Re: Implement make-bow-stencil, make-tie-stencil for use in markup-commands undertie and overtie (issue 270640043 by address@hidden)

[thomasmorley65]

On 2015/11/08 23:54:37, dak wrote:
> On 2015/11/08 23:22:51, thomasmorley651 wrote:
> > https://codereview.appspot.com/270640043/diff/20001/scm/stencil.scm
> > File scm/stencil.scm (right):
> >
> >
https://codereview.appspot.com/270640043/diff/20001/scm/stencil.scm#newcode88
> > scm/stencil.scm:88: (sqrt (+ (* width width) (* height height))))
> > On 2015/11/08 21:22:04, dak wrote:
> > > Is there a reason you are actually taking the absolute values of
width and
> > > height?  You don't need them for calculating the length here.
> >
> > Not sure what you mean.
> > Isn't it simple Pythagoras?

See bottom.

> >
> >
https://codereview.appspot.com/270640043/diff/20001/scm/stencil.scm#newcode100
> > scm/stencil.scm:100: (/ height length-to-print))))
> > On 2015/11/08 21:22:04, dak wrote:
> > > This looks like a total mess.  Do you even need all this for
something?
> What
> > > are you trying to do?
> > >
> > > Perhaps express it in words and we'll try finding a direct
representation
> that
> > > does not need all this juggling with angles and stuff.
> >
> > You ask for quadrant and angle-start/stop-X-axis, right?
> >
> > I hoped I had put in enough comments to explain what's done and why,
obviously
> > not sufficient.
> >
> > In general I have to points P(x1 y1) and Q(x2 y2) and want to create
a bow
> > connecting them.
> > Therefore I first boil down it, to create a bow from Zero(0 0) to a
point on
> the
> > (positive-part) of X-axis with with the coordinates
(direct-distance-P-Q 0),
> > because it's far easier to calculate.
> > After this is done the bow is rotated around Zero to have it the
same
> > orientation like the direct connection of P and Q.
> > Last step is to move the bow from Zero to P.
> >
> > For the rotating part I need the value of the angle which depends on
the
> > quadrants of Q relative to P. Calculated using Zero and P moved to
'new-stop'
> >
> > Hope this is clearer now.
> >
> > In general I regard the section containing quadrant and
> angle-start/stop-X-axis
> > the weakest part of the code.
> > Any suggestion is highly welcome.

> What do you need angles and quadrants for?

> Assuming that you create your bow as a bow from (0,0) to (1,0),
> you can then transform a point (x0,y0) on this bow to one from P(x1
y1) to Q(x2
> y2)
> by using (x0*(x2-x1)-y0*(y2-y1)+x1, x0*(y2-y1)+y0*(x2-x1)+y1)
> assuming that I did not make a mistake here.  No quadrants, no angles,
no
> trigonometry,
> no square roots.

New patch follows your suggestions, thanks a lot for it.
One problem remaining, for the length I still use square roots - don't
know how to do it different.

https://codereview.appspot.com/270640043/