Getting ICoreWebView2_7 in Tauri to Print a PDF

I'm trying to silently create a PDF from HTML in a Tauri application. As far as I could find this is currently not supported in Tauri, so I need to directly communicate with platform specific interfaces.

I found that for windows I need to get the ICoreWebView2_7 of a window since that has a PrintToPdf method. How do I get that? (Or is there some other better way to solve this problem?)

I managed to get the ICoreWebView2 from webview2_com_sys like this.

let _ = main_window.with_webview(|webview| {
    #[cfg(windows)] 
    unsafe {
        let corewebview = webview.controller().CoreWebView2().expect("");
    }
}

But the printToPDF method is on ICoreWebView2_7. So how do i get ICoreWebView2_7 from ICoreWebView2?

Solution

This is still fairly complex and will require you to specify these two dependencies (which should already be implicitely in your project because they are used by tauri itself). I used the matching versions for Tauri 1.6.1 which are fairly old at this point:

webview2-com = "0.19.1"
windows = "0.39.0"

then you can just cast (in this case to ICoreWebView2_10):

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]

use tauri::Manager;
use webview2_com::{Microsoft::Web::WebView2::Win32::*, *};
use windows::core::Interface;

fn main() {
    tauri::Builder::default()
        .setup(|app| {
            let main_window = app.get_window("main").unwrap();
            main_window
                .with_webview(|webview| {
                    #[cfg(windows)]
                    unsafe {
                        let Ok(webview) = webview
                            .controller()
                            .CoreWebView2()
                            .unwrap()
                            .cast::<ICoreWebView2_10>() // This is where the magic happens.
                        else {
                            panic!("Failed to cast PlatformWebview.");
                        };

                        //webview.PrintToPdf().expect("Failed to print to pdf.");
                    }
                })
                .expect("Failed to get webview.");
            Ok(())
        })
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
}