feat: add help button opening the user guide

Cargo.toml

@@ -34,6 +34,7 @@ deunicode = "1.6"
 url = { version = "2", default-features = false, features = ["std"] }
 uuid = { version = "1", features = ["v4"] }
 email_address = "0.2"
+open = "5"
 
 [dev-dependencies]
 tempfile = "3.14"

src/mvu/mod.rs

@@ -54,6 +54,8 @@ pub enum Msg {
     SaveRequested(PathBuf),
     SaveCancelled,
     SaveCompleted(Result<PathBuf, String>),
+    OpenHelp,
+    HelpOpened(Result<(), String>),
     ThumbnailDecoded {
         path: PathBuf,
         image: eframe::egui::ColorImage,
@@ -76,6 +78,7 @@ pub enum Command {
     HashFile { path: PathBuf, _retry: bool },
     LoadThumbnail { path: PathBuf, _retry: bool },
     PickExtraFieldsFile,
+    OpenUrl { url: String },
     SaveArchive(SavePayload),
 }
 
@@ -209,6 +212,24 @@ pub fn update(model: &mut AppModel, msg: Msg, cmds: &mut Vec<Command>) {
             Ok(path) => surface_event(model, format!("Archive saved: {}", path.display()), false),
             Err(err) => surface_event(model, format!("Failed to save archive:\n\n{err}"), true),
         },
+        Msg::OpenHelp => {
+            cmds.push(Command::OpenUrl {
+                url: "https://athemis.github.io/ELNPack/".to_string(),
+            });
+            surface_event(
+                model,
+                "Opening ELNPack user guide in your browser…".into(),
+                false,
+            );
+        }
+        Msg::HelpOpened(result) => match result {
+            Ok(()) => surface_event(model, "Help opened in browser.".into(), false),
+            Err(err) => surface_event(
+                model,
+                format!("Could not open help page: {err}"),
+                true,
+            ),
+        },
     }
 }
 
@@ -300,6 +321,10 @@ pub fn run_command(cmd: Command) -> Msg {
             .map(|_| payload.output.clone());
             Msg::SaveCompleted(res.map_err(|e| e.to_string()))
         }
+        Command::OpenUrl { url } => {
+            let res = open::that(url).map(|_| ());
+            Msg::HelpOpened(res.map_err(|e| e.to_string()))
+        }
     }
 }
 

src/ui/mod.rs

@@ -104,6 +104,7 @@ impl eframe::App for ElnPackApp {
             ui.horizontal(|ui| {
                 ui.heading("ELN Entry");
                 ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                    self.render_help_button(ui);
                     self.render_theme_controls(ui);
                     ui.separator();
                     self.render_save_button(ui);
@@ -166,6 +167,19 @@ impl ElnPackApp {
         egui::widgets::global_theme_preference_switch(ui);
     }
 
+    /// Render a compact help button that opens the hosted user guide in a browser tab.
+    fn render_help_button(&mut self, ui: &mut egui::Ui) {
+        ui.add_space(2.0);
+        let button = egui::Button::new(egui_phosphor::regular::QUESTION);
+        if ui
+            .add(button)
+            .on_hover_text("Open the ELNPack user guide")
+            .clicked()
+        {
+            self.inbox.push(Msg::OpenHelp);
+        }
+    }
+
     /// Renders the "Save ELN archive" button and, when activated, opens a file-save dialog to request saving the current entry.
     ///
     /// The button is enabled only when the entry title is not empty and there are no invalid extra fields. When the user selects a file the chosen path is normalized to have the `.eln` extension and a `Msg::SaveRequested(path)` is queued; if the dialog is cancelled a `Msg::SaveCancelled` is queued.