- the menu item should be grayed out, as long as not a text _and_ a path
are selected
Sure, when we implement graying out for menu items in general, we won't forget about this one
- once I put the text on the path, I can move it around, but it's still
dependend on the shape of the path.
This is as designed. It adds flexibility. I agree that it may feel a bit strange at first but I don't want to remove this capability. If only because other programs may create SVG with text thus moved from its path, and we must be able to view and edit these files.
- while I can move the text around, I can't move the path without the
text following
Yes, because the relative position of path and text is stored in the text, not in path (if only because you can attach more than one text to one path).
don't make the text movable
Disagree, see above
and make the path visible if the text is selected, as a blue line or such, so that even when the path is invisible, you can easily edit it.
I don't think this is really necessary. If your path is invisible, you can still select it by selecting the text attached to it and pressing Shift+D (same key as for finding a clone's original).
- alignment (right, center, left, justify) of the text should apply in a
way as that the path is the whole line
I haven't looked into that yet, but I think I agree; whether this is easy/possible to implement in SVG is another matter. SVG textpath has one feature that really drives me mad: when a text is too long for its path, the spec says that the rest of the text must not be shown! (Instead of e.g. continuing along the direction of the last path segment.) I think this is really stupid and ugly, but we must obey if we are to be compliant.
One more aside note: Inkscape is the only SVG renderer that I tested fully implementing the correct character positioning algorithm from the spec. Others apparently use a simpler and less correct algorithm. This can be seen with paths that have sharp corners: in Inkscape, as you move text along such path (e.g. by kerning it forward bit by bit), each letter "flows around" a sharp corner smoothly; in all other renderers, it "jumps" so that there's always a large gap between letters over such a sharp node.
- put text not only on a path but also with a offset, underneath and
centered... you know... :)
That's what moving text and kerning is for. You can move text off the path a bit, or you can go to the first char of the text in text tool and press alt+up a few times to vertically shift all characters (perpendicular to the path in each point). Horizontal kerning also works. It's very flexible.