fix: Add display for unknown battery state (#316)

docs/config/README.md

@@ -119,6 +119,18 @@ The module is only visible when the device's battery is below 10%.
 | `display`            | [link](#battery-display) | Display threshold and style for the module.       |
 | `disabled`           | `false`                  | Disables the `battery` module.                    |
 
+<details>
+<summary>There are also options for some uncommon battery states.</summary>
+
+| Variable         | Description                                         |
+|------------------|-----------------------------------------------------|
+| `unknown_symbol` | The symbol shown when the battery state is unknown. |
+| `empty_symbol`   | The symbol shown when the battery state is empty.   |
+
+Note: Battery indicator will be hidden if the status is `unknown` or `empty` unless you specify the option in the config.
+
+</details>
+
 ### Example
 
 ```toml

src/module.rs

@@ -75,6 +75,20 @@ impl<'a> Module<'a> {
         self.segments.last_mut().unwrap()
     }
 
+    /// Should config exists, get a reference to a newly created segment in the module
+    pub fn new_segment_if_config_exists(&mut self, name: &str) -> Option<&mut Segment> {
+        // Use the provided value unless overwritten by config
+        if let Some(value) = self.config_value_str(name) {
+            let mut segment = Segment::new(name);
+            segment.set_style(self.style);
+            segment.set_value(value);
+            self.segments.push(segment);
+            Some(self.segments.last_mut().unwrap())
+        } else {
+            None
+        }
+    }
+
     /// Whether a module has non-empty segments
     pub fn is_empty(&self) -> bool {
         self.segments.iter().all(|segment| segment.is_empty())

src/modules/battery.rs

@@ -45,6 +45,17 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
             battery::State::Discharging => {
                 module.new_segment("discharging_symbol", BATTERY_DISCHARGING);
             }
+            battery::State::Unknown => {
+                log::debug!("Unknown detected");
+                module.new_segment_if_config_exists("unknown_symbol")?;
+            }
+            battery::State::Empty => {
+                module.new_segment_if_config_exists("empty_symbol")?;
+            }
+            _ => {
+                log::debug!("Unhandled battery state `{}`", state);
+                return None;
+            }
             _ => return None,
         }