feat: uses sigusr to clear/update display

README.md

@@ -1,14 +1,66 @@
 CLI bard — See all your last notifications in the terminal
 ==========================================================
 
-The CLI bard is a very simple command line application that displays the last
-D-Bus notifications in a single line of the terminal.
+The *CLI bard* is a very simple command line application that displays the last
+notifications received on the D-Bus (the common notification system under Linux).
 
-It is not an interactive application, it just displays a single line, and
-overwrites it when a new notification comes.
+It is not an interactive application, it just displays incoming notifications.
 At any time, as much as possible of the last notifications are displayed.
-The display refreshes when a notification is added at the end of the line.
+The display refreshes when a notification is received.
 
-CLI bard is written in Python and is available under the AGPLv3 license.
+The CLI bard is written in Python and is available under the AGPLv3 license.
+
+
+Install
+=======
+
+The CLI bard relies on your terminal using a font patched with the "Powerline"
+characters. The recommended fonts are the ones from the
+[Nerd font project](https://www.nerdfonts.com/).
+
+
+Usage
+=====
+
+Command arguments
+-----------------
+
+>  usage: clibard.py [-h] [-l {h,v,horizontal,vertical}] [--test NB_ITEMS] [--send NB_ITEMS]
+> options:
+>   -h, --help            show this help message and exit
+>   -l {h,v,horizontal,vertical}, --layout {h,v,horizontal,vertical}
+>                         How to display notifications. `horizontal` = as many of the last notifications that fit on a single line, clear out the old ones. `vertical` = keep
+>                         printing new notifications on new lines.
+
+
+Signaling
+---------
+
+The CLI bard does respond to POSIX "user signals".
+Signals can be issued with the `kill` command, using the `--signal` flag along
+with 10 (SIGUSR1) or 12 (SIGUSR2) as an argument.
+SIGUSR1 will refresh the display, SIGUSR2 will erase any notification in the
+cache and clear the display (if it can).
+
+Note that with the horizontal layout, refreshing the display actually changes
+the display. Erasing the cache will remove any on-screen notification.
+With the vertical layout, this does nothing on the display.
+
+
+Layouts
+=======
+
+The default layout is the horizontal one.
+This will display on a single line, and overwrite it as soon as an update is
+received.
+When refreshing its display in the horizontal layout, the displayed dates will
+be refreshed as well.
+However, it does not show all the cached notifications, but only the few last
+ones that can fit the current width of the terminal.
+
+The vertical layout simply prints a new line as soon as the CLI bard receive
+a notification. The display cannot be cleared nor refreshed.
+Most notably, the dates of notifications will all be "now".
+However, the terminal does display all the received notifications, if you can
+scroll back enough.
 
-To run it, just run the `clibard.py` script in a wide-enough terminal.

src/clibard/clibard.py

@@ -224,6 +224,7 @@ class Broker:
         self.deck = collections.deque()
 
         signal.signal(signal.SIGUSR1, self.sigusr1)
+        signal.signal(signal.SIGUSR2, self.sigusr2)
 
         DBusGMainLoop(set_as_default=True)
 
@@ -259,6 +260,10 @@ class Broker:
 
 
     def sigusr1(self, signum, stack):
+        self.print()
+
+
+    def sigusr2(self, signum, stack):
         self.deck.clear()
         self.print()