how to properly position arrow heads with respect to a curve?

Question

Given an arc of circle:

If I add arrows on both ends I get the following ugly result:

I'd rather like to see:

I've managed to get the above manually, by converting the stroke to a path, and either editing the nodes to shape the arrow as I wish as shown below,

or, better, select the arrow (converted to a path), enter the group (e.g. double click and click on the arrow head), rotate and translate the arrow heads:

But how could I obtain a proper positioning of the arrows in a more straightforward and faster manner?

Answer 1

There is no proper way. Use whatever way you like! Several methods are possible. Here's one:

1. Draw the arc. If you used the Circle and Ellipses Tool to create the arc, convert the shape to a path using Path > Object to Path

2. Using the Bézier Tool, add two straight line segments a, and b to the arc

3. Add the arrow heads to the stroke

Answer 2

Not a full answer, but it seems that the longer the Bezier handle on the end nodes, the better the alignment of the arrow head to the curve:

Note in the figure that the curve with long handles looks OK, and also behaves well when editing the curve.

When creating a new path, you can explicitly define the handles for each node by dragging, as explained in the manual.

Answer 3

As told in other answers, there's no proper (=100% automatic) way. Here's another workaround. It works only with Bezier curves (=paths). If the curve is a circle arc or spline, you must convert it at first to path.

See the image above. In the left there's the unwanted (=automatic) arrow position. In the right a new node is added by double-clicking with the node tool. It's a guard which protects the rest of the curve when you adjust the arrow.

In the next image the arrow is rotated by dragging the ending direction handle. You may need to pull the handle out of the node. It happens by holding the shift key as you drag.