Electron 4.0.0: webContents.print() must be called twice or with an empty object

[c3er]

• Output of node_modules/.bin/electron --version: v4.0.0
• Operating System (Platform and Version): Windows 10 64 Bit, Version 1809
• Output of node_modules/.bin/electron --version on last known working Electron version (if applicable): v3.0.13

Expected Behavior

If I call webContents.print(), the print dialog shall open. If I give a callback function, the callback shall be called.

Actual behavior

I must call webContents.print() twice before the print dialog opens. There is a workaround: If I give an empty object as parameter, the behavior is as expected: webContents.print({})

Additionally, I observed that the callback, if given, gets not called. This works also as expected under Electron 3.0.13.

To Reproduce

I made a repository with multiple examples to the described behavior.

To clone the repository:

$ git clone https://github.com/c3er/electronPrintingIssue.git

All examples should start after typing the following commands in their respective directories:

$ npm install
$ npm start

You can either click File -> Print in the main menu or press Ctrl+P - behavior is the same.

Additional Information

Explanation to the examples:

• 01_expected_3.0.13: This shows the expected behavior under Electron 3.0.13. I press Ctrl+P and the printing dialog appears immediately.
• 02_bug_4.0.0: This shows the described bug under Electron 4.0.0. I must press Ctrl+P twice before the dialog opens. The debugger (VS Code) shows that the function gets called every time.
• 03_workaround_4.0.0: This shows the described workaround under Electron 4.0.0 by giving an empty object as parameter.
• 04_callback-called_3.0.13: As expected, a given callback gets called and gives some output to the console.
• 05_callback-not-called_4.0.0: The given callback seems not to be called. There is no output in the console.

[javan]

I must call webContents.print() twice before the print dialog opens.

Confirmed. Additionally, I'm seeing that after the dialog opens once it won't open again until relaunching.

[javan]

Just tested on macOS (10.14.2) and webContents.print() doesn't work at all. The print dialog never opens.

[javan]

Did some more testing on macOS. Printing works as expected in the 4-0 betas up through 4.0.0-beta.9. Doesn't work in 4.0.0-beta.10, 4.0.0-beta.11, or 4.0.0.

#15976 was introduced in 4.0.0-beta.10 so the issue mostly likely lies somewhere in #15023 or #15143.

[bengotow]

Hey folks—just wanted to add, I had this problem as well but was able to work around it by using window.print() instead (which seems to work fine.) Unfortunately you don't get a callback in that case...

[abdellaui]

does anyone have another clear solution as calling webContents.print() twice or window.print()?

[javan]

Here's my current workaround:

- contents.print()
+ contents.executeJavaScript("window.print()")

[takkiraz]

@javan your current workaround works, but is there another way for printing silent.

[javan]

The window.print() API doesn't allow that, AFAIK. You could try using Electron v4.0.0-beta.9 or earlier until this issue is fixed.

[nitsakh]

Closing as this appears fixed in latest electron 5 beta. Feel free to reopen otherwise.

[maplemike]

Silent printing still fails in latest beta as mentioned in #16193

[maikonmatheus]

Silent printing still fails in Electron 5.0.3. I had to downgrade to electron@3.1.8 for use the silent print.

[Catlite91]

Silent printing still fails in Electron 5.0.6.

[popod]

@Catlite91 The backport which fix the "silent printing" issue is here #19038 Follow this PR to get notified when it will be merged into 5.x.x.