Color CPU graph based on usage; green idle, red full utilization.

src/widgets/cpu.rs

@@ -2,8 +2,7 @@ use std::collections::vec_deque::VecDeque;
 use std::fs::File;
 use std::io::{BufRead, BufReader, Result};
 
-use i3monkit::Block;
+use i3monkit::{Block, ColorRGB, Widget, WidgetUpdate};
-use i3monkit::{Widget, WidgetUpdate};
 
 use crate::spark;
 
@@ -23,6 +22,19 @@ pub struct CpuWidget {
     history: VecDeque<f32>,
 }
 
+fn color_lerp(c1: ColorRGB, c2: ColorRGB, alpha: f32) -> ColorRGB {
+    // TODO(wathiede): actual lerp.
+    ColorRGB(
+        (c1.0 as f32 * (1. - alpha) + c2.0 as f32 * alpha) as u8,
+        (c1.1 as f32 * (1. - alpha) + c2.1 as f32 * alpha) as u8,
+        (c1.2 as f32 * (1. - alpha) + c2.2 as f32 * alpha) as u8,
+    )
+}
+
+fn color_to_string(c: ColorRGB) -> String {
+    format!("#{:02x}{:02x}{:02x}", c.0, c.1, c.2)
+}
+
 impl CpuWidget {
     fn read_status(id: u32) -> Result<(u64, u64, u64, u64)> {
         let name = format!("cpu{}", id);
@@ -87,7 +99,21 @@ impl CpuWidget {
                 min: Some(0.),
                 max: Some(1.),
             };
-            Some(g.render(&self.history.iter().cloned().collect::<Vec<f32>>()))
+            let sg = g.render(&self.history.iter().cloned().collect::<Vec<f32>>());
+            let colored_sg = self
+                .history
+                .iter()
+                .zip(sg.chars())
+                .map(|(v, g)| {
+                    let c = color_lerp(ColorRGB::green(), ColorRGB::red(), *v);
+                    format!(
+                        r##"<span foreground="{}">{}</span>"##,
+                        color_to_string(c),
+                        g
+                    )
+                })
+                .collect();
+            Some(colored_sg)
         } else {
             Some("N/A".to_string())
         }
@@ -138,7 +164,7 @@ impl Widget for CpuWidget {
                 let mut data = Block::new();
 
                 data.use_pango();
-                data.append_full_text(&format!("{}: {}", self.id + 1, history));
+                data.append_full_text(&history);
 
                 return Some(WidgetUpdate {
                     refresh_interval: std::time::Duration::new(1, 0),