First version of side-by-side diff.

This constitutes the first prototype of a side-by-side diff. It is not
possible to switch between unidiff and side-by-side diff at all at this
stage.

Signed-off-by: Ragnar Ouchterlony <ragnar@lysator.liu.se>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

5 files changed, 325 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 60d8c58..cb7875e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,171 +1,172 @@
 CGIT_VERSION = v0.8.3
 CGIT_SCRIPT_NAME = cgit.cgi
 CGIT_SCRIPT_PATH = /var/www/htdocs/cgit
 CGIT_DATA_PATH = $(CGIT_SCRIPT_PATH)
 CGIT_CONFIG = /etc/cgitrc
 CACHE_ROOT = /var/cache/cgit
 SHA1_HEADER = <openssl/sha.h>
 GIT_VER = 1.6.4.3
 GIT_URL = http://www.kernel.org/pub/software/scm/git/git-$(GIT_VER).tar.bz2
 INSTALL = install
 
 # Define NO_STRCASESTR if you don't have strcasestr.
 #
 # Define NEEDS_LIBICONV if linking with libc is not enough (eg. Darwin).
 #
 
 #-include config.mak
 
 #
 # Platform specific tweaks
 #
 
 uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
 uname_O := $(shell sh -c 'uname -o 2>/dev/null || echo not')
 uname_R := $(shell sh -c 'uname -r 2>/dev/null || echo not')
 
 ifeq ($(uname_O),Cygwin)
         NO_STRCASESTR = YesPlease
         NEEDS_LIBICONV = YesPlease
 endif
 
 #
 # Let the user override the above settings.
 #
 -include cgit.conf
 
 #
 # Define a way to invoke make in subdirs quietly, shamelessly ripped
 # from git.git
 #
 QUIET_SUBDIR0  = +$(MAKE) -C # space to separate -C and subdir
 QUIET_SUBDIR1  =
 
 ifneq ($(findstring $(MAKEFLAGS),w),w)
 PRINT_DIR = --no-print-directory
 else # "make -w"
 NO_SUBDIR = :
 endif
 
 ifndef V
         QUIET_CC       = @echo '   ' CC $@;
         QUIET_MM       = @echo '   ' MM $@;
         QUIET_SUBDIR0  = +@subdir=
         QUIET_SUBDIR1  = ;$(NO_SUBDIR) echo '   ' SUBDIR $$subdir; \
                          $(MAKE) $(PRINT_DIR) -C $$subdir
 endif
 
 #
 # Define a pattern rule for automatic dependency building
 #
 %.d: %.c
         $(QUIET_MM)$(CC) $(CFLAGS) -MM $< | sed -e 's/\($*\)\.o:/\1.o $@:/g' >$@
 
 #
 # Define a pattern rule for silent object building
 #
 %.o: %.c
         $(QUIET_CC)$(CC) -o $*.o -c $(CFLAGS) $<
 
 
 EXTLIBS = git/libgit.a git/xdiff/lib.a -lz -lcrypto
 OBJECTS =
 OBJECTS += cache.o
 OBJECTS += cgit.o
 OBJECTS += cmd.o
 OBJECTS += configfile.o
 OBJECTS += html.o
 OBJECTS += parsing.o
 OBJECTS += scan-tree.o
 OBJECTS += shared.o
 OBJECTS += ui-atom.o
 OBJECTS += ui-blob.o
 OBJECTS += ui-clone.o
 OBJECTS += ui-commit.o
 OBJECTS += ui-diff.o
 OBJECTS += ui-log.o
 OBJECTS += ui-patch.o
 OBJECTS += ui-plain.o
 OBJECTS += ui-refs.o
 OBJECTS += ui-repolist.o
 OBJECTS += ui-shared.o
 OBJECTS += ui-snapshot.o
+OBJECTS += ui-ssdiff.o
 OBJECTS += ui-stats.o
 OBJECTS += ui-summary.o
 OBJECTS += ui-tag.o
 OBJECTS += ui-tree.o
 
 ifdef NEEDS_LIBICONV
         EXTLIBS += -liconv
 endif
 
 
 .PHONY: all libgit test install uninstall clean force-version get-git \
         doc man-doc html-doc clean-doc
 
 all: cgit
 
 VERSION: force-version
         @./gen-version.sh "$(CGIT_VERSION)"
 -include VERSION
 
