Add convenience function ncplane_home(). Add an ncblitter_e param
to ncplane_qrcode(), and split int maxversion into value-result
int* ymax and int* xmax. Write the actual sizes of the resulting
visual into these parameters. Update the qrcode demo. Add the
qrcode PoC. Update demos to ncplane_home(), where possible.
ncplane_qrcode() now takes an ncblitter_e and two value-result int*s
in the place of a single value int. The final size of the displayed qrcode
is written to *ymax and *xmax. If the code can't fit within the specified
dimensions, an error is returned. Standard rules for pluggable blitters
apply regarding fallback etc. #699
The Plot unit tests were reaching directly into the objects,
which meant the implementations couldn't include anything
we didn't want public. This was annoying, so I've changed it.
This required adding ncdplot_sample() and ncuplot_sample(),
which we should have had anyway.
Each plane has a "base cell", which like all other cells is
initialized to the null glyph, opaque default foreground color,
and opaque default background color. Prior to this change, at
each cell of a plane, we decided whether to use that cell (the
"viscell") or the base cell depending on whether the viscell had
a non-null glyph. We now evaluate each component independently.
If the viscell has a null glyph, we use the base cell's glyph.
If the viscell has a default foreground, we use the base's fg.
If the viscell has a default background, we use the base's bg.
This was done because (a) it seems more intuitive (if I set a cell
to red, I expect red, not red iff there's a glyph in that cell
for this plane), and (b) because otherwise it was impossible to
do a multicolor overlay without blowing away underlying glyphs
(since without a glyph, you always reduced to the same base cell,
which could have only one fore- and background per render).
Existing code will need to change any instances where cells
lacking glyphs are colored, and those colors are not desired.
Since any such coloring had no effect before, it seems unlikely
that any ought exist (this did bring to light an instance in
the "qrcode" demo where we were staining overmuch of the plane).
This closes#395, the last big open worry regarding our API.
