Re: GSoC 2020: blot diameter and positioning of flags

[Owen Lamb]

On Wed, Aug 5, 2020 at 10:57 PM Werner LEMBERG <wl@gnu.org> wrote:

>
> Well, LilyPond's solution is more versatile...
>

I agree, to a point. It's more versatile for the user, but not necessarily
for the font designer. At any rate, it's not exactly something we can
overturn when the specification has already been around for a few years.

If I understand you correctly, you want to suggest to the SMuFL people
> that there is a parameter to control the roundness of corners in stems
> and the like.  What else would be necessary?
>

That is correct--roundness would be assumed to be 0 unless the metadata
specifies otherwise, and would be either the diameter or radius of the
"blot," measured in staff spaces like every other engravingDefault. In
addition, a boolean metadata value, e.g. minimalStems, would dictate
whether stem placement should be affected by that roundness (Emmentaler) or
not (Bravura). Besides the potential change in y-position, minimal
stems would also attach to the right side of the stem, not the left side.
That way, if the stem width is modified, the flag still looks as expected.

It would have to be discussed further, I think, whether other primitives
such as staff lines and slurs should also be expected to incorporate the
roundness value as well.

Could you provide images that show the reference (or attachment)
> points of the flags?  I think this makes it easier to discuss the
> necessary vertical offsets.
>

Sure! I've lined the stems up with a staff line for clarity and included
Frescobaldi's display-grob-anchors.ily, slightly modified to make sure the
anchor dots don't dwarf the actual grobs. As you can see, Bravura's flags
are expected to be anchored exactly at the stem's top-left corner, while
Emmentaler's are moved far enough down to steer clear of the rounded
corners. (At the moment, I'm having all flags attach to the left edge of
the stem, as per SMuFL specs. This isn't ideal, of course, given
LilyPond's customizable stem width; hopefully the minimalStems distinction
would fix it.) Is this satisfactory?

Bravura anchor placement.png
Description: PNG image

Emmentaler anchor placement.png
Description: PNG image