 
 CFLAGS += -g -Wall -Igit
 CFLAGS += -DSHA1_HEADER='$(SHA1_HEADER)'
 CFLAGS += -DCGIT_VERSION='"$(CGIT_VERSION)"'
 CFLAGS += -DCGIT_CONFIG='"$(CGIT_CONFIG)"'
 CFLAGS += -DCGIT_SCRIPT_NAME='"$(CGIT_SCRIPT_NAME)"'
 CFLAGS += -DCGIT_CACHE_ROOT='"$(CACHE_ROOT)"'
 
 ifdef NO_ICONV
         CFLAGS += -DNO_ICONV
 endif
 ifdef NO_STRCASESTR
         CFLAGS += -DNO_STRCASESTR
 endif
 
 cgit: $(OBJECTS) libgit
         $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o cgit $(OBJECTS) $(EXTLIBS)
 
 cgit.o: VERSION
 
 -include $(OBJECTS:.o=.d)
 
 libgit:
         $(QUIET_SUBDIR0)git $(QUIET_SUBDIR1) NO_CURL=1 libgit.a
         $(QUIET_SUBDIR0)git $(QUIET_SUBDIR1) NO_CURL=1 xdiff/lib.a
 
 test: all
         $(QUIET_SUBDIR0)tests $(QUIET_SUBDIR1) all
 
 install: all
         $(INSTALL) -m 0755 -d $(DESTDIR)$(CGIT_SCRIPT_PATH)
         $(INSTALL) -m 0755 cgit $(DESTDIR)$(CGIT_SCRIPT_PATH)/$(CGIT_SCRIPT_NAME)
         $(INSTALL) -m 0755 -d $(DESTDIR)$(CGIT_DATA_PATH)
         $(INSTALL) -m 0644 cgit.css $(DESTDIR)$(CGIT_DATA_PATH)/cgit.css
         $(INSTALL) -m 0644 cgit.png $(DESTDIR)$(CGIT_DATA_PATH)/cgit.png
 
 uninstall:
         rm -f $(CGIT_SCRIPT_PATH)/$(CGIT_SCRIPT_NAME)
         rm -f $(CGIT_DATA_PATH)/cgit.css
         rm -f $(CGIT_DATA_PATH)/cgit.png
 
 doc: man-doc html-doc pdf-doc
 
 man-doc: cgitrc.5.txt
         a2x -f manpage cgitrc.5.txt
 
 html-doc: cgitrc.5.txt
         a2x -f xhtml --stylesheet=cgit-doc.css cgitrc.5.txt
 
 pdf-doc: cgitrc.5.txt
         a2x -f pdf cgitrc.5.txt
 
 clean: clean-doc
         rm -f cgit VERSION *.o *.d
 
 clean-doc:
         rm -f cgitrc.5 cgitrc.5.html cgitrc.5.pdf cgitrc.5.xml cgitrc.5.fo
 
 get-git:
         curl $(GIT_URL) | tar -xj && rm -rf git && mv git-$(GIT_VER) git
diff --git a/cgit.css b/cgit.css
index c47ebc9..bf58b8a 100644
--- a/cgit.css
+++ b/cgit.css
@@ -1,603 +1,638 @@
 body, table, form {
         padding: 0em;
         margin: 0em;
 }
 
 body {
         font-family: sans-serif;
         font-size: 10pt;
         color: #333;
         background: white;
         padding: 4px;
 }
 
 a {
         color: blue;
         text-decoration: none;
 }
 
 a:hover {
         text-decoration: underline;
 }
 
 table {
       border-collapse: collapse;
 }
 
 table#header {
         width: 100%;
         margin-bottom: 1em;
 }
 
 table#header td.logo {
         width: 96px;
 }
 
 table#header td.main {
         font-size: 250%;
         padding-left: 10px;
         white-space: nowrap;
 }
 
 table#header td.main a {
         color: #000;
 }
 
 table#header td.form {
         text-align: right;
         vertical-align: bottom;
         padding-right: 1em;
         padding-bottom: 2px;
         white-space: nowrap;
 }
 
 table#header td.form form,
 table#header td.form input,
 table#header td.form select {
         font-size: 90%;
 }
 
 table#header td.sub {
         color: #777;
         border-top: solid 1px #ccc;
         padding-left: 10px;
 }
 
 table.tabs {
         /* border-bottom: solid 2px #ccc; */
         border-collapse: collapse;
         margin-top: 2em;
         margin-bottom: 0px;
         width: 100%;
 }
 
 table.tabs td {
         padding: 0px 1em;
         vertical-align: bottom;
 }
 
 table.tabs td a {
         padding: 2px 0.75em;
         color: #777;
         font-size: 110%;
 }
 
 table.tabs td a.active {
         color: #000;
         background-color: #ccc;
 }
 
 table.tabs td.form {
         text-align: right;
 }
 
 table.tabs td.form form {
         padding-bottom: 2px;
         font-size: 90%;
         white-space: nowrap;
 }
 
 table.tabs td.form input,
 table.tabs td.form select {
         font-size: 90%;
 }
 
 div.content {
         margin: 0px;
         padding: 2em;
         border-top: solid 3px #ccc;
         border-bottom: solid 3px #ccc;
 }
 
 
 table.list {
         width: 100%;
         border: none;
         border-collapse: collapse;
 }
 
