Fix #1129 and add request_timer to LayoutCtx (#1278)

* Fix #1129 and add request_timer to LayoutCtx

* Update CHANGELOG.md

* Fix formatting

CHANGELOG.md

@@ -45,6 +45,7 @@ You can find its changes [documented below](#060---2020-06-01).
 - `RawLabel` widget displays text `Data`. ([#1252] by [@cmyr])
 - 'Tabs' widget allowing static and dynamic tabbed layouts. ([#1160] by [@rjwittams])
 - `RichText` and `Attribute` types for creating rich text ([#1255] by [@cmyr])
+- `request_timer` can now be called from `LayoutCtx` ([#1278] by [@Majora320])
 
 ### Changed
 
@@ -98,6 +99,7 @@ You can find its changes [documented below](#060---2020-06-01).
 - Windows: fix crash on resize from incompatible resources ([#1191 by [@raphlinus]])
 - GTK: Related dependencies are now optional, facilitating a pure X11 build. ([#1241] by [@finnerale])
 - `widget::Image` now computes the layout correctly when unbound in one direction. ([#1189] by [@JAicewizard])
+- The scroll bar now shows when the contents of a scrollable area change size. ([#1278] by [@Majora320])
 
 ### Visual
 
@@ -484,6 +486,7 @@ Last release without a changelog :(
 [#1251]: https://github.com/linebender/druid/pull/1251
 [#1252]: https://github.com/linebender/druid/pull/1252
 [#1255]: https://github.com/linebender/druid/pull/1255
+[#1278]: https://github.com/linebender/druid/pull/1278
 
 [Unreleased]: https://github.com/linebender/druid/compare/v0.6.0...master
 [0.6.0]: https://github.com/linebender/druid/compare/v0.5.0...v0.6.0

druid/src/contexts.rs

@@ -292,14 +292,6 @@ impl_context_method!(EventCtx<'_, '_>, UpdateCtx<'_, '_>, LifeCycleCtx<'_, '_>,
         self.widget_state.request_anim = true;
     }
 
-    /// Request a timer event.
-    ///
-    /// The return value is a token, which can be used to associate the
-    /// request with the event.
-    pub fn request_timer(&mut self, deadline: Duration) -> TimerToken {
-        self.state.request_timer(&mut self.widget_state, deadline)
-    }
-
     /// Indicate that your children have changed.
     ///
     /// Widgets must call this method after adding a new child.
@@ -317,7 +309,7 @@ impl_context_method!(EventCtx<'_, '_>, UpdateCtx<'_, '_>, LifeCycleCtx<'_, '_>,
     }
 });
 
-// methods on event, update, and lifecycle
+// methods on everyone but paintctx
 impl_context_method!(
     EventCtx<'_, '_>,
     UpdateCtx<'_, '_>,
@@ -346,6 +338,14 @@ impl_context_method!(
         pub fn get_external_handle(&self) -> ExtEventSink {
             self.state.ext_handle.clone()
         }
+
+        /// Request a timer event.
+        ///
+        /// The return value is a token, which can be used to associate the
+        /// request with the event.
+        pub fn request_timer(&mut self, deadline: Duration) -> TimerToken {
+            self.state.request_timer(&mut self.widget_state, deadline)
+        }
     }
 );
 

druid/src/widget/scroll.rs

@@ -144,13 +144,20 @@ impl<T: Data, W: Widget<T>> Widget<T> for Scroll<T, W> {
         let child_bc = BoxConstraints::new(Size::ZERO, max_bc);
         let child_size = self.child.layout(ctx, &child_bc, data, env);
         log_size_warnings(child_size);
+        let old_size = self.scroll_component.content_size;
         self.scroll_component.content_size = child_size;
         self.child
             .set_layout_rect(ctx, data, env, child_size.to_rect());
 
         let self_size = bc.constrain(child_size);
         let _ = self.scroll_component.scroll(Vec2::new(0.0, 0.0), self_size);
         self.child.set_viewport_offset(self.offset());
+
+        if old_size != self.scroll_component.content_size {
+            self.scroll_component
+                .reset_scrollbar_fade(|d| ctx.request_timer(d), env);
+        }
+
         self_size
     }