Created attachment 122133 [details]
Illustration of wide canvas showing workflow of 'fit to height' request

SUMMARY
Currently, Krita has the ability to "fit to width" (hotkey: 3). But it seems there isn't a way to "fit to height" of canvas.

STEPS TO REPRODUCE
No steps to reproduce. Functionality isn't in place yet. (Hence the possibility that this is a wishlist issue rather than a dug report.)

OBSERVED RESULT
No way to fit the canvas to the screen using HEIGHT as the measure.

EXPECTED RESULT
While working on a wide canvas (eg, 1000 pixels high by 6000 wide), I would like to press a hotkey, and have the canvas resize so that the 1000 pixels fill my screen from top to bottom, using the cursor position as the centre of the zoom.

This would be similar to the current functionality of pressing the '3' key, which, in the example dimension above, would resize the screen view such that the 6000 pixel dimension would fit the screen from left to right. (One notable difference here is that the "fit to width" function zooms to the centre of the canvas, not to the centre of the cursor.)

SOFTWARE/OS VERSIONS
Windows: 10
Linux: Zorin 15

(As far as I know, this is in all versions. I have the same issues on my Win 10 machine, and a Linux Zorin 15 machine.)

ADDITIONAL INFORMATION
This functionality is needed for keeping track of where I am on a canvas. In my work as a live digital sketchnoter, I draw live interpretations of what people say in meetings and conferences.

This means I usually prepare a very wide canvas, with a prepared background image, and logo and various things. This would be on the left of my canvas. Since my window is just a normal sized window, I want the height of the canvas visible.

I'm attaching a pic showing roughly what I mean.

In the pic, I show a very wide canvas (1000 high by 6000 pixels wide), with the Krita UI superimposed over it, showing a view that is 1000 pixels high by 2000 pixels wide. It's showing what's going on on the left hand side of the wide canvas.

Over the course of a talk, I would draw something, perhaps zooming in on a detail, (eg, the speech bubble that says, "Fit to height?"), and then zoom back to the height of the canvas again so that the audience could see the "full" view (ie, 1000 by 2000 pixels). 

Once I'm done with that first part of the canvas, I would use the space key to drag along to the middle part of the canvas, showing the blank central portion. I would then draw in that. Zooming in and out as needed for showing details.

Right now, there is no way for my to instantly hit the height. I have to manually scroll zoom to the height using my mouse wheel. 

In the illustration, I've also shown the centre of canvas, and the centre of cursor. Currently, the '3' key fits to width, using the centre of the canvas as the mapping point for the height. What it SHOULD ideally do for this workflow is to use the centre of cursor for the mapping, so that the zoom keeps the image in place, and just fixes the width. The "fit to height" functionality should use centre of cursor, not centre of canvas.

I hope this explanation makes sense. I've marked it as minor, cos I'm sure not all users have this need. For me, it's mission critical, but for typical users, it's trivial, and probably not even needed. It would be amazing if you could do something like this though!

Thanks for reading my lengthy report!

Blue skies
Roy