From 9f1afe05c3ab7228e21ba3666c6e35d693149b37 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@samba.org>
Date: Sun, 19 Feb 2006 22:44:47 +1100
Subject: [PATCH] gitk: New improved gitk

This is a new version of gitk which is much faster and has much better
graph layout.  It achieves the speed by only drawing the parts of the
canvases that are actually visible.  It also draws the commits in the
order that git-rev-list produces them, so if you use -d, you need to
have a recent enough git-rev-list that understands the --date-order
flag.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 gitk | 1551 +++++++++++++++++++++++++++++++---------------------------
 1 file changed, 824 insertions(+), 727 deletions(-)

diff --git a/gitk b/gitk
index f4c662423c..502f2665af 100755
--- a/gitk
+++ b/gitk
@@ -34,13 +34,17 @@ proc parse_args {rargs} {
 
 proc start_rev_list {rlargs} {
     global startmsecs nextupdate ncmupdate
-    global commfd leftover tclencoding
+    global commfd leftover tclencoding datemode
 
     set startmsecs [clock clicks -milliseconds]
     set nextupdate [expr {$startmsecs + 100}]
     set ncmupdate 1
+    set order "--topo-order"
+    if {$datemode} {
+	set order "--date-order"
+    }
     if {[catch {
-	set commfd [open [concat | git-rev-list --header --topo-order \
+	set commfd [open [concat | git-rev-list --header $order \
 			      --parents $rlargs] r]
     } err]} {
 	puts stderr "Error executing git-rev-list: $err"
@@ -77,7 +81,7 @@ proc getcommits {rargs} {
 proc getcommitlines {commfd}  {
     global oldcommits commits parents cdate children nchildren
     global commitlisted phase nextupdate
-    global stopped redisplaying leftover
+    global stopped leftover
     global canv
 
     set stuff [read $commfd]
@@ -105,7 +109,7 @@ proc getcommitlines {commfd}  {
 	set i [string first "\0" $stuff $start]
 	if {$i < 0} {
 	    append leftover [string range $stuff $start end]
-	    return
+	    break
 	}
 	set cmit [string range $stuff $start [expr {$i - 1}]]
 	if {$start == 0} {
@@ -140,23 +144,10 @@ proc getcommitlines {commfd}  {
 	set commitlisted($id) 1
 	parsecommit $id $cmit 1 [lrange $ids 1 end]
 	drawcommit $id 1
-	if {[clock clicks -milliseconds] >= $nextupdate} {
-	    doupdate 1
-	}
-	while {$redisplaying} {
-	    set redisplaying 0
-	    if {$stopped == 1} {
-		set stopped 0
-		set phase "getcommits"
-		foreach id $commits {
-		    drawcommit $id 1
-		    if {$stopped} break
-		    if {[clock clicks -milliseconds] >= $nextupdate} {
-			doupdate 1
-		    }
-		}
-	    }
-	}
+    }
+    layoutmore
+    if {[clock clicks -milliseconds] >= $nextupdate} {
+	doupdate 1
     }
 }
 
@@ -193,7 +184,7 @@ proc updatecommits {rargs} {
     global parsed_args
     global canv mainfont
     global oldcommits commits
-    global parents nchildren children ncleft
+    global parents nchildren children
 
     set old_args $parsed_args
     parse_args $rargs
@@ -276,12 +267,11 @@ proc updatecommits {rargs} {
 }
 
 proc updatechildren {id olds} {
-    global children nchildren parents nparents ncleft
+    global children nchildren parents nparents
 
     if {![info exists nchildren($id)]} {
 	set children($id) {}
 	set nchildren($id) 0
-	set ncleft($id) 0
     }
     set parents($id) $olds
     set nparents($id) [llength $olds]
@@ -289,11 +279,9 @@ proc updatechildren {id olds} {
 	if {![info exists nchildren($p)]} {
 	    set children($p) [list $id]
 	    set nchildren($p) 1
-	    set ncleft($p) 1
 	} elseif {[lsearch -exact $children($p) $id] < 0} {
 	    lappend children($p) $id
 	    incr nchildren($p)
-	    incr ncleft($p)
 	}
     }
 }
@@ -457,7 +445,7 @@ proc makewindow {rargs} {
     set canv .ctop.top.clist.canv
     canvas $canv -height $geometry(canvh) -width $geometry(canv1) \
 	-bg white -bd 0 \
-	-yscrollincr $linespc -yscrollcommand "$cscroll set"
+	-yscrollincr $linespc -yscrollcommand "scrollcanv $cscroll"
     .ctop.top.clist add $canv
     set canv2 .ctop.top.clist.canv2
     canvas $canv2 -height $geometry(canvh) -width $geometry(canv2) \
@@ -631,6 +619,11 @@ proc makewindow {rargs} {
     $rowctxmenu add command -label "Write commit to file" -command writecommit
 }
 
+proc scrollcanv {cscroll f0 f1} {
+    $cscroll set $f0 $f1
+    drawfrac $f0 $f1
+}
+
 # when we make a key binding for the toplevel, make sure
 # it doesn't get triggered when that key is pressed in the
 # find string entry widget.
@@ -763,9 +756,9 @@ proc about {} {
     toplevel $w
     wm title $w "About gitk"
     message $w.m -text {
-Gitk version 1.2
+Gitk - a commit viewer for git
 
-Copyright © 2005 Paul Mackerras
+Copyright © 2005-2006 Paul Mackerras
 
 Use and redistribute under the terms of the GNU General Public License} \
 	    -justify center -aspect 400
@@ -774,6 +767,694 @@ Use and redistribute under the terms of the GNU General Public License} \
     pack $w.ok -side bottom
 }
 
