Hello,

it seems doable, but wrong result.

Circle tool: CTRL + SHIFT to create a perfect circle from the center, the snapping cursor is attached correctly to the point, BUT the created circle is off from point.

Is it normal behaviour? Any help?

Thank you

Camillo

Not possible in Inkscape as long no nodes are involved afaik. The only vector drawing app I know that have "Collision snapping" is "VectorStyler":

Snapping to center along a path and drawing a circle from there is possible - but you can snap it afterwards if needed:

Polygon

Not possible in Inkscape

How do you create these videos, I would love to make one to explain better what's happening.

Thank you

Cmaillo

These are GIFs - not videos. I use LICEcap.app on macOS.

Polygon

Not possible in Inkscape

I have made a gif :-)

It seems the snapping of the circle Is working but the circle does not link to the line

As I said above - just the bounding box will snap, or a node but not the circumference.

Polygon

As I said above - just the bounding box will snap, or a node but not the circumference.

Ok that's unfortunate, thanks.

Do you how I could have the same result?

My workaround to move circles tangential to lines : temporarily using rotation centers :

1. Draw a perpendicular line (the red one, hold ctrl when rotating line using rotation handles to have 15° steps) to the first one (blue)
2. Drag circle so that its rotation center meets the red one.
3. Drag rotation center to the intersection of red line and circle. Remove red line.
4. You can place circle tangent to line using the moved rotation center. If you shift-clic on rotation center, it will go back to its original position.

Here's another method based on the geometry you forgot from school.

And here's a streamlined method.

Correction: The very last step should be [ctrl+shift+drag] to scale the circle proportionally.

Is there a snapping indicator when adjusting the circle´s diameter? I can´t find any.

When scaling, I see the hint "Quadrant point to cusp node" and a red X snap indicator at the tangent point. You can just make it out in the gif above. When rotating the circle, I see the hint "Quadrant point to path" but not the corresponding snap indicator. I use the node or ellipse tool to confirm that my circle aligns to the tangent

@PaddyCAD

Let's add that when using snapping, quadrant points are considered as smooth nodes : you must enable snapping to Nodes > Smooth nodes.

A slight variation of Paddy_CAD's method, using guides. As he explained, you must hold ctrl and shift when resizing circle.

If I've understood correctly the question... after drawing the guides, try hover on the lines intersection until the snap kicks in, then draw your circle using Alt+Ctrl, dragging mouse along the perpendicular guide to the intended circle center.

@Marco Riva

I tried your way : begun drawing the circle at path > guide intersection and hold alt and Ctrl but unfortunately I can't snap along the guide to get a perfect tangential circle : the circle rolls around the guide / line intersection. Am I missing something ?

@David248 no, you aren't missing anything, I'm afraid. The only suggestion could be are:

1. to move the cursor the most accurately possible along the perpendicular guide to the desired diameter and/or
2. draw another guide parallel to the first (distance between guides=diameter), then drag as per #1 until the snaps shows "handle to guide" detection.
   
   Could be, at least visually acceptable.