 table.list tr {
         background: white;
 }
 
 table.list tr.logheader {
         background: #eee;
 }
 
 table.list tr:hover {
         background: #eee;
 }
 
 table.list tr.nohover:hover {
         background: white;
 }
 
 table.list th {
         font-weight: bold;
         /* color: #888;
         border-top: dashed 1px #888;
         border-bottom: dashed 1px #888;
         */
         padding: 0.1em 0.5em 0.05em 0.5em;
         vertical-align: baseline;
 }
 
 table.list td {
         border: none;
         padding: 0.1em 0.5em 0.1em 0.5em;
 }
 
 table.list td.logsubject {
         font-family: monospace;
         font-weight: bold;
 }
 
 table.list td.logmsg {
         font-family: monospace;
         white-space: pre;
         padding: 1em 0.5em 2em 0.5em;
 }
 
 table.list td a {
         color: black;
 }
 
 table.list td a:hover {
         color: #00f;
 }
 
 img {
         border: none;
 }
 
 input#switch-btn {
         margin: 2px 0px 0px 0px;
 }
 
 td#sidebar input.txt {
         width: 100%;
         margin: 2px 0px 0px 0px;
 }
 
 table#grid {
         margin: 0px;
 }
 
 td#content {
         vertical-align: top;
         padding: 1em 2em 1em 1em;
         border: none;
 }
 
 div#summary {
         vertical-align: top;
         margin-bottom: 1em;
 }
 
 table#downloads {
         float: right;
         border-collapse: collapse;
         border: solid 1px #777;
         margin-left: 0.5em;
         margin-bottom: 0.5em;
 }
 
 table#downloads th {
         background-color: #ccc;
 }
 
 div#blob {
         border: solid 1px black;
 }
 
 div.error {
         color: red;
         font-weight: bold;
         margin: 1em 2em;
 }
 
 a.ls-blob, a.ls-dir, a.ls-mod {
         font-family: monospace;
 }
 
 td.ls-size {
         text-align: right;
         font-family: monospace;
         width: 10em;
 }
 
 td.ls-mode {
         font-family: monospace;
         width: 10em;
 }
 
 table.blob {
         margin-top: 0.5em;
         border-top: solid 1px black;
 }
 
 table.blob td.lines {
         margin: 0; padding: 0 0 0 0.5em;
         vertical-align: top;
         color: black;
 }
 
 table.blob td.linenumbers {
         margin: 0; padding: 0 0.5em 0 0.5em;
         vertical-align: top;
         text-align: right;
         border-right: 1px solid gray;
 }
 
 table.blob pre {
         padding: 0; margin: 0;
 }
 
 table.blob a.no {
         color: gray;
         text-align: right;
         text-decoration: none;
 }
 
 table.blob a.no a:hover {
         color: black;
 }
 
 table.bin-blob {
         margin-top: 0.5em;
         border: solid 1px black;
 }
 
 table.bin-blob th {
         font-family: monospace;
         white-space: pre;
         border: solid 1px #777;
         padding: 0.5em 1em;
 }
 
 table.bin-blob td {
         font-family: monospace;
         white-space: pre;
         border-left: solid 1px #777;
         padding: 0em 1em;
 }
 
 table.nowrap td {
         white-space: nowrap;
 }
 
 table.commit-info {
         border-collapse: collapse;
         margin-top: 1.5em;
 }
 
 table.commit-info th {
         text-align: left;
         font-weight: normal;
         padding: 0.1em 1em 0.1em 0.1em;
         vertical-align: top;
 }
 
 table.commit-info td {
         font-weight: normal;
         padding: 0.1em 1em 0.1em 0.1em;
 }
 
 div.commit-subject {
         font-weight: bold;
         font-size: 125%;
         margin: 1.5em 0em 0.5em 0em;
         padding: 0em;
 }
 
 div.commit-msg {
         white-space: pre;
         font-family: monospace;
 }
 
 div.diffstat-header {
         font-weight: bold;
         padding-top: 1.5em;
 }
 
 table.diffstat {
         border-collapse: collapse;
         border: solid 1px #aaa;
         background-color: #eee;
 }
 
 table.diffstat th {
         font-weight: normal;
         text-align: left;
         text-decoration: underline;
         padding: 0.1em 1em 0.1em 0.1em;
         font-size: 100%;
 }
 
 table.diffstat td {
         padding: 0.2em 0.2em 0.1em 0.1em;
         font-size: 100%;
         border: none;
 }
 
 table.diffstat td.mode {
         white-space: nowrap;
 }
 
 table.diffstat td span.modechange {
         padding-left: 1em;
         color: red;
 }
 
 table.diffstat td.add a {
         color: green;
 }
 
 table.diffstat td.del a {
         color: red;
 }
 
 table.diffstat td.upd a {
         color: blue;
 }
 
 table.diffstat td.graph {
         width: 500px;
         vertical-align: middle;
 }
 
 table.diffstat td.graph table {
         border: none;
 }
 
 table.diffstat td.graph td {
         padding: 0px;
         border: 0px;
         height: 7pt;
 }
 
