git-gui: Avoid console scrollbars unless they are necessary

We shouldn't create scrollbars for the horziontal or vertical sides
unless there is enough content to make it worth drawing these widgets
on screen.  This way users don't loose screen space to objects that
won't help them navigate the display.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/console.tcl

@@ -6,6 +6,7 @@ class console {
 field t_short
 field t_long
 field w
+field w_t
 field console_cr
 field is_toplevel    1; # are we our own window?
 
@@ -36,6 +37,7 @@ method _init {} {
 	}
 
 	set console_cr 1.0
+	set w_t $w.m.t
 
 	frame $w.m
 	label $w.m.l1 \
@@ -43,38 +45,34 @@ method _init {} {
 		-anchor w \
 		-justify left \
 		-font font_uibold
-	text $w.m.t \
+	text $w_t \
 		-background white -borderwidth 1 \
 		-relief sunken \
 		-width 80 -height 10 \
 		-wrap none \
 		-font font_diff \
 		-state disabled \
-		-xscrollcommand [list $w.m.sbx set] \
-		-yscrollcommand [list $w.m.sby set]
+		-xscrollcommand [cb _sb_set $w.m.sbx h] \
+		-yscrollcommand [cb _sb_set $w.m.sby v]
 	label $w.m.s -text [mc "Working... please wait..."] \
 		-anchor w \
 		-justify left \
 		-font font_uibold
-	scrollbar $w.m.sbx -command [list $w.m.t xview] -orient h
-	scrollbar $w.m.sby -command [list $w.m.t yview]
 	pack $w.m.l1 -side top -fill x
 	pack $w.m.s -side bottom -fill x
-	pack $w.m.sbx -side bottom -fill x
-	pack $w.m.sby -side right -fill y
-	pack $w.m.t -side left -fill both -expand 1
+	pack $w_t -side left -fill both -expand 1
 	pack $w.m -side top -fill both -expand 1 -padx 5 -pady 10
 
 	menu $w.ctxm -tearoff 0
 	$w.ctxm add command -label [mc "Copy"] \
-		-command "tk_textCopy $w.m.t"
+		-command "tk_textCopy $w_t"
 	$w.ctxm add command -label [mc "Select All"] \
-		-command "focus $w.m.t;$w.m.t tag add sel 0.0 end"
+		-command "focus $w_t;$w_t tag add sel 0.0 end"
 	$w.ctxm add command -label [mc "Copy All"] \
 		-command "
-			$w.m.t tag add sel 0.0 end
-			tk_textCopy $w.m.t
-			$w.m.t tag remove sel 0.0 end
+			$w_t tag add sel 0.0 end
+			tk_textCopy $w_t
+			$w_t tag remove sel 0.0 end
 		"
 
 	if {$is_toplevel} {
@@ -85,9 +83,9 @@ method _init {} {
 		bind $w <Visibility> [list focus $w]
 	}
 
-	bind_button3 $w.m.t "tk_popup $w.ctxm %X %Y"
-	bind $w.m.t <$M1B-Key-a> "$w.m.t tag add sel 0.0 end;break"
-	bind $w.m.t <$M1B-Key-A> "$w.m.t tag add sel 0.0 end;break"
+	bind_button3 $w_t "tk_popup $w.ctxm %X %Y"
+	bind $w_t <$M1B-Key-a> "$w_t tag add sel 0.0 end;break"
+	bind $w_t <$M1B-Key-A> "$w_t tag add sel 0.0 end;break"
 }
 
 method exec {cmd {after {}}} {
@@ -104,8 +102,8 @@ method exec {cmd {after {}}} {
 method _read {fd after} {
 	set buf [read $fd]
 	if {$buf ne {}} {
-		if {![winfo exists $w.m.t]} {_init $this}
-		$w.m.t conf -state normal
+		if {![winfo exists $w_t]} {_init $this}
+		$w_t conf -state normal
 		set c 0
 		set n [string length $buf]
 		while {$c < $n} {
@@ -115,20 +113,20 @@ method _read {fd after} {
 			if {$lf < 0} {set lf [expr {$n + 1}]}
 
 			if {$lf < $cr} {
-				$w.m.t insert end [string range $buf $c $lf]
-				set console_cr [$w.m.t index {end -1c}]
+				$w_t insert end [string range $buf $c $lf]
+				set console_cr [$w_t index {end -1c}]
 				set c $lf
 				incr c
 			} else {
-				$w.m.t delete $console_cr end
-				$w.m.t insert end "\n"
-				$w.m.t insert end [string range $buf $c $cr]
+				$w_t delete $console_cr end
+				$w_t insert end "\n"
+				$w_t insert end [string range $buf $c $cr]
 				set c $cr
 				incr c
 			}
 		}
-		$w.m.t conf -state disabled
-		$w.m.t see end
+		$w_t conf -state disabled
+		$w_t see end
 	}
 
 	fconfigure $fd -blocking 1
@@ -171,11 +169,11 @@ method chain {cmdlist {ok 1}} {
 }
 
 method insert {txt} {
-	if {![winfo exists $w.m.t]} {_init $this}
-	$w.m.t conf -state normal
-	$w.m.t insert end "$txt\n"
-	set console_cr [$w.m.t index {end -1c}]
-	$w.m.t conf -state disabled
+	if {![winfo exists $w_t]} {_init $this}
+	$w_t conf -state normal
+	$w_t insert end "$txt\n"
+	set console_cr [$w_t index {end -1c}]
+	$w_t conf -state disabled
 }
 
 method done {ok} {
@@ -200,4 +198,24 @@ method done {ok} {
 	delete_this
 }
 
+method _sb_set {sb orient first last} {
+	if {$first == 0 && $last == 1} {
+		if {[winfo exists $sb]} {
+			destroy $sb
+		}
+		return
+	}
+
+	if {![winfo exists $sb]} {
+		if {$orient eq {h}} {
+			scrollbar $sb -orient h -command [list $w_t xview]
+			pack $sb -fill x -side bottom -before $w_t
+		} else {
+			scrollbar $sb -orient v -command [list $w_t yview]
+			pack $sb -fill y -side right -before $w_t
+		}
+	}
+	catch {$sb set $first $last}
+}
+
 }