+proc shortids {ids} {
+    set res {}
+    foreach id $ids {
+	if {[llength $id] > 1} {
+	    lappend res [shortids $id]
+	} elseif {[regexp {^[0-9a-f]{40}$} $id]} {
+	    lappend res [string range $id 0 7]
+	} else {
+	    lappend res $id
+	}
+    }
+    return $res
+}
+
+proc incrange {l x o} {
+    set n [llength $l]
+    while {$x < $n} {
+	set e [lindex $l $x]
+	if {$e ne {}} {
+	    lset l $x [expr {$e + $o}]
+	}
+	incr x
+    }
+    return $l
+}
+
+proc ntimes {n o} {
+    set ret {}
+    for {} {$n > 0} {incr n -1} {
+	lappend ret $o
+    }
+    return $ret
+}
+
+proc usedinrange {id l1 l2} {
+    global children commitrow
+
+    if {[info exists commitrow($id)]} {
+	set r $commitrow($id)
+	if {$l1 <= $r && $r <= $l2} {
+	    return [expr {$r - $l1 + 1}]
+	}
+    }
+    foreach c $children($id) {
+	if {[info exists commitrow($c)]} {
+	    set r $commitrow($c)
+	    if {$l1 <= $r && $r <= $l2} {
+		return [expr {$r - $l1 + 1}]
+	    }
+	}
+    }
+    return 0
+}
+
+proc sanity {row {full 0}} {
+    global rowidlist rowoffsets
+
+    set col -1
+    set ids $rowidlist($row)
+    foreach id $ids {
+	incr col
+	if {$id eq {}} continue
+	if {$col < [llength $ids] - 1 &&
+	    [lsearch -exact -start [expr {$col+1}] $ids $id] >= 0} {
+	    puts "oops: [shortids $id] repeated in row $row col $col: {[shortids $rowidlist($row)]}"
+	}
+	set o [lindex $rowoffsets($row) $col]
+	set y $row
+	set x $col
+	while {$o ne {}} {
+	    incr y -1
+	    incr x $o
+	    if {[lindex $rowidlist($y) $x] != $id} {
+		puts "oops: rowoffsets wrong at row [expr {$y+1}] col [expr {$x-$o}]"
+		puts "  id=[shortids $id] check started at row $row"
+		for {set i $row} {$i >= $y} {incr i -1} {
+		    puts "  row $i ids={[shortids $rowidlist($i)]} offs={$rowoffsets($i)}"
+		}
+		break
+	    }
+	    if {!$full} break
+	    set o [lindex $rowoffsets($y) $x]
+	}
+    }
+}
+
+proc makeuparrow {oid x y z} {
+    global rowidlist rowoffsets uparrowlen idrowranges
+
+    for {set i 1} {$i < $uparrowlen && $y > 1} {incr i} {
+	incr y -1
+	incr x $z
+	set off0 $rowoffsets($y)
+	for {set x0 $x} {1} {incr x0} {
+	    if {$x0 >= [llength $off0]} {
+		set x0 [llength $rowoffsets([expr {$y-1}])]
+		break
+	    }
+	    set z [lindex $off0 $x0]
+	    if {$z ne {}} {
+		incr x0 $z
+		break
+	    }
+	}
+	set z [expr {$x0 - $x}]
+	set rowidlist($y) [linsert $rowidlist($y) $x $oid]
+	set rowoffsets($y) [linsert $rowoffsets($y) $x $z]
+    }
+    set tmp [lreplace $rowoffsets($y) $x $x {}]
+    set rowoffsets($y) [incrange $tmp [expr {$x+1}] -1]
+    lappend idrowranges($oid) $y
+}
+
+proc initlayout {} {
+    global rowidlist rowoffsets displayorder
+    global rowlaidout rowoptim
+    global idinlist rowchk
+
+    set rowidlist(0) {}
+    set rowoffsets(0) {}
+    catch {unset idinlist}
+    catch {unset rowchk}
+    set rowlaidout 0
+    set rowoptim 0
+}
+
+proc visiblerows {} {
+    global canv numcommits linespc
+
+    set ymax [lindex [$canv cget -scrollregion] 3]
+    if {$ymax eq {} || $ymax == 0} return
+    set f [$canv yview]
+    set y0 [expr {int([lindex $f 0] * $ymax)}]
+    set r0 [expr {int(($y0 - 3) / $linespc) - 1}]
+    if {$r0 < 0} {
+	set r0 0
+    }
+    set y1 [expr {int([lindex $f 1] * $ymax)}]
+    set r1 [expr {int(($y1 - 3) / $linespc) + 1}]
+    if {$r1 >= $numcommits} {
+	set r1 [expr {$numcommits - 1}]
+    }
+    return [list $r0 $r1]
+}
+
+proc layoutmore {} {
+    global rowlaidout rowoptim commitidx numcommits optim_delay
+    global uparrowlen
+
+    set row $rowlaidout
+    set rowlaidout [layoutrows $row $commitidx 0]
+    set orow [expr {$rowlaidout - $uparrowlen - 1}]
+    if {$orow > $rowoptim} {
+	checkcrossings $rowoptim $orow
+	optimize_rows $rowoptim 0 $orow
+	set rowoptim $orow
+    }
+    set canshow [expr {$rowoptim - $optim_delay}]
+    if {$canshow > $numcommits} {
+	showstuff $canshow
+    }
+}
+
+proc showstuff {canshow} {
+    global numcommits
+    global canvy0 linespc
+    global linesegends idrowranges idrangedrawn
+
+    set row $numcommits
+    set numcommits $canshow
+    allcanvs conf -scrollregion \
+	[list 0 0 0 [expr {$canvy0 + ($numcommits - 0.5) * $linespc + 2}]]
+    set rows [visiblerows]
+    set r0 [lindex $rows 0]
+    set r1 [lindex $rows 1]
+    for {set r $row} {$r < $canshow} {incr r} {
+	if {[info exists linesegends($r)]} {
+	    foreach id $linesegends($r) {
+		set i -1
+		foreach {s e} $idrowranges($id) {
+		    incr i
+		    if {$e ne {} && $e < $numcommits && $s <= $r1 && $e >= $r0
+			&& ![info exists idrangedrawn($id,$i)]} {
+			drawlineseg $id $i 1
+			set idrangedrawn($id,$i) 1
+		    }
+		}
+	    }
+	}
+    }
+    if {$canshow > $r1} {
+	set canshow $r1
+    }
+    while {$row < $canshow} {
+	drawcmitrow $row
+	incr row
+    }
+}
+
+proc layoutrows {row endrow last} {
+    global rowidlist rowoffsets displayorder
+    global uparrowlen downarrowlen maxwidth mingaplen
+    global nchildren parents nparents
+    global idrowranges linesegends
+    global commitidx
+    global idinlist rowchk
+
+    set idlist $rowidlist($row)
+    set offs $rowoffsets($row)
+    while {$row < $endrow} {
+	set id [lindex $displayorder $row]
+	set oldolds {}
+	set newolds {}
+	foreach p $parents($id) {
+	    if {![info exists idinlist($p)]} {
+		lappend newolds $p
+	    } elseif {!$idinlist($p)} {
+		lappend oldolds $p
+	    }
+	}
+	set nev [expr {[llength $idlist] + [llength $newolds]
+		       + [llength $oldolds] - $maxwidth + 1}]
+	if {$nev > 0} {
+	    if {!$last && $row + $uparrowlen + $mingaplen >= $commitidx} break
+	    for {set x [llength $idlist]} {[incr x -1] >= 0} {} {
+		set i [lindex $idlist $x]
+		if {![info exists rowchk($i)] || $row >= $rowchk($i)} {
+		    set r [usedinrange $i [expr {$row - $downarrowlen}] \
+			       [expr {$row + $uparrowlen + $mingaplen}]]
+		    if {$r == 0} {
+			set idlist [lreplace $idlist $x $x]
+			set offs [lreplace $offs $x $x]
+			set offs [incrange $offs $x 1]
+			set idinlist($i) 0
+			lappend linesegends($row) $i
+			lappend idrowranges($i) [expr {$row-1}]
+			if {[incr nev -1] <= 0} break
+			continue
+		    }
+		    set rowchk($id) [expr {$row + $r}]
+		}
+	    }
+	    set rowidlist($row) $idlist
+	    set rowoffsets($row) $offs
+	}
+	set col [lsearch -exact $idlist $id]
+	if {$col < 0} {
+	    set col [llength $idlist]
+	    lappend idlist $id
+	    set rowidlist($row) $idlist
+	    set z {}
+	    if {$nchildren($id) > 0} {
+		set z [expr {[llength $rowidlist([expr {$row-1}])] - $col}]
+		unset idinlist($id)
+	    }
+	    lappend offs $z
+	    set rowoffsets($row) $offs
+	    if {$z ne {}} {
+		makeuparrow $id $col $row $z
+	    }
+	} else {
+	    unset idinlist($id)
+	}
+	if {[info exists idrowranges($id)]} {
+	    lappend linesegends($row) $id
+	    lappend idrowranges($id) $row
+	}
+	incr row
+	set offs [ntimes [llength $idlist] 0]
+	set l [llength $newolds]
+	set idlist [eval lreplace \$idlist $col $col $newolds]
+	set o 0
+	if {$l != 1} {
+	    set offs [lrange $offs 0 [expr {$col - 1}]]
+	    foreach x $newolds {
+		lappend offs {}
+		incr o -1
+	    }
+	    incr o
+	    set tmp [expr {[llength $idlist] - [llength $offs]}]
+	    if {$tmp > 0} {
+		set offs [concat $offs [ntimes $tmp $o]]
+	    }
+	} else {
+	    lset offs $col {}
+	}
+	foreach i $newolds {
+	    set idinlist($i) 1
+	    set idrowranges($i) $row
+	}
+	incr col $l
+	foreach oid $oldolds {
+	    set idinlist($oid) 1
+	    set idlist [linsert $idlist $col $oid]
+	    set offs [linsert $offs $col $o]
+	    makeuparrow $oid $col $row $o
+	    incr col
+	}
+	set rowidlist($row) $idlist
+	set rowoffsets($row) $offs
+    }
+    return $row
+}
+
+proc addextraid {id row} {
+    global displayorder commitrow lineid commitinfo nparents
+    global commitidx
+
+    incr commitidx
+    lappend displayorder $id
+    set commitrow($id) $row
+    set lineid($row) $id
+    readcommit $id
+    if {![info exists commitinfo($id)]} {
+	set commitinfo($id) {"No commit information available"}
+	set nparents($id) 0
+    }
+}
+
+proc layouttail {} {
+    global rowidlist rowoffsets idinlist commitidx
+    global idrowranges linesegends
+
+    set row $commitidx
+    set idlist $rowidlist($row)
+    while {$idlist ne {}} {
+	set col [expr {[llength $idlist] - 1}]
+	set id [lindex $idlist $col]
+	addextraid $id $row
+	unset idinlist($id)
+	lappend linesegends($row) $id
+	lappend idrowranges($id) $row
+	incr row
+	set offs [ntimes $col 0]
+	set idlist [lreplace $idlist $col $col]
+	set rowidlist($row) $idlist
+	set rowoffsets($row) $offs
+    }
+
+    foreach id [array names idinlist] {
+	addextraid $id $row
+	set rowidlist($row) [list $id]
+	set rowoffsets($row) 0
+	makeuparrow $id 0 $row 0
+	lappend linesegends($row) $id
+	lappend idrowranges($id) $row
+	incr row
+    }
+}
+
+proc insert_pad {row col npad} {
+    global rowidlist rowoffsets
+
+    set pad [ntimes $npad {}]
+    set rowidlist($row) [eval linsert \$rowidlist($row) $col $pad]
+    set tmp [eval linsert \$rowoffsets($row) $col $pad]
+    set rowoffsets($row) [incrange $tmp [expr {$col + $npad}] [expr {-$npad}]]
+}
+
+proc optimize_rows {row col endrow} {
+    global rowidlist rowoffsets idrowranges
