perf: improve backdrop blur quality

crates/gpui/src/styled.rs

@@ -759,7 +759,12 @@ pub trait Styled: Sized {
         self
     }
 
-    /// Sets the blur radius applied to content behind this element.
+    /// Sets the blur extent applied to content behind this element.
+    ///
+    /// The radius approximates the filter's three-sigma support. At render
+    /// scale, positive radii below the pyramid's roughly 3.7-device-pixel
+    /// minimum use that minimum. Non-positive and non-finite values disable
+    /// the effect.
     fn backdrop_blur(mut self, blur_radius: Pixels) -> Self {
         self.style().backdrop_blur = Some(blur_radius);
         self

crates/gpui/src/window.rs

@@ -3709,13 +3709,21 @@ impl Window {
     }
 
     /// Paint a backdrop blur region into the scene for the next frame.
+    ///
+    /// `blur_radius` approximates the filter's three-sigma support. At render
+    /// scale, positive radii below the pyramid's roughly 3.7-device-pixel
+    /// minimum use that minimum.
     pub fn paint_backdrop_blur(
         &mut self,
         bounds: Bounds<Pixels>,
         corner_radii: Corners<Pixels>,
         blur_radius: Pixels,
     ) {
         self.invalidator.debug_assert_paint();
+        if !blur_radius.0.is_finite() || blur_radius <= Pixels::ZERO {
+            return;
+        }
+
         let scale_factor = self.scale_factor();
         let content_mask = self.content_mask();
         self.next_frame.scene.insert_primitive(BackdropBlur {