1 files changed, 73 insertions, 0 deletions
diff --git a/examples/render-quad/src/system.rs b/examples/render-quad/src/system.rs
new file mode 100644
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+++ b/examples/render-quad/src/system.rs
@@ -0,0 +1,73 @@
+//! An example system that just alternates the colours of our triangle
+
+use stockton_skeleton::types::Vector3;
+
+/// RGB Channels
+#[derive(Debug, Clone, Copy)]
+enum ColorChannel {
+    Red,
+    Green,
+    Blue,
+}
+
+/// A component for our entity.
+#[derive(Debug, Clone, Copy)]
+pub struct ExampleState {
+    channel: ColorChannel,
+    falling: bool,
+    col_val: Vector3,
+}
+
+impl ExampleState {
+    pub fn color(&self) -> Vector3 {
+        self.col_val
+    }
+}
+
+impl Default for ExampleState {
+    fn default() -> Self {
+        Self {
+            channel: ColorChannel::Red,
+            falling: true,
+            col_val: Vector3::new(1.0, 1.0, 1.0),
+        }
+    }
+}
+
+/// The speed at which we change colour
+const TRANSITION_SPEED: f32 = 0.1;
+
+/// Keep changing the colour of any ExampleStates in our world.
+#[system(for_each)]
+pub fn mutate_state(state: &mut ExampleState) {
+    // Which value we're changing
+    let val = match state.channel {
+        ColorChannel::Red => &mut state.col_val.x,
+        ColorChannel::Green => &mut state.col_val.y,
+        ColorChannel::Blue => &mut state.col_val.z,
+    };
+
+    if state.falling {
+        *val -= TRANSITION_SPEED;
+
+        // Fall, then rise
+        if *val <= 0.0 {
+            *val = 0.0;
+            state.falling = false;
+        }
+    } else {
+        *val += TRANSITION_SPEED;
+
+        if *val >= 1.0 {
+            *val = 1.0;
+
+            // Rather than going back to falling, go to the next channel
+            state.falling = true;
+            state.channel = match state.channel {
+                ColorChannel::Red => ColorChannel::Green,
+                ColorChannel::Green => ColorChannel::Blue,
+                ColorChannel::Blue => ColorChannel::Red,
+            }
+        }
+    }
+}