T19: the main window lets the desktop through while Background opacity is under 1, blurred or clear as Background blur says, set at open and as the settings change; Ely's new ColumnShell::glass grounds every column and the title bar in the palette's glass, which the opacity sets, and the Ely pin moves to it past 27 of Ely's own commits; dialogs stay solid; the terminal paints no second ground; shot names the window's AppKit views

src/blur.rs

@@ -0,0 +1,46 @@
+use gpui::{Window, WindowBackgroundAppearance};
+
+use crate::settings::Settings;
+
+/// What the window shows of the desktop: blurred or clear while the background lets it through.
+pub fn appearance(settings: &Settings) -> WindowBackgroundAppearance {
+    if settings.background_opacity >= 1.0 {
+        WindowBackgroundAppearance::Opaque
+    } else if settings.background_blur {
+        WindowBackgroundAppearance::Blurred
+    } else {
+        WindowBackgroundAppearance::Transparent
+    }
+}
+
+/// Sets `window` to what the settings ask when it differs from `shown`; logs the way taken.
+pub fn follow(window: &Window, shown: &mut WindowBackgroundAppearance, settings: &Settings) {
+    let wanted = appearance(settings);
+    if wanted != *shown {
+        *shown = wanted;
+        window.set_background_appearance(wanted);
+        log::info!("blur: the window is {wanted:?} on {}", std::env::consts::OS);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use gpui::WindowBackgroundAppearance::{Blurred, Opaque, Transparent};
+
+    use super::*;
+
+    #[test]
+    fn the_desktop_shows_only_through_a_background_it_can_pass() {
+        let at = |opacity, blur| {
+            appearance(&Settings {
+                background_opacity: opacity,
+                background_blur: blur,
+                ..Settings::default()
+            })
+        };
+        assert_eq!(at(1.0, true), Opaque);
+        assert_eq!(at(1.0, false), Opaque);
+        assert_eq!(at(0.88, true), Blurred);
+        assert_eq!(at(0.3, false), Transparent);
+    }
+}