+
+    for {} {$row < $endrow} {incr row} {
+	set idlist $rowidlist($row)
+	set offs $rowoffsets($row)
+	set haspad 0
+	for {} {$col < [llength $offs]} {incr col} {
+	    if {[lindex $idlist $col] eq {}} {
+		set haspad 1
+		continue
+	    }
+	    set z [lindex $offs $col]
+	    if {$z eq {}} continue
+	    set isarrow 0
+	    set x0 [expr {$col + $z}]
+	    set y0 [expr {$row - 1}]
+	    set z0 [lindex $rowoffsets($y0) $x0]
+	    if {$z0 eq {}} {
+		set id [lindex $idlist $col]
+		if {[info exists idrowranges($id)] &&
+		    $y0 > [lindex $idrowranges($id) 0]} {
+		    set isarrow 1
+		}
+	    }
+	    if {$z < -1 || ($z < 0 && $isarrow)} {
+		set npad [expr {-1 - $z + $isarrow}]
+		set offs [incrange $offs $col $npad]
+		insert_pad $y0 $x0 $npad
+		if {$y0 > 0} {
+		    optimize_rows $y0 $x0 $row
+		}
+		set z [lindex $offs $col]
+		set x0 [expr {$col + $z}]
+		set z0 [lindex $rowoffsets($y0) $x0]
+	    } elseif {$z > 1 || ($z > 0 && $isarrow)} {
+		set npad [expr {$z - 1 + $isarrow}]
+		set y1 [expr {$row + 1}]
+		set offs2 $rowoffsets($y1)
+		set x1 -1
+		foreach z $offs2 {
+		    incr x1
+		    if {$z eq {} || $x1 + $z < $col} continue
+		    if {$x1 + $z > $col} {
+			incr npad
+		    }
+		    set rowoffsets($y1) [incrange $offs2 $x1 $npad]
+		    break
+		}
+		set pad [ntimes $npad {}]
+		set idlist [eval linsert \$idlist $col $pad]
+		set tmp [eval linsert \$offs $col $pad]
+		incr col $npad
+		set offs [incrange $tmp $col [expr {-$npad}]]
+		set z [lindex $offs $col]
+		set haspad 1
+	    }
+	    if {$z0 ne {} && $z < 0 && $z0 > 0} {
+		insert_pad $y0 $x0 1
+		set offs [incrange $offs $col 1]
+		optimize_rows $y0 [expr {$x0 + 1}] $row
+	    }
+	}
+	if {!$haspad} {
+	    for {set col [llength $idlist]} {[incr col -1] >= 0} {} {
+		set o [lindex $offs $col]
+		if {$o eq {} || $o <= 0} break
+	    }
+	    if {[incr col] < [llength $idlist]} {
+		set y1 [expr {$row + 1}]
+		set offs2 $rowoffsets($y1)
+		set x1 -1
+		foreach z $offs2 {
+		    incr x1
+		    if {$z eq {} || $x1 + $z < $col} continue
+		    set rowoffsets($y1) [incrange $offs2 $x1 1]
+		    break
+		}
+		set idlist [linsert $idlist $col {}]
+		set tmp [linsert $offs $col {}]
+		incr col
+		set offs [incrange $tmp $col -1]
+	    }
+	}
+	set rowidlist($row) $idlist
+	set rowoffsets($row) $offs
+	set col 0
+    }
+}
+
+proc xc {row col} {
+    global canvx0 linespc
+    return [expr {$canvx0 + $col * $linespc}]
+}
+
+proc yc {row} {
+    global canvy0 linespc
+    return [expr {$canvy0 + $row * $linespc}]
+}
+
+proc drawlineseg {id i wid} {
+    global rowoffsets rowidlist idrowranges
+    global canv colormap lthickness
+
+    set startrow [lindex $idrowranges($id) [expr {2 * $i}]]
+    set row [lindex $idrowranges($id) [expr {2 * $i + 1}]]
+    if {$startrow == $row} return
+    assigncolor $id
+    set coords {}
+    set col [lsearch -exact $rowidlist($row) $id]
+    if {$col < 0} {
+	puts "oops: drawline: id $id not on row $row"
+	return
+    }
+    set lasto {}
+    set ns 0
+    while {1} {
+	set o [lindex $rowoffsets($row) $col]
+	if {$o eq {}} break
+	if {$o ne $lasto} {
+	    # changing direction
+	    set x [xc $row $col]
+	    set y [yc $row]
+	    lappend coords $x $y
+	    set lasto $o
+	}
+	incr col $o
+	incr row -1
+    }
+    if {$coords eq {}} return
+    set last [expr {[llength $idrowranges($id)] / 2 - 1}]
+    set arrow [expr {2 * ($i > 0) + ($i < $last)}]
+    set arrow [lindex {none first last both} $arrow]
+    set wid [expr {$wid * $lthickness}]
+    set x [xc $row $col]
+    set y [yc $row]
+    lappend coords $x $y
+    set t [$canv create line $coords -width $wid \
+	       -fill $colormap($id) -tags lines.$id -arrow $arrow]
+    $canv lower $t
+    bindline $t $id
+}
+
+proc drawparentlinks {id row col olds wid} {
+    global rowoffsets rowidlist canv colormap lthickness
+
+    set row2 [expr {$row + 1}]
+    set x [xc $row $col]
+    set y [yc $row]
+    set y2 [yc $row2]
+    set ids $rowidlist($row2)
+    set offs $rowidlist($row2)
+    # rmx = right-most X coord used
+    set rmx 0
+    set wid [expr {$wid * $lthickness}]
+    foreach p $olds {
+	set i [lsearch -exact $ids $p]
+	if {$i < 0} {
+	    puts "oops, parent $p of $id not in list"
+	    continue
+	}
+	assigncolor $p
+	# should handle duplicated parents here...
+	set coords [list $x $y]
+	if {$i < $col - 1} {
+	    lappend coords [xc $row [expr {$i + 1}]] $y
+	} elseif {$i > $col + 1} {
+	    lappend coords [xc $row [expr {$i - 1}]] $y
+	}
+	set x2 [xc $row2 $i]
+	if {$x2 > $rmx} {
+	    set rmx $x2
+	}
+	lappend coords $x2 $y2
+	set t [$canv create line $coords -width $wid \
+		   -fill $colormap($p) -tags lines.$p]
+	$canv lower $t
+	bindline $t $p
+    }
+    return $rmx
+}
+
+proc drawlines {id xtra} {
+    global colormap canv
+    global idrowranges idrangedrawn
+    global children iddrawn commitrow rowidlist
+
+    $canv delete lines.$id
+    set wid [expr {$xtra + 1}]
+    set nr [expr {[llength $idrowranges($id)] / 2}]
+    for {set i 0} {$i < $nr} {incr i} {
+	if {[info exists idrangedrawn($id,$i)]} {
+	    drawlineseg $id $i $wid
+	}
+    }
+    if {[info exists children($id)]} {
+	foreach child $children($id) {
+	    if {[info exists iddrawn($child)]} {
+		set row $commitrow($child)
+		set col [lsearch -exact $rowidlist($row) $child]
+		if {$col >= 0} {
+		    drawparentlinks $child $row $col [list $id] $wid
+		}
+	    }
+	}
+    }
+}
+
+proc drawcmittext {id row col rmx} {
+    global linespc canv canv2 canv3 canvy0
+    global commitlisted commitinfo rowidlist
+    global rowtextx idpos idtags idheads idotherrefs
+    global linehtag linentag linedtag
+    global mainfont namefont
+
+    set ofill [expr {[info exists commitlisted($id)]? "blue": "white"}]
+    set x [xc $row $col]
+    set y [yc $row]
+    set orad [expr {$linespc / 3}]
+    set t [$canv create oval [expr {$x - $orad}] [expr {$y - $orad}] \
+	       [expr {$x + $orad - 1}] [expr {$y + $orad - 1}] \
+	       -fill $ofill -outline black -width 1]
+    $canv raise $t
+    $canv bind $t <1> {selcanvline {} %x %y}
+    set xt [xc $row [llength $rowidlist($row)]]
+    if {$xt < $rmx} {
+	set xt $rmx
+    }
+    set rowtextx($row) $xt
+    set idpos($id) [list $x $xt $y]
+    if {[info exists idtags($id)] || [info exists idheads($id)]
+	|| [info exists idotherrefs($id)]} {
+	set xt [drawtags $id $x $xt $y]
+    }
+    set headline [lindex $commitinfo($id) 0]
+    set name [lindex $commitinfo($id) 1]
+    set date [lindex $commitinfo($id) 2]
+    set date [formatdate $date]
+    set linehtag($row) [$canv create text $xt $y -anchor w \
+			    -text $headline -font $mainfont ]
+    $canv bind $linehtag($row) <Button-3> "rowmenu %X %Y $id"
+    set linentag($row) [$canv2 create text 3 $y -anchor w \
+			    -text $name -font $namefont]
+    set linedtag($row) [$canv3 create text 3 $y -anchor w \
+			    -text $date -font $mainfont]
+}
+
+proc drawcmitrow {row} {
+    global displayorder rowidlist rowoffsets
+    global idrowranges idrangedrawn iddrawn
+    global commitinfo commitlisted parents numcommits
+
+    if {![info exists rowidlist($row)]} return
+    foreach id $rowidlist($row) {
+	if {![info exists idrowranges($id)]} continue
+	set i -1
+	foreach {s e} $idrowranges($id) {
+	    incr i
+	    if {$row < $s} continue
+	    if {$e eq {}} break
+	    if {$row <= $e} {
+		if {$e < $numcommits && ![info exists idrangedrawn($id,$i)]} {
+		    drawlineseg $id $i 1
+		    set idrangedrawn($id,$i) 1
+		}
+		break
+	    }
+	}
+    }
+
+    set id [lindex $displayorder $row]
+    if {[info exists iddrawn($id)]} return
+    set col [lsearch -exact $rowidlist($row) $id]
+    if {$col < 0} {
+	puts "oops, row $row id $id not in list"
+	return
+    }
+    if {![info exists commitinfo($id)]} {
+	readcommit $id
+	if {![info exists commitinfo($id)]} {
+	    set commitinfo($id) {"No commit information available"}
+	    set nparents($id) 0
+	}
+    }
+    assigncolor $id
+    if {[info exists commitlisted($id)] && [info exists parents($id)]
+	&& $parents($id) ne {}} {
+	set rmx [drawparentlinks $id $row $col $parents($id) 1]
+    } else {
+	set rmx 0
+    }
+    drawcmittext $id $row $col $rmx
+    set iddrawn($id) 1
+}
+
+proc drawfrac {f0 f1} {
+    global numcommits canv
+    global linespc
+
+    set ymax [lindex [$canv cget -scrollregion] 3]
+    if {$ymax eq {} || $ymax == 0} return
+    set y0 [expr {int($f0 * $ymax)}]
+    set row [expr {int(($y0 - 3) / $linespc) - 1}]
+    if {$row < 0} {
+	set row 0
+    }
+    set y1 [expr {int($f1 * $ymax)}]
+    set endrow [expr {int(($y1 - 3) / $linespc) + 1}]
+    if {$endrow >= $numcommits} {
+	set endrow [expr {$numcommits - 1}]
+    }
+    for {} {$row <= $endrow} {incr row} {
+	drawcmitrow $row
+    }
+}
+
+proc drawvisible {} {
+    global canv
+    eval drawfrac [$canv yview]
+}
+
+proc clear_display {} {
+    global iddrawn idrangedrawn
+
+    allcanvs delete all
+    catch {unset iddrawn}
+    catch {unset idrangedrawn}
+}
+
 proc assigncolor {id} {
     global colormap commcolors colors nextcolor
     global parents nparents children nchildren
@@ -781,7 +1462,7 @@ proc assigncolor {id} {
 
