gui: scroll the host body and grow the default window for the QR

The QR panel pushed the Stop hosting button below the fold at the old
520x480 default. Wraps host_running/host_form in a vertical ScrollArea
(header stays pinned) and bumps the initial height to 640 so the common
case fits without scrolling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.lock

@@ -4176,6 +4176,7 @@ dependencies = [
  "nix 0.30.1",
  "notify-rust",
  "pipewire",
+ "qrcode",
  "serde",
  "serde_json",
  "thiserror 2.0.18",
@@ -4420,6 +4421,12 @@ version = "0.1.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e0c5ccf5294c6ccd63a74f1565028353830a9c2f5eb0c682c355c471726a6e3f"
 
+[[package]]
+name = "qrcode"
+version = "0.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d68782463e408eb1e668cf6152704bd856c78c5b6417adaee3203d8f4c1fc9ec"
+
 [[package]]
 name = "quick-error"
 version = "2.0.1"

Cargo.toml

@@ -55,6 +55,11 @@ egui_glow = { version = "0.34.2", default-features = false, features = ["winit",
 winit = { version = "0.30", default-features = false, features = ["rwh_06", "x11", "wayland", "wayland-dlopen"], optional = true }
 glutin = { version = "0.32", optional = true }
 glutin-winit = { version = "0.5", optional = true }
+# QR-encode the host ticket so a phone (or a second laptop with a webcam) can
+# pick it up without typing 140 chars. default-features = false to skip the
+# `image` crate dep tree — we render the modules to an `egui::ColorImage`
+# directly.
+qrcode = { version = "0.14", default-features = false, optional = true }
 
 [profile.release]
 lto = "thin"
@@ -64,4 +69,4 @@ strip = "symbols"
 [features]
 # Opt-in graphical front-end (pixelpass --gui). Default-off so the headless
 # build never pulls the GUI toolkit tree.
-gui = ["dep:eframe", "dep:notify-rust", "dep:ksni", "dep:egui_glow", "dep:winit", "dep:glutin", "dep:glutin-winit"]
+gui = ["dep:eframe", "dep:notify-rust", "dep:ksni", "dep:egui_glow", "dep:winit", "dep:glutin", "dep:glutin-winit", "dep:qrcode"]

src/gui/mod.rs

@@ -66,8 +66,11 @@ use winit::window::{Window, WindowAttributes, WindowId};
 use self::child::{ChildEvent, ChildProc};
 use self::tray::{TrayAction, TrayHandle, TrayStatus};
 
-/// Initial / minimum window size, in logical points.
-const INNER_SIZE: [f64; 2] = [520.0, 480.0];
+/// Initial / minimum window size, in logical points. Initial height fits the
+/// host screen (ticket + Copy + QR + Stop) without needing to scroll on a 1080p
+/// display; the host screen still wraps in a ScrollArea for the case where the
+/// user shrinks the window below MIN_INNER_SIZE proportions.
+const INNER_SIZE: [f64; 2] = [520.0, 640.0];
 const MIN_INNER_SIZE: [f64; 2] = [460.0, 380.0];
 
 /// Events delivered to the winit loop from off the UI thread (or from egui).
@@ -323,8 +326,11 @@ impl Gfx {
     fn show(&mut self, event_loop: &ActiveEventLoop) -> anyhow::Result<()> {
         match std::mem::replace(&mut self.win, WinState::Between) {
             WinState::Hidden { context } => {
-                let window =
-                    glutin_winit::finalize_window(event_loop, window_attributes(), &self.gl_config)?;
+                let window = glutin_winit::finalize_window(
+                    event_loop,
+                    window_attributes(),
+                    &self.gl_config,
+                )?;
                 let surface = create_surface(&self.gl_display, &self.gl_config, &window)?;
                 let context = context
                     .make_current(&surface)
@@ -382,7 +388,8 @@ impl Gfx {
             viewport_output,
         } = eg.egui_ctx.run_ui(raw_input, run_ui);
 
-        eg.egui_winit.handle_platform_output(window, platform_output);
+        eg.egui_winit
+            .handle_platform_output(window, platform_output);
 
         // Apply any window commands egui emitted (we issue none directly, but
         // egui may request e.g. IME changes) and read the next repaint delay.
@@ -466,11 +473,7 @@ impl App {
     /// actually present, otherwise quit.
     fn on_close(&mut self, event_loop: &ActiveEventLoop) {
         let hide = self.state.close_to_tray
-            && self
-                .state
-                .tray
-                .as_ref()
-                .is_some_and(TrayHandle::registered);
+            && self.state.tray.as_ref().is_some_and(TrayHandle::registered);
         if hide {
             if let Some(gfx) = self.gfx.as_mut() {
                 gfx.hide();
@@ -496,12 +499,7 @@ impl ApplicationHandler<UserEvent> for App {
         }
     }
 
