Add DPI scale factor to the render root state

masonry/src/app/render_root.rs

@@ -147,6 +147,7 @@ pub(crate) struct RenderRootState {
     /// Pass tracing configuration, used to skip tracing to limit overhead.
     pub(crate) trace: PassTracing,
     pub(crate) inspector_state: InspectorState,
+    pub(crate) scale_factor: f64,
 }
 
 pub(crate) struct MutateCallback {
@@ -290,6 +291,7 @@ impl RenderRoot {
                     is_picking_widget: false,
                     hovered_widget: None,
                 },
+                scale_factor,
             },
             widget_arena: WidgetArena {
                 widgets: TreeArena::new(),
@@ -339,6 +341,7 @@ impl RenderRoot {
         match event {
             WindowEvent::Rescale(scale_factor) => {
                 self.scale_factor = scale_factor;
+                self.global_state.scale_factor = scale_factor;
                 self.request_render_all();
                 Handled::Yes
             }

masonry/src/core/contexts.rs

@@ -780,6 +780,23 @@ impl_context_method!(
     }
 );
 
+// Methods on all context types except LayoutCtx and ComposeCtx.
+// Access selected global state information.
+impl_context_method!(
+    MutateCtx<'_>,
+    QueryCtx<'_>,
+    EventCtx<'_>,
+    UpdateCtx<'_>,
+    PaintCtx<'_>,
+    AccessCtx<'_>,
+    {
+        /// Get DPI scaling factor.
+        pub fn get_scale_factor(&self) -> f64 {
+            self.global_state.scale_factor
+        }
+    }
+);
+
 // Methods on all context types
 // Access status information (hovered/pointer captured/disabled/etc).
 impl_context_method!(