try to send updates rather than the full screen on every frame

this is not a very intelligent method at the moment, but it should
(probably?) be an improvement over the current method. it probably fails
pretty miserably on scrolling though - need to figure out a better idea
for that.

4 files changed, 66 insertions, 13 deletions

diff --git a/termcast_server/index.html b/termcast_server/index.html
index 459d9c1..7e37c06 100644
--- a/termcast_server/index.html
+++ b/termcast_server/index.html
@@ -51,7 +51,7 @@ socket.onmessage = function (e) {
         menudiv.innerHTML = menu;
         menudiv.style.setProperty('display', 'block');
     }
-    else if (type == "update_screen") {
+    else if (type == "redraw_screen") {
         document.querySelector('.menu').style.setProperty('display', 'none');
         var termdiv = document.querySelector('.term');
         term = '<table class="screen">';
@@ -84,6 +84,30 @@ socket.onmessage = function (e) {
         termdiv.innerHTML = term;
         termdiv.style.setProperty('display', 'block');
     }
+    else if (type == "update_screen") {
+        var termtable = document.querySelector('.term tbody');
+        data.updates.forEach(function (update) {
+            var tr = termtable.children[update.row];
+            var td = tr.children[update.col];
+            var contents = update.cell.contents;
+            if (contents == " ") {
+                contents = "&nbsp;";
+            }
+            td.innerHTML = contents;
+            if (update.cell.fgcolor) {
+                td.style.setProperty('color', colors[update.cell.fgcolor]);
+            }
+            else {
+                td.style.removeProperty('color');
+            }
+            if (update.cell.bgcolor) {
+                td.style.setProperty('background-color', colors[update.cell.bgcolor]);
+            }
+            else {
+                td.style.removeProperty('background-color');
+            }
+        })
+    }
     else if (type == "streamer_disconnect") {
         socket.send(JSON.stringify({"type": "request_streamer_list"}));
     }
diff --git a/termcast_server/ssh.py b/termcast_server/ssh.py
index d828fca..360c3f7 100644
--- a/termcast_server/ssh.py
+++ b/termcast_server/ssh.py
@@ -106,7 +106,7 @@ class Connection(object):
         else:
             return self.select_stream()
 
-    def msg_new_data(self, connection_id, prev_buf, data, screen):
+    def msg_new_data(self, connection_id, prev_buf, data, screen, updates):
         if self.watching_id != connection_id:
             return
 
diff --git a/termcast_server/termcast.py b/termcast_server/termcast.py
index 743274b..f99971d 100644
--- a/termcast_server/termcast.py
+++ b/termcast_server/termcast.py
@@ -68,17 +68,36 @@ class Handler(object):
             term.append([])
             for j in range(0, self.cols):
                 cell = self.vt.cell(i, j)
-                contents = cell.contents()
-                if len(contents) == 0:
-                    contents = " "
                 term[i].append({
-                    "contents": contents,
+                    "contents": cell.contents(),
                     "fgcolor": cell.fgcolor().color(),
                     "bgcolor": cell.bgcolor().color(),
                 })
 
         return term
 
+    def get_term_updates(self, screen):
+        changes = []
+        for i in range(0, self.rows):
+            for j in range(0, self.cols):
+                cell = self.vt.cell(i, j)
+                prev_cell = screen[i][j]
+                contents = cell.contents()
+                fgcolor = cell.fgcolor().color()
+                bgcolor = cell.bgcolor().color()
+                if contents != prev_cell["contents"] or fgcolor != prev_cell["fgcolor"] or bgcolor != prev_cell["bgcolor"]:
+                    changes.append({
+                        "row": i,
+                        "col": j,
+                        "cell": {
+                            "contents": contents,
+                            "fgcolor": fgcolor,
+                            "bgcolor": bgcolor,
+                        },
+                    })
+
+        return changes
+
     def total_time(self):
         return self._human_readable_duration(time.time() - self.created_at)
 
@@ -171,13 +190,15 @@ class Connection(object):
                 print('*** recv failed: ' + str(e))
 
             if len(buf) > 0:
+                prev_screen = self.handler.get_term()
                 self.handler.process(buf)
                 self.publisher.notify(
                     "new_data",
                     self.connection_id,
                     self.handler.buf,
                     buf,
-                    self.handler.get_term()
+                    self.handler.get_term(),
+                    self.handler.get_term_updates(prev_screen)
                 )
             else:
                 self.publisher.notify("streamer_disconnect", self.connection_id)
@@ -192,7 +213,8 @@ class Connection(object):
             self.connection_id,
             self.handler.buf,
             b'',
-            self.handler.get_term()
+            self.handler.get_term(),
+            None
         )
         self.client.send(b"msg watcher connected\n")
 
diff --git a/termcast_server/web.py b/termcast_server/web.py
index 8b9f9e3..1c64fd4 100644
--- a/termcast_server/web.py
+++ b/termcast_server/web.py
@@ -34,14 +34,21 @@ class WebSocketHandler(tornado.websocket.WebSocketHandler):
     def on_finish(self):
         self.publisher.unsubscribe(self)
 
-    def msg_new_data(self, connection_id, prev_buf, data, screen):
+    def msg_new_data(self, connection_id, prev_buf, data, screen, updates):
         if self.watching_id != connection_id:
             return
 
-        reply = {
-            "type": "update_screen",
-            "screen": screen,
-        }
+        if updates:
+            reply = {
+                "type": "update_screen",
+                "updates": updates,
+            }
+        else:
+            reply = {
+                "type": "redraw_screen",
+                "screen": screen,
+            }
+
         try:
             self.write_message(json.dumps(reply))
         except: