Use proper Windows APIs for checking/setting default app (#5000)

# Description of Changes
Use proper Windows APIs for checking/setting default app

---------

Co-authored-by: Connor Yoh <con.yoh13@gmail.com>
Co-authored-by: ConnorYoh <40631091+ConnorYoh@users.noreply.github.com>

frontend/public/locales/en-GB/translation.json

@@ -63,7 +63,7 @@
     },
     "settingsOpened": {
       "title": "Settings Opened",
-      "message": "Please select Stirling PDF in your system settings"
+      "message": "In Windows Settings, search for 'PDF' and select Stirling PDF as your default app"
     },
     "error": {
       "title": "Error",

frontend/src-tauri/Cargo.lock

@@ -4250,6 +4250,7 @@ dependencies = [
  "tokio",
  "url",
  "urlencoding",
+ "windows 0.58.0",
 ]
 
 [[package]]
@@ -4437,7 +4438,7 @@ dependencies = [
  "tao-macros",
  "unicode-segmentation",
  "url",
- "windows",
+ "windows 0.61.3",
  "windows-core 0.61.2",
  "windows-version",
  "x11-dl",
@@ -4514,7 +4515,7 @@ dependencies = [
  "webkit2gtk",
  "webview2-com",
  "window-vibrancy",
- "windows",
+ "windows 0.61.3",
 ]
 
 [[package]]
@@ -4683,7 +4684,7 @@ dependencies = [
  "tauri-plugin",
  "thiserror 2.0.17",
  "url",
- "windows",
+ "windows 0.61.3",
  "zbus",
 ]
 
@@ -4761,7 +4762,7 @@ dependencies = [
  "url",
  "webkit2gtk",
  "webview2-com",
- "windows",
+ "windows 0.61.3",
 ]
 
 [[package]]
@@ -4787,7 +4788,7 @@ dependencies = [
  "url",
  "webkit2gtk",
  "webview2-com",
- "windows",
+ "windows 0.61.3",
  "wry",
 ]
 
@@ -5624,10 +5625,10 @@ checksum = "d4ba622a989277ef3886dd5afb3e280e3dd6d974b766118950a08f8f678ad6a4"
 dependencies = [
  "webview2-com-macros",
  "webview2-com-sys",
- "windows",
+ "windows 0.61.3",
  "windows-core 0.61.2",
- "windows-implement",
+ "windows-implement 0.60.2",
- "windows-interface",
+ "windows-interface 0.59.3",
 ]
 
 [[package]]
@@ -5648,7 +5649,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "36695906a1b53a3bf5c4289621efedac12b73eeb0b89e7e1a89b517302d5d75c"
 dependencies = [
  "thiserror 2.0.17",
- "windows",
+ "windows 0.61.3",
  "windows-core 0.61.2",
 ]
 
@@ -5698,6 +5699,16 @@ dependencies = [
  "windows-version",
 ]
 
+[[package]]
+name = "windows"
+version = "0.58.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd04d41d93c4992d421894c18c8b43496aa748dd4c081bac0dc93eb0489272b6"
+dependencies = [
+ "windows-core 0.58.0",
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "windows"
 version = "0.61.3"
@@ -5720,14 +5731,27 @@ dependencies = [
  "windows-core 0.61.2",
 ]
 
+[[package]]
+name = "windows-core"
+version = "0.58.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ba6d44ec8c2591c134257ce647b7ea6b20335bf6379a27dac5f1641fcf59f99"
+dependencies = [
+ "windows-implement 0.58.0",
+ "windows-interface 0.58.0",
+ "windows-result 0.2.0",
+ "windows-strings 0.1.0",
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "windows-core"
 version = "0.61.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c0fdd3ddb90610c7638aa2b3a3ab2904fb9e5cdbecc643ddb3647212781c4ae3"
 dependencies = [
- "windows-implement",
+ "windows-implement 0.60.2",
- "windows-interface",
+ "windows-interface 0.59.3",
  "windows-link 0.1.3",
  "windows-result 0.3.4",
  "windows-strings 0.4.2",
@@ -5739,8 +5763,8 @@ version = "0.62.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b8e83a14d34d0623b51dce9581199302a221863196a1dde71a7663a4c2be9deb"
 dependencies = [
- "windows-implement",
+ "windows-implement 0.60.2",
- "windows-interface",
+ "windows-interface 0.59.3",
  "windows-link 0.2.1",
  "windows-result 0.4.1",
  "windows-strings 0.5.1",
@@ -5757,6 +5781,17 @@ dependencies = [
  "windows-threading",
 ]
 
+[[package]]
+name = "windows-implement"
+version = "0.58.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2bbd5b46c938e506ecbce286b6628a02171d56153ba733b6c741fc627ec9579b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.108",
+]
+
 [[package]]
 name = "windows-implement"
 version = "0.60.2"
@@ -5768,6 +5803,17 @@ dependencies = [
  "syn 2.0.108",
 ]
 