     if {[info exists colormap($id)]} return
     set ncolors [llength $colors]
-    if {$nparents($id) <= 1 && $nchildren($id) == 1} {
+    if {$nchildren($id) == 1} {
 	set child [lindex $children($id) 0]
 	if {[info exists colormap($child)]
 	    && $nparents($child) == 1} {
@@ -846,25 +1527,16 @@ proc assigncolor {id} {
 }
 
 proc initgraph {} {
-    global canvy canvy0 lineno numcommits nextcolor linespc
-    global nchildren ncleft
-    global displist nhyperspace
+    global numcommits nextcolor linespc
+    global nchildren
 
     allcanvs delete all
     set nextcolor 0
-    set canvy $canvy0
-    set lineno -1
     set numcommits 0
-    foreach v {mainline mainlinearrow sidelines colormap cornercrossings
-		crossings idline lineid} {
+    foreach v {colormap cornercrossings	crossings lineid} {
 	global $v
 	catch {unset $v}
     }
-    foreach id [array names nchildren] {
-	set ncleft($id) $nchildren($id)
-    }
-    set displist {}
-    set nhyperspace 0
 }
 
 proc bindline {t id} {
@@ -876,121 +1548,10 @@ proc bindline {t id} {
     $canv bind $t <Button-1> "lineclick %x %y $id 1"
 }
 
