Add changed byte highlighting to viewer.py

can/viewer.py

@@ -53,11 +53,14 @@ def __init__(self, stdscr, bus, data_structs, testing=False):
         self.bus = bus
         self.data_structs = data_structs
 
-        # Initialise the ID dictionary, start timestamp, scroll and variable for pausing the viewer
+        # Initialise the ID dictionary, Previous values dict, start timestamp,
+        # scroll and variables for pausing the viewer and enabling byte highlighting
         self.ids = {}
         self.start_time = None
         self.scroll = 0
         self.paused = False
+        self.highlight_changed_bytes = False
+        self.previous_values = {}
 
         # Get the window dimensions - used for resizing the window
         self.y, self.x = self.stdscr.getmaxyx()
@@ -70,6 +73,8 @@ def __init__(self, stdscr, bus, data_structs, testing=False):
 
         # Used to color error frames red
         curses.init_pair(1, curses.COLOR_RED, -1)
+        # Used to color changed bytes
+        curses.init_pair(2, curses.COLOR_CYAN, curses.COLOR_BLUE)
 
         if not testing:  # pragma: no cover
             self.run()
@@ -103,6 +108,11 @@ def run(self):
                 self.scroll = 0
                 self.draw_header()
 
+            # Toggle byte change highlighting pressing 'h'
+            elif key == ord("h"):
+                self.highlight_changed_bytes = not self.highlight_changed_bytes
+                self.draw_header()
+
             # Sort by pressing 's'
             elif key == ord("s"):
                 # Sort frames based on the CAN-Bus ID
@@ -241,14 +251,36 @@ def draw_can_bus_message(self, msg, sorting=False):
         )
         self.draw_line(self.ids[key]["row"], 35, arbitration_id_string, color)
         self.draw_line(self.ids[key]["row"], 47, str(msg.dlc), color)
+
+        try:
+            previous_byte_values = self.previous_values[key]
+        except KeyError:  # no row of previous values exists for the current message ID
+            # initialise a row to store the values for comparison next time
+            self.previous_values[key] = dict()
+            previous_byte_values = self.previous_values[key]
         for i, b in enumerate(msg.data):
             col = 52 + i * 3
             if col > self.x - 2:
                 # Data does not fit
                 self.draw_line(self.ids[key]["row"], col - 4, "...", color)
                 break
+            if self.highlight_changed_bytes:
+                try:
+                    if b != previous_byte_values[i]:
+                        # set colour to highlight a changed value
+                        data_color = curses.color_pair(2)
+                    else:
+                        data_color = color
+                except KeyError:
+                    # previous entry for byte didnt exist - default to rest of line colour
+                    data_color = color
+                finally:
+                    # write the new value to the previous values dict for next time
+                    previous_byte_values[i] = b
+            else:
+                data_color = color
             text = "{:02X}".format(b)
-            self.draw_line(self.ids[key]["row"], col, text, color)
+            self.draw_line(self.ids[key]["row"], col, text, data_color)
 
         if self.data_structs:
             try:
@@ -286,7 +318,12 @@ def draw_header(self):
         self.draw_line(0, 35, "ID", curses.A_BOLD)
         self.draw_line(0, 47, "DLC", curses.A_BOLD)
         self.draw_line(0, 52, "Data", curses.A_BOLD)
-        if self.data_structs:  # Only draw if the dictionary is not empty
+
+        # Indicate that byte change highlighting is enabled
+        if self.highlight_changed_bytes:
+            self.draw_line(0, 57, "(changed)", curses.color_pair(2))
+        # Only draw if the dictionary is not empty
+        if self.data_structs:
             self.draw_line(0, 77, "Parsed values", curses.A_BOLD)
 
     def redraw_screen(self):
@@ -353,6 +390,7 @@ def parse_args(args):
         "\n        | ESQ/q   | Exit the viewer         |"
         "\n        | c       | Clear the stored frames |"
         "\n        | s       | Sort the stored frames  |"
+        "\n        | h       | Toggle byte highlights  |"
         "\n        | SPACE   | Pause the viewer        |"
         "\n        | UP/DOWN | Scroll the viewer       |"
         "\n        +---------+-------------------------+",
@@ -460,6 +498,14 @@ def parse_args(args):
         default=2,
     )
 
+    # suppressed as the user doesn't need to change it
+    optional.add_argument(
+        "--app_name",
+        dest="app_name",
+        help=argparse.SUPPRESS,
+        default="python-can-viewer",
+    )
+
     # Print help message when no arguments are given
     if not args:
         parser.print_help(sys.stderr)

doc/scripts.rst

@@ -28,7 +28,21 @@ A screenshot of the application can be seen below:
 .. image:: images/viewer.png
     :width: 100%
 
-The first column is the number of times a frame with the particular ID that has been received, next is the timestamp of the frame relative to the first received message. The third column is the time between the current frame relative to the previous one. Next is the length of the frame, the data and then the decoded data converted according to the ``-d`` argument. The top red row indicates an error frame.
+The first column is the number of times a frame with the particular ID that has been received, next is the timestamp of the frame relative to the first received message. The third column is the time between the current frame relative to the previous one. Next is the length of the frame, the data and then the decoded data converted according to the ``-d`` argument. The top red row indicates an error frame. 
+There are several keyboard shortcuts that can be used with the viewer script, they function as follows:
+
+* ESCAPE - Quit the viewer script
+* q - as ESCAPE
+* c - Clear the stored frames
+* s - Sort the stored frames
+* h - Toggle highlighting of changed bytes in the data field - see the below image
+* SPACE - Pause the viewer
+* UP/DOWN - Scroll the viewer
+
+.. image:: images/viewer_changed_bytes_highlighting.png
+    :width: 50%
+
+A byte in the data field is highlighted blue if the value is different from the last time the message was received.
 
 Command line arguments
 ^^^^^^^^^^^^^^^^^^^^^^