In FontLab I'm sure Python can do it.

hhp

In RoboFont this would do:

f = CurrentFont()
f["a"] = f["q"] & f["d"]

... but only because RoboFont has implemented the Boolean operators (in this case &, «and») for glyph operations. I don’t know if other editors have similar options.

The result would still need some manual cleaning though:

Edit: This only seems to work with PS curves, not TT curves.

If the point indices are the same, and known, this would work in any Robofab environment:

f = CurrentFont()
f["a"] = f["d"].copy()

# contour 0, segment 1, point 2
f["a"][0][1][2].x = f["q"][0][1][2].x
f["a"][0][1][2].y = f["q"][0][1][2].y

# contour 0, segment 2, point 0
f["a"][0][2][0].x = f["q"][0][2][0].x
f["a"][0][2][0].y = f["q"][0][2][0].y

# contour 0, segment 3, point 0
f["a"][0][3][0].x = f["q"][0][3][0].x
f["a"][0][3][0].y = f["q"][0][3][0].y

but in practice it doesn’t because in Roboto the q is narrower than the d, so the right side of the new «a» won’t end up vertical.

Jens, I can do the intersection with a native FontForge script (but not with an assignment as you did). Here is what I get with the medium weight:

There is too much cleaning to do.

The Robofab code of your second post is exactly the type of code I had in mind. As for the right side, there is no need to change the x coordinate, changing the y coordinate fixes the height and then the right side stays vertical.

Is that something that can be programmed as a tool to be used in a GUI environment, so that corrections can then be made on the fly?

You can certainly create the GUI in vanilla, but the complexity of the script increases the more corrections you want to enable, obviously. You could actually do this outside of Fontlab using defcon, but I don't think there's an advantage to that.

Jason C

After all, it is unclear I would gain much with Robofab; to create a new character, I can do something fairly close to the code above, but I need to use the pen to draw (or redraw) the character; here is something that works from the Fontforge script menu and creates uni0251 for Roboto.

f=fontforge.activeFont()
ld=f["d"].foreground
lq=f["q"].foreground
# Contour 0, point 6
ld[0][6].x = lq[0][6].x
ld[0][6].y = lq[0][6].y
# Contour 0, point 7
ld[0][7].x = lq[0][7].x
ld[0][7].y = lq[0][7].y
# Contour 0, point 8
ld[0][8].y = lq[0][8].y
# Create the new character
f.createChar(0x0251,"uni0251")
# Draw the modified layer ld
pen=f["uni0251"].glyphPen()
ld.draw(pen)
pen=None
f["uni0251"].width = f["d"].width

Since ld is only a copy, the character d is left unchanged.

Added: to get the same numbering for the points in the resulting glyph, I have to draw contour 1 before contour 0. So it is

ld[1].draw(pen);  ld[0].draw(pen)

instead of ld.draw(pen). (weird!)

Of course, for the italic, we need to calculate the x coordinate of point 8. To cover all cases we thus need to add something like

m=(ld[0][8].x -ld[0][9].x)*1.0/(ld[0][8].y-ld[0][9].y)
ld[0][8].x =ld[0][9].x + (lq[0][8].y-ld[0][9].y)*m

before ld[0][8].y = lq[0][8].y. This works fine even for the thin italic where there are four points between the top and the bottom of the right part of the d and q.

Here is the picture with d (green) in the background.

Correction: there are two other points close to 9; there is thus a 9,10,11 cluster and then a 12,13,14 cluster. Hmm, no! I looked closer and there is a cluster of four points, 9,10,11,12 and then two point 13,14

Robofab wouldn’t gain you anything indeed, it is just the environment that I’m most proficient in at the moment, and it’s not confined to a specific editor.