feat: promisify webContents.printToPDF() (#16795)

atom/browser/api/atom_api_web_contents.cc

@@ -1499,11 +1499,12 @@ std::vector<printing::PrinterBasicInfo> WebContents::GetPrinterList() {
   return printers;
 }
 
-void WebContents::PrintToPDF(
-    const base::DictionaryValue& settings,
-    const PrintPreviewMessageHandler::PrintToPDFCallback& callback) {
+v8::Local<v8::Promise> WebContents::PrintToPDF(
+    const base::DictionaryValue& settings) {
+  scoped_refptr<util::Promise> promise = new util::Promise(isolate());
   PrintPreviewMessageHandler::FromWebContents(web_contents())
-      ->PrintToPDF(settings, callback);
+      ->PrintToPDF(settings, promise);
+  return promise->GetHandle();
 }
 #endif
 

atom/browser/api/atom_api_web_contents.h

@@ -174,9 +174,7 @@ class WebContents : public mate::TrackableObject<WebContents>,
   void Print(mate::Arguments* args);
   std::vector<printing::PrinterBasicInfo> GetPrinterList();
   // Print current page as PDF.
-  void PrintToPDF(
-      const base::DictionaryValue& settings,
-      const PrintPreviewMessageHandler::PrintToPDFCallback& callback);
+  v8::Local<v8::Promise> PrintToPDF(const base::DictionaryValue& settings);
 #endif
 
   // DevTools workspace api.

atom/browser/printing/print_preview_message_handler.cc

@@ -89,7 +89,7 @@ void PrintPreviewMessageHandler::OnMetafileReadyForPrinting(
   const PrintHostMsg_DidPrintContent_Params& content = params.content;
   if (!content.metafile_data_region.IsValid() ||
       params.expected_pages_count <= 0) {
-    RunPrintToPDFCallback(ids.request_id, nullptr);
+    RejectPromise(ids.request_id);
     return;
   }
 
@@ -102,10 +102,9 @@ void PrintPreviewMessageHandler::OnMetafileReadyForPrinting(
         base::BindOnce(&PrintPreviewMessageHandler::OnCompositePdfDocumentDone,
                        weak_ptr_factory_.GetWeakPtr(), ids));
   } else {
-    RunPrintToPDFCallback(
-        ids.request_id,
-        base::RefCountedSharedMemoryMapping::CreateFromWholeRegion(
-            content.metafile_data_region));
+    ResolvePromise(ids.request_id,
+                   base::RefCountedSharedMemoryMapping::CreateFromWholeRegion(
+                       content.metafile_data_region));
   }
 }
 
@@ -117,11 +116,11 @@ void PrintPreviewMessageHandler::OnCompositePdfDocumentDone(
 
   if (status != printing::mojom::PdfCompositor::Status::SUCCESS) {
     DLOG(ERROR) << "Compositing pdf failed with error " << status;
-    RunPrintToPDFCallback(ids.request_id, nullptr);
+    RejectPromise(ids.request_id);
     return;
   }
 
-  RunPrintToPDFCallback(
+  ResolvePromise(
       ids.request_id,
       base::RefCountedSharedMemoryMapping::CreateFromWholeRegion(region));
 }
@@ -131,23 +130,23 @@ void PrintPreviewMessageHandler::OnPrintPreviewFailed(
     const PrintHostMsg_PreviewIds& ids) {
   StopWorker(document_cookie);
 
-  RunPrintToPDFCallback(ids.request_id, nullptr);
+  RejectPromise(ids.request_id);
 }
 
 void PrintPreviewMessageHandler::OnPrintPreviewCancelled(
     int document_cookie,
     const PrintHostMsg_PreviewIds& ids) {
   StopWorker(document_cookie);
 
-  RunPrintToPDFCallback(ids.request_id, nullptr);
+  RejectPromise(ids.request_id);
 }
 
 void PrintPreviewMessageHandler::PrintToPDF(
     const base::DictionaryValue& options,
-    const PrintToPDFCallback& callback) {
+    scoped_refptr<atom::util::Promise> promise) {
   int request_id;
   options.GetInteger(printing::kPreviewRequestID, &request_id);
-  print_to_pdf_callback_map_[request_id] = callback;
+  promise_map_[request_id] = std::move(promise);
 
   auto* focused_frame = web_contents()->GetFocusedFrame();
   auto* rfh = focused_frame && focused_frame->HasSelection()
@@ -156,28 +155,44 @@ void PrintPreviewMessageHandler::PrintToPDF(
   rfh->Send(new PrintMsg_PrintPreview(rfh->GetRoutingID(), options));
 }
 
