push empty samples to compensate time lag

this can happen when the script freezes or the device goes to sleep

waybar-collectd/src/main.rs

@@ -27,7 +27,7 @@ fn main() {
             .iter()
             .map(|g| Graph::new(g, &mut proto))
             .collect();
-        let mut runner = Runner::new(graphs, proto);
+        let mut runner = Runner::new(graphs, proto, config.global.period);
 
         loop {
             let r = runner.tick();

waybar-collectd/src/observables.rs

@@ -85,4 +85,8 @@ impl ObservableCollection {
     pub fn sample(&self, proto: &mut Protocol) -> Result<Vec<f32>, ProtocolError> {
         self.observables.iter().map(|o| o.sample(proto)).collect()
     }
+
+    pub fn get_num_observables(&self) -> usize {
+        self.observables.len()
+    }
 }

waybar-collectd/src/runner.rs

@@ -1,6 +1,8 @@
 use core::fmt;
+use std::time::SystemTime;
 
 use draw::{StackedConfig, StackedSeries, StackedSeriesConfig, stacked};
+use imageproc::image::codecs::pnm::SampleEncoding;
 use protocol::Protocol;
 
 use crate::{
@@ -68,17 +70,41 @@ impl fmt::Display for RunnerError {
 pub struct Runner {
     graphs: Vec<Graph>,
     proto: Protocol,
+    last_sample: SystemTime,
+    sampling_period: f32,
 }
 
 impl Runner {
-    pub fn new(graphs: Vec<Graph>, proto: Protocol) -> Runner {
+    pub fn new(graphs: Vec<Graph>, proto: Protocol, sampling_period: f32) -> Runner {
         Runner {
             graphs: graphs,
             proto: proto,
+            last_sample: SystemTime::UNIX_EPOCH,
+            sampling_period: sampling_period,
         }
     }
     pub fn tick(&mut self) -> Result<(), RunnerError> {
+        let now = SystemTime::now();
+        let dt = if self.last_sample == SystemTime::UNIX_EPOCH {
+            self.sampling_period
+        } else {
+            now.duration_since(self.last_sample)
+                .expect("time jumped back")
+                .as_secs_f32()
+        };
+        self.last_sample = now;
+
         for g in &mut self.graphs {
+            // fill in empty samples for missing data
+            if dt >= 2. {
+                let dt_round = dt.round() as u32;
+                for _ in 0..dt_round {
+                    let dummy = vec![0.; g.observable.get_num_observables()];
+                    g.series.push(dummy)
+                }
+            }
+
+            // sample data
             let sample = g
                 .observable
                 .sample(&mut self.proto)