FINALLY FIXED STUPID TEST UI ISSUES (true painter.rs moment) + scrolling

src/core/position/mod.rs

@@ -9,6 +9,7 @@ mod stack;
 pub use align::*;
 pub use offset::*;
 pub use pad::*;
+pub use scroll::*;
 pub use sized::*;
 pub use span::*;
 pub use stack::*;

src/core/position/scroll.rs

@@ -3,9 +3,10 @@ use crate::prelude::*;
 pub struct Scroll {
     inner: WidgetId,
     axis: Axis,
-    snap_end: bool,
     amt: f32,
-    draw_len: f32,
+    snap_end: bool,
+    container_len: f32,
+    content_len: f32,
 }
 
 impl Widget for Scroll {
@@ -17,10 +18,14 @@ impl Widget for Scroll {
             .apply_rest()
             .within_len(container_len)
             .to_abs(output_len);
-        let container_len = container_len.to_abs(output_len);
-        self.draw_len = content_len;
-        // let region = UiRegion::FULL.offset(self.amt);
-        // painter.widget_within(&self.inner, region);
+        self.container_len = container_len.to_abs(output_len);
+        self.content_len = content_len;
+        if self.snap_end {
+            self.amt = self.content_len - self.container_len;
+        }
+        self.update_amt();
+        let region = UiRegion::FULL.offset(Vec2::from_axis(self.axis, -self.amt, 0.0));
+        painter.widget_within(&self.inner, region);
     }
 
     fn desired_width(&mut self, _: &mut SizeCtx) -> Len {
@@ -33,7 +38,26 @@ impl Widget for Scroll {
 }
 
 impl Scroll {
+    pub fn new(inner: WidgetId, axis: Axis) -> Self {
+        Self {
+            inner,
+            axis,
+            amt: 0.0,
+            snap_end: true,
+            container_len: 0.0,
+            content_len: 0.0,
+        }
+    }
+
+    pub fn update_amt(&mut self) {
+        self.amt = self.amt.max(0.0);
+        let len = (self.content_len - self.container_len).max(0.0);
+        self.amt = self.amt.min(len);
+        self.snap_end = self.amt == len;
+    }
+
     pub fn scroll(&mut self, amt: f32) {
-        self.amt += amt;
+        self.amt -= amt;
+        self.update_amt();
     }
 }