Add SCROLLBAR_MIN_SIZE to env, and use Entry

druid/src/env.rs

@@ -342,13 +342,20 @@ impl Env {
     ) -> Result<(), ValueTypeError> {
         let env = Arc::make_mut(&mut self.0);
         let key = key.into();
-        // TODO: use of Entry might be more efficient
-        if let Some(existing) = env.map.get(&key) {
-            if !existing.is_same_type(&raw) {
-                return Err(ValueTypeError::new(any::type_name::<V>(), raw));
+        let entry = env.map.entry(key);
+        match entry {
+            std::collections::hash_map::Entry::Occupied(mut e) => {
+                let existing = e.get_mut();
+                if !existing.is_same_type(&raw) {
+                    return Err(ValueTypeError::new(any::type_name::<V>(), raw));
+                } else {
+                    *existing = raw;
+                }
+            }
+            std::collections::hash_map::Entry::Vacant(e) => {
+                e.insert(raw);
             }
         }
-        env.map.insert(key, raw);
         Ok(())
     }
 
@@ -521,7 +528,9 @@ impl Env {
             .adding(Env::DEBUG_WIDGET_ID, false)
             .adding(Env::DEBUG_WIDGET, false);
 
-        crate::theme::add_to_env(env)
+        let env = crate::theme::add_to_env(env);
+
+        crate::scroll_component::add_to_env(env)
     }
 }
 

druid/src/scroll_component.rs

@@ -17,15 +17,18 @@
 
 use std::time::Duration;
 
-use crate::kurbo::{Point, Rect, Vec2};
 use crate::theme;
 use crate::widget::{Axis, Viewport};
+use crate::{
+    kurbo::{Point, Rect, Vec2},
+    Key,
+};
 use crate::{Env, Event, EventCtx, LifeCycle, LifeCycleCtx, PaintCtx, RenderContext, TimerToken};
 
-//TODO: Add this to env
 /// Minimum length for any scrollbar to be when measured on that
 /// scrollbar's primary axis.
-pub const SCROLLBAR_MIN_SIZE: f64 = 45.0;
+pub const SCROLLBAR_MIN_SIZE: Key<f64> =
+    Key::new("org.linebender.scroll-component.scrollbar-min-size");
 
 #[derive(Debug, Copy, Clone)]
 /// Which scroll bars of a scroll area are currently enabled.
@@ -192,7 +195,7 @@ impl ScrollComponent {
         let percent_scrolled = scroll_offset.y / (content_size.height - viewport_size.height);
 
         let length = (percent_visible * viewport_size.height).ceil();
-        let length = length.max(SCROLLBAR_MIN_SIZE);
+        let length = length.max(env.get(SCROLLBAR_MIN_SIZE));
 
         let vertical_padding = bar_pad + bar_pad + bar_width;
 
@@ -227,7 +230,7 @@ impl ScrollComponent {
         let percent_scrolled = scroll_offset.x / (content_size.width - viewport_size.width);
 
         let length = (percent_visible * viewport_size.width).ceil();
-        let length = length.max(SCROLLBAR_MIN_SIZE);
+        let length = length.max(env.get(SCROLLBAR_MIN_SIZE));
 
         let horizontal_padding = bar_pad + bar_pad + bar_width;
 
@@ -495,3 +498,7 @@ impl ScrollComponent {
         }
     }
 }
+/// An initial scroll bar.
+pub(crate) fn add_to_env(env: Env) -> Env {
+    env.adding(SCROLLBAR_MIN_SIZE, 45.0)
+}