[Tile-dev] Scrollbar '-command' callbacks

[Joe E. <jen...@fl...>]

In the latest change to scrollbar.tcl (r1.12 -> 1.13):

 proc tile::scrollbar::Scroll {w n units} {
     set cmd [$w cget -command]
-    if {$cmd ne ""} {
-       uplevel #0 "$cmd scroll $n $units"
-    }
+    if {[llength $cmd]} {
+       uplevel #0 [concat $cmd scroll $n $units]
+    }
 }

This forces the -command option to be a list ([llength $cmd]),
but still treats it as a string ([concat] instead of [linsert _ end ...])

The new formulation may have a small performance boost in
the common case where the -command is a pure list, but
it's not fully backwards-compatible, since there are 
valid script prefixes that aren't lists.

We had discussed earlier interpreting callback options
that append arguments as command prefixes instead of script
prefixes; is this something we want to do?  (Callback options
that don't append arguments would still be interpreted as
scripts.)  Personally, I think it's a good idea, but there
are backwards-compatibility issues.


--Joe English

  jen...@fl...