feat: Show error message if WebView2 not installed (#285)

* feat: Show error message if WebView2 not installed
on Windows

* fix: Add missing dependency

* fix: Do not import lib on OS where not needed
Don't need to import Windows lib on Linux

* feat: Link to troubleshooting page directly

* chore: Update comments

* docs: Show error message in troubleshooting guide
Show the "WebView2 not installed" error message in the troubleshooting
guide

* fix: Resolve clippy error

* fix: Resolve clippy error (again)

5 files changed, 52 insertions, 3 deletions

diff --git a/docs/TROUBLESHOOTING.md b/docs/TROUBLESHOOTING.md
index aed174e0..d36b1e1f 100644
--- a/docs/TROUBLESHOOTING.md
+++ b/docs/TROUBLESHOOTING.md
@@ -4,7 +4,13 @@ Got an issue with FlightCore? Hopefully one of the steps below will help you res
 
 ## FlightCore won't launch
 
-If you are on Windows on FlightCore won't start, make sure you have WebView2 installed. You can grab the latest version from the Microsoft website: \
+If you are on Windows and FlightCore won't start but instead shows an error message like this
+
+![webview2 error message windows](assets/flightcore-webview2-windows-error-message.png)
+
+that means that WebView2 is not installed. WebView2 is an embedded browser framework used by FlightCore to display its GUI.
+
+To install it, you can grab the latest version from the Microsoft website: \
 https://developer.microsoft.com/en-us/microsoft-edge/webview2/#download-section
 
 ![webview2 download screenshot](assets/webview2-download-screenshot.png)
diff --git a/docs/assets/flightcore-webview2-windows-error-message.png b/docs/assets/flightcore-webview2-windows-error-message.png
new file mode 100644
index 00000000..bbe4422f
--- /dev/null
+++ b/docs/assets/flightcore-webview2-windows-error-message.png
diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 5c0285da..960039ad 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -112,6 +112,7 @@ dependencies = [
  "tauri-plugin-store",
  "tokio",
  "ts-rs",
+ "winapi",
  "zip",
  "zip-extract",
 ]
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 0f68a560..0f65d665 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -64,6 +64,8 @@ log = "0.4.17"
 zip-extract = "0.1.2"
 # open urls
 open = "3.2.0"
+# Windows API stuff
+winapi = "0.3.9"
 
 [features]
 # by default Tauri runs in production mode
diff --git a/src-tauri/src/main.rs b/src-tauri/src/main.rs
index 3aa17459..2e4b3370 100644
--- a/src-tauri/src/main.rs
+++ b/src-tauri/src/main.rs
@@ -9,6 +9,11 @@ use std::{
     time::Duration,
 };
 
+#[cfg(target_os = "windows")]
+use std::ptr::null_mut;
+#[cfg(target_os = "windows")]
+use winapi::um::winuser::{MessageBoxW, MB_ICONERROR, MB_OK, MB_USERICON};
+
 use app::{
     constants::{APP_USER_AGENT, MASTER_SERVER_URL, REFRESH_DELAY, SERVER_BROWSER_ENDPOINT},
     *,
@@ -66,7 +71,7 @@ fn main() {
         },
     ));
 
-    tauri::Builder::default()
+    match tauri::Builder::default()
         .plugin(tauri_plugin_store::Builder::default().build())
         .setup(|app| {
             let app_handle = app.app_handle();
@@ -148,7 +153,42 @@ fn main() {
             close_application,
         ])
         .run(tauri::generate_context!())
-        .expect("error while running tauri application");
+    {
+        Ok(()) => (),
+        Err(err) => {
+            // Failed to launch system native web view
+
+            // Log error on Linux
+            #[cfg(not(target_os = "windows"))]
+            {
+                log::error!("{err}");
+            }
+
+            // On Windows we can show an error window using Windows API to show how to install WebView2
+            #[cfg(target_os = "windows")]
+            {
+                log::error!("WebView2 not installed: {err}");
+                // Display a message box to the user with a button to open the installation instructions
+                let title = "WebView2 not found"
+                    .encode_utf16()
+                    .chain(Some(0))
+                    .collect::<Vec<_>>();
+                let message = "FlightCore requires WebView2 to run.\n\nClick OK to open installation instructions.".encode_utf16().chain(Some(0)).collect::<Vec<_>>();
+                unsafe {
+                    let result = MessageBoxW(
+                        null_mut(),
+                        message.as_ptr(),
+                        title.as_ptr(),
+                        MB_OK | MB_ICONERROR | MB_USERICON,
+                    );
+                    if result == 1 {
+                        // Open the installation instructions URL in the user's default web browser
+                        open::that("https://github.com/R2NorthstarTools/FlightCore/blob/main/docs/TROUBLESHOOTING.md#flightcore-wont-launch").unwrap();
+                    }
+                }
+            }
+        }
+    };
 }
 
 #[tauri::command]