-proc drawlines {id xtra delold} {
-    global mainline mainlinearrow sidelines lthickness colormap canv
-
-    if {$delold} {
-	$canv delete lines.$id
-    }
-    if {[info exists mainline($id)]} {
-	set t [$canv create line $mainline($id) \
-		   -width [expr {($xtra + 1) * $lthickness}] \
-		   -fill $colormap($id) -tags lines.$id \
-		   -arrow $mainlinearrow($id)]
-	$canv lower $t
-	bindline $t $id
-    }
-    if {[info exists sidelines($id)]} {
-	foreach ls $sidelines($id) {
-	    set coords [lindex $ls 0]
-	    set thick [lindex $ls 1]
-	    set arrow [lindex $ls 2]
-	    set t [$canv create line $coords -fill $colormap($id) \
-		       -width [expr {($thick + $xtra) * $lthickness}] \
-		       -arrow $arrow -tags lines.$id]
-	    $canv lower $t
-	    bindline $t $id
-	}
-    }
-}
-
-# level here is an index in displist
-proc drawcommitline {level} {
-    global parents children nparents displist
-    global canv canv2 canv3 mainfont namefont canvy linespc
-    global lineid linehtag linentag linedtag commitinfo
-    global colormap numcommits currentparents dupparents
-    global idtags idline idheads idotherrefs
-    global lineno lthickness mainline mainlinearrow sidelines
-    global commitlisted rowtextx idpos lastuse displist
-    global oldnlines olddlevel olddisplist
-
-    incr numcommits
-    incr lineno
-    set id [lindex $displist $level]
-    set lastuse($id) $lineno
-    set lineid($lineno) $id
-    set idline($id) $lineno
-    set ofill [expr {[info exists commitlisted($id)]? "blue": "white"}]
-    if {![info exists commitinfo($id)]} {
-	readcommit $id
-	if {![info exists commitinfo($id)]} {
-	    set commitinfo($id) {"No commit information available"}
-	    set nparents($id) 0
-	}
-    }
-    assigncolor $id
-    set currentparents {}
-    set dupparents {}
-    if {[info exists commitlisted($id)] && [info exists parents($id)]} {
-	foreach p $parents($id) {
-	    if {[lsearch -exact $currentparents $p] < 0} {
-		lappend currentparents $p
-	    } else {
-		# remember that this parent was listed twice
-		lappend dupparents $p
-	    }
-	}
-    }
-    set x [xcoord $level $level $lineno]
-    set y1 $canvy
-    set canvy [expr {$canvy + $linespc}]
-    allcanvs conf -scrollregion \
-	[list 0 0 0 [expr {$y1 + 0.5 * $linespc + 2}]]
-    if {[info exists mainline($id)]} {
-	lappend mainline($id) $x $y1
-	if {$mainlinearrow($id) ne "none"} {
-	    set mainline($id) [trimdiagstart $mainline($id)]
-	}
-    }
-    drawlines $id 0 0
-    set orad [expr {$linespc / 3}]
-    set t [$canv create oval [expr {$x - $orad}] [expr {$y1 - $orad}] \
-	       [expr {$x + $orad - 1}] [expr {$y1 + $orad - 1}] \
-	       -fill $ofill -outline black -width 1]
-    $canv raise $t
-    $canv bind $t <1> {selcanvline {} %x %y}
-    set xt [xcoord [llength $displist] $level $lineno]
-    if {[llength $currentparents] > 2} {
-	set xt [expr {$xt + ([llength $currentparents] - 2) * $linespc}]
-    }
-    set rowtextx($lineno) $xt
-    set idpos($id) [list $x $xt $y1]
-    if {[info exists idtags($id)] || [info exists idheads($id)]
-	|| [info exists idotherrefs($id)]} {
-	set xt [drawtags $id $x $xt $y1]
-    }
-    set headline [lindex $commitinfo($id) 0]
-    set name [lindex $commitinfo($id) 1]
-    set date [lindex $commitinfo($id) 2]
-    set date [formatdate $date]
-    set linehtag($lineno) [$canv create text $xt $y1 -anchor w \
-			       -text $headline -font $mainfont ]
-    $canv bind $linehtag($lineno) <Button-3> "rowmenu %X %Y $id"
-    set linentag($lineno) [$canv2 create text 3 $y1 -anchor w \
-			       -text $name -font $namefont]
-    set linedtag($lineno) [$canv3 create text 3 $y1 -anchor w \
-			       -text $date -font $mainfont]
-
-    set olddlevel $level
-    set olddisplist $displist
-    set oldnlines [llength $displist]
-}
-
 proc drawtags {id x xt y1} {
     global idtags idheads idotherrefs
     global linespc lthickness
-    global canv mainfont idline rowtextx
+    global canv mainfont commitrow rowtextx
 
     set marks {}
     set ntags 0
@@ -1033,7 +1594,7 @@ proc drawtags {id x xt y1} {
 		       $xr $yt $xr $yb $xl $yb $x [expr {$yb - $delta}] \
 		       -width 1 -outline black -fill yellow -tags tag.$id]
 	    $canv bind $t <1> [list showtag $tag 1]
-	    set rowtextx($idline($id)) [expr {$xr + $linespc}]
+	    set rowtextx($commitrow($id)) [expr {$xr + $linespc}]
 	} else {
 	    # draw a head or other ref
 	    if {[incr nheads -1] >= 0} {
@@ -1054,11 +1615,32 @@ proc drawtags {id x xt y1} {
     return $xt
 }
 
-proc notecrossings {id lo hi corner} {
-    global olddisplist crossings cornercrossings
+proc checkcrossings {row endrow} {
+    global displayorder parents rowidlist
+
+    for {} {$row < $endrow} {incr row} {
+	set id [lindex $displayorder $row]
+	set i [lsearch -exact $rowidlist($row) $id]
+	if {$i < 0} continue
+	set idlist $rowidlist([expr {$row+1}])
+	foreach p $parents($id) {
+	    set j [lsearch -exact $idlist $p]
+	    if {$j > 0} {
+		if {$j < $i - 1} {
+		    notecrossings $row $p $j $i [expr {$j+1}]
+		} elseif {$j > $i + 1} {
+		    notecrossings $row $p $i $j [expr {$j-1}]
+		}
+	    }
+	}
+    }
+}
+
+proc notecrossings {row id lo hi corner} {
+    global rowidlist crossings cornercrossings
 
     for {set i $lo} {[incr i] < $hi} {} {
-	set p [lindex $olddisplist $i]
+	set p [lindex $rowidlist($row) $i]
 	if {$p == {}} continue
 	if {$i == $corner} {
 	    if {![info exists cornercrossings($id)]
@@ -1094,491 +1676,29 @@ proc xcoord {i level ln} {
     return $x
 }
 