+[[package]]
+name = "windows-interface"
+version = "0.58.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "053c4c462dc91d3b1504c6fe5a726dd15e216ba718e84a0e46a88fbe5ded3515"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.108",
+]
+
 [[package]]
 name = "windows-interface"
 version = "0.59.3"
@@ -5812,6 +5858,15 @@ dependencies = [
  "windows-strings 0.4.2",
 ]
 
+[[package]]
+name = "windows-result"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d1043d8214f791817bab27572aaa8af63732e11bf84aa21a45a78d6c317ae0e"
+dependencies = [
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "windows-result"
 version = "0.3.4"
@@ -5830,6 +5885,16 @@ dependencies = [
  "windows-link 0.2.1",
 ]
 
+[[package]]
+name = "windows-strings"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4cd9b125c486025df0eabcb585e62173c6c9eddcec5d117d3b6e8c30e2ee4d10"
+dependencies = [
+ "windows-result 0.2.0",
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "windows-strings"
 version = "0.4.2"
@@ -6252,7 +6317,7 @@ dependencies = [
  "webkit2gtk",
  "webkit2gtk-sys",
  "webview2-com",
- "windows",
+ "windows 0.61.3",
  "windows-core 0.61.2",
  "windows-version",
  "x11-dl",

frontend/src-tauri/Cargo.toml

@@ -45,3 +45,11 @@ rand = "0.8"
 [target.'cfg(target_os = "macos")'.dependencies]
 core-foundation = "0.10"
 core-services = "1.0"
+
+[target.'cfg(target_os = "windows")'.dependencies]
+windows = { version = "0.58", features = [
+    "Win32_Foundation",
+    "Win32_System_Com",
+    "Win32_UI_Shell",
+    "Win32_System_ApplicationInstallationAndServicing",
+] }

frontend/src-tauri/src/commands/default_app.rs

@@ -1,8 +1,5 @@
 use crate::utils::add_log;
 
-#[cfg(any(target_os = "windows", target_os = "linux"))]
-use std::process::Command;
-
 /// Check if Stirling PDF is the default PDF handler
 #[tauri::command]
 pub fn is_default_pdf_handler() -> Result<bool, String> {
@@ -51,50 +48,80 @@ pub fn set_as_default_pdf_handler() -> Result<String, String> {
 
 #[cfg(target_os = "windows")]
 fn check_default_windows() -> Result<bool, String> {
-    use std::os::windows::process::CommandExt;
+    use windows::core::HSTRING;
-    const CREATE_NO_WINDOW: u32 = 0x08000000;
+    use windows::Win32::Foundation::RPC_E_CHANGED_MODE;
+    use windows::Win32::System::Com::{
+        CoCreateInstance, CoInitializeEx, CoUninitialize, CLSCTX_INPROC_SERVER,
+        COINIT_APARTMENTTHREADED,
+    };
+    use windows::Win32::UI::Shell::{
+        IApplicationAssociationRegistration, ApplicationAssociationRegistration,
+        ASSOCIATIONTYPE, ASSOCIATIONLEVEL,
+    };
 
-    // Query the default handler for .pdf extension
+    unsafe {
-    let output = Command::new("cmd")
+        // Initialize COM for this thread
-        .args(["/C", "assoc .pdf"])
+        let hr = CoInitializeEx(None, COINIT_APARTMENTTHREADED);
-        .creation_flags(CREATE_NO_WINDOW)
+        // RPC_E_CHANGED_MODE means COM is already initialized, which is fine
-        .output()
+        if hr.is_err() && hr != RPC_E_CHANGED_MODE {
-        .map_err(|e| format!("Failed to check default app: {}", e))?;
+            return Err(format!("Failed to initialize COM: {:?}", hr));
+        }
 
-    let assoc = String::from_utf8_lossy(&output.stdout);
+        let result = (|| -> Result<bool, String> {
-    add_log(format!("Windows PDF association: {}", assoc.trim()));
+            // Create the IApplicationAssociationRegistration instance
+            let reg: IApplicationAssociationRegistration =
+                CoCreateInstance(&ApplicationAssociationRegistration, None, CLSCTX_INPROC_SERVER)
+                    .map_err(|e| format!("Failed to create COM instance: {}", e))?;
 
-    // Get the ProgID for .pdf files
+            // Query the current default handler for .pdf extension
-    if let Some(prog_id) = assoc.trim().strip_prefix(".pdf=") {
+            let extension = HSTRING::from(".pdf");
-        // Query what application handles this ProgID
-        let output = Command::new("cmd")
-            .args(["/C", &format!("ftype {}", prog_id)])
-            .creation_flags(CREATE_NO_WINDOW)
-            .output()
-            .map_err(|e| format!("Failed to query file type: {}", e))?;
 
-        let ftype = String::from_utf8_lossy(&output.stdout);
+            let default_app = reg.QueryCurrentDefault(
-        add_log(format!("Windows file type: {}", ftype.trim()));
+                &extension,
+                ASSOCIATIONTYPE(0), // AT_FILEEXTENSION
+                ASSOCIATIONLEVEL(1), // AL_EFFECTIVE - gets the effective default (user or machine level)
+            )
+            .map_err(|e| format!("Failed to query current default: {}", e))?;
 
