Velocity element

src/elements/velocity_handler.rs

@@ -0,0 +1,164 @@
+use std::sync::Arc;
+
+use crate::{
+    component,
+    prelude::ElementRenderer,
+    style::RawTransform,
+    widget::{Element, Widget},
+    NoRenderRoot,
+};
+
+pub struct VelocityRenderer<'a>(&'a mut RawTransform, &'a mut Vec<(i32, i32)>, usize, u16);
+
+pub struct VelocityHandler {
+    children: Vec<Arc<Widget>>,
+    progress: Vec<(i32, i32)>,
+    render: (u16, u16),
+    tick: u16,
+}
+
+impl VelocityHandler {
+    pub fn new() -> Self {
+        Self {
+            children: Vec::new(),
+            progress: Vec::new(),
+            render: (0, 0),
+            tick: 0,
+        }
+    }
+}
+
+impl Element for VelocityHandler {
+    fn render(
+        &mut self,
+        scope: &mut crate::prelude::RenderScope,
+        _: &crate::render_scope::RenderContext,
+    ) {
+        scope.use_area(self.render.0, self.render.1);
+    }
+
+    fn after_render(
+        &mut self,
+        parent_scope: &mut crate::render_scope::RenderScope,
+        render_context: &crate::render_scope::RenderContext,
+    ) {
+        let mut transform = {
+            let (width, height) = parent_scope.get_size_or_parent();
+            let mut t = parent_scope.get_transform().clone();
+            t.width = width;
+            t.height = height;
+            t.transform_parent(parent_scope.get_parent_transform());
+            t
+        };
+
+        let mut scope = crate::render_scope::RenderScope::new();
+        scope.set_parent_transform(transform.clone());
+
+        transform.width = 0;
+        transform.height = 0;
+        let mut renderer = VelocityRenderer(&mut transform, &mut self.progress, 0, self.tick);
+        for widget in &self.children {
+            scope.render_widget(&mut renderer, render_context.get_context(), widget);
+        }
+
+        self.render = (transform.width, transform.height);
+
+        if self.tick == 1000 {
+            self.tick = 0;
+        } else {
+            self.tick += 1;
+        }
+    }
+
+    fn draw_child(&mut self, element: &Arc<Widget>) {
+        self.progress.push((0, 0));
+        self.children.push(element.clone());
+        element.inject(|w| w.component(NoRenderRoot));
+    }
+
+    fn undraw_child(&mut self, element: &Arc<Widget>) {
+        if let Some(i) = self.children.iter().position(|v| Arc::ptr_eq(v, element)) {
+            self.children.remove(i);
+            self.progress.remove(i);
+        }
+    }
+
+    fn is_ghost(&mut self) -> bool {
+        true
+    }
+
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
+        self
+    }
+}
+
+impl ElementRenderer for VelocityRenderer<'_> {
+    fn before_draw(&mut self, scope: &mut crate::prelude::RenderScope, widget: &Arc<Widget>) {
+        let t = scope.get_transform_mut();
+
+        if let Some(Velocity(vx, vy)) = widget.get() {
+            if let Some((ax, ay)) = self.1.get_mut(self.2) {
+                add_i32_to_u16(&mut t.x, *ax);
+                add_i32_to_u16(&mut t.y, *ay);
+
+                if apply_velocity(self.3, vx, &mut t.x) {
+                    apply_value(ax, vx);
+                }
+                if apply_velocity(self.3, vy, &mut t.y) {
+                    apply_value(ay, vy);
+                }
+            } else {
+                self.1.push((0, 0));
+            }
+        }
+
+        self.2 += 1;
+
+        self.0.width = self.0.width.max(t.x + t.width + (t.px * 2));
+        self.0.height = self.0.height.max(t.y + t.height + (t.py * 2));
+
+        t.x += self.0.x + self.0.px;
+        t.y += self.0.y + self.0.py;
+        t.offset_y = self.0.offset_y;
+    }
+}
+
+fn apply_velocity(ticks: u16, velocity: i32, x: &mut u16) -> bool {
+    let abs_v = velocity.abs();
+    if abs_v == 0 {
+        return false;
+    }
+
+    let interval = (1000 / abs_v).max(1); // prevent divide-by-zero
+    if ticks as i32 % interval == 0 {
+        if velocity > 0 {
+            *x = x.saturating_add(1);
+        } else {
+            *x = x.saturating_sub(1);
+        }
+        return true;
+    }
+    false
+}
+
+fn add_i32_to_u16(value: &mut u16, delta: i32) {
+    if delta >= 0 {
+        *value = value.saturating_add(delta as u16);
+    } else {
+        *value = value.saturating_sub((-delta) as u16);
+    }
+}
+
+fn apply_value(x: &mut i32, velocity: i32) {
+    *x = if velocity > 0 {
+        x.saturating_add(1)
+    } else {
+        x.saturating_sub(1)
+    };
+}
+
+component!(Velocity(pub i32, pub i32));