fix: always callback error with invalid print settings (#24476)

docs/api/web-contents.md

@@ -1311,6 +1311,8 @@ Returns [`PrinterInfo[]`](structures/printer-info.md)
   * `success` Boolean - Indicates success of the print call.
   * `failureReason` String - Error description called back if the print fails.
 
+When a custom `pageSize` is passed, Chromium attempts to validate platform specific minumum values for `width_microns` and `height_microns`. Width and height must both be minimum 353 microns but may be higher on some operating systems.
+
 Prints window's web page. When `silent` is set to `true`, Electron will pick
 the system's default printer if `deviceName` is empty and the default settings for printing.
 
@@ -1334,13 +1336,12 @@ win.webContents.print(options, (success, errorType) => {
   * `landscape` Boolean (optional) - `true` for landscape, `false` for portrait.
   * `marginsType` Integer (optional) - Specifies the type of margins to use. Uses 0 for
     default margin, 1 for no margin, and 2 for minimum margin.
-    and `width` in microns.
   * `scaleFactor` Number (optional) - The scale factor of the web page. Can range from 0 to 100.
   * `pageRanges` Record<string, number> (optional) - The page range to print.
     * `from` Number - the first page to print.
     * `to` Number - the last page to print (inclusive).
   * `pageSize` String | Size (optional) - Specify page size of the generated PDF. Can be `A3`,
-  `A4`, `A5`, `Legal`, `Letter`, `Tabloid` or an Object containing `height`
+  `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.
 

lib/browser/api/web-contents.ts

@@ -72,6 +72,19 @@ const PDFPageSizes: Record<string, MediaSize> = {
   }
 };
 
+// The minimum micron size Chromium accepts is that where:
+// Per printing/units.h:
+//  * kMicronsPerInch - Length of an inch in 0.001mm unit.
+//  * kPointsPerInch - Length of an inch in CSS's 1pt unit.
+//
+// Formula: (kPointsPerInch / kMicronsPerInch) * size >= 1
+//
+// Practically, this means microns need to be > 352 microns.
+// We therefore need to verify this or it will silently fail.
+const isValidCustomPageSize = (width: number, height: number) => {
+  return [width, height].every(x => x > 352);
+};
+
 // Default printing setting
 const defaultPrintingSetting = {
   // Customizable.
@@ -315,13 +328,20 @@ WebContents.prototype.printToPDF = function (options) {
         const error = new Error('height and width properties are required for pageSize');
         return Promise.reject(error);
       }
-      // Dimensions in Microns
-      // 1 meter = 10^6 microns
+
+      // Dimensions in Microns - 1 meter = 10^6 microns
+      const height = Math.ceil(pageSize.height);
+      const width = Math.ceil(pageSize.width);
+      if (!isValidCustomPageSize(width, height)) {
+        const error = new Error('height and width properties must be minimum 352 microns.');
+        return Promise.reject(error);
+      }
+
       printSettings.mediaSize = {
         name: 'CUSTOM',
         custom_display_name: 'Custom',
-        height_microns: Math.ceil(pageSize.height),
-        width_microns: Math.ceil(pageSize.width)
+        height_microns: height,
+        width_microns: width
       };
     } else if (Object.prototype.hasOwnProperty.call(PDFPageSizes, pageSize)) {
       printSettings.mediaSize = PDFPageSizes[pageSize];
@@ -356,12 +376,19 @@ WebContents.prototype.print = function (options = {}, callback) {
         if (!pageSize.height || !pageSize.width) {
           throw new Error('height and width properties are required for pageSize');
         }
+
         // Dimensions in Microns - 1 meter = 10^6 microns
+        const height = Math.ceil(pageSize.height);
+        const width = Math.ceil(pageSize.width);
+        if (!isValidCustomPageSize(width, height)) {
+          throw new Error('height and width properties must be minimum 352 microns.');
+        }
+
         (options as any).mediaSize = {
           name: 'CUSTOM',
           custom_display_name: 'Custom',
-          height_microns: Math.ceil(pageSize.height),
-          width_microns: Math.ceil(pageSize.width)
+          height_microns: height,
+          width_microns: width
         };
       } else if (PDFPageSizes[pageSize]) {
         (options as any).mediaSize = PDFPageSizes[pageSize];

