[PATCH] gitk: let you easily specify lines of context in diff view

[Steffen Prohaska <prohaska@zib.de>]

More lines of context sometimes help to better understand a diff.
This patch introduces a text field above the box displaying the
blobdiffs. You can type in the number of lines of context that
you wish to view.

Minor improvements are needed:
   * The value you type in is only used on the next update.
   * lines of context is initially always 3.

Signed-off-by: Steffen Prohaska <prohaska@zib.de>
---
 gitk |   25 +++++++++++++++++++++++--
 1 files changed, 23 insertions(+), 2 deletions(-)

The patch may need some polishing. I know some tcl but this is the 
first time I tried tk:
   * I initialized diffcontext globally, ok?
   * I don't know how to update the view after entering a new value. 
  
    Steffen

diff --git a/gitk b/gitk
index 39e452a..4e9acff 100755
--- a/gitk
+++ b/gitk
@@ -500,6 +500,7 @@ proc makewindow {} {
     global textfont mainfont uifont tabstop
     global findtype findtypemenu findloc findstring fstring geometry
     global entries sha1entry sha1string sha1but
+    global diffcontextstring
     global maincursor textcursor curtextcursor
     global rowctxmenu fakerowmenu mergemax wrapcomment
     global highlight_files gdttype
@@ -714,7 +715,12 @@ proc makewindow {} {
 	-command changediffdisp -variable diffelide -value {0 1}
     radiobutton .bleft.mid.new -text "New version" \
 	-command changediffdisp -variable diffelide -value {1 0}
-    pack .bleft.mid.diff .bleft.mid.old .bleft.mid.new -side left
+    label .bleft.mid.labeldiffcontext -text "      Lines of context: " \
+    -font $uifont
+    entry .bleft.mid.diffcontext -width 5 -font $textfont -textvariable diffcontextstring
+    trace add variable diffcontextstring write diffcontextchange
+    lappend entries .bleft.mid.diffcontext
+    pack .bleft.mid.diff .bleft.mid.old .bleft.mid.new .bleft.mid.labeldiffcontext .bleft.mid.diffcontext -side left
     set ctext .bleft.ctext
     text $ctext -background $bgcolor -foreground $fgcolor \
 	-tabs "[expr {$tabstop * $charspc}]" \
@@ -4872,12 +4878,25 @@ proc gettreediffline {gdtf ids} {
     return 0
 }
 
+proc diffcontextchange {n1 n2 op} {
+    global diffcontextstring diffcontext
+
+    if {[string is integer $diffcontextstring]} {
+        if {$diffcontextstring > 0} {
+            set diffcontext $diffcontextstring
+# TODO: need to trigger update of diff display
+# tried dodiffindex but that corrupted the history view
+        }
+    }
+}
+
 proc getblobdiffs {ids} {
     global diffopts blobdifffd diffids env
     global diffinhdr treediffs
+    global diffcontext
 
     set env(GIT_DIFF_OPTS) $diffopts
-    if {[catch {set bdf [open [diffcmd $ids {-p -C}] r]} err]} {
+    if {[catch {set bdf [open [diffcmd $ids "-p -C -U$diffcontext"] r]} err]} {
 	puts "error getting diffs: $err"
 	return
     }
@@ -7537,6 +7556,8 @@ set markingmatches 0
 
 set optim_delay 16
 
+set diffcontext 3 
+
 set nextviewnum 1
 set curview 0
 set selectedview 0
-- 
1.5.3.rc3.20.g06b4