-void PrintPreviewMessageHandler::RunPrintToPDFCallback(
+scoped_refptr<atom::util::Promise> PrintPreviewMessageHandler::GetPromise(
+    int request_id) {
+  auto it = promise_map_.find(request_id);
+  DCHECK(it != promise_map_.end());
+
+  auto promise = it->second;
+  promise_map_.erase(it);
+
+  return promise;
+}
+
+void PrintPreviewMessageHandler::ResolvePromise(
     int request_id,
     scoped_refptr<base::RefCountedMemory> data_bytes) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
-  v8::Isolate* isolate = v8::Isolate::GetCurrent();
-  v8::Locker locker(isolate);
+  auto promise = GetPromise(request_id);
+
+  v8::Isolate* isolate = promise->isolate();
+  mate::Locker locker(isolate);
   v8::HandleScope handle_scope(isolate);
-  if (data_bytes && data_bytes->size()) {
-    v8::Local<v8::Value> buffer =
-        node::Buffer::Copy(isolate,
-                           reinterpret_cast<const char*>(data_bytes->front()),
-                           data_bytes->size())
-            .ToLocalChecked();
-    print_to_pdf_callback_map_[request_id].Run(v8::Null(isolate), buffer);
-  } else {
-    v8::Local<v8::String> error_message =
-        v8::String::NewFromUtf8(isolate, "Failed to generate PDF");
-    print_to_pdf_callback_map_[request_id].Run(
-        v8::Exception::Error(error_message), v8::Null(isolate));
-  }
-  print_to_pdf_callback_map_.erase(request_id);
+  v8::Context::Scope context_scope(
+      v8::Local<v8::Context>::New(isolate, promise->GetContext()));
+
+  v8::Local<v8::Value> buffer =
+      node::Buffer::Copy(isolate,
+                         reinterpret_cast<const char*>(data_bytes->front()),
+                         data_bytes->size())
+          .ToLocalChecked();
+
+  promise->Resolve(buffer);
+}
+
+void PrintPreviewMessageHandler::RejectPromise(int request_id) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  auto promise = GetPromise(request_id);
+  promise->RejectWithErrorMessage("Failed to generate PDF");
 }
 
 }  // namespace atom

atom/browser/printing/print_preview_message_handler.h

@@ -7,6 +7,7 @@
 
 #include <map>
 
+#include "atom/common/promise_util.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "components/services/pdf_compositor/public/interfaces/pdf_compositor.mojom.h"
@@ -28,13 +29,10 @@ class PrintPreviewMessageHandler
     : public content::WebContentsObserver,
       public content::WebContentsUserData<PrintPreviewMessageHandler> {
  public:
-  using PrintToPDFCallback =
-      base::Callback<void(v8::Local<v8::Value>, v8::Local<v8::Value>)>;
-
   ~PrintPreviewMessageHandler() override;
 
   void PrintToPDF(const base::DictionaryValue& options,
-                  const PrintToPDFCallback& callback);
+                  scoped_refptr<atom::util::Promise> promise);
 
  protected:
   // content::WebContentsObserver implementation.
@@ -57,11 +55,15 @@ class PrintPreviewMessageHandler
                             const PrintHostMsg_PreviewIds& ids);
   void OnPrintPreviewCancelled(int document_cookie,
                                const PrintHostMsg_PreviewIds& ids);
-  void RunPrintToPDFCallback(int request_id,
-                             scoped_refptr<base::RefCountedMemory> data_bytes);
 
-  using PrintToPDFCallbackMap = std::map<int, PrintToPDFCallback>;
-  PrintToPDFCallbackMap print_to_pdf_callback_map_;
+  scoped_refptr<atom::util::Promise> GetPromise(int request_id);
+
+  void ResolvePromise(int request_id,
+                      scoped_refptr<base::RefCountedMemory> data_bytes);
+  void RejectPromise(int request_id);
+
+  using PromiseMap = std::map<int, scoped_refptr<atom::util::Promise>>;
+  PromiseMap promise_map_;
 
   base::WeakPtrFactory<PrintPreviewMessageHandler> weak_ptr_factory_;
 

docs/api/promisification.md

@@ -28,17 +28,16 @@ When a majority of affected functions are migrated, this flag will be enabled by
 - [ses.clearAuthCache(options[, callback])](https://github.com/electron/electron/blob/master/docs/api/session.md#clearAuthCache)
 - [contents.executeJavaScript(code[, userGesture, callback])](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#executeJavaScript)
 - [contents.print([options], [callback])](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#print)
-- [contents.printToPDF(options, callback)](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#printToPDF)
 - [contents.savePage(fullPath, saveType, callback)](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#savePage)
 - [webFrame.executeJavaScript(code[, userGesture, callback])](https://github.com/electron/electron/blob/master/docs/api/web-frame.md#executeJavaScript)
 - [webFrame.executeJavaScriptInIsolatedWorld(worldId, scripts[, userGesture, callback])](https://github.com/electron/electron/blob/master/docs/api/web-frame.md#executeJavaScriptInIsolatedWorld)
 - [webviewTag.executeJavaScript(code[, userGesture, callback])](https://github.com/electron/electron/blob/master/docs/api/webview-tag.md#executeJavaScript)
-- [webviewTag.printToPDF(options, callback)](https://github.com/electron/electron/blob/master/docs/api/webview-tag.md#printToPDF)
 
