[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #9, bug #65910 (group groff): In some cases pic can't draw an arc of the desired length in one go, it has to break it down into multiple pieces. If you imagine a very flat ellipse and a dash length which wraps around the foci there is no one circlar arc which can draw the line,

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #8, bug #65910 (group groff): Arc length, naïvely computed, would seem to be a poor metric. The reason is floating-point division. For some positions on the ellipse the delta-x is very close to zero, so when you divide by the delta-x the number blows up to hugeness. If we

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #7, bug #65910 (group groff): `dashed_ellipse()` Maybe I should give up on English for the day. ___ Reply to this item at: ___

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #6, bug #65910 (group groff): Of course I misspoke right out of the gate. The GNU pic function that breaks up a dashed ellipse in to a bunch of elliptical arcs is called `dashes_ellipse()`. The function that draws the arc pieces themselves is called `ellipse_arc()`.

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #5, bug #65910 (group groff): I'm not yet convinced that deep mathematical sophistication is required here. (If it is, I'll try to recover what meager allotment of that I may once have had.) The GNU _pic_ function that breaks up a dashed ellipse in to a bunch of elliptical

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #4, bug #65910 (group groff): I think you're right that this is problem is nestled pretty deeply in _pic_. It reproduces even when telling GNU _pic_ to produce TeX output. $ cat EXPERIMENTS/dashed-ellipse-8x3.ptex .PS linethick=2; ellipse dashed 0.25 width 8 height 3 .PE

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Update of bug #65910 (group groff): Status:None => Confirmed ___ Follow-up Comment #3: Reproduces as far back as _groff_ 1.22.3 (using _grops_), so not a fresh bug.

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Follow-up Comment #2, bug #65910 (group groff): I've spent some time on this but I don't think I have got very far. I have written some debug code in gropdf to try and show what is happening. Attached are examples. I hope the patterns may mean something to someone more mathematical than I.

[bug #65910] [pic] some dashed ellipse sizes produce irregular dashes

Update of bug #65910 (group groff): Summary: Some dashed ellipse sizes produce irregular dashes => [pic] some dashed ellipse sizes produce irregular dashes ___ Reply to this item at: