gitk: Improve appearance of first child links

The point where the line for a parent joins to the first child
shown is visually different from the lines to the other children,
because the line doesn't branch, but terminates at the child.
Because of this, we now treat the first child a little differently
in the optimizer, and we draw its link in drawlineseg rather
than drawparentlinks.  This improves the appearance of the graph.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

gitk

@@ -1148,6 +1148,15 @@ proc optimize_rows {row col endrow} {
 		set z [lindex $offs $col]
 		set haspad 1
 	    }
+	    if {$z0 eq {} && !$isarrow} {
+		# this line links to its first child on row $row-2
+		set rm2 [expr {$row - 2}]
+		set id [lindex $displayorder $rm2]
+		set xc [lsearch -exact [lindex $rowidlist $rm2] $id]
+		if {$xc >= 0} {
+		    set z0 [expr {$xc - $x0}]
+		}
+	    }
 	    if {$z0 ne {} && $z < 0 && $z0 > 0} {
 		insert_pad $y0 $x0 1
 		set offs [incrange $offs $col 1]
@@ -1155,11 +1164,26 @@ proc optimize_rows {row col endrow} {
 	    }
 	}
 	if {!$haspad} {
+	    set o {}
 	    for {set col [llength $idlist]} {[incr col -1] >= 0} {} {
 		set o [lindex $offs $col]
+		if {$o eq {}} {
+		    # check if this is the link to the first child
+		    set id [lindex $idlist $col]
+		    if {[info exists idrowranges($id)] &&
+			$row == [lindex $idrowranges($id) 0]} {
+			# it is, work out offset to child
+			set y0 [expr {$row - 1}]
+			set id [lindex $displayorder $y0]
+			set x0 [lsearch -exact [lindex $rowidlist $y0] $id]
+			if {$x0 >= 0} {
+			    set o [expr {$x0 - $col}]
+			}
+		    }
+		}
 		if {$o eq {} || $o <= 0} break
 	    }
-	    if {[incr col] < [llength $idlist]} {
+	    if {$o ne {} && [incr col] < [llength $idlist]} {
 		set y1 [expr {$row + 1}]
 		set offs2 [lindex $rowoffsets $y1]
 		set x1 -1
@@ -1203,6 +1227,7 @@ proc linewidth {id} {
 
 proc drawlineseg {id i} {
     global rowoffsets rowidlist idrowranges
+    global displayorder
     global canv colormap
 
     set startrow [lindex $idrowranges($id) [expr {2 * $i}]]
@@ -1230,13 +1255,29 @@ proc drawlineseg {id i} {
 	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 x [xc $row $col]
     set y [yc $row]
     lappend coords $x $y
+    if {$i == 0} {
+	# draw the link to the first child as part of this line
+	incr row -1
+	set child [lindex $displayorder $row]
+	set ccol [lsearch -exact [lindex $rowidlist $row] $child]
+	if {$ccol >= 0} {
+	    set x [xc $row $ccol]
+	    set y [yc $row]
+	    if {$ccol < $col - 1} {
+		lappend coords [xc $row [expr {$col - 1}]] $yc
+	    } elseif {$ccol > $col + 1} {
+		lappend coords [xc $row [expr {$col + 1}]] $yc
+	    }
+	    lappend coords $x $y
+	}
+    }
+    if {[llength $coords] < 4} return
+    set last [expr {[llength $idrowranges($id)] / 2 - 1}]
+    set arrow [expr {2 * ($i > 0) + ($i < $last)}]
+    set arrow [lindex {none first last both} $arrow]
     set t [$canv create line $coords -width [linewidth $id] \
 	       -fill $colormap($id) -tags lines.$id -arrow $arrow]
     $canv lower $t
@@ -1244,7 +1285,7 @@ proc drawlineseg {id i} {
 }
 
 proc drawparentlinks {id row col olds} {
-    global rowidlist canv colormap
+    global rowidlist canv colormap idrowranges
 
     set row2 [expr {$row + 1}]
     set x [xc $row $col]
@@ -1254,6 +1295,12 @@ proc drawparentlinks {id row col olds} {
     # rmx = right-most X coord used
     set rmx 0
     foreach p $olds {
+	if {[info exists idrowranges($p)] &&
+	    $row2 == [lindex $idrowranges($p) 0] &&
+	    $row2 < [lindex $idrowranges($p) 1]} {
+	    # drawlineseg will do this one for us
+	    continue
+	}
 	set i [lsearch -exact $ids $p]
 	if {$i < 0} {
 	    puts "oops, parent $p of $id not in list"