M4.78: File > Print opens the Print dialog and prints through the system

The Print dialog (Ctrl/Cmd+P) edits the document's print settings in the
sections General, Marks and Bleed, Output, Graphics, Color Management,
Advanced and Summary, with a preview of each printed page under the section
list (drag the art to move its placement). It drives print.setup,
print.preview and file.print; the preview pages now carry their transform,
printed area and trim box. Print sends the job's PDF to the chosen printer
through the new PrintService (lp on macOS/Linux, the shell print verb on
Windows, a hidden frame and the browser's print dialog on the web); without
one, or with PDF File, it saves the PDF. Done only keeps the settings.
UI commands file.print, print.printers and print.printerSetup.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/vectorcraft-web/src/web.rs

@@ -8,6 +8,7 @@ use vectorcraft_engine::Session;
 use vectorcraft_engine::cmd::fileio;
 use vectorcraft_engine::cmd::recovery::RecoveryStore;
 use vectorcraft_ui_egui::place::{DropTarget, PlaceArrival, PlaceInbox};
+use vectorcraft_ui_egui::print::{PrintJob, PrintService, Printer};
 use vectorcraft_ui_egui::{Services, VectorcraftApp};
 use wasm_bindgen::JsCast as _;
 
@@ -174,6 +175,8 @@ fn services(inbox: Inbox, place_inbox: PlaceInbox, ctx: egui::Context) -> Servic
         })),
         inbox: Some(inbox),
         recovery_store: Some(Arc::new(BrowserStore)),
+        // File → Print: the browser's print dialog.
+        print: Some(Box::new(BrowserPrint)),
         ..Default::default()
     }
 }
@@ -225,11 +228,7 @@ fn download(path: &str, bytes: &[u8]) -> Result<(), String> {
     let name = std::path::Path::new(path).file_name().map(|n| n.to_string_lossy().to_string()).unwrap_or_else(|| "vectorcraft".into());
     let window = web_sys::window().ok_or("no window")?;
     let document = window.document().ok_or("no document")?;
-    let parts = js_sys::Array::of1(&js_sys::Uint8Array::from(bytes));
-    let opts = web_sys::BlobPropertyBag::new();
-    opts.set_type(fileio::format_for_name(&name).map_or("application/octet-stream", |f| f.mime));
-    let blob = web_sys::Blob::new_with_u8_array_sequence_and_options(&parts, &opts).map_err(js)?;
-    let url = web_sys::Url::create_object_url_with_blob(&blob).map_err(js)?;
+    let url = blob_url(bytes, fileio::format_for_name(&name).map_or("application/octet-stream", |f| f.mime))?;
     let a: web_sys::HtmlAnchorElement = document.create_element("a").map_err(js)?.dyn_into().map_err(|_| "not an anchor")?;
     a.set_href(&url);
     a.set_download(&name);
@@ -245,3 +244,63 @@ fn download(path: &str, bytes: &[u8]) -> Result<(), String> {
     window.set_timeout_with_callback_and_timeout_and_arguments_0(revoke.unchecked_ref(), 10_000).map_err(js)?;
     Ok(())
 }
+
+/// An object URL of a blob of `bytes` with media type `mime` (revoke it when done).
+fn blob_url(bytes: &[u8], mime: &str) -> Result<String, String> {
+    let parts = js_sys::Array::of1(&js_sys::Uint8Array::from(bytes));
+    let opts = web_sys::BlobPropertyBag::new();
+    opts.set_type(mime);
+    let blob = web_sys::Blob::new_with_u8_array_sequence_and_options(&parts, &opts).map_err(js_err)?;
+    web_sys::Url::create_object_url_with_blob(&blob).map_err(js_err)
+}
+
+/// File → Print in the browser: the job's PDF in a hidden frame, printed through the browser's
+/// print dialog (which picks the printer).
+struct BrowserPrint;
+
+/// The frame holding the last print job (the next job replaces it).
+const PRINT_FRAME_ID: &str = "vectorcraft-print-frame";
+
+impl PrintService for BrowserPrint {
+    fn printers(&mut self) -> Vec<Printer> {
+        // Browsers don't tell pages about printers: their print dialog lists them.
+        vec![]
+    }
+
+    fn print(&mut self, job: &PrintJob) -> Result<String, String> {
+        print_pdf(job.pdf)?;
+        Ok(format!("Printing “{}”: pick the printer in the browser's print dialog", job.title))
+    }
+}
+
+fn print_pdf(pdf: &[u8]) -> Result<(), String> {
+    let document = web_sys::window().and_then(|w| w.document()).ok_or("no document")?;
+    // The previous job's frame and its blob go first.
+    if let Some(old) = document.get_element_by_id(PRINT_FRAME_ID) {
+        if let Some(url) = old.get_attribute("src") {
+            web_sys::Url::revoke_object_url(&url).ok();
+        }
+        old.remove();
+    }
+    let url = blob_url(pdf, "application/pdf")?;
+    let frame: web_sys::HtmlIFrameElement = document.create_element("iframe").map_err(js_err)?.dyn_into().map_err(|_| "not a frame")?;
+    frame.set_id(PRINT_FRAME_ID);
+    // Out of sight but laid out: browsers don't print a frame that isn't.
+    let style = frame.style();
+    for (k, v) in [("position", "fixed"), ("right", "0"), ("bottom", "0"), ("width", "0"), ("height", "0"), ("border", "0")] {
+        style.set_property(k, v).map_err(js_err)?;
+    }
+    let loaded = frame.clone();
+    let onload = wasm_bindgen::closure::Closure::once_into_js(move || {
+        if let Some(w) = loaded.content_window() {
+            w.focus().ok();
+            if let Err(e) = w.print() {
+                log::error!("printing failed: {e:?}");
+            }
+        }
+    });
+    frame.set_onload(Some(onload.unchecked_ref()));
+    frame.set_src(&url);
+    document.body().ok_or("no body")?.append_child(&frame).map_err(js_err)?;
+    Ok(())
+}