-# it seems Tk can't draw arrows on the end of diagonal line segments...
-proc trimdiagend {line} {
-    while {[llength $line] > 4} {
-	set x1 [lindex $line end-3]
-	set y1 [lindex $line end-2]
-	set x2 [lindex $line end-1]
-	set y2 [lindex $line end]
-	if {($x1 == $x2) != ($y1 == $y2)} break
-	set line [lreplace $line end-1 end]
-    }
-    return $line
-}
-
-proc trimdiagstart {line} {
-    while {[llength $line] > 4} {
-	set x1 [lindex $line 0]
-	set y1 [lindex $line 1]
-	set x2 [lindex $line 2]
-	set y2 [lindex $line 3]
-	if {($x1 == $x2) != ($y1 == $y2)} break
-	set line [lreplace $line 0 1]
-    }
-    return $line
-}
-
-proc drawslants {id needonscreen nohs} {
-    global canv mainline mainlinearrow sidelines
-    global canvx0 canvy xspc1 xspc2 lthickness
-    global currentparents dupparents
-    global lthickness linespc canvy colormap lineno geometry
-    global maxgraphpct maxwidth
-    global displist onscreen lastuse
-    global parents commitlisted
-    global oldnlines olddlevel olddisplist
-    global nhyperspace numcommits nnewparents
-
-    if {$lineno < 0} {
-	lappend displist $id
-	set onscreen($id) 1
-	return 0
-    }
-
-    set y1 [expr {$canvy - $linespc}]
-    set y2 $canvy
-
-    # work out what we need to get back on screen
-    set reins {}
-    if {$onscreen($id) < 0} {
-	# next to do isn't displayed, better get it on screen...
-	lappend reins [list $id 0]
-    }
-    # make sure all the previous commits's parents are on the screen
-    foreach p $currentparents {
-	if {$onscreen($p) < 0} {
-	    lappend reins [list $p 0]
-	}
-    }
-    # bring back anything requested by caller
-    if {$needonscreen ne {}} {
-	lappend reins $needonscreen
-    }
-
-    # try the shortcut
-    if {$currentparents == $id && $onscreen($id) == 0 && $reins eq {}} {
-	set dlevel $olddlevel
-	set x [xcoord $dlevel $dlevel $lineno]
-	set mainline($id) [list $x $y1]
-	set mainlinearrow($id) none
-	set lastuse($id) $lineno
-	set displist [lreplace $displist $dlevel $dlevel $id]
-	set onscreen($id) 1
-	set xspc1([expr {$lineno + 1}]) $xspc1($lineno)
-	return $dlevel
-    }
-
-    # update displist
-    set displist [lreplace $displist $olddlevel $olddlevel]
-    set j $olddlevel
-    foreach p $currentparents {
-	set lastuse($p) $lineno
-	if {$onscreen($p) == 0} {
-	    set displist [linsert $displist $j $p]
-	    set onscreen($p) 1
-	    incr j
-	}
-    }
-    if {$onscreen($id) == 0} {
-	lappend displist $id
-	set onscreen($id) 1
-    }
-
-    # remove the null entry if present
-    set nullentry [lsearch -exact $displist {}]
-    if {$nullentry >= 0} {
-	set displist [lreplace $displist $nullentry $nullentry]
-    }
-
-    # bring back the ones we need now (if we did it earlier
-    # it would change displist and invalidate olddlevel)
-    foreach pi $reins {
-	# test again in case of duplicates in reins
-	set p [lindex $pi 0]
-	if {$onscreen($p) < 0} {
-	    set onscreen($p) 1
-	    set lastuse($p) $lineno
-	    set displist [linsert $displist [lindex $pi 1] $p]
-	    incr nhyperspace -1
-	}
-    }
-
-    set lastuse($id) $lineno
-
-    # see if we need to make any lines jump off into hyperspace
-    set displ [llength $displist]
-    if {$displ > $maxwidth} {
-	set ages {}
-	foreach x $displist {
-	    lappend ages [list $lastuse($x) $x]
-	}
-	set ages [lsort -integer -index 0 $ages]
-	set k 0
-	while {$displ > $maxwidth} {
-	    set use [lindex $ages $k 0]
-	    set victim [lindex $ages $k 1]
-	    if {$use >= $lineno - 5} break
-	    incr k
-	    if {[lsearch -exact $nohs $victim] >= 0} continue
-	    set i [lsearch -exact $displist $victim]
-	    set displist [lreplace $displist $i $i]
-	    set onscreen($victim) -1
-	    incr nhyperspace
-	    incr displ -1
-	    if {$i < $nullentry} {
-		incr nullentry -1
-	    }
-	    set x [lindex $mainline($victim) end-1]
-	    lappend mainline($victim) $x $y1
-	    set line [trimdiagend $mainline($victim)]
-	    set arrow "last"
-	    if {$mainlinearrow($victim) ne "none"} {
-		set line [trimdiagstart $line]
-		set arrow "both"
-	    }
-	    lappend sidelines($victim) [list $line 1 $arrow]
-	    unset mainline($victim)
-	}
-    }
-
-    set dlevel [lsearch -exact $displist $id]
-
-    # If we are reducing, put in a null entry
-    if {$displ < $oldnlines} {
-	# does the next line look like a merge?
-	# i.e. does it have > 1 new parent?
-	if {$nnewparents($id) > 1} {
-	    set i [expr {$dlevel + 1}]
-	} elseif {$nnewparents([lindex $olddisplist $olddlevel]) == 0} {
-	    set i $olddlevel
-	    if {$nullentry >= 0 && $nullentry < $i} {
-		incr i -1
-	    }
-	} elseif {$nullentry >= 0} {
-	    set i $nullentry
-	    while {$i < $displ
-		   && [lindex $olddisplist $i] == [lindex $displist $i]} {
-		incr i
-	    }
-	} else {
-	    set i $olddlevel
-	    if {$dlevel >= $i} {
-		incr i
-	    }
-	}
-	if {$i < $displ} {
-	    set displist [linsert $displist $i {}]
-	    incr displ
-	    if {$dlevel >= $i} {
-		incr dlevel
-	    }
-	}
-    }
-
-    # decide on the line spacing for the next line
-    set lj [expr {$lineno + 1}]
-    set maxw [expr {$maxgraphpct * $geometry(canv1) / 100}]
-    if {$displ <= 1 || $canvx0 + $displ * $xspc2 <= $maxw} {
-	set xspc1($lj) $xspc2
-    } else {
-	set xspc1($lj) [expr {($maxw - $canvx0 - $xspc2) / ($displ - 1)}]
-	if {$xspc1($lj) < $lthickness} {
-	    set xspc1($lj) $lthickness
-	}
-    }
-
-    foreach idi $reins {
-	set id [lindex $idi 0]
-	set j [lsearch -exact $displist $id]
-	set xj [xcoord $j $dlevel $lj]
-	set mainline($id) [list $xj $y2]
-	set mainlinearrow($id) first
-    }
-
-    set i -1
-    foreach id $olddisplist {
-	incr i
-	if {$id == {}} continue
-	if {$onscreen($id) <= 0} continue
-	set xi [xcoord $i $olddlevel $lineno]
-	if {$i == $olddlevel} {
-	    foreach p $currentparents {
-		set j [lsearch -exact $displist $p]
-		set coords [list $xi $y1]
-		set xj [xcoord $j $dlevel $lj]
-		if {$xj < $xi - $linespc} {
-		    lappend coords [expr {$xj + $linespc}] $y1
-		    notecrossings $p $j $i [expr {$j + 1}]
-		} elseif {$xj > $xi + $linespc} {
-		    lappend coords [expr {$xj - $linespc}] $y1
-		    notecrossings $p $i $j [expr {$j - 1}]
-		}
-		if {[lsearch -exact $dupparents $p] >= 0} {
-		    # draw a double-width line to indicate the doubled parent
-		    lappend coords $xj $y2
-		    lappend sidelines($p) [list $coords 2 none]
-		    if {![info exists mainline($p)]} {
-			set mainline($p) [list $xj $y2]
-			set mainlinearrow($p) none
-		    }
-		} else {
-		    # normal case, no parent duplicated
-		    set yb $y2
-		    set dx [expr {abs($xi - $xj)}]
-		    if {0 && $dx < $linespc} {
-			set yb [expr {$y1 + $dx}]
-		    }
-		    if {![info exists mainline($p)]} {
-			if {$xi != $xj} {
-			    lappend coords $xj $yb
-			}
-			set mainline($p) $coords
-			set mainlinearrow($p) none
-		    } else {
-			lappend coords $xj $yb
-			if {$yb < $y2} {
-			    lappend coords $xj $y2
-			}
-			lappend sidelines($p) [list $coords 1 none]
-		    }
-		}
-	    }
-	} else {
-	    set j $i
-	    if {[lindex $displist $i] != $id} {
-		set j [lsearch -exact $displist $id]
-	    }
-	    if {$j != $i || $xspc1($lineno) != $xspc1($lj)
-		|| ($olddlevel < $i && $i < $dlevel)
-		|| ($dlevel < $i && $i < $olddlevel)} {
-		set xj [xcoord $j $dlevel $lj]
-		lappend mainline($id) $xi $y1 $xj $y2
-	    }
-	}
-    }
-    return $dlevel
-}
-
-# search for x in a list of lists
-proc llsearch {llist x} {
-    set i 0
-    foreach l $llist {
-	if {$l == $x || [lsearch -exact $l $x] >= 0} {
-	    return $i
-	}
-	incr i
-    }
-    return -1
-}
-
-proc drawmore {reading} {
-    global displayorder numcommits ncmupdate nextupdate
-    global stopped nhyperspace parents commitlisted
-    global maxwidth onscreen displist currentparents olddlevel
-
-    set n [llength $displayorder]
-    while {$numcommits < $n} {
-	set id [lindex $displayorder $numcommits]
-	set ctxend [expr {$numcommits + 10}]
-	if {!$reading && $ctxend > $n} {
-	    set ctxend $n
-	}
-	set dlist {}
-	if {$numcommits > 0} {
-	    set dlist [lreplace $displist $olddlevel $olddlevel]
-	    set i $olddlevel
-	    foreach p $currentparents {
-		if {$onscreen($p) == 0} {
-		    set dlist [linsert $dlist $i $p]
-		    incr i
-		}
-	    }
-	}
-	set nohs {}
-	set reins {}
-	set isfat [expr {[llength $dlist] > $maxwidth}]
-	if {$nhyperspace > 0 || $isfat} {
-	    if {$ctxend > $n} break
-	    # work out what to bring back and
-	    # what we want to don't want to send into hyperspace
-	    set room 1
-	    for {set k $numcommits} {$k < $ctxend} {incr k} {
-		set x [lindex $displayorder $k]
-		set i [llsearch $dlist $x]
-		if {$i < 0} {
-		    set i [llength $dlist]
-		    lappend dlist $x
-		}
-		if {[lsearch -exact $nohs $x] < 0} {
-		    lappend nohs $x
-		}
-		if {$reins eq {} && $onscreen($x) < 0 && $room} {
-		    set reins [list $x $i]
-		}
-		set newp {}
-		if {[info exists commitlisted($x)]} {
-		    set right 0
-		    foreach p $parents($x) {
-			if {[llsearch $dlist $p] < 0} {
-			    lappend newp $p
-			    if {[lsearch -exact $nohs $p] < 0} {
-				lappend nohs $p
-			    }
-			    if {$reins eq {} && $onscreen($p) < 0 && $room} {
-				set reins [list $p [expr {$i + $right}]]
-			    }
-			}
-			set right 1
-		    }
-		}
-		set l [lindex $dlist $i]
-		if {[llength $l] == 1} {
-		    set l $newp
-		} else {
-		    set j [lsearch -exact $l $x]
-		    set l [concat [lreplace $l $j $j] $newp]
-		}
-		set dlist [lreplace $dlist $i $i $l]
-		if {$room && $isfat && [llength $newp] <= 1} {
-		    set room 0
-		}
-	    }
-	}
-
-	set dlevel [drawslants $id $reins $nohs]
-	drawcommitline $dlevel
-	if {[clock clicks -milliseconds] >= $nextupdate
-	    && $numcommits >= $ncmupdate} {
-	    doupdate $reading
-	    if {$stopped} break
-	}
-    }
-}
-
-# level here is an index in todo
-proc updatetodo {level noshortcut} {
-    global ncleft todo nnewparents
-    global commitlisted parents onscreen
-
-    set id [lindex $todo $level]
-    set olds {}
-    if {[info exists commitlisted($id)]} {
-	foreach p $parents($id) {
-	    if {[lsearch -exact $olds $p] < 0} {
-		lappend olds $p
-	    }
-	}
-    }
-    if {!$noshortcut && [llength $olds] == 1} {
-	set p [lindex $olds 0]
-	if {$ncleft($p) == 1 && [lsearch -exact $todo $p] < 0} {
-	    set ncleft($p) 0
-	    set todo [lreplace $todo $level $level $p]
-	    set onscreen($p) 0
-	    set nnewparents($id) 1
-	    return 0
-	}
-    }
-
-    set todo [lreplace $todo $level $level]
-    set i $level
-    set n 0
-    foreach p $olds {
-	incr ncleft($p) -1
-	set k [lsearch -exact $todo $p]
-	if {$k < 0} {
-	    set todo [linsert $todo $i $p]
-	    set onscreen($p) 0
-	    incr i
-	    incr n
-	}
-    }
-    set nnewparents($id) $n
-
-    return 1
-}
-
-proc decidenext {{noread 0}} {
-    global ncleft todo
-    global datemode cdate
-    global commitinfo
-
-    # choose which one to do next time around
-    set todol [llength $todo]
-    set level -1
-    set latest {}
-    for {set k $todol} {[incr k -1] >= 0} {} {
-	set p [lindex $todo $k]
-	if {$ncleft($p) == 0} {
-	    if {$datemode} {
-		if {![info exists commitinfo($p)]} {
-		    if {$noread} {
-			return {}
-		    }
-		    readcommit $p
-		}
-		if {$latest == {} || $cdate($p) > $latest} {
-		    set level $k
-		    set latest $cdate($p)
-		}
-	    } else {
-		set level $k
-		break
-	    }
-	}
-    }
-
-    return $level
-}
-
 proc drawcommit {id reading} {
-    global phase todo nchildren datemode nextupdate revlistorder ncleft
-    global numcommits ncmupdate displayorder todo onscreen parents
-    global commitlisted commitordered
+    global phase todo nchildren nextupdate
+    global displayorder parents
+    global commitrow commitidx lineid
 
