git-gui: Font chooser to handle a large number of font families

Simon Sasburg noticed that on X11 if there are more fonts than can
fit in the height of the screen Tk's native tk_optionMenu does not
offer scroll arrows to the user and it is not possible to review
all choices or to select those that are off-screen.  On Mac OS X
the tk_optionMenu works properly but is awkward to navigate if the
list is long.

This is a rewrite of our font selection by providing a new modal
dialog that the user can launch from the git-gui Options panel.
The dialog offers the user a scrolling list of fonts in a pane.
An example text shows the user what the font looks like at the size
they have selected.  But I have to admit the example pane is less
than ideal.  For example in the case of our diff font we really
should show the user an example diff complete with our native diff
syntax coloring.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Acked-by: NSimon Sasburg <simon.sasburg@gmail.com>

lib/choose_font.tcl

+# git-gui font chooser
+# Copyright (C) 2007 Shawn Pearce
+
+class choose_font {
+
+field w
+field w_family    ; # UI widget of all known family names
+field w_example   ; # Example to showcase the chosen font
+
+field f_family    ; # Currently chosen family name
+field f_size      ; # Currently chosen point size
+
+field v_family    ; # Name of global variable for family
+field v_size      ; # Name of global variable for size
+
+variable all_families [list]  ; # All fonts known to Tk
+
+constructor pick {path title a_family a_size} {
+	variable all_families
+
+	set v_family $a_family
+	set v_size $a_size
+
+	upvar #0 $v_family pv_family
+	upvar #0 $v_size pv_size
+
+	set f_family $pv_family
+	set f_size $pv_size
+
+	make_toplevel top w
+	wm title $top "[appname] ([reponame]): $title"
+	wm geometry $top "+[winfo rootx $path]+[winfo rooty $path]"
+
+	label $w.header -text $title -font font_uibold
+	pack $w.header -side top -fill x
+
+	frame $w.buttons
+	button $w.buttons.select \
+		-text [mc Select] \
+		-default active \
+		-command [cb _select]
+	button $w.buttons.cancel \
+		-text [mc Cancel] \
+		-command [list destroy $w]
+	pack $w.buttons.select -side right
+	pack $w.buttons.cancel -side right -padx 5
+	pack $w.buttons -side bottom -fill x -pady 10 -padx 10
+
+	frame $w.inner
+
+	frame $w.inner.family
+	label $w.inner.family.l \
+		-text [mc "Font Family"] \
+		-anchor w
+	set w_family $w.inner.family.v
+	text $w_family \
+		-background white \
+		-borderwidth 1 \
+		-relief sunken \
+		-cursor $::cursor_ptr \
+		-wrap none \
+		-width 30 \
+		-height 10 \
+		-yscrollcommand [list $w.inner.family.sby set]
+	scrollbar $w.inner.family.sby -command [list $w_family yview]
+	pack $w.inner.family.l -side top -fill x
+	pack $w.inner.family.sby -side right -fill y
+	pack $w_family -fill both -expand 1
+
+	frame $w.inner.size
+	label $w.inner.size.l \
+		-text [mc "Font Size"] \
+		-anchor w
+	spinbox $w.inner.size.v \
+		-textvariable @f_size \
+		-from 2 -to 80 -increment 1 \
+		-width 3
+	bind $w.inner.size.v <FocusIn> {%W selection range 0 end}
+	pack $w.inner.size.l -fill x -side top
+	pack $w.inner.size.v -fill x -padx 2
+
+	grid configure $w.inner.family $w.inner.size -sticky nsew
+	grid rowconfigure $w.inner 0 -weight 1
+	grid columnconfigure $w.inner 0 -weight 1
+	pack $w.inner -fill both -expand 1 -padx 5 -pady 5
+
+	frame $w.example
+	label $w.example.l \
+		-text [mc "Font Example"] \
+		-anchor w
+	set w_example $w.example.t
+	text $w_example \
+		-background white \
+		-borderwidth 1 \
+		-relief sunken \
+		-height 3 \
+		-width 40
+	$w_example tag conf example -justify center
+	$w_example insert end [mc "This is example text.\nIf you like this text, it can be your font."] example
+	$w_example conf -state disabled
+	pack $w.example.l -fill x
+	pack $w_example -fill x
+	pack $w.example -fill x -padx 5
+
+	if {$all_families eq {}} {
+		set all_families [lsort [font families]]
+	}
+
+	$w_family tag conf pick
+	$w_family tag bind pick <Button-1> [cb _pick_family %x %y]\;break
+	$w_family tag conf cpck -background lightgray
+	foreach f $all_families {
+		set sel [list pick]
+		if {$f eq $f_family} {
+			lappend sel cpck
+		}
+		$w_family insert end "$f\n" $sel
+	}
+	$w_family conf -state disabled
+	_update $this
+
+	trace add variable @f_size write [cb _update]
+	bind $w <Key-Escape> [list destroy $w]
+	bind $w <Key-Return> [cb _select]\;break
+	bind $w <Visibility> "
+		grab $w
+		focus $w
+	"
+	tkwait window $w
+}
+
+method _select {} {
+	upvar #0 $v_family pv_family
+	upvar #0 $v_size pv_size
+
+	set pv_family $f_family
+	set pv_size $f_size
+
+	destroy $w
+}
+
+method _pick_family {x y} {
+	variable all_families
+
+	set i [lindex [split [$w_family index @$x,$y] .] 0]
+	set n [lindex $all_families [expr {$i - 1}]]
+	if {$n ne {}} {
+		$w_family tag remove cpck 0.0 end
+		$w_family tag add cpck $i.0 [expr {$i + 1}].0
+		set f_family $n
+		_update $this
+	}
+}
+
+method _update {args} {
+	variable all_families
+
+	set i [lsearch -exact $all_families $f_family]
+	if {$i < 0} return
+
+	$w_example tag conf example -font [list $f_family $f_size]
+	$w_family see [expr {$i + 1}].0
+}
+
+}

lib/option.tcl

@@ -255,17 +255,23 @@ proc do_options {} {
 
 		frame $w.global.$name
 		label $w.global.$name.l -text "$text:"
-		pack $w.global.$name.l -side left -anchor w -fill x
-		eval tk_optionMenu $w.global.$name.family \
-			global_config_new(gui.$font^^family) \
-			$all_fonts
-		spinbox $w.global.$name.size \
-			-textvariable global_config_new(gui.$font^^size) \
-			-from 2 -to 80 -increment 1 \
-			-width 3
-		bind $w.global.$name.size <FocusIn> {%W selection range 0 end}
-		pack $w.global.$name.size -side right -anchor e
-		pack $w.global.$name.family -side right -anchor e
+		button $w.global.$name.b \
+			-text [mc "Change Font"] \
+			-command [list \
+				choose_font::pick \
+				$w \
+				[mc "Choose %s" $text] \
+				global_config_new(gui.$font^^family) \
+				global_config_new(gui.$font^^size) \
+				]
+		label $w.global.$name.f -textvariable global_config_new(gui.$font^^family)
+		label $w.global.$name.s -textvariable global_config_new(gui.$font^^size)
+		label $w.global.$name.pt -text [mc "pt."]
+		pack $w.global.$name.l -side left -anchor w
+		pack $w.global.$name.b -side right -anchor e
+		pack $w.global.$name.pt -side right -anchor w
+		pack $w.global.$name.s -side right -anchor w
+		pack $w.global.$name.f -side right -anchor w
 		pack $w.global.$name -side top -anchor w -fill x
 	}