 table.diffstat td.graph td.add {
         background-color: #5c5;
 }
 
 table.diffstat td.graph td.rem {
         background-color: #c55;
 }
 
 div.diffstat-summary {
         color: #888;
         padding-top: 0.5em;
 }
 
 table.diff {
         width: 100%;
 }
 
 table.diff td {
         font-family: monospace;
         white-space: pre;
 }
 
 table.diff td div.head {
         font-weight: bold;
         margin-top: 1em;
         color: black;
 }
 
 table.diff td div.hunk {
         color: #009;
 }
 
 table.diff td div.add {
         color: green;
 }
 
 table.diff td div.del {
         color: red;
 }
 
 .sha1 {
         font-family: monospace;
         font-size: 90%;
 }
 
 .left {
         text-align: left;
 }
 
 .right {
         text-align: right;
 }
 
 table.list td.reposection {
         font-style: italic;
         color: #888;
 }
 
 a.button {
         font-size: 80%;
         padding: 0em 0.5em;
 }
 
 a.primary {
         font-size: 100%;
 }
 
 a.secondary {
         font-size: 90%;
 }
 
 td.toplevel-repo {
 
 }
 
 table.list td.sublevel-repo {
         padding-left: 1.5em;
 }
 
 div.pager {
         text-align: center;
         margin: 1em 0em 0em 0em;
 }
 
 div.pager a {
         color: #777;
         margin: 0em 0.5em;
 }
 
 span.age-mins {
         font-weight: bold;
         color: #080;
 }
 
 span.age-hours {
         color: #080;
 }
 
 span.age-days {
         color: #040;
 }
 
 span.age-weeks {
         color: #444;
 }
 
 span.age-months {
         color: #888;
 }
 
 span.age-years {
         color: #bbb;
 }
 div.footer {
         margin-top: 0.5em;
         text-align: center;
         font-size: 80%;
         color: #ccc;
 }
 a.branch-deco {
         margin: 0px 0.5em;
         padding: 0px 0.25em;
         background-color: #88ff88;
         border: solid 1px #007700;
 }
 a.tag-deco {
         margin: 0px 0.5em;
         padding: 0px 0.25em;
         background-color: #ffff88;
         border: solid 1px #777700;
 }
 a.remote-deco {
         margin: 0px 0.5em;
         padding: 0px 0.25em;
         background-color: #ccccff;
         border: solid 1px #000077;
 }
 a.deco {
         margin: 0px 0.5em;
         padding: 0px 0.25em;
         background-color: #ff8888;
         border: solid 1px #770000;
 }
 
 div.commit-subject a {
         margin-left: 1em;
         font-size: 75%;
 }
 
 table.stats {
         border: solid 1px black;
         border-collapse: collapse;
 }
 
 table.stats th {
         text-align: left;
         padding: 1px 0.5em;
         background-color: #eee;
         border: solid 1px black;
 }
 
 table.stats td {
         text-align: right;
         padding: 1px 0.5em;
         border: solid 1px black;
 }
 
 table.stats td.total {
         font-weight: bold;
         text-align: left;
 }
 
 table.stats td.sum {
         color: #c00;
         font-weight: bold;
         /*background-color: #eee; */
 }
 
 table.stats td.left {
         text-align: left;
 }
 
 table.vgraph {
         border-collapse: separate;
         border: solid 1px black;
         height: 200px;
 }
 
 table.vgraph th {
         background-color: #eee;
         font-weight: bold;
         border: solid 1px white;
         padding: 1px 0.5em;
 }
 
 table.vgraph td {
         vertical-align: bottom;
         padding: 0px 10px;
 }
 
 table.vgraph div.bar {
         background-color: #eee;
 }
 
 table.hgraph {
         border: solid 1px black;
         width: 800px;
 }
 
 table.hgraph th {
         background-color: #eee;
         font-weight: bold;
         border: solid 1px black;
         padding: 1px 0.5em;
 }
 
 table.hgraph td {
         vertical-align: center;
         padding: 2px 2px;
 }
 
 table.hgraph div.bar {
         background-color: #eee;
         height: 1em;
 }
+
+table.ssdiff td.add {
+        color: black;
+        background: #afa;
+}
+
+table.ssdiff td.add_dark {
+        color: black;
+        background: #9c9;
+}
+
+table.ssdiff td.del {
+        color: black;
+        background: #faa;
+}
+
+table.ssdiff td.del_dark {
+        color: black;
+        background: #c99;
+}
+
+table.ssdiff td.changed {
+        color: black;
+        background: #ffa;
+}
+
+table.ssdiff td.changed_dark {
+        color: black;
+        background: #cc9;
+}
+
+table.ssdiff td.hunk {
+        color: #black;
+        background: #ccf;
+}
diff --git a/ui-diff.c b/ui-diff.c
index 2196745..0c6f8d7 100644
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -1,313 +1,324 @@
 /* ui-diff.c: show diff between two blobs
  *
  * Copyright (C) 2006 Lars Hjemli
  *
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  */
 
