WPF - Iframe scrolling doesn't work after scrolling via clicking on the scrollbar

[kelemenattila]

Hi,
I have an issue with iFrame scrolling. we are using external page in our project. We faced an issue that if we scroll by clicking on scrollbar we can't scroll anymore via mouse wheel inside the iFrame. I tried to reproduce the issue in the latest version of MinimalExample WPF and unfortunately I faced with it. I attached my little html "site" with a ramdom website inside an Iframe.

<title>test</title>

<style>
	body, html {
		margin: 0;
		padding: 0;
		width: 100%;
		height: 100%;
	}
	#iframe_extern_url {
	    position: absolute;
	    top: 0px;
	    left: 0px;
	    right: 0px;
	    bottom: 0px;
	    overflow: auto;
	    z-index: 1000;
        width: 90%;
        height: 90%;
		margin: 0;
	}
</style>
<iframe id="iframe_extern_url" src="https://peter.sh/experiments/chromium-command-line-switches/#disable-threaded-scrolling"></portal>

[amaitland]

This is likely an issue in CEF (Chromium Embedded Framework). CefSharp uses Off Screen Rendering (OSR in the WPF implementation. Mouse/keyboard events are forwarded to the browser.

There have been a number of issues with OSR when using OOPIF.

• OSR: Mouse wheel events are not always routed to iframes chromiumembedded/cef#3325
• OSR (branch 3904): iframes doesn't handle input events (site-per-process?) chromiumembedded/cef#2789
• OSR: Scrolling impossible when auto-scroll enabled by middle mouse button in PDF viewer chromiumembedded/cef#3271

Try the --disable-site-isolation-trials command line arg as a workaround.

If the problem reprduces with a current supported version of CEF then you'll need to open an issue on https://github.com/chromiumembedded/cef/issues (search first to see if one already exists that matches). Post a link back here if you open an issue.

https://bitbucket.org/chromiumembedded/cef/wiki/BranchesAndBuilding.md#markdown-header-current-release-branches-supported

[kelemenattila]

Hi. The workaround resolves the scrolling issue, but if the flag is set, our Print functionality (Opening pdf from a blob in a new Chromium window) doesn't work anymore :( Do you have any idea why us happening this? The pdf from blob is opened in a separate window. I think because the session is not provided for the the chromium window.

[amaitland]

What version are you using? Please make sure you've tested with the current stable version (M116).

As this is most likely an upstream issue, please also test with the CEF Sample Application (cefclient).

Download cefclient from https://cef-builds.spotifycdn.com/cef_binary_116.0.27%2Bgd8c85ac%2Bchromium-116.0.5845.190_windows64_client.tar.bz2

Run with (it's very important you test with the args listed below, test is meaningless otherwise).

 cefclient.exe --multi-threaded-message-loop --no-sandbox --off-screen-rendering-enabled --enable-gpu

If the problem reliably reproduces with cefclient then please create an issue on https://github.com/chromiumembedded/cef/issues/new/choose

Do you have any idea why us happening this? The pdf from blob is opened in a separate window. I think because the session is not provided for the the chromium window.

Did you check the log file for errors?

[kelemenattila]

Hi. I tried in the latest version (117) .net core version, and the scroll still doesn't work.

[amaitland]

As this is most likely an upstream issue, please also test with the CEF Sample Application (cefclient).

Still waiting on results of your testing.

[kelemenattila]

Hi. I downloaded the cefclient and tested with the mentioned args... The client works well if I start like :

I tried with same args in MinimalExample .Net Core verions on same Version>

Unfortunately the issue in minimal example still persists. After click on Scrollbar and move, the mouse wheel doesn't work anymore :|

[amaitland]

I downloaded the cefclient and tested with the mentioned args... The client works well if I start like :

What is that supposed to be an image of exactly? If that's how you launched the browser then you've some how removed the dashes which mean the command line args will be ignored.

Start cefclient from a command prompt using

 cefclient.exe --multi-threaded-message-loop --no-sandbox --off-screen-rendering-enabled --enable-gpu

Likely your testing was incorrectly performed.

I tried with same args in MinimalExample .Net Core verions on same Version>

It doesn't work that way, those argument represent the features that the WPF version uses. Not values to change.