*** Bug 265388 has been marked as a duplicate of this bug. ***

Zoom with mouse scroll without press ctrl is perfect also for future touch gui implementation.

*** Bug 307126 has been marked as a duplicate of this bug. ***

*** Bug 372416 has been marked as a duplicate of this bug. ***

I took a look and the change to remove the ctrl key requirement is trivial, but it would necessitate a few other changes to prevent conflicts and unwanted behavior:

- With a mouse+scrollwheel, when the image is zoomed in, a scroll is already used to pan up and down; that behavior would need to be re-assigned to something else--or just gotten rid of, since you more easily can drag to pan anyway (I would be in favor of this)

- For laptop users who scroll with a two-finger up-and-down scroll gesture, the very similar two-finger drag gesture is already bound to pan&zoom. This would either need to be removed, or else the two-finger scroll behavior would have to not apply to touchpads, and zooming would use a pinch gesture instead: https://bugs.kde.org/show_bug.cgi?id=378021

This would be a really nice addition.

(In reply to Nate Graham from comment #5)
> I took a look and the change to remove the ctrl key requirement is trivial,
> but it would necessitate a few other changes to prevent conflicts and
> unwanted behavior:
> 
> - With a mouse+scrollwheel, when the image is zoomed in, a scroll is already
> used to pan up and down; that behavior would need to be re-assigned to
> something else--or just gotten rid of, since you more easily can drag to pan
> anyway (I would be in favor of this)

Agreed.

> 
> - For laptop users who scroll with a two-finger up-and-down scroll gesture,
> the very similar two-finger drag gesture is already bound to pan&zoom. This
> would either need to be removed, or else the two-finger scroll behavior
> would have to not apply to touchpads, and zooming would use a pinch gesture
> instead: https://bugs.kde.org/show_bug.cgi?id=378021

IMO, the behavior should be like this:

Mouse+keyboard - scroll to zoom, click+drag to pan
Touchpad - Pinch to zoom, two-finger drag to pan
Touchscreen - Pinch to zoom, one-finger drag to pan

Is is possible to differentiate between input devices?

>Touchpad - Pinch to zoom, two-finger drag to pan

Actually, you bring up a good point about the two-finger scroll. Some people might prefer two finger scroll to zoom instead of pan, and have panning with Ctrl+two-finger or something.

> Touchpad - Pinch to zoom, two-finger drag to pan

This is what macOS Preview does, FWIW, and it's very nice. I would support making that the default, and if necessary, adding a setting to toggle between this and zoom-with-two-finger-scroll gesture.

I've submitted a diff to the repository in Phabricator that would address this.  It adds a "Zoom" option under the mouse wheel settings, allowing for the zoom behavior you get when you hold ctrl to work without holding ctrl.  

Diff:  https://phabricator.kde.org/D15809

Git commit ddfcaa0f3e4bb5c0db851950c1bf3891515cff64 by Nate Graham, on behalf of Chris Suran.
Committed on 02/10/2018 at 22:28.
Pushed by ngraham into branch 'master'.

Add Zoom scroll wheel option

Summary:
Adding a Zoom option for scrolling in the configuration
FIXED-IN: 18.12.0

Test Plan: Test scrolling in image and folder view for each configuration selection.

Reviewers: #gwenview, ngraham

Reviewed By: ngraham

Subscribers: sourabhboss, muhlenpfordt, ngraham

Tags: #gwenview

Differential Revision: https://phabricator.kde.org/D15809

M  +1    -0    app/configdialog.cpp
M  +45   -20   app/imageviewconfigpage.ui
M  +14   -10   lib/documentview/documentview.cpp
M  +1    -0    lib/gwenviewconfig.kcfg
M  +2    -1    lib/mousewheelbehavior.h

https://commits.kde.org/gwenview/ddfcaa0f3e4bb5c0db851950c1bf3891515cff64

Cheers! What a coincidence; I *just* switched my main workstation to Plasma, and the Ctrl key to zoom in Gwenview has always irritated me. Thanks so much for listening to your users!