Using LoadHtml/LoadUrl for displaying errors breaks back button #2985
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amaitland
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amaitland
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OK! So I missed the initial reply but he pointed towards some code that seems like the correct way to do this, the InterstitialPageDelegate. I found a decent example of this in another project for showing an ssl error page: We would need to add some low level binders for the InterstitialPageDelegate but I don't think that would be too difficult. I have a bit of an issue at work currently but once I get a bit of free time will go about implementing. I don't think this is a rush, but it certainly seems like a nicer way to do proper intermediate pages. |
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Using DevTools it's possible to navigate to a specific history entry.
Haven't tested yet, will when I get s change. Still a workaround, might be a slightly nicer one. |
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I think there's a better workaround for displaying errors, initial testing looks promising. Via chromiumWebBrowser.LoadError += OnBrowserLoadError;
private async void OnBrowserLoadError(object sender, LoadErrorEventArgs e)
{
//Actions that trigger a download will raise an aborted error.
//Aborted is generally safe to ignore
if (e.ErrorCode == CefErrorCode.Aborted)
{
return;
}
//using LoadHtml/LoadUrl creates an additional history entry that
//prevents the back button from working correctly.
//Use Devools Page.SetDocumentContent to change the content
using (var client = browser.GetDevToolsClient())
{
var response = await client.Page.GetFrameTreeAsync();
var frames = response.FrameTree;
var mainFrame = frames.Frame;
var errorHtml = string.Format("<html><body><h2>Failed to load URL {0} with error {1} ({2}).</h2></body></html>",
e.FailedUrl, e.ErrorText, e.ErrorCode);
_ = client.Page.SetDocumentContentAsync(mainFrame.Id, errorHtml);
//AddressChanged isn't called for failed Urls so we need to manually update the Url TextBox
this.InvokeOnUiThreadIfRequired(() => urlTextBox.Text = e.FailedUrl);
}
}The |
amaitland
removed
the
upstream
- Updated example error handlers to use SetMainFrameDocumentContentAsync for displaying error messages so back/forward navigation works correctly. - DevToolsExtensions updated to use IChromiumWebBrowserBase instead of IWebBrowser so they're usable for WinForms hosted popups Issue #2985
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Two new private void OnLoadError(object sender, LoadErrorEventArgs args)
{
//Aborted is generally safe to ignore
//Actions like starting a download will trigger an Aborted error
//which doesn't require any user action.
if(args.ErrorCode == CefErrorCode.Aborted)
{
return;
}
var errorHtml = string.Format("<html><body><h2>Failed to load URL {0} with error {1} ({2}).</h2></body></html>",
args.FailedUrl, args.ErrorText, args.ErrorCode);
_ = args.Browser.SetMainFrameDocumentContentAsync(errