[Groff] Drop shadows in pic

[Larry Kollar]

I looked for "drop shadows" in the archives, and didn't see anything. Is there 
an easier way to do them than to lay down the shadows first, then draw more 
boxes on top of them like this?

.PS 4i
.ft HB
.ps -1
linethick=1;

# lay down drop-shadows first
box wid 2 ht 1.5 color "slateblue";
move to last box.s;
down;
move 0.6;
box wid 2 ht 1 color "slateblue";
move 0.6;
X: box wid 2 ht 1 color "slateblue";
move 0.6;
box wid 2 ht 1 color "slateblue";
move to X.s;
move left 2.4 down 0.6;
box wid 2 ht 1 color "slateblue";
move to X.s;
move right 2.4 down 0.6;
box wid 2 ht 1 color "slateblue";

# now draw on top of the drop-shadows
move to 1st box.n+(-0.1,0.1);

box wid 2 ht 1.5 color "skyblue" outline "black" \
        "natter" "natter natter" "natter";
move to last box.s;
down;
line 0.6;
box wid 2 ht 1 color "skyblue" outline "black" \
        "gromish" "natter natter";
line 0.6;
box wid 2 ht 1 color "skyblue" outline "black" \
        "natter natter" "gromish gromish";
line 0.6;
box wid 2 ht 1 color "skyblue" outline "black" \
        "natter" "natter";

move to last line .n;
line left 2.4 down 0.6;
box wid 2 ht 1 color "skyblue" outline "black" \
        "natter" "gromish";

move to last line .n;
line right 2.4 down 0.6;
box wid 2 ht 1 color "skyblue" outline "black" \
        "natter" "gromish";
.PE

I don't have the coding skills to add a "shadow" attribute to boxes, which 
would be the proper solution. Anything relative to the box should pretend the 
shadow isn't there, so (as in the example) lines exit the box on top rather 
than the shadow.

Am I missing something obvious?

-- Larry