animations: implement a rain animation for weather

src/animations/Rain.h

@@ -0,0 +1,48 @@
+#pragma once
+#include <Figments.h>
+
+class RainAnimation: public Figment {
+private:
+  struct Raindrop {
+    int size = 20;
+    int x = random(255);
+    int y = random(255);
+    CHSV fg{180, 255, 255};
+    CHSV nextColor{180, 255, 255};
+
+    void render(Display* dpy) const {
+      Surface sfc{dpy, {x - size, y - size}, {x + size, y + size}};
+      paint(sfc);
+    }
+
+    void paint(Surface& sfc) const {
+      sfc.paintShader([=](CRGB& pixel, const VirtualCoordinates& coords, const PhysicalCoordinates, const VirtualCoordinates& surfaceCoords) {
+        int distance = 255 - (min(128, abs(128 - surfaceCoords.x)) + min(128, abs(128 - surfaceCoords.y)));
+        pixel += CHSV{fg.h, fg.s, scale8_video(fg.v, distance)};
+      });
+    }
+
+    void update() {
+      if (random(255) >= 100) {
+        y++;
+        if (y >= 255) {
+          y = 0;
+          x += 13;
+          x %= 255;
+          fg = nextColor;
+        }
+      }
+    }
+  };
+
+  SpriteList<Raindrop, 10> m_drops;
+  uint16_t m_noiseOffset;
+  CHSV m_curColor{180, 255, 255};
+  AnimatedNumber m_hue;
+public:
+  RainAnimation();
+  //void handleEvent(const InputEvent& evt) override;
+  void loop() override;
+  void render(Display* dpy) const override;
+  void handleEvent(const InputEvent& evt) override;
+};