 #include "cgit.h"
 #include "html.h"
 #include "ui-shared.h"
+#include "ui-ssdiff.h"
 
 unsigned char old_rev_sha1[20];
 unsigned char new_rev_sha1[20];
 
 static int files, slots;
 static int total_adds, total_rems, max_changes;
 static int lines_added, lines_removed;
 
 static struct fileinfo {
         char status;
         unsigned char old_sha1[20];
         unsigned char new_sha1[20];
         unsigned short old_mode;
         unsigned short new_mode;
         char *old_path;
         char *new_path;
         unsigned int added;
         unsigned int removed;
         unsigned long old_size;
         unsigned long new_size;
         int binary:1;
 } *items;
 
+static int use_ssdiff = 0;
 
 static void print_fileinfo(struct fileinfo *info)
 {
         char *class;
 
         switch (info->status) {
         case DIFF_STATUS_ADDED:
                 class = "add";
                 break;
         case DIFF_STATUS_COPIED:
                 class = "cpy";
                 break;
         case DIFF_STATUS_DELETED:
                 class = "del";
                 break;
         case DIFF_STATUS_MODIFIED:
                 class = "upd";
                 break;
         case DIFF_STATUS_RENAMED:
                 class = "mov";
                 break;
         case DIFF_STATUS_TYPE_CHANGED:
                 class = "typ";
                 break;
         case DIFF_STATUS_UNKNOWN:
                 class = "unk";
                 break;
         case DIFF_STATUS_UNMERGED:
                 class = "stg";
                 break;
         default:
                 die("bug: unhandled diff status %c", info->status);
         }
 
         html("<tr>");
         htmlf("<td class='mode'>");
         if (is_null_sha1(info->new_sha1)) {
                 cgit_print_filemode(info->old_mode);
         } else {
                 cgit_print_filemode(info->new_mode);
         }
 
         if (info->old_mode != info->new_mode &&
             !is_null_sha1(info->old_sha1) &&
             !is_null_sha1(info->new_sha1)) {
                 html("<span class='modechange'>[");
                 cgit_print_filemode(info->old_mode);
                 html("]</span>");
         }
         htmlf("</td><td class='%s'>", class);
         cgit_diff_link(info->new_path, NULL, NULL, ctx.qry.head, ctx.qry.sha1,
                        ctx.qry.sha2, info->new_path);
         if (info->status == DIFF_STATUS_COPIED || info->status == DIFF_STATUS_RENAMED)
                 htmlf(" (%s from %s)",
                       info->status == DIFF_STATUS_COPIED ? "copied" : "renamed",
                       info->old_path);
         html("</td><td class='right'>");
         if (info->binary) {
                 htmlf("bin</td><td class='graph'>%d -> %d bytes",
                       info->old_size, info->new_size);
                 return;
         }
         htmlf("%d", info->added + info->removed);
         html("</td><td class='graph'>");
         htmlf("<table summary='file diffstat' width='%d%%'><tr>", (max_changes > 100 ? 100 : max_changes));
         htmlf("<td class='add' style='width: %.1f%%;'/>",
               info->added * 100.0 / max_changes);
         htmlf("<td class='rem' style='width: %.1f%%;'/>",
               info->removed * 100.0 / max_changes);
         htmlf("<td class='none' style='width: %.1f%%;'/>",
               (max_changes - info->removed - info->added) * 100.0 / max_changes);
         html("</tr></table></td></tr>\n");
 }
 
 static void count_diff_lines(char *line, int len)
 {
         if (line && (len > 0)) {
                 if (line[0] == '+')
                         lines_added++;
                 else if (line[0] == '-')
                         lines_removed++;
         }
 }
 
 static void inspect_filepair(struct diff_filepair *pair)
 {
         int binary = 0;
         unsigned long old_size = 0;
         unsigned long new_size = 0;
         files++;
         lines_added = 0;
         lines_removed = 0;
         cgit_diff_files(pair->one->sha1, pair->two->sha1, &old_size, &new_size,
                         &binary, count_diff_lines);
         if (files >= slots) {
                 if (slots == 0)
                         slots = 4;
                 else
                         slots = slots * 2;
                 items = xrealloc(items, slots * sizeof(struct fileinfo));
         }
         items[files-1].status = pair->status;
         hashcpy(items[files-1].old_sha1, pair->one->sha1);
         hashcpy(items[files-1].new_sha1, pair->two->sha1);
         items[files-1].old_mode = pair->one->mode;
         items[files-1].new_mode = pair->two->mode;
         items[files-1].old_path = xstrdup(pair->one->path);
         items[files-1].new_path = xstrdup(pair->two->path);
         items[files-1].added = lines_added;
         items[files-1].removed = lines_removed;
         items[files-1].old_size = old_size;
         items[files-1].new_size = new_size;
         items[files-1].binary = binary;
         if (lines_added + lines_removed > max_changes)
                 max_changes = lines_added + lines_removed;
         total_adds += lines_added;
         total_rems += lines_removed;
 }
 
