Modified the schematic-to-layout script to be better at being

used in a re-entrant manner.  Applied to an existing layout,
it will no longer keep generating new instances and ports over
top existing ones.  Could use improvement by attempting to
retain the location of a device when the instance changes
device type (such as when a device parameter was changed in
the netlist).  However, the current set of changes should
help, whether the re-entrant use is purposeful or accidental.

VERSION

@@ -1 +1 @@
-8.3.462
+8.3.463

tcltk/toolkit.tcl

@@ -195,16 +195,46 @@ proc magic::generate_layout_add {subname subpins complist library} {
 
     box 0 0 0 0
 
-    # Generate pins
+    # Generate pins.  This routine can be made re-entrant;  if a
+    # cell exists, then its contents are compared to the incoming
+    # netlist contents.  Pins that exist in the netlist but not
+    # the layout are added.  Pins that exist in the layout but not
+    # in the netlist are removed.
+
     if {[llength $subpins] > 0} {
 	set pinlist [split $subpins]
-	set i 0
+
+	# Determine if this cell already has pins.
+	set existpins []
+	for {set i [port first]} {$i > -1} {set i [port $i next]} {
+            lappend existpins [port $i name]
+	}
+	set addpins []
 	foreach pin $pinlist {
+	    if {[lsearch $existpins $pin] == -1} {
+		lappend addpins $pin
+	    }
+	}
+
+	set rmpins []
+	foreach pin $existpins {
+	    if {[lsearch $pinlist $pin] == -1} {
+		lappend rmpins $pin
+	    }
+	}
+
+	set i 0
+	foreach pin $addpins {
 	    # Escape [ and ] in pin name
 	    set pin_esc [string map {\[ \\\[ \] \\\]} $pin]
 	    magic::create_new_pin $pin_esc $i
 	    incr i
 	}
+	foreach pin $rmpins {
+	    set llayer [goto $pin]
+	    select area $llayer
+	    erase label
+	}
     }
 
     # Set initial position for importing cells
@@ -213,6 +243,24 @@ proc magic::generate_layout_add {subname subpins complist library} {
     set posy [expr {round(3 / [cif scale out])}]
     box position ${posx}i ${posy}i
 
+    # Find all instances in the circuit
+    select top cell
+    set compexist [instance list children]
+    set compcells []
+    # Find the matching cell defs
+    foreach comp $compexist {
+	lappend compcells [instance list celldef $comp]
+    }
+
+    # Diagnostic
+    puts stdout "Cells already in the layout of ${subname}:"
+    for {set i 0} {$i < [llength $compexist]} {incr i} {
+	set comp [lindex $compexist $i]
+	set ccell [lindex $compcells $i]
+	puts stdout "${comp} (${ccell})"
+    }
+    flush stdout
+
     # Seed layout with components
     foreach comp $complist {
 	set pinlist {}
@@ -297,12 +345,30 @@ proc magic::generate_layout_add {subname subpins complist library} {
 	    lappend outparts [lindex $param 1]
 	}
 
-	if {[catch {eval [join $outparts]}]} {
-	    # Assume this is not a gencell, and get an instance.
-	    magic::get_and_move_inst $devtype $instname $mult
-	} else {
-	    # Move forward for next gencell
-	    magic::move_forward_by_width $instname
+	set inst_exists false
+	set existidx [lsearch $compexist $instname]
+	if {$existidx > -1} {
+	    set existcell [lindex $compcells $existidx]
+	    if {$devtype == $existcell} {
+		set inst_exists true
+	    } else {
+		# Instance name exists but is the wrong device type.
+		# To do:  Attempt to maintain the same position
+		pushbox
+		select cell $instname
+		delete
+		popbox
+ 	    }
+	}
+
+	if {$inst_exists == false} {
+	    if {[catch {eval [join $outparts]}]} {
+		# Assume this is not a gencell, and get an instance.
+		magic::get_and_move_inst $devtype $instname $mult
+	    } else {
+		# Move forward for next gencell
+		magic::move_forward_by_width $instname
+	    }
 	}
     }
     save $subname
@@ -393,7 +459,8 @@ proc magic::netlist_to_layout {netfile library} {
    set curtop [cellname list self]
 
    foreach subckt $allsubs {
-        puts stdout "Test: pre-generating subcircuit $subckt"
+	# Diagnostic output
+        puts stdout "Pre-generating subcircuit $subckt placeholder"
 	load $subckt -silent
    }
    load $curtop