iris: drive animation from painter frame time

src/widget/layout/scroll_area.rs

@@ -1,5 +1,4 @@
 use crate::prelude::*;
-use std::time::Instant;
 
 pub struct ScrollArea {
     inner: StrongWidget,
@@ -19,11 +18,10 @@ impl Scrollable for ScrollArea {
 }
 
 impl Widget for ScrollArea {
-    fn tick(&mut self, now: Instant) -> bool {
-        self.tick_fling(now)
-    }
-
     fn draw(&mut self, painter: &mut Painter) {
+        if self.ctl.advance(painter.frame_time()) {
+            painter.request_next_frame();
+        }
         let axis = self.ctl.axis();
         let container_len = painter.px_size().axis(axis);
         self.container_len = container_len;
@@ -87,7 +85,7 @@ mod tests {
     use super::*;
     use crate::layout_tests::TestRsc;
     use crate::sense::{CursorButton, DRAG_SLOP, PointerRequests};
-    use std::time::Duration;
+    use std::time::{Duration, Instant};
 
     fn area() -> (Fixture, WidgetId) {
         area_on(Axis::Y)
@@ -146,9 +144,7 @@ mod tests {
         }
 
         fn fling_frame(&mut self, now: Instant) -> bool {
-            let still = self.get().tick(now);
-            self.draw();
-            still
+            self.render.update_at(&self.root, &mut self.rsc, now)
         }
     }
 
@@ -158,11 +154,7 @@ mod tests {
 
     fn drag(f: &mut Fixture, id: WidgetId, sense: CursorSense, pos: Vec2, t: Instant) {
         let pointer = PointerRequests::default();
-        let flung = f.get().drag(&pointer, id, sense, pos, t);
-        if flung {
-            let id = f.area.id();
-            f.rsc.ui.animate(id);
-        }
+        f.get().drag(&pointer, id, sense, pos, t);
         f.draw();
     }