 ### Converted Functions
 
 - [app.getFileIcon(path[, options], callback)](https://github.com/electron/electron/blob/master/docs/api/app.md#getFileIcon)
 - [contents.capturePage([rect, ]callback)](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#capturePage)
+- [contents.printToPDF(options, callback)](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#printToPDF)
 - [contentTracing.getCategories(callback)](https://github.com/electron/electron/blob/master/docs/api/content-tracing.md#getCategories)
 - [contentTracing.startRecording(options, callback)](https://github.com/electron/electron/blob/master/docs/api/content-tracing.md#startRecording)
 - [contentTracing.stopRecording(resultFilePath, callback)](https://github.com/electron/electron/blob/master/docs/api/content-tracing.md#stopRecording)
@@ -50,5 +49,6 @@ When a majority of affected functions are migrated, this flag will be enabled by
 - [protocol.isProtocolHandled(scheme, callback)](https://github.com/electron/electron/blob/master/docs/api/protocol.md#isProtocolHandled)
 - [shell.openExternal(url[, options, callback])](https://github.com/electron/electron/blob/master/docs/api/shell.md#openExternal)
 - [webviewTag.capturePage([rect, ]callback)](https://github.com/electron/electron/blob/master/docs/api/webview-tag.md#capturePage)
+- [webviewTag.printToPDF(options, callback)](https://github.com/electron/electron/blob/master/docs/api/webview-tag.md#printToPDF)
 - [win.capturePage([rect, ]callback)](https://github.com/electron/electron/blob/master/docs/api/browser-window.md#capturePage)
 - [desktopCapturer.getSources(options, callback)](https://github.com/electron/electron/blob/master/docs/api/desktop-capturer.md#getSources)

docs/api/web-contents.md

@@ -1202,6 +1202,25 @@ settings.
 The `callback` will be called with `callback(error, data)` on completion. The
 `data` is a `Buffer` that contains the generated PDF data.
 
+**[Deprecated Soon](promisification.md)**
+
+#### `contents.printToPDF(options)`
+
+* `options` Object
+  * `marginsType` Integer (optional) - Specifies the type of margins to use. Uses 0 for
+    default margin, 1 for no margin, and 2 for minimum margin.
+  * `pageSize` String | Size (optional) - Specify page size of the generated PDF. Can be `A3`,
+    `A4`, `A5`, `Legal`, `Letter`, `Tabloid` or an Object containing `height`
+    and `width` in microns.
+  * `printBackground` Boolean (optional) - Whether to print CSS backgrounds.
+  * `printSelectionOnly` Boolean (optional) - Whether to print selection only.
+  * `landscape` Boolean (optional) - `true` for landscape, `false` for portrait.
+
+* Returns `Promise<Buffer>` - Resolves with the generated PDF data.
+
+Prints window's web page as PDF with Chromium's preview printing custom
+settings.
+
 The `landscape` will be ignored if `@page` CSS at-rule is used in the web page.
 
 By default, an empty `options` will be regarded as:

docs/api/webview-tag.md

@@ -542,6 +542,24 @@ Prints `webview`'s web page. Same as `webContents.print([options])`.
 
 Prints `webview`'s web page as PDF, Same as `webContents.printToPDF(options, callback)`.
 
+**[Deprecated Soon](promisification.md)**
+
+### `<webview>.printToPDF(options)`
+
+* `options` Object
+  * `marginsType` Integer (optional) - Specifies the type of margins to use. Uses 0 for
+    default margin, 1 for no margin, and 2 for minimum margin.
+  * `pageSize` String | Size (optional) - Specify page size of the generated PDF. Can be `A3`,
+    `A4`, `A5`, `Legal`, `Letter`, `Tabloid` or an Object containing `height`
+    and `width` in microns.
+  * `printBackground` Boolean (optional) - Whether to print CSS backgrounds.
+  * `printSelectionOnly` Boolean (optional) - Whether to print selection only.
+  * `landscape` Boolean (optional) - `true` for landscape, `false` for portrait.
+
+* Returns `Promise<Buffer>` - Resolves with the generated PDF data.
+
+Prints `webview`'s web page as PDF, Same as `webContents.printToPDF(options)`.
+
 ### `<webview>.capturePage([rect, ]callback)`
 
 * `rect` [Rectangle](structures/rectangle.md) (optional) - The bounds to capture

lib/browser/api/web-contents.js

@@ -263,7 +263,7 @@ WebContents.prototype.takeHeapSnapshot = function (filePath) {
 }
 