     if {$phase != "incrdraw"} {
 	set phase incrdraw
 	set displayorder {}
 	set todo {}
+	set commitidx 0
+	initlayout
 	initgraph
-	catch {unset commitordered}
-    }
-    set commitordered($id) 1
-    if {$nchildren($id) == 0} {
-	lappend todo $id
-	set onscreen($id) 0
-    }
-    if {$revlistorder} {
-	set level [lsearch -exact $todo $id]
-	if {$level < 0} {
-	    error_popup "oops, $id isn't in todo"
-	    return
-	}
-	lappend displayorder $id
-	updatetodo $level 0
-    } else {
-	set level [decidenext 1]
-	if {$level == {} || $level < 0} return
-	while 1 {
-	    set id [lindex $todo $level]
-	    if {![info exists commitordered($id)]} {
-		break
-	    }
-	    lappend displayorder [lindex $todo $level]
-	    if {[updatetodo $level $datemode]} {
-		set level [decidenext 1]
-		if {$level == {} || $level < 0} break
-	    }
-	}
     }
-    drawmore $reading
+    set commitrow($id) $commitidx
+    set lineid($commitidx) $id
+    incr commitidx
+    lappend displayorder $id
 }
 
 proc finishcommits {} {
     global phase oldcommits commits
     global canv mainfont ctext maincursor textcursor
-    global parents displayorder todo
+    global parents todo
 
     if {$phase == "incrdraw" || $phase == "removecommits"} {
 	foreach id $oldcommits {
@@ -1613,61 +1733,22 @@ proc settextcursor {c} {
     set curtextcursor $c
 }
 
-proc drawgraph {} {
-    global nextupdate startmsecs ncmupdate
-    global displayorder onscreen
-
-    if {$displayorder == {}} return
-    set startmsecs [clock clicks -milliseconds]
-    set nextupdate [expr {$startmsecs + 100}]
-    set ncmupdate 1
-    initgraph
-    foreach id $displayorder {
-	set onscreen($id) 0
-    }
-    drawmore 0
-}
-
 proc drawrest {} {
-    global phase stopped redisplaying selectedline
-    global datemode todo displayorder ncleft
-    global numcommits ncmupdate
-    global nextupdate startmsecs revlistorder
+    global phase
+    global numcommits
+    global startmsecs
+    global canvy0 numcommits linespc
+    global rowlaidout commitidx
+
+    set row $rowlaidout
+    layoutrows $rowlaidout $commitidx 1
+    layouttail
+    optimize_rows $row 0 $commitidx
+    showstuff $commitidx
 
-    set level [decidenext]
-    if {$level >= 0} {
-	set phase drawgraph
-	while 1 {
-	    lappend displayorder [lindex $todo $level]
-	    set hard [updatetodo $level $datemode]
-	    if {$hard} {
-		set level [decidenext]
-		if {$level < 0} break
-	    }
-	}
-    }
-    if {$todo != {}} {
-	puts "ERROR: none of the pending commits can be done yet:"
-	foreach p $todo {
-	    puts "  $p ($ncleft($p))"
-	}
-    }
-
-    drawmore 0
     set phase {}
     set drawmsecs [expr {[clock clicks -milliseconds] - $startmsecs}]
     #puts "overall $drawmsecs ms for $numcommits commits"
-    if {$redisplaying} {
-	if {$stopped == 0 && [info exists selectedline]} {
-	    selectline $selectedline 0
-	}
-	if {$stopped == 1} {
-	    set stopped 0
-	    after idle drawgraph
-	} else {
-	    set redisplaying 0
-	}
-    }
 }
 
 proc findmatches {f} {
@@ -1734,10 +1815,13 @@ proc dofind {} {
 	    if {$matches == {}} continue
 	    set doesmatch 1
 	    if {$ty == "Headline"} {
+		drawcmitrow $l
 		markmatches $canv $l $f $linehtag($l) $matches $mainfont
 	    } elseif {$ty == "Author"} {
+		drawcmitrow $l
 		markmatches $canv2 $l $f $linentag($l) $matches $namefont
 	    } elseif {$ty == "Date"} {
+		drawcmitrow $l
 		markmatches $canv3 $l $f $linedtag($l) $matches $mainfont
 	    }
 	}
@@ -1886,7 +1970,7 @@ proc findpatches {} {
 
 proc readfindproc {} {
     global findprocfile finddidsel
-    global idline matchinglines findinsertpos
+    global commitrow matchinglines findinsertpos
 
     set n [gets $findprocfile line]
     if {$n < 0} {
@@ -1903,11 +1987,11 @@ proc readfindproc {} {
 	stopfindproc
 	return
     }
-    if {![info exists idline($id)]} {
+    if {![info exists commitrow($id)]} {
 	puts stderr "spurious id: $id"
 	return
     }
-    set l $idline($id)
+    set l $commitrow($id)
     insertmatch $l $id
 }
 
@@ -2090,6 +2174,7 @@ proc findcont {id} {
 proc markheadline {l id} {
     global canv mainfont linehtag commitinfo
 
