Ruler is great for measuring the distances between outlines, but in some cases a “smarter” ruler could be of use. Currently, to measure the distance between two diagonal lines, you need to manually look for the angle (or for the shortest measure).
I think, it would be easier, if the ruler displayed some information when it is perpendicular to at least one of the intersected lines. For instance, it could snap to that position. The intersected lines to which it is perpendicular could be highlighted.
Something similar might work for curves. The ruler would snap to the centre of the curve.
This behaviour could be optional (activated by a key or in the preferences).
You can arrange the measurement line to align with the diagonal (or tangent of the curve) and then double click its knob to turn it perpendicular. This is precise.
Or what I do, is to hold down ctrl-opt-cmd to temporarily access the measure tool, and then click and drag across the diagonal or curve, move back and forth a little, and you quickly get a pretty good idea what the thickness is at the point. I have never needed that much measuring precision, and the quick result is usually precise to 1 unit.
That’s what I do too. My suggestion is more about convenience than precision. Don’t you think that it would come in handy to know immediately that you’re measuring at the right angle?
Perpendicular to an outline or the tangent of an outline? I think that this would only be handy for very specific designs. In the majority of cases, this method simply would not yield the ‘right’ angle, especially not on curves, or concave stems. Plus, an additional snap line might confuse users or be in the way. Weighing the pros and cons, I am not really convinced of the idea.
I like your “If it ain’t broke, don’t fix it” approach. I also agree that it would probably be useless for measuring concave stems. However, I’d still argue that this could be convenient in many other cases. (It could even help with finding an ending angle for a curved element or measuring the angle of a diagonal.) And snapping could be optional.
There is another way of approaching this problem. Since what we do is we drag back and forth, looking for what in most cases is the smallest number (the shortest distance), this could be somehow streamlined. For instance when the measured number decreases and then starts to increase (so when a minimum is found), ruler could leave a trace (like a lighter ruler with a number between the outlines or something like that).
What do you think? Am I the only one who thinks that this can be improved?