Add configurable native glass window backgrounds

apps/desktop/src-tauri/src/appearance.rs

@@ -0,0 +1,128 @@
+//! Native materials are applied on the UI thread. Unsupported systems stay
+//! opaque; stored preferences are retained for the user's next supported session.
+use crate::settings::BackgroundMaterial;
+use serde::Serialize;
+use tauri::WebviewWindow;
+
+#[derive(Clone, Debug, Serialize)]
+pub struct AppearanceStatus {
+    pub requested_material: BackgroundMaterial,
+    pub effective_material: BackgroundMaterial,
+    pub opacity: u8,
+    pub native_effect: bool,
+    pub fallback_reason: Option<String>,
+}
+
+pub fn apply(
+    window: &WebviewWindow,
+    material: BackgroundMaterial,
+    opacity: u8,
+    high_contrast: bool,
+) -> AppearanceStatus {
+    let mut status = AppearanceStatus {
+        requested_material: material,
+        effective_material: BackgroundMaterial::Solid,
+        opacity,
+        native_effect: false,
+        fallback_reason: None,
+    };
+    if high_contrast || material == BackgroundMaterial::Solid || opacity == 100 {
+        #[cfg(windows)]
+        {
+            let _ = window_vibrancy::clear_acrylic(window);
+        }
+        if high_contrast {
+            status.fallback_reason = Some("High contrast uses an opaque background.".into());
+        }
+        return status;
+    }
+    #[cfg(windows)]
+    {
+        if !native_backdrop_available() {
+            status.fallback_reason = Some("Glass requires Windows 11 22H2 or newer with desktop composition enabled and high contrast off. Using a solid background.".into());
+            return status;
+        }
+        let _ = window_vibrancy::clear_acrylic(window);
+        // Keep the webview clear; the frontend draws a theme-aware readable tint.
+        let result = window
+            .set_background_color(Some(tauri::window::Color(0, 0, 0, 0)))
+            .map_err(|error| error.to_string())
+            .and_then(|()| {
+                match material {
+                    BackgroundMaterial::Glass => {
+                        window_vibrancy::apply_acrylic(window, Some((0, 0, 0, 0)))
+                    }
+                    BackgroundMaterial::Frosted => {
+                        window_vibrancy::apply_acrylic(window, Some((0, 0, 0, 0)))
+                    }
+                    BackgroundMaterial::Solid => unreachable!(),
+                }
+                .map_err(|error| error.to_string())
+            });
+        match result {
+            Ok(()) => {
+                status.effective_material = material;
+                status.native_effect = true;
+            }
+            Err(_) => {
+                status.fallback_reason =
+                    Some("Native transparency is unavailable. Using a solid background.".into());
+            }
+        }
+    }
+    #[cfg(not(windows))]
+    {
+        let _ = window;
+        status.fallback_reason = Some(
+            if cfg!(target_os = "macos") {
+                "Native glass is unavailable in this macOS build. Using a solid background."
+            } else {
+                "Native glass is unavailable on this desktop. Using a solid background."
+            }
+            .into(),
+        );
+    }
+    status
+}
+
+#[cfg(windows)]
+fn native_backdrop_available() -> bool {
+    use windows_sys::Win32::UI::Accessibility::{HCF_HIGHCONTRASTON, HIGHCONTRASTW};
+    use windows_sys::Win32::{
+        Graphics::Dwm::DwmIsCompositionEnabled,
+        UI::WindowsAndMessaging::{SystemParametersInfoW, SPI_GETHIGHCONTRAST},
+    };
+    let mut composition = 0;
+    let mut contrast = HIGHCONTRASTW {
+        cbSize: std::mem::size_of::<HIGHCONTRASTW>() as u32,
+        dwFlags: 0,
+        lpszDefaultScheme: std::ptr::null_mut(),
+    };
+    // Failure to query accessibility/composition is treated conservatively.
+    unsafe {
+        if DwmIsCompositionEnabled(&mut composition) < 0
+            || composition == 0
+            || SystemParametersInfoW(
+                SPI_GETHIGHCONTRAST,
+                contrast.cbSize,
+                &mut contrast as *mut _ as *mut _,
+                0,
+            ) == 0
+            || contrast.dwFlags & HCF_HIGHCONTRASTON != 0
+        {
+            return false;
+        }
+    }
+    // The established crate checks the HRESULT of the public backdrop API on
+    // Windows 11 22H2+. Its older undocumented path cannot confirm success.
+    let mut version = windows_sys::Win32::System::SystemInformation::OSVERSIONINFOW {
+        dwOSVersionInfoSize: std::mem::size_of::<
+            windows_sys::Win32::System::SystemInformation::OSVERSIONINFOW,
+        >() as u32,
+        ..unsafe { std::mem::zeroed() }
+    };
+    unsafe {
+        windows_sys::Wdk::System::SystemServices::RtlGetVersion(&mut version) >= 0
+            && version.dwBuildNumber >= 22621
+    }
+}