Mousewheel zooming by two steps, not one

[Stratadrake]

Using Inkscape (0.48, Windows) and I have noticed some oddities with using Ctrl+mousewheel to zoom in and out.

Normally, when you zoom it is by a factor of 1.4x (i.e, 50 - 70 - 100 - 140 - 200 %). However, I have experienced many times where the mousewheel instead zooms by a factor of 2x (50 - 100 - 200 %).

I'm not entirely sure whether this is a bug or a feature, but it does have a pattern:

- If the mouse pointer is currently hovering over a visible object (e.g. fill or stroke), the mousewheel zooms by two steps.
- If the pointer is hovering over empty canvas, it zooms by one step.

This occurs regardless of tool and selection, and only with the mouse wheel -- zooming by keyboard is always one step at a time.

It can be particularly unexpected for objects with an empty fill, or while fine-tuning paths with the Node tool.

[su_v (suv-lp)]

Reproduced with Inkscape 0.48 and 0.48+devel r9819 on OS X 10.5.8 using the default settings (mouse wheel zooms with Ctrl, zoom in/out by 142% ).

Possibly the underlying issue reported earlier in bug #509906 “smoother zoom factor when using mousewheel”?

[su_v (suv-lp)]

Same behavior also in Inkscape 0.47 and 0.46 (default preferences).

[Brynn (brynn4inks-deactivatedaccount)]

Hi Friends,
I'm having the same experience in Inkscape version 0.48.1. Also want to report that this is using a touchpad mouse, where sliding a finger along the left edge of the mouse works like a traditional mouse wheel.

All best :-)

[Stratadrake (strata-ranger)]

I have a small clarification to add: I just noticed that the difference in zooming depends not on whether there's an object visible underneath the cursor, but an object that is selectable. Objects that reside in locked (but still visible) layers don't affect the zoom behavior; only objects in un-locked layers trigger the bug.

(And yes, bug still occurs in 0.48.1)

[Paulio (bleedindeadly)]

When I'm zooming in (with the scroll wheel) to work on something, I often can't scroll back out to 100% exactly.
For example, my zoom steps closest to 100% could be 91% and 128%, skipping over 100%.
I realize I can hit '1' on the keyboard to reset to 100%, but it'd be nice if 100% was added as another zoom step no matter what else is happening with the scaling.

It's a minor tweak, but it'd speed up my workflow if I could mouse-wheel out to 100% with confidence and not have to check if it was sitting at 99% or 101%. Working with imported rasters, a 1:1 scale becomes very important.

[Stratadrake (strata-ranger)]

I've noticed that too - probably a rounding error somewhere in the calculations. Inkscape should probably "snap" the actual value to the nearest zoom step in cases like these.

[John Smith (john-smithi)]

Patch that should fix the double zoom, when over an object.
Please let me know if there are any side affects.

[su_v (suv-lp)]

> Please let me know if there are any side affects.

Anything special to look out for?

Quick tests with Inkscape 0.48+devel r11781+657463.patch on OS X 10.7.4 (GTK+/X11 2.24.13, GTK+/Quartz 2.24.13) look ok.
Tested input devices (with default preferences):
- built-in trackpad (MBP)
- external mouse (Logitech M305)
Not tested with tablet.

[John Smith (john-smithi)]

> Anything special to look out for?
Probably only if any tools/objects override the Ctrl+Scroll functionality for anything else.

[John Smith (john-smithi)]

Seems there are no special overrides ...
Committed as r11798.

[su_v (suv-lp)]

>> Anything special to look out for?
> Probably only if any tools/objects override the Ctrl+Scroll functionality
> for anything else.

@John - the fix doesn't work if the preferences are changed to zoom by default with the scroll wheel (Preferences > Behavior > Scrolling: [x] Mouse wheel zooms by default), see
Bug #1072007 “mouse scroll zoom depends on if the cursor is over an object”
<https://bugs.launchpad.net/inkscape/+bug/1072007>

[su_v (suv-lp)]

Diff for lp:inkscape/0.48.x

[jazzynico (jazzynico)]

Backported to the branch, revision 9922.