 void cgit_print_diffstat(const unsigned char *old_sha1,
                          const unsigned char *new_sha1)
 {
         int i;
 
         html("<div class='diffstat-header'>");
         cgit_diff_link("Diffstat", NULL, NULL, ctx.qry.head, ctx.qry.sha1,
                        ctx.qry.sha2, NULL);
         html("</div>");
         html("<table summary='diffstat' class='diffstat'>");
         max_changes = 0;
         cgit_diff_tree(old_sha1, new_sha1, inspect_filepair, NULL);
         for(i = 0; i<files; i++)
                 print_fileinfo(&items[i]);
         html("</table>");
         html("<div class='diffstat-summary'>");
         htmlf("%d files changed, %d insertions, %d deletions",
               files, total_adds, total_rems);
         html("</div>");
 }
 
 
 /*
  * print a single line returned from xdiff
  */
 static void print_line(char *line, int len)
 {
         char *class = "ctx";
         char c = line[len-1];
 
         if (line[0] == '+')
                 class = "add";
         else if (line[0] == '-')
                 class = "del";
         else if (line[0] == '@')
                 class = "hunk";
 
         htmlf("<div class='%s'>", class);
         line[len-1] = '\0';
         html_txt(line);
         html("</div>");
         line[len-1] = c;
 }
 
 static void header(unsigned char *sha1, char *path1, int mode1,
                    unsigned char *sha2, char *path2, int mode2)
 {
         char *abbrev1, *abbrev2;
         int subproject;
 
         subproject = (S_ISGITLINK(mode1) || S_ISGITLINK(mode2));
         html("<div class='head'>");
         html("diff --git a/");
         html_txt(path1);
         html(" b/");
         html_txt(path2);
 
         if (is_null_sha1(sha1))
                 path1 = "dev/null";
         if (is_null_sha1(sha2))
                 path2 = "dev/null";
 
         if (mode1 == 0)
                 htmlf("<br/>new file mode %.6o", mode2);
 
         if (mode2 == 0)
                 htmlf("<br/>deleted file mode %.6o", mode1);
 
         if (!subproject) {
                 abbrev1 = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
                 abbrev2 = xstrdup(find_unique_abbrev(sha2, DEFAULT_ABBREV));
                 htmlf("<br/>index %s..%s", abbrev1, abbrev2);
                 free(abbrev1);
                 free(abbrev2);
                 if (mode1 != 0 && mode2 != 0) {
                         htmlf(" %.6o", mode1);
                         if (mode2 != mode1)
                                 htmlf("..%.6o", mode2);
                 }
                 html("<br/>--- a/");
                 if (mode1 != 0)
                         cgit_tree_link(path1, NULL, NULL, ctx.qry.head,
                                        sha1_to_hex(old_rev_sha1), path1);
                 else
                         html_txt(path1);
                 html("<br/>+++ b/");
                 if (mode2 != 0)
                         cgit_tree_link(path2, NULL, NULL, ctx.qry.head,
                                        sha1_to_hex(new_rev_sha1), path2);
                 else
                         html_txt(path2);
         }
         html("</div>");
+        if (use_ssdiff)
+                cgit_ssdiff_header();
 }
 
 static void filepair_cb(struct diff_filepair *pair)
 {
         unsigned long old_size = 0;
         unsigned long new_size = 0;
         int binary = 0;
+        linediff_fn print_line_fn = print_line;
 
         header(pair->one->sha1, pair->one->path, pair->one->mode,
                pair->two->sha1, pair->two->path, pair->two->mode);
+        if (use_ssdiff) {
+                cgit_ssdiff_header();
+                print_line_fn = cgit_ssdiff_line_cb;
+        }
         if (S_ISGITLINK(pair->one->mode) || S_ISGITLINK(pair->two->mode)) {
                 if (S_ISGITLINK(pair->one->mode))
                         print_line(fmt("-Subproject %s", sha1_to_hex(pair->one->sha1)), 52);
                 if (S_ISGITLINK(pair->two->mode))
                         print_line(fmt("+Subproject %s", sha1_to_hex(pair->two->sha1)), 52);
                 return;
         }
-        if (cgit_diff_files(pair->one->sha1, pair->two->sha1, &old_size, 
-                            &new_size, &binary, print_line))
+        if (cgit_diff_files(pair->one->sha1, pair->two->sha1, &old_size,
+                            &new_size, &binary, print_line_fn))
                 cgit_print_error("Error running diff");
         if (binary)
                 html("Binary files differ");
+        if (use_ssdiff)
+                cgit_ssdiff_footer();
 }
 
 void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefix)
 {
         enum object_type type;
         unsigned long size;
         struct commit *commit, *commit2;
 
