make it so. It has been so in my two or three years with the software.
Introduced in darktable 4.6.0 (June 2023) if anyone’s interested
Documented here: darktable user manual - rotate and perspective
While the module is active (and none of the structure buttons are selected) you can right-click and drag anywhere on the image to define a horizontal or vertical line. This will cause the rotation parameter to be automatically adjusted to make the drawn line horizontal/vertical with respect to the image frame.
Note: This functionality (right-click and drag to set horizontal/vertical) is also available when the module is inactive, as long as no other function (e.g. drawn mask creation) claims the right-hand mouse button.
It’s sort of a nifty function.
But rotating the image is something one normally do only once during editing – if at all.
So why this function is so easily available during the whole of processing, has puzzled me somewhat.
On the other hand I have no suggestion for how the click and drag could be better used for other purposes, though.
It’s for quick minor adjustments
A great way to fix a crooked horizon.
Thanks for stumbling on this…I’d forgotten all about it!
I never forget the lady, a very untechnical but excellent landscape/seascape/nature photographer, looking at some of my pictures, and saying, “Thad! Get your horizons straight!”
That might have been twenty years ago, but only yesterday I was processing some pics that were way off. I often use that right click. And I try to remember to do it before cropping, otherwise I usually have to revisit the crop.
Blame the camera design. The button is normal positioned so that when you push it the camera rotates. There was a time when some manufacturers put the shutter button on the front of the camera to prevent this. Luckily right click and drag fixes all these problems. And the auto line analysis of the rotate and perspective module does a great job with verticals tilting in. Who needs a tilt shift lens anymore (just kidding, but it is a great feature)
Actually, I’ve been struggling with this since I got this camera (Sony a7iv) and wondering why. I know I do not hold a camera anything like “text-book” style but I don’t recall having this problem before, and when I went for a trip, taking my a6500, it wasn’t happening to me.
Maybe it is combination of the downward press and the centre evf on the FF, rather than the rangefinder style of the aps-c. Push and pivot. I’m trying to consciously use the fingers on the grip to counter the effect.
Most of my pics are at a shutter speed high enough to cope (and thanks too to IBIS), but it is too much of a bad habit.
Indeed this may explain some of my just-off verticals. But not the worst! Blush!
Oh, I tend to refer to “verticals” rather than horizons because I’m indoors and using some wall edge or something as the reliable reference
You might try back button focus, its helped me with this problem, though I still shake and sway.
Thanks for the suggestion. It has never appealed to me, but I might give it more thought in this context
Somewhat off topic to dt, but I heartily recommend back button focus. It took a few weeks to completely acclimate myself to it, but (at least on my Canon bodies) being able to let the camera continuously focus right up to the moment I release the shutter has made a huge improvement in my shots.
I spend a lot of time with the shutter button half pressed, waiting for moments, AF-C keeping its eye on an eye. So I guess I’m doing much the same thing, but with just one button.
I guess its very much a personal comfort thing. Might vary with the shutter-button feel too. I recall (but not the brand) picking up a friend’s camera and the button seemed to go straight through “half” and just take the shot with barely any push at all.
I generally find having focus tied to the shutter button makes more sense for action shots, burst shooting, lots of AF-C work. But back button focus is great for landscape photography and more relaxed shooting. You obviously have far fewer accidental shots as well with back button focus.
I really like the way my Fuji works where I can still use back button focus when the camera is set to manual focus. It’s the best of both worlds. And if you keep the back button pressed in, it works like AF-C, so you essentially have the best of 3 worlds.
Oh yes, I can see how it would be really good for static stuff, landscapes: that makes sense to me now.
Can’t really call my stuff action photography, but musicians, even classical ones, are always moving, smiles are fleeting, expressions and glances are momentary. So it’s a kind of action. 
All AF-C stuff at wide apertures, shallow depth of field.
Back to topic, sometimes I’ll just raise the camera and shoot. And my muscle memory needs more training on horizontal camera for those times especially.
or by a Canon R7 or similar camera that offers auto level correction for wonky photographers 