M2: terminal UI (ratatui)

- layout: header, top menu (quicklook, cpu, mem, swap, load), left sidebar,
  process list and alert footer
- decorations/colors, bars, per-plugin render implementations
- hotkeys: quit, help, modes, sorting, cursor, nice, kill, filters, toggles
- TestBackend layout test

crates/glances-core/src/units.rs

@@ -67,6 +67,35 @@ pub fn auto_unit(number: f64, low_precision: bool, min_symbol: &str, none_symbol
     format!("{number:.decimal_precision$}")
 }
 
+/// Render a progress bar the way the Python `Bar` class does.
+pub fn bar_percent(percent: f64, size: usize, bar_char: &str, display_value: bool) -> String {
+    let size = if display_value { size.saturating_sub(6) } else { size };
+    let value = percent.clamp(0.0, 100.0);
+    let scaled = size as f64 * value / 100.0;
+    let whole = scaled.floor() as usize;
+    let frac = scaled - whole as f64;
+    let mut bar = bar_char.repeat(whole);
+    let mut whole = whole;
+    if frac > 0.0 {
+        // curses_bars = [empty; 5] + [bar; 5]: index 5..7 draws a partial block.
+        if (frac * 8.0) as usize >= 5 {
+            bar.push_str(bar_char);
+        } else {
+            bar.push(' ');
+        }
+        whole += 1;
+    }
+    bar.push_str(&" ".repeat(size.saturating_sub(whole)));
+    if display_value {
+        if percent >= 100.0 {
+            bar = format!("{bar} {}{:3.0}%", if percent > 100.0 { ">" } else { " " }, 100.0);
+        } else {
+            bar = format!("{bar}{percent:5.1}%");
+        }
+    }
+    bar
+}
+
 /// Parse a value like `'12.5 MB'` into a float (port of `string_value_to_float`).
 pub fn string_value_to_float(s: &str) -> Option<f64> {
     let cleaned: String = s.chars().filter(|c| *c != ' ').collect();