         if (!new_rev)
                 new_rev = ctx.qry.head;
         get_sha1(new_rev, new_rev_sha1);
         type = sha1_object_info(new_rev_sha1, &size);
         if (type == OBJ_BAD) {
                 cgit_print_error(fmt("Bad object name: %s", new_rev));
                 return;
         }
         commit = lookup_commit_reference(new_rev_sha1);
         if (!commit || parse_commit(commit))
                 cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(new_rev_sha1)));
 
         if (old_rev)
                 get_sha1(old_rev, old_rev_sha1);
         else if (commit->parents && commit->parents->item)
                 hashcpy(old_rev_sha1, commit->parents->item->object.sha1);
         else
                 hashclr(old_rev_sha1);
 
         if (!is_null_sha1(old_rev_sha1)) {
                 type = sha1_object_info(old_rev_sha1, &size);
                 if (type == OBJ_BAD) {
                         cgit_print_error(fmt("Bad object name: %s", sha1_to_hex(old_rev_sha1)));
                         return;
                 }
                 commit2 = lookup_commit_reference(old_rev_sha1);
                 if (!commit2 || parse_commit(commit2))
                         cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(old_rev_sha1)));
         }
         cgit_print_diffstat(old_rev_sha1, new_rev_sha1);
 
         html("<table summary='diff' class='diff'>");
         html("<tr><td>");
         cgit_diff_tree(old_rev_sha1, new_rev_sha1, filepair_cb, prefix);
         html("</td></tr>");
         html("</table>");
 }
diff --git a/ui-ssdiff.c b/ui-ssdiff.c
new file mode 100644
index 0000000..3591ab4
--- a/dev/null
+++ b/ui-ssdiff.c
@@ -0,0 +1,264 @@
+#include "cgit.h"
+#include "html.h"
+#include "ui-shared.h"
+
+extern int use_ssdiff;
+
+static int current_old_line, current_new_line;
+
+struct deferred_lines {
+        int line_no;
+        char *line;
+        struct deferred_lines *next;
+};
+
+static struct deferred_lines *deferred_old, *deferred_old_last;
+static struct deferred_lines *deferred_new, *deferred_new_last;
+
+static int line_from_hunk(char *line, char type)
+{
+        char *buf1, *buf2;
+        int len;
+
+        buf1 = strchr(line, type);
+        if (buf1 == NULL)
+                return 0;
+        buf1 += 1;
+        buf2 = strchr(buf1, ',');
+        if (buf2 == NULL)
+                return 0;
+        len = buf2 - buf1;
+        buf2 = xmalloc(len + 1);
+        strncpy(buf2, buf1, len);
+        buf2[len] = '\0';
+        int res = atoi(buf2);
+        free(buf2);
+        return res;
+}
+
+static char *replace_tabs(char *line)
+{
+        char *prev_buf = line;
+        char *cur_buf;
+        int linelen = strlen(line);
+        int n_tabs = 0;
+        int i;
+        char *result;
+        char *spaces = "        ";
+
+        if (linelen == 0) {
+                result = xmalloc(1);
+                result[0] = '\0';
+                return result;
+        }
+
+        for (i = 0; i < linelen; i++)
+                if (line[i] == '\t')
+                        n_tabs += 1;
+        result = xmalloc(linelen + n_tabs * 8 + 1);
+        result[0] = '\0';
+
+        while (1) {
+                cur_buf = strchr(prev_buf, '\t');
+                if (!cur_buf) {
+                        strcat(result, prev_buf);
+                        break;
+                } else {
+                        strcat(result, " ");
+                        strncat(result, spaces, 8 - (strlen(result) % 8));
+                        strncat(result, prev_buf, cur_buf - prev_buf);
+                }
+                prev_buf = cur_buf + 1;
+        }
+        return result;
+}
+
+static void deferred_old_add(char *line, int line_no)
+{
+        struct deferred_lines *item = xmalloc(sizeof(struct deferred_lines));
+        item->line = xstrdup(line);
+        item->line_no = line_no;
+        item->next = NULL;
+        if (deferred_old) {
+                deferred_old_last->next = item;
+                deferred_old_last = item;
+        } else {
+                deferred_old = deferred_old_last = item;
+        }
+}
+
+static void deferred_new_add(char *line, int line_no)
+{
+        struct deferred_lines *item = xmalloc(sizeof(struct deferred_lines));
+        item->line = xstrdup(line);
+        item->line_no = line_no;
+        item->next = NULL;
+        if (deferred_new) {
+                deferred_new_last->next = item;
+                deferred_new_last = item;
+        } else {
+                deferred_new = deferred_new_last = item;
+        }
+}
+
+static void print_ssdiff_line(char *class, int old_line_no, char *old_line,
+                              int new_line_no, char *new_line)
+{
+        html("<tr>");
+        if (old_line_no > 0)
+                htmlf("<td class='%s'>%d </td><td class='%s'>", class,
+                      old_line_no, class);
+        else
+                htmlf("<td class='%s_dark'>  </td><td class='%s_dark'>", class, class);
+
+        if (old_line) {
+                old_line = replace_tabs(old_line + 1);