-    fn window_event(
-        &mut self,
-        event_loop: &ActiveEventLoop,
-        _id: WindowId,
-        event: WindowEvent,
-    ) {
+    fn window_event(&mut self, event_loop: &ActiveEventLoop, _id: WindowId, event: WindowEvent) {
         if matches!(event, WindowEvent::CloseRequested) {
             self.on_close(event_loop);
             return;
@@ -788,6 +786,10 @@ struct HostState {
     /// Endpoint ids of the currently-connected viewers, in arrival order.
     /// Drives the per-viewer list and its Kick buttons.
     viewers: Vec<String>,
+    /// QR-code rendering of the current ticket, lazily built on the first draw
+    /// after a Ticket event lands. Cleared on session start/stop so the next
+    /// session's ticket regenerates it.
+    qr_texture: Option<egui::TextureHandle>,
 }
 
 /// The host config summary echoed back by the child's `host_info` event.
@@ -960,11 +962,16 @@ impl PixelPassApp {
         });
         ui.separator();
 
-        if running {
-            self.host_running(ui);
-        } else {
-            self.host_form(ui);
-        }
+        // Scroll the body, not the header — Menu/Host stay pinned at the top.
+        // Needed once the QR panel landed: ticket + Copy + QR + Stop overflows a
+        // shrunken window.
+        egui::ScrollArea::vertical().show(ui, |ui| {
+            if running {
+                self.host_running(ui);
+            } else {
+                self.host_form(ui);
+            }
+        });
     }
 
     fn host_form(&mut self, ui: &mut egui::Ui) {
@@ -1116,14 +1123,42 @@ impl PixelPassApp {
                     .weak(),
                 );
             }
+
+            // Lazy QR build: first draw after a Ticket event has `qr_texture =
+            // None`, so we encode the ticket and load the texture once. The
+            // 4-module quiet zone (white border) matters — phone scanners reject
+            // QR codes flush against a non-white edge.
+            if self.host.qr_texture.is_none()
+                && let Ok(code) = qrcode::QrCode::new(ticket.as_bytes())
+            {
+                let w = code.width();
+                let quiet = 4;
+                let full = w + 2 * quiet;
+                let colors = code.into_colors();
+                let mut pixels = vec![egui::Color32::WHITE; full * full];
+                for y in 0..w {
+                    for x in 0..w {
+                        if colors[y * w + x] == qrcode::Color::Dark {
+                            pixels[(y + quiet) * full + (x + quiet)] = egui::Color32::BLACK;
+                        }
+                    }
+                }
+                let img = egui::ColorImage::new([full, full], pixels);
+                self.host.qr_texture = Some(ui.ctx().load_texture(
+                    "host_qr",
+                    img,
+                    egui::TextureOptions::NEAREST,
+                ));
+            }
+            if let Some(tex) = &self.host.qr_texture {
+                ui.add_space(8.0);
+                ui.add(egui::Image::new(tex).fit_to_exact_size(egui::vec2(200.0, 200.0)));
+            }
         }
 
         if let Some(reason) = &self.host.last_refusal {
             ui.add_space(8.0);
-            ui.colored_label(
-                egui::Color32::from_rgb(220, 160, 60),
-                format!("⚠ {reason}"),
-            );
+            ui.colored_label(egui::Color32::from_rgb(220, 160, 60), format!("⚠ {reason}"));
         }
 
         ui.add_space(16.0);
@@ -1145,6 +1180,7 @@ impl PixelPassApp {
         self.host.capturing = false;
         self.host.copied = false;
         self.host.viewers.clear();
+        self.host.qr_texture = None;
 
         let mut args = vec![
             "--host".to_string(),
@@ -1177,6 +1213,7 @@ impl PixelPassApp {
         self.host.ticket = None;
         self.host.copied = false;
         self.host.viewers.clear();
+        self.host.qr_texture = None;
     }
 
     /// Drain the host child's event channel into state, and detect an
@@ -1243,7 +1280,10 @@ impl PixelPassApp {
                 if !self.host.viewers.contains(&id) {
                     notify(
                         "PixelPass — viewer connected",
-                        format!("endpoint {} is now watching ({active}/{max})", short_id(&id)),
+                        format!(
+                            "endpoint {} is now watching ({active}/{max})",
+                            short_id(&id)
+                        ),
                     );
                     self.host.viewers.push(id);
                 }
@@ -1491,10 +1531,9 @@ mod tests {
     fn sample_ticket() -> (String, String) {
         let sk = iroh::SecretKey::from_bytes(&[7u8; 32]);
         let id = sk.public().to_string();
-        let ticket = iroh_tickets::endpoint::EndpointTicket::new(iroh::EndpointAddr::new(
-            sk.public(),
-        ))
-        .to_string();
+        let ticket =
+            iroh_tickets::endpoint::EndpointTicket::new(iroh::EndpointAddr::new(sk.public()))
+                .to_string();
         (ticket, id)
     }