patches/chromium/printing.patch

@@ -90,7 +90,7 @@ index adb208ba3589e32536527219aaf4e89e3ee3311a..301f6416898445eed814d67901254ef8
  }
  
 diff --git a/chrome/browser/printing/print_view_manager_base.cc b/chrome/browser/printing/print_view_manager_base.cc
-index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc473bbd0da 100644
+index 8a743d0dd74b087059ff812019ae568a22c5fa01..551dbc7b0bfdbf4ca549278bb3dfc4e3abb5cf0f 100644
 --- a/chrome/browser/printing/print_view_manager_base.cc
 +++ b/chrome/browser/printing/print_view_manager_base.cc
 @@ -27,10 +27,7 @@
@@ -194,7 +194,19 @@ index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc4
  #endif
  
    ReleasePrinterQuery();
-@@ -463,9 +476,13 @@ void PrintViewManagerBase::OnNotifyPrintJobEvent(
+@@ -382,6 +395,11 @@ void PrintViewManagerBase::OnScriptedPrint(
+ }
+ 
+ void PrintViewManagerBase::OnShowInvalidPrinterSettingsError() {
++  if (!callback_.is_null()) {
++    std::string cb_str = "Invalid printer settings";
++    std::move(callback_).Run(printing_succeeded_, cb_str);
++  }
++
+   base::ThreadTaskRunnerHandle::Get()->PostTask(
+       FROM_HERE, base::BindOnce(&ShowWarningMessageBox,
+                                 l10n_util::GetStringUTF16(
+@@ -463,9 +481,13 @@ void PrintViewManagerBase::OnNotifyPrintJobEvent(
            content::NotificationService::NoDetails());
        break;
      }
@@ -210,7 +222,7 @@ index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc4
        NOTREACHED();
        break;
      }
-@@ -560,8 +577,10 @@ bool PrintViewManagerBase::CreateNewPrintJob(
+@@ -560,8 +582,10 @@ bool PrintViewManagerBase::CreateNewPrintJob(
    DCHECK(!quit_inner_loop_);
    DCHECK(query);
  
@@ -223,7 +235,7 @@ index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc4
  
    // We can't print if there is no renderer.
    if (!web_contents()->GetRenderViewHost() ||
-@@ -582,8 +601,6 @@ bool PrintViewManagerBase::CreateNewPrintJob(
+@@ -582,8 +606,6 @@ bool PrintViewManagerBase::CreateNewPrintJob(
    print_job_->SetSource(source, /*source_id=*/"");
  #endif
  
@@ -232,7 +244,7 @@ index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc4
    printing_succeeded_ = false;
    return true;
  }
-@@ -632,14 +649,22 @@ void PrintViewManagerBase::ReleasePrintJob() {
+@@ -632,14 +654,22 @@ void PrintViewManagerBase::ReleasePrintJob() {
    content::RenderFrameHost* rfh = printing_rfh_;
    printing_rfh_ = nullptr;
  
@@ -257,7 +269,7 @@ index 8a743d0dd74b087059ff812019ae568a22c5fa01..20c43be03706617a276d210190897dc4
    // Don't close the worker thread.
    print_job_ = nullptr;
  }
-@@ -675,7 +700,7 @@ bool PrintViewManagerBase::RunInnerMessageLoop() {
+@@ -675,7 +705,7 @@ bool PrintViewManagerBase::RunInnerMessageLoop() {
  }
  
  bool PrintViewManagerBase::OpportunisticallyCreatePrintJob(int cookie) {

spec-main/api-web-contents-spec.ts

@@ -141,6 +141,17 @@ describe('webContents module', () => {
       }).to.throw('Unsupported pageSize: i-am-a-bad-pagesize');
     });
 
+    it('throws when an invalid custom pageSize is passed', () => {
+      expect(() => {
+        w.webContents.print({
+          pageSize: {
+            width: 100,
+            height: 200
+          }
+        });
+      }).to.throw('height and width properties must be minimum 352 microns.');
+    });
+
     it('does not crash with custom margins', () => {
       expect(() => {
         w.webContents.print({