+                html_txt(old_line);
+                free(old_line);
+        }
+
+        html("  </td>");
+
+        if (new_line_no > 0)
+                htmlf("<td class='%s'>  %d </td><td class='%s'>", class,
+                      new_line_no, class);
+        else
+                htmlf("<td class='%s_dark'>  </td><td class='%s_dark'>", class, class);
+
+        if (new_line) {
+                new_line = replace_tabs(new_line + 1);
+                html_txt(new_line);
+                free(new_line);
+        }
+
+        html("</td></tr>");
+}
+
+static void print_deferred_old_lines()
+{
+        struct deferred_lines *iter_old, *tmp;
+
+        iter_old = deferred_old;
+        while (iter_old) {
+                print_ssdiff_line("del", iter_old->line_no,
+                                  iter_old->line, -1, NULL);
+                tmp = iter_old->next;
+                free(iter_old);
+                iter_old = tmp;
+        }
+}
+
+static void print_deferred_new_lines()
+{
+        struct deferred_lines *iter_new, *tmp;
+
+        iter_new = deferred_new;
+        while (iter_new) {
+                print_ssdiff_line("add", -1, NULL, iter_new->line_no,
+                                  iter_new->line);
+                tmp = iter_new->next;
+                free(iter_new);
+                iter_new = tmp;
+        }
+}
+
+static void print_deferred_changed_lines()
+{
+        struct deferred_lines *iter_old, *iter_new, *tmp;
+
+        iter_old = deferred_old;
+        iter_new = deferred_new;
+        while (iter_old || iter_new) {
+                if (iter_old && iter_new)
+                        print_ssdiff_line("changed", iter_old->line_no,
+                                          iter_old->line,
+                                          iter_new->line_no, iter_new->line);
+                else if (iter_old)
+                        print_ssdiff_line("changed", iter_old->line_no,
+                                          iter_old->line, -1, NULL);
+                else if (iter_new)
+                        print_ssdiff_line("changed", -1, NULL,
+                                          iter_new->line_no, iter_new->line);
+
+                if (iter_old) {
+                        tmp = iter_old->next;
+                        free(iter_old);
+                        iter_old = tmp;
+                }
+
+                if (iter_new) {
+                        tmp = iter_new->next;
+                        free(iter_new);
+                        iter_new = tmp;
+                }
+        }
+}
+
+void cgit_ssdiff_print_deferred_lines()
+{
+        if (!deferred_old && !deferred_new)
+                return;
+
+        if (deferred_old && !deferred_new)
+                print_deferred_old_lines();
+        else if (!deferred_old && deferred_new)
+                print_deferred_new_lines();
+        else
+                print_deferred_changed_lines();
+
+        deferred_old = deferred_old_last = NULL;
+        deferred_new = deferred_new_last = NULL;
+}
+
+/*
+ * print a single line returned from xdiff
+ */
+void cgit_ssdiff_line_cb(char *line, int len)
+{
+        char c = line[len - 1];
+
+        line[len - 1] = '\0';
+
+        if (line[0] == '@') {
+                current_old_line = line_from_hunk(line, '-');
+                current_new_line = line_from_hunk(line, '+');
+        }
+
+        if (line[0] == ' ') {
+                if (deferred_old || deferred_new)
+                        cgit_ssdiff_print_deferred_lines();
+                print_ssdiff_line("ctx", current_old_line, line,
+                                  current_new_line, line);
+                current_old_line += 1;
+                current_new_line += 1;
+        } else if (line[0] == '+') {
+                deferred_new_add(line, current_new_line);
+                current_new_line += 1;
+        } else if (line[0] == '-') {
+                deferred_old_add(line, current_old_line);
+                current_old_line += 1;
+        } else if (line[0] == '@') {
+                html("<tr><td colspan='4' class='hunk'>");
+                html_txt(line);
+                html("</td></tr>");
+        } else {
+                html("<tr><td colspan='4' class='ctx'>");
+                html_txt(line);
+                html("</td></tr>");
+        }
+        line[len - 1] = c;
+}
+
+void cgit_ssdiff_header()
+{
+        current_old_line = 0;
+        current_new_line = 0;
+        html("<table class='ssdiff'>");
+}
+
+void cgit_ssdiff_footer()
+{
+        if (deferred_old || deferred_new)
+                cgit_ssdiff_print_deferred_lines();
+        html("</table>");
+}
diff --git a/ui-ssdiff.h b/ui-ssdiff.h
new file mode 100644
index 0000000..a0b1efe
--- a/dev/null
+++ b/ui-ssdiff.h
@@ -0,0 +1,12 @@
+#ifndef UI_SSDIFF_H
+#define UI_SSDIFF_H
+
+extern void cgit_ssdiff_print_deferred_lines();
+
+extern void cgit_ssdiff_line_cb(char *line, int len);
+
+extern void cgit_ssdiff_header();
+
+extern void cgit_ssdiff_footer();
+
+#endif /* UI_SSDIFF_H */