 // Translate the options of printToPDF.
-WebContents.prototype.printToPDF = function (options, callback) {
+WebContents.prototype.printToPDF = function (options) {
   const printingSetting = Object.assign({}, defaultPrintingSetting)
   if (options.landscape) {
     printingSetting.landscape = options.landscape
@@ -282,7 +282,7 @@ WebContents.prototype.printToPDF = function (options, callback) {
     const pageSize = options.pageSize
     if (typeof pageSize === 'object') {
       if (!pageSize.height || !pageSize.width) {
-        return callback(new Error('Must define height and width for pageSize'))
+        return Promise.reject(new Error('Must define height and width for pageSize'))
       }
       // Dimensions in Microns
       // 1 meter = 10^6 microns
@@ -295,7 +295,7 @@ WebContents.prototype.printToPDF = function (options, callback) {
     } else if (PDFPageSizes[pageSize]) {
       printingSetting.mediaSize = PDFPageSizes[pageSize]
     } else {
-      return callback(new Error(`Does not support pageSize with ${pageSize}`))
+      return Promise.reject(new Error(`Does not support pageSize with ${pageSize}`))
     }
   } else {
     printingSetting.mediaSize = PDFPageSizes['A4']
@@ -304,9 +304,9 @@ WebContents.prototype.printToPDF = function (options, callback) {
   // Chromium expects this in a 0-100 range number, not as float
   printingSetting.scaleFactor *= 100
   if (features.isPrintingEnabled()) {
-    this._printToPDF(printingSetting, callback)
+    return this._printToPDF(printingSetting)
   } else {
-    console.error('Error: Printing feature is disabled.')
+    return Promise.reject(new Error('Printing feature is disabled'))
   }
 }
 
@@ -342,6 +342,9 @@ WebContents.prototype.loadFile = function (filePath, options = {}) {
   }))
 }
 
+WebContents.prototype.capturePage = deprecate.promisify(WebContents.prototype.capturePage)
+WebContents.prototype.printToPDF = deprecate.promisify(WebContents.prototype.printToPDF)
+
 const addReplyToEvent = (event) => {
   event.reply = (...args) => {
     event.sender.sendToFrame(event.frameId, ...args)
@@ -385,8 +388,6 @@ WebContents.prototype._init = function () {
   // render-view-deleted event, so ignore the listeners warning.
   this.setMaxListeners(0)
 
-  this.capturePage = deprecate.promisify(this.capturePage)
-
   // Dispatch IPC messages to the ipc module.
   this.on('-ipc-message', function (event, internal, channel, args) {
     if (internal) {

lib/common/web-view-methods.js

@@ -60,11 +60,11 @@ exports.asyncCallbackMethods = new Set([
   'sendInputEvent',
   'setLayoutZoomLevelLimits',
   'setVisualZoomLevelLimits',
-  'print',
-  'printToPDF'
+  'print'
 ])
 
 exports.asyncPromiseMethods = new Set([
   'capturePage',
-  'executeJavaScript'
+  'executeJavaScript',
+  'printToPDF'
 ])

lib/renderer/web-view/web-view-impl.js

@@ -1,6 +1,6 @@
 'use strict'
 
-const { webFrame } = require('electron')
+const { webFrame, deprecate } = require('electron')
 
 const v8Util = process.atomBinding('v8_util')
 const ipcRenderer = require('@electron/internal/renderer/ipc-renderer-internal')
@@ -287,6 +287,8 @@ const setupMethods = (WebViewElement) => {
   for (const method of asyncPromiseMethods) {
     WebViewElement.prototype[method] = createPromiseHandler(method)
   }
+
+  WebViewElement.prototype.printToPDF = deprecate.promisify(WebViewElement.prototype.printToPDF)
 }
 
 module.exports = { setupAttributes, setupMethods, guestViewInternal, webFrame, WebViewImpl }

spec/api-web-contents-spec.js

@@ -1268,7 +1268,22 @@ describe('webContents module', () => {
       }
     })
 
-    it('can print to PDF', (done) => {
+    it('can print to PDF', async () => {
+      w.destroy()
+      w = new BrowserWindow({
+        show: false,
+        webPreferences: {
+          sandbox: true
+        }
+      })
+      await w.loadURL('data:text/html,%3Ch1%3EHello%2C%20World!%3C%2Fh1%3E')
+      const data = await w.webContents.printToPDF({})
+      assert.strictEqual(data instanceof Buffer, true)
+      assert.notStrictEqual(data.length, 0)
+    })
+
+    // TODO(miniak): remove when promisification is complete
+    it('can print to PDF (callback)', (done) => {
       w.destroy()
       w = new BrowserWindow({
         show: false,