Most drawing programs that I know of (eg. Visio) give shapes handles in order to connect two shapes with a line. These handles allow lines to be "locked on" to the shape so if you move the shape, the line stays connected and moves with it; the two connected shapes are still connected after the move.

If you draw a circle, the application may place a handle every 45 degrees around the circle, which creates a problem of: What if I want to connect the circle at 33 degrees? I can't, unless the app lets me create a new handle, but that's the same problem really.

What is the problem that handles solve? I can imagine how handles would make things simpler on the programming side, but is it significantly simpler than allowing lines to be attached at any point along the circle? I am assuming this is difficult to achieve given that not many (or none) of the apps support it. Is there a difficult programming problem behind this that makes handles necessary? Or are we being lazy?

  • Consider lines connecting to different sides, different 'ports' of a shape having different meaning. This might be one of the reasons.
    – 9000
    Commented Jul 23, 2015 at 4:03
  • It's not simpler, because the handles have to be restricted to the shape anyway. The handles are there because where a line intersects can convey meaning. Commented Jul 23, 2015 at 4:46
  • I agree mostly with @whatsisname. They are not simpler in that they require a mode for dealing with the handle rather than using any old point in a rendered image. They may be easier in an OOP implementation in that you don't have easy access to the rendered image. Regardless I think the benefit is to allow easier visual formatting for the user. With only a few options there isn't any pixel by pixel updating to get the layout just right. In a lot of programs there is an alternate mode for connecting freely like there is for moving freely vs a grid. Have you tried ctrl, alt, shift, etc?
    – dhj
    Commented Jul 23, 2015 at 4:53
  • @9000. I'm not following what you mean by intersections and ports conveying "meaning". Can you give an example of the kind of "meaning" we are talking about? How do the handles help convey meaning where allowing a "free" connection does not? How is a free connection ambiguous? Thx!
    – Mike Bundy
    Commented Jul 23, 2015 at 5:19
  • 1
    Handles make connections more uniform. Without handles (or some other kind of coarse snap mechanism), connections will not look the same. Say, you want to connect to the first circle at 33° degrees. But if there are no snaps, how would you know where 33° is? Then you want to connect to another circle, how do you know where 33° (or at least the same relative location as on the first circle) is?
    – Nick Alexeev
    Commented Jul 23, 2015 at 5:19

3 Answers 3


It's design for the majority use-case

This is an example of use case design. For many drawing/canvas programs (e.g. Visio, PowerPoint, Slides) users want to:

  1. Connect shapes quickly, which means that hunting around for the right angle can be unnecessarily frustrating.

  2. Maintain a reasonable layout in the overall diagram, which usually results in preferred connections at 45- or 90- degree points. This is NOT always the case, but it IS the majority/pareto/80-20 case.

Because of #1 and #2, designers elect to provide snap points at 45- and 90- angles to help users accomplish #1 quickly while addressing the majority case in #2.

Without the snap points (e.g. if a user could snap to any point in a circle circumference) it can be tough for users to get the right angle for the majority case:

enter image description here

I am not defending this practice (personally, I think the snap behavior could be improved but that's beyond the scope of the question). But this is the UX design rationale for the snap points.

  • Oh! This is a good answer. I didn't make the Visio connection when I read the question. Yes, this is a perfect description of 'flow chart connector' handles and why they are the way they are.
    – DA01
    Commented Jul 23, 2015 at 19:42

What is the problem that handles solve?

The problem is how to make it easier to create smooth curves in drawing software. The handles are essentially a visual way to directly interact with the line vs. writing mathematical formulas.

More info: Bezier curves

If you want a handle on a circle at the 33 degree mark, rotate the circle 33 degrees.

EDIT: This answer pertains to vector illustration programs such as Adobe Illustrator. Tohster's answer is more applicable to flow charting and diagraming software such as Visio.


I agree with the 2 answers above and would add that the handles provide an affordance by conveying that there are areas on the shape that can be interacted with.

Looking at the figure on the left, without the handles, it would be difficult to know what can be done with the shape. It also feels like a non-editable graphic compared to the one on the right.


download bmml source – Wireframes created with Balsamiq Mockups

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.