events: implement a first attempt at an eventing system

src/platform/smart_leds_lib.rs

@@ -1,6 +1,7 @@
 use smart_leds_trait::SmartLedsWrite;
 
 use crate::buffers::Pixbuf;
+use crate::events::Variant;
 use crate::render::{HardwarePixel, Output, PixelView, Sample};
 use crate::power::brightness_for_mw;
 use crate::geometry::*;
@@ -18,7 +19,8 @@ pub struct StrideOutput<P: Pixbuf, T: FastWrite> {
     pixbuf: P,
     stride_map: StrideMapping,
     target: T,
-    max_mw: u32
+    max_mw: u32,
+    brightness: u8
 }
 
 impl<P: Pixbuf, T: FastWrite> StrideOutput<P, T> {
@@ -28,7 +30,8 @@ impl<P: Pixbuf, T: FastWrite> StrideOutput<P, T> {
             pixbuf,
             stride_map,
             target,
-            max_mw
+            max_mw,
+            brightness: 255
         }
     }
 }
@@ -46,11 +49,18 @@ impl<P: Pixbuf<Pixel=T::Color>, T: FastWrite> Output for StrideOutput<P, T> {
     }
 
     fn commit(&mut self) {
-        let b = brightness_for_mw(self.pixbuf.as_milliwatts(), 255, self.max_mw);
+        let b = brightness_for_mw(self.pixbuf.as_milliwatts(), self.brightness, self.max_mw);
         if self.target.fast_write(self.pixbuf.iter_with_brightness(b)).is_err() {
             panic!("Could not write frame!");
         };
     }
+
+    fn on_event(&mut self, event: &crate::events::Event) {
+        match event {
+            crate::events::Event::PropertyChange("output.brightness", new_brightness) => self.brightness = new_brightness.clone().into(),
+            _ => ()
+        }
+    }
 }
 
 pub trait FastWrite: Send {