Return value from CallDevToolsProtocolMethod from RC6/cWebView2

I host WebView2 in my vb6 app using RC6. I would like to call CallDevToolsProtocolMethod Page.printToPDF and get the base64 of the pdf back, but I believe the current version of RC6 does not provide a return value when calling CallDevToolsProtocolMethod, probably because it is async. I tried to check the various events but none trigger, so it seems there is no way to get the return value from CallDevToolsProtocolMethod Page.printToPDF.

Any ideas?

Quote:

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Originally Posted by pawlos2nd

I tried to check the various events but none trigger, so it seems there is no way to get the return value from CallDevToolsProtocolMethod Page.printToPDF.

Any ideas?

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Did you try JSMessage event? It can be "manually" triggered by your JS code with something like vbH().RaiseMessageEvent('title_change', document.title) -- this will trigger JSMessage with sMsg = "title_change" and sMsgContent populated accordingly.

Try implementing your async handler in JS so that on ready it just calls back into VB6 with simple vbH().RaiseMessageEvent passing unique 'pdf_ready' message type with base64 encoded PDF in second sMsgContent parameter.

cheers,
</wqw>

I appreciate your answer, but I dont think it works because Page.printToPDF is a DevTools Protocol method. Page JS cannot invoke CDP — there is no window/chrome.webview API for it, so JS has no "on ready" event and never receives printToPDF's base64?

Yes, I see -- my bad I didn't realize CallDevToolsProtocolMethod is a method of cWebView2 which you probably call with something like

Code:

---

  '--- CDP options: sizes in INCHES (A4 = 8.27 x 11.69)
  sParams = "{""printBackground"":true," & _
            """paperWidth"":8.27,""paperHeight"":11.69," & _
            """marginTop"":0.4,""marginBottom"":0.4," & _
            """marginLeft"":0.4,""marginRight"":0.4," & _
            """preferCSSPageSize"":true}"

  '--- Invoke CDP; returns {"data":"<base64>"}
  Call WV.CallDevToolsProtocolMethod("Page.printToPDF", sParams)

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Olaf will have to chime in but by the looks of it I think there is probably a completion event missing by the wrapper the same way DocumentTitleChanged event is missing and has to be handled in JS as a workaround.

cheers,
</wqw>