-        // Check if it contains "Stirling" or our app name
+            // Convert PWSTR to String
-        let is_default = ftype.to_lowercase().contains("stirling");
+            let default_str = default_app.to_string()
-        Ok(is_default)
+                .map_err(|e| format!("Failed to convert default app string: {}", e))?;
-    } else {
+
-        Ok(false)
+            add_log(format!("Windows PDF handler ProgID: {}", default_str));
+
+            // Check if it contains "Stirling" (case-insensitive)
+            // Note: This checks the ProgID registered by the installer
+            let is_default = default_str.to_lowercase().contains("stirling");
+            Ok(is_default)
+        })();
+
+        // Clean up COM
+        CoUninitialize();
+
+        result
     }
 }
 
 #[cfg(target_os = "windows")]
 fn set_default_windows() -> Result<String, String> {
-    // On Windows 10+, we need to open the Default Apps settings
+    use std::process::Command;
-    // as programmatic setting requires a signed installer
-    Command::new("cmd")
-        .args(["/C", "start", "ms-settings:defaultapps"])
-        .spawn()
-        .map_err(|e| format!("Failed to open default apps settings: {}", e))?;
 
-    add_log("Opened Windows Default Apps settings".to_string());
+    // Windows 10+ approach: Open Settings app directly to default apps
-    Ok("opened_settings".to_string())
+    // This is more reliable than COM APIs which require pre-registration
+    // ms-settings:defaultapps opens the default apps settings page
+    let result = Command::new("cmd")
+        .args(["/C", "start", "ms-settings:defaultapps"])
+        .output()
+        .map_err(|e| format!("Failed to open Windows Settings: {}", e))?;
+
+    if result.status.success() {
+        add_log("Opened Windows default apps settings".to_string());
+        Ok("opened_dialog".to_string())
+    } else {
+        let error = String::from_utf8_lossy(&result.stderr);
+        add_log(format!("Failed to open settings: {}", error));
+        Err(format!("Failed to open default apps settings: {}", error))
+    }
 }
 
 // ============================================================================
@@ -184,6 +211,8 @@ fn set_default_macos() -> Result<String, String> {
 
 #[cfg(target_os = "linux")]
 fn check_default_linux() -> Result<bool, String> {
+    use std::process::Command;
+
     // Use xdg-mime to check the default application for PDF files
     let output = Command::new("xdg-mime")
         .args(["query", "default", "application/pdf"])
@@ -200,6 +229,8 @@ fn check_default_linux() -> Result<bool, String> {
 
 #[cfg(target_os = "linux")]
 fn set_default_linux() -> Result<String, String> {
+    use std::process::Command;
+
     // Use xdg-mime to set the default application for PDF files
     let result = Command::new("xdg-mime")
         .args(["default", "stirling-pdf.desktop", "application/pdf"])

frontend/src/desktop/hooks/useDefaultApp.ts

@@ -33,11 +33,11 @@ export const useDefaultApp = () => {
           body: t('defaultApp.success.message', 'Stirling PDF is now your default PDF editor'),
         });
         setIsDefault(true);
-      } else if (result === 'opened_settings') {
+      } else if (result === 'opened_dialog') {
         alert({
           alertType: 'neutral',
           title: t('defaultApp.settingsOpened.title', 'Settings Opened'),
-          body: t('defaultApp.settingsOpened.message', 'Please select Stirling PDF in your system settings'),
+          body: t('defaultApp.settingsOpened.message', 'Please select Stirling PDF in the file association dialogue'),
         });
       }
     } catch (error) {

frontend/src/desktop/hooks/useEndpointConfig.ts

@@ -88,8 +88,7 @@ export function useEndpointEnabled(endpoint: string): {
     try {
       setError(null);
 
-      const response = await apiClient.get<boolean>('/api/v1/config/endpoint-enabled', {
+      const response = await apiClient.get<boolean>(`/api/v1/config/endpoint-enabled?endpoint=${encodeURIComponent(endpoint)}`, {
-        params: { endpoint },
         suppressErrorToast: true,
       });
 

frontend/src/desktop/services/defaultAppService.ts

@@ -22,10 +22,10 @@ export const defaultAppService = {
    * Set or prompt to set Stirling PDF as default PDF handler
    * Returns a status string indicating what happened
    */
-  async setAsDefaultPdfHandler(): Promise<'set_successfully' | 'opened_settings' | 'error'> {
+  async setAsDefaultPdfHandler(): Promise<'set_successfully' | 'opened_dialog' | 'error'> {
     try {
       const result = await invoke<string>('set_as_default_pdf_handler');
-      return result as 'set_successfully' | 'opened_settings';
+      return result as 'set_successfully' | 'opened_dialog';
     } catch (error) {
       console.error('[DefaultApp] Failed to set default handler:', error);
       return 'error';