git-gui: Jump to original line in blame viewer

When the user clicks on a commit link within one of the columns
in the blame viewer we now jump them not just to that commit/file
pair but also to the line of the original file.  This saves the
user a lot of time, as they don't need to search through the new
file data for the chunk they were previously looking at.

We also restore the prior view when the user clicks the back button
to return to a pior commit/file pair that they were looking at.

Turned out this was quite tricky to get working in Tk.  Every time
I tried to jump the text widgets to the correct locations by way
of the "yview moveto" or "see" subcommands Tk performed the change
until the current event finished dispatching, and then reset the
views back to 0, making the change never take place.  Forcing Tk
to run the pending events before we jump the UI resolves the issue.

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

1 files changed, 42 insertions, 13 deletions

diff --git a/lib/blame.tcl b/lib/blame.tcl
index f0dafff18e..44c2bb9d84 100644
--- a/lib/blame.tcl
+++ b/lib/blame.tcl
@@ -310,10 +310,10 @@ constructor new {i_commit i_path} {
 	bind $w.file_pane <Configure> \
 	"if {{$w.file_pane} eq {%W}} {[cb _resize %h]}"
 
-	_load $this
+	_load $this {}
 }
 
-method _load {} {
+method _load {jump} {
 	_hide_tooltip $this
 
 	if {$total_lines != 0 || $current_fd ne {}} {
@@ -331,6 +331,10 @@ method _load {} {
 			$i conf -state disabled
 		}
 
+		$w_cviewer conf -state normal
+		$w_cviewer delete 0.0 end
+		$w_cviewer conf -state disabled
+
 		set highlight_line -1
 		set highlight_column {}
 		set highlight_commit {}
@@ -356,7 +360,6 @@ method _load {} {
 	} else {
 		$w_back conf -state normal
 	}
-	lappend history [list $commit $path]
 
 	# Index 0 is always empty.  There is never line 0 as
 	# we use only 1 based lines, as that matches both with
@@ -374,7 +377,7 @@ method _load {} {
 		set fd [open "| $cmd" r]
 	}
 	fconfigure $fd -blocking 0 -translation lf -encoding binary
-	fileevent $fd readable [cb _read_file $fd]
+	fileevent $fd readable [cb _read_file $fd $jump]
 	set current_fd $fd
 }
 
@@ -386,7 +389,7 @@ method _history_menu {} {
 		menu $m -tearoff 0
 	}
 
-	for {set i [expr {[llength $history] - 2}]
+	for {set i [expr {[llength $history] - 1}]
 		} {$i >= 0} {incr i -1} {
 		set e [lindex $history $i]
 		set c [lindex $e 0]
@@ -406,21 +409,22 @@ method _history_menu {} {
 			}
 		}
 
-		$m add command -label $t -command [cb _goback $i $c $f]
+		$m add command -label $t -command [cb _goback $i]
 	}
 	set X [winfo rootx $w_back]
 	set Y [expr {[winfo rooty $w_back] + [winfo height $w_back]}]
 	tk_popup $m $X $Y
 }
 
-method _goback {i c f} {
+method _goback {i} {
+	set dat [lindex $history $i]
 	set history [lrange $history 0 [expr {$i - 1}]]
-	set commit $c
-	set path $f
-	_load $this
+	set commit [lindex $dat 0]
+	set path [lindex $dat 1]
+	_load $this [lrange $dat 2 5]
 }
 
-method _read_file {fd} {
+method _read_file {fd jump} {
 	if {$fd ne $current_fd} {
 		catch {close $fd}
 		return
@@ -450,6 +454,22 @@ method _read_file {fd} {
 
 	if {[eof $fd]} {
 		close $fd
+
+		# If we don't force Tk to update the widgets *right now*
+		# none of our jump commands will cause a change in the UI.
+		#
+		update
+
+		if {[llength $jump] == 1} {
+			set highlight_line [lindex $jump 0]
+			$w_file see "$highlight_line.0"
+		} elseif {[llength $jump] == 4} {
+			set highlight_column [lindex $jump 0]
+			set highlight_line [lindex $jump 1]
+			$w_file xview moveto [lindex $jump 2]
+			$w_file yview moveto [lindex $jump 3]
+		}
+
 		_exec_blame $this $w_asim @asim_data [list] {}
 	}
 } ifdeleted { catch {close $fd} }
@@ -502,6 +522,7 @@ method _read_blame {fd cur_w cur_d cur_s} {
 			set file [string range $line 9 end]
 			set n    $r_line_count
 			set lno  $r_final_line
+			set oln  $r_orig_line
 			set cmit $r_commit
 
 			if {[regexp {^0{40}$} $cmit]} {
@@ -550,7 +571,7 @@ method _read_blame {fd cur_w cur_d cur_s} {
 						$i tag remove g$g $lno.0 $lno_e
 					}
 				}
-				lset line_data $lno [list $cmit $file]
+				lset line_data $lno [list $cmit $file $oln]
 
 				$cur_w delete $lno.0 "$lno.0 lineend"
 				if {$lno == $first_lno} {
@@ -578,6 +599,7 @@ method _read_blame {fd cur_w cur_d cur_s} {
 
 				incr n -1
 				incr lno
+				incr oln
 				incr blame_lines
 			}
 
@@ -641,9 +663,16 @@ method _load_commit {cur_w cur_d pos} {
 	set lno [lindex [split [$cur_w index $pos] .] 0]
 	set dat [lindex $line_data $lno]
 	if {$dat ne {}} {
+		lappend history [list \
+			$commit $path \
+			$highlight_column \
+			$highlight_line \
+			[lindex [$w_file xview] 0] \
+			[lindex [$w_file yview] 0] \
+			]
 		set commit [lindex $dat 0]
 		set path   [lindex $dat 1]
-		_load $this
+		_load $this [list [lindex $dat 2]]
 	}
 }