disable zoom/pan when dragging helices

[Andrew Uzilov]

In some cases, it is very difficult to drag around helices to position
them correctly. For example, go to this example:

http://users.soe.ucsc.edu/~auzilov/BugReports/undiff.U3b.cutscores.ss__vs__ParkerSteitz.html

Click and drag on G86 (between IL3 and IL4). The view starts jumping
around all crazy. I think this happens because VARNA tries to update
the zoom level and positioning after every event (like click + cursor
position change). This makes it confusing because after you drag,
your zoom changes, and your cursor is no longer positioned in the same
place relative to the original RNA, which means additional cursor
movements will not do what you wanted them to do.

If you disable zoom and position updates while dragging, this should
go away. The ONLY part of the RNA that should move is the part you
are dragging. The rest of the RNA should NOT move (pan or zoom or
anything).

This would make the user interface much smoother and is my #1
suggestion for improving it!

[Yann Ponty]

Excellent suggestion!

Your diagnostic is indeed correct, but there is also something else
happening here:
Since the G86 Helix is very small, then you can only "grab" it close
to its center.
It follows that a small absolute move of the mouse after "grabbing"
the helix results
in a large angular shift for the helix (and everything "attached" to
it will follow).

Just a small hint to calm your nerves until the next version fixes
this issue:
Try "grabbing" the helix and then "move away" along the helix main
axis.
This should not change the layout but, once you are "away", the
angular increment becomes smoother and it is easier to edit the
drawing.

Here is a small screencast for that (including real footage of my most
outrageous French accent ;) ) if the above explanation seems a bit
cryptic:
http://www.lix.polytechnique.fr/~ponty/vids/VARNA-SmootherHelices.avi

Best,

Yann

On Nov 11, 7:33 am, Andrew Uzilov <andrew.uzi...@gmail.com> wrote:
> In some cases, it is very difficult to drag around helices to position
> them correctly. For example, go to this example:
>

> http://users.soe.ucsc.edu/~auzilov/BugReports/undiff.U3b.cutscores.ss...

[Andrew V. Uzilov]

(Reposting because the previous post might bounce --- wrong account used.)

The video is quite helpful, and yes, that is a good workaround. I
still think that cases exist where changing the zoom and position
while dragging leads to suboptimal behavior, and I think in general
users expect the zoom and position (the "canvas" so to speak) to
remain fixed. This is how Adobe Photoshop and Illustrator and other
programs operate when you drag around elements.

Thanks for looking into it!

Cheers,
Andrew