+    drawcmitrow $l
     set bbox [$canv bbox $linehtag($l)]
     set t [$canv create rect $bbox -outline {} -tags matches -fill yellow]
     $canv lower $t
@@ -2123,7 +2208,7 @@ proc unmarkmatches {} {
 
 proc selcanvline {w x y} {
     global canv canvy0 ctext linespc
-    global lineid linehtag linentag linedtag rowtextx
+    global rowtextx
     set ymax [lindex [$canv cget -scrollregion] 3]
     if {$ymax == {}} return
     set yfrac [lindex [$canv yview] 0]
@@ -2151,7 +2236,7 @@ proc commit_descriptor {p} {
 # append some text to the ctext widget, and make any SHA1 ID
 # that we know about be a clickable link.
 proc appendwithlinks {text} {
-    global ctext idline linknum
+    global ctext commitrow linknum
 
     set start [$ctext index "end - 1c"]
     $ctext insert end $text
@@ -2161,11 +2246,11 @@ proc appendwithlinks {text} {
 	set s [lindex $l 0]
 	set e [lindex $l 1]
 	set linkid [string range $text $s $e]
-	if {![info exists idline($linkid)]} continue
+	if {![info exists commitrow($linkid)]} continue
 	incr e
 	$ctext tag add link "$start + $s c" "$start + $e c"
 	$ctext tag add link$linknum "$start + $s c" "$start + $e c"
-	$ctext tag bind link$linknum <1> [list selectline $idline($linkid) 1]
+	$ctext tag bind link$linknum <1> [list selectline $commitrow($linkid) 1]
 	incr linknum
     }
     $ctext tag conf link -foreground blue -underline 1
@@ -2178,24 +2263,12 @@ proc selectline {l isnew} {
     global lineid linehtag linentag linedtag
     global canvy0 linespc parents nparents children
     global cflist currentid sha1entry
-    global commentend idtags idline linknum
+    global commentend idtags linknum
     global mergemax
 
     $canv delete hover
     normalline
-    if {![info exists lineid($l)] || ![info exists linehtag($l)]} return
-    $canv delete secsel
-    set t [eval $canv create rect [$canv bbox $linehtag($l)] -outline {{}} \
-	       -tags secsel -fill [$canv cget -selectbackground]]
-    $canv lower $t
-    $canv2 delete secsel
-    set t [eval $canv2 create rect [$canv2 bbox $linentag($l)] -outline {{}} \
-	       -tags secsel -fill [$canv2 cget -selectbackground]]
-    $canv2 lower $t
-    $canv3 delete secsel
-    set t [eval $canv3 create rect [$canv3 bbox $linedtag($l)] -outline {{}} \
-	       -tags secsel -fill [$canv3 cget -selectbackground]]
-    $canv3 lower $t
+    if {![info exists lineid($l)]} return
     set y [expr {$canvy0 + $l * $linespc}]
     set ymax [lindex [$canv cget -scrollregion] 3]
     set ytop [expr {$y - $linespc - 1}]
@@ -2229,8 +2302,23 @@ proc selectline {l isnew} {
 	    set newtop 0
 	}
 	allcanvs yview moveto [expr {$newtop * 1.0 / $ymax}]
+	drawvisible
     }
 
+    if {![info exists linehtag($l)]} return
+    $canv delete secsel
+    set t [eval $canv create rect [$canv bbox $linehtag($l)] -outline {{}} \
+	       -tags secsel -fill [$canv cget -selectbackground]]
+    $canv lower $t
+    $canv2 delete secsel
+    set t [eval $canv2 create rect [$canv2 bbox $linentag($l)] -outline {{}} \
+	       -tags secsel -fill [$canv2 cget -selectbackground]]
+    $canv2 lower $t
+    $canv3 delete secsel
+    set t [eval $canv3 create rect [$canv3 bbox $linedtag($l)] -outline {{}} \
+	       -tags secsel -fill [$canv3 cget -selectbackground]]
+    $canv3 lower $t
+
     if {$isnew} {
 	addtohistory [list selectline $l 0]
     }
@@ -2662,22 +2750,27 @@ proc setcoords {} {
 
     set linespc [font metrics $mainfont -linespace]
     set charspc [font measure $mainfont "m"]
-    set canvy0 [expr {3 + 0.5 * $linespc}]
-    set canvx0 [expr {3 + 0.5 * $linespc}]
+    set canvy0 [expr {int(3 + 0.5 * $linespc)}]
+    set canvx0 [expr {int(3 + 0.5 * $linespc)}]
     set lthickness [expr {int($linespc / 9) + 1}]
     set xspc1(0) $linespc
     set xspc2 $linespc
 }
 
 proc redisplay {} {
-    global stopped redisplaying phase
-    if {$stopped > 1} return
-    if {$phase == "getcommits"} return
-    set redisplaying 1
-    if {$phase == "drawgraph" || $phase == "incrdraw"} {
-	set stopped 1
-    } else {
-	drawgraph
+    global canv canvy0 linespc numcommits
+    global selectedline
+
+    set ymax [lindex [$canv cget -scrollregion] 3]
+    if {$ymax eq {} || $ymax == 0} return
+    set span [$canv yview]
+    clear_display
+    allcanvs conf -scrollregion \
+	[list 0 0 0 [expr {$canvy0 + ($numcommits - 0.5) * $linespc + 2}]]
+    allcanvs yview moveto [lindex $span 0]
+    drawvisible
+    if {[info exists selectedline]} {
+	selectline $selectedline 0
     }
 }
 
@@ -2724,7 +2817,7 @@ proc sha1change {n1 n2 op} {
 }
 
 proc gotocommit {} {
-    global sha1string currentid idline tagids
+    global sha1string currentid commitrow tagids
     global lineid numcommits
 
     if {$sha1string == {}
@@ -2749,8 +2842,8 @@ proc gotocommit {} {
 	    }
 	}
     }
-    if {[info exists idline($id)]} {
-	selectline $idline($id) 1
+    if {[info exists commitrow($id)]} {
+	selectline $commitrow($id) 1
 	return
     }
     if {[regexp {^[0-9a-fA-F]{4,}$} $sha1string]} {
@@ -2905,7 +2998,7 @@ proc lineclick {x y id isnew} {
     normalline
     $canv delete hover
     # draw this line thicker than normal
-    drawlines $id 1 1
+    drawlines $id 1
     set thickerline $id
     if {$isnew} {
 	set ymax [lindex [$canv cget -scrollregion] 3]
@@ -2959,15 +3052,15 @@ proc lineclick {x y id isnew} {
 proc normalline {} {
     global thickerline
     if {[info exists thickerline]} {
-	drawlines $thickerline 0 1
+	drawlines $thickerline 0
 	unset thickerline
     }
 }
 
 proc selbyid {id} {
-    global idline
-    if {[info exists idline($id)]} {
-	selectline $idline($id) 1
+    global commitrow
+    if {[info exists commitrow($id)]} {
+	selectline $commitrow($id) 1
     }
 }
 
@@ -2980,9 +3073,9 @@ proc mstime {} {
 }
 
 proc rowmenu {x y id} {
-    global rowctxmenu idline selectedline rowmenuid
+    global rowctxmenu commitrow selectedline rowmenuid
 
-    if {![info exists selectedline] || $idline($id) eq $selectedline} {
+    if {![info exists selectedline] || $commitrow($id) eq $selectedline} {
 	set state disabled
     } else {
 	set state normal
@@ -3185,13 +3278,14 @@ proc domktag {} {
 }
 
 proc redrawtags {id} {
-    global canv linehtag idline idpos selectedline
+    global canv linehtag commitrow idpos selectedline
 
-    if {![info exists idline($id)]} return
+    if {![info exists commitrow($id)]} return
+    drawcmitrow $commitrow($id)
     $canv delete tag.$id
     set xt [eval drawtags $id $idpos($id)]
-    $canv coords $linehtag($idline($id)) $xt [lindex $idpos($id) 2]
-    if {[info exists selectedline] && $selectedline == $idline($id)} {
+    $canv coords $linehtag($commitrow($id)) $xt [lindex $idpos($id) 2]
+    if {[info exists selectedline] && $selectedline == $commitrow($id)} {
 	selectline $selectedline 0
     }
 }
@@ -3697,6 +3791,9 @@ set maxgraphpct 50
 set maxwidth 16
 set revlistorder 0
 set fastdate 0
+set uparrowlen 7
+set downarrowlen 7
+set mingaplen 30
 
 set colors {green red blue magenta darkgrey brown orange}
 
@@ -3711,7 +3808,6 @@ foreach arg $argv {
     switch -regexp -- $arg {
 	"^$" { }
 	"^-d" { set datemode 1 }
-	"^-r" { set revlistorder 1 }
 	default {
 	    lappend revtreeargs $arg
 	}
@@ -3721,8 +3817,9 @@ foreach arg $argv {
 set history {}
 set historyindex 0
 
+set optim_delay 16
+
 set stopped 0
-set redisplaying 0
 set stuffsaved 0
 set patchnum 0
 setcoords