git-gui: Support keyboard traversal in browser.

Users want to navigate the file list shown in our branch browser
windows using the keyboard.  So we now support basic traversal
with the arrow keys:

  Up/Down:  Move the "selection bar" to focus on a different name.

  Return:   Move into the subtree, or open the annotated file.
  M1-Right: Ditto.

  M1-Up:    Move to the parent tree.
  M1-Left:  Ditto.

Probably the only feature missing from this is to key a leading part
of the file name and jump directly to that file (or subtree).

This change did require a bit of refactoring, to pull the navigation
logic out of the mouse click procedure and into more generic routines
which can also be used in bindings.

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

git-gui.sh

@@ -2957,7 +2957,7 @@ proc reset_hard_wait {fd} {
 set next_browser_id 0
 
 proc new_browser {commit} {
-	global next_browser_id cursor_ptr
+	global next_browser_id cursor_ptr M1B
 	global browser_commit browser_status browser_stack browser_path browser_busy
 
 	set w .browser[incr next_browser_id]
@@ -3007,6 +3007,16 @@ proc new_browser {commit} {
 
 	bind $w_list <Button-1>        "browser_click 0 $w_list @%x,%y;break"
 	bind $w_list <Double-Button-1> "browser_click 1 $w_list @%x,%y;break"
+	bind $w_list <$M1B-Up>         "browser_parent $w_list;break"
+	bind $w_list <$M1B-Left>       "browser_parent $w_list;break"
+	bind $w_list <Up>              "browser_move -1 $w_list;break"
+	bind $w_list <Down>            "browser_move 1 $w_list;break"
+	bind $w_list <$M1B-Right>      "browser_enter $w_list;break"
+	bind $w_list <Return>          "browser_enter $w_list;break"
+	bind $w_list <Prior>           "browser_page -1 $w_list;break"
+	bind $w_list <Next>            "browser_page 1 $w_list;break"
+	bind $w_list <Left>            break
+	bind $w_list <Right>           break
 
 	bind $w <Visibility> "focus $w"
 	bind $w <Destroy> "
@@ -3022,22 +3032,42 @@ proc new_browser {commit} {
 	ls_tree $w_list $browser_commit($w_list) {}
 }
 
-proc browser_click {was_double_click w pos} {
-	global browser_files browser_status browser_path
-	global browser_commit browser_stack browser_busy
+proc browser_move {dir w} {
+	global browser_files browser_busy
 
 	if {$browser_busy($w)} return
-	set lno [lindex [split [$w index $pos] .] 0]
-	set info [lindex $browser_files($w) [expr {$lno - 1}]]
+	set lno [lindex [split [$w index in_sel.first] .] 0]
+	incr lno $dir
+	if {[lindex $browser_files($w) [expr {$lno - 1}]] ne {}} {
+		$w tag remove in_sel 0.0 end
+		$w tag add in_sel $lno.0 [expr {$lno + 1}].0
+		$w see $lno.0
+	}
+}
 
-	$w conf -state normal
-	$w tag remove sel 0.0 end
+proc browser_page {dir w} {
+	global browser_files browser_busy
+
+	if {$browser_busy($w)} return
+	$w yview scroll $dir pages
+	set lno [expr {int(
+		  [lindex [$w yview] 0]
+		* [llength $browser_files($w)]
+		+ 1)}]
+	if {[lindex $browser_files($w) [expr {$lno - 1}]] ne {}} {
 		$w tag remove in_sel 0.0 end
-	if {$info ne {}} {
 		$w tag add in_sel $lno.0 [expr {$lno + 1}].0
-		if {$was_double_click} {
-			switch -- [lindex $info 0] {
-			parent {
+		$w see $lno.0
+	}
+}
+
+proc browser_parent {w} {
+	global browser_files browser_status browser_path
+	global browser_stack browser_busy
+
+	if {$browser_busy($w)} return
+	set info [lindex $browser_files($w) 0]
+	if {[lindex $info 0] eq {parent}} {
 		set parent [lindex $browser_stack($w) end-1]
 		set browser_stack($w) [lrange $browser_stack($w) 0 end-2]
 		if {$browser_stack($w) eq {}} {
@@ -3048,6 +3078,20 @@ proc browser_click {was_double_click w pos} {
 		set browser_status($w) "Loading $browser_path($w)..."
 		ls_tree $w [lindex $parent 0] [lindex $parent 1]
 	}
+}
+
+proc browser_enter {w} {
+	global browser_files browser_status browser_path
+	global browser_commit browser_stack browser_busy
+
+	if {$browser_busy($w)} return
+	set lno [lindex [split [$w index in_sel.first] .] 0]
+	set info [lindex $browser_files($w) [expr {$lno - 1}]]
+	if {$info ne {}} {
+		switch -- [lindex $info 0] {
+		parent {
+			browser_parent $w
+		}
 		tree {
 			set name [lindex $info 2]
 			set escn [escape_path $name]
@@ -3066,8 +3110,22 @@ proc browser_click {was_double_click w pos} {
 		}
 		}
 	}
+}
+
+proc browser_click {was_double_click w pos} {
+	global browser_files browser_busy
+
+	if {$browser_busy($w)} return
+	set lno [lindex [split [$w index $pos] .] 0]
+	focus $w
+
+	if {[lindex $browser_files($w) [expr {$lno - 1}]] ne {}} {
+		$w tag remove in_sel 0.0 end
+		$w tag add in_sel $lno.0 [expr {$lno + 1}].0
+		if {$was_double_click} {
+			browser_enter $w
+		}
 	}
-	$w conf -state disabled
 }
 
 proc ls_tree {w tree_id name} {
@@ -3079,7 +3137,6 @@ proc ls_tree {w tree_id name} {
 
 	$w conf -state normal
 	$w tag remove in_sel 0.0 end
-	$w tag remove sel 0.0 end
 	$w delete 0.0 end
 	if {$browser_stack($w) ne {}} {
 		$w image create end \
@@ -3147,6 +3204,10 @@ proc read_ls_tree {fd w} {
 		set browser_status($w) Ready.
 		set browser_busy($w) 0
 		array unset browser_buffer $w
+		if {$n > 0} {
+			$w tag add in_sel 1.0 2.0
+			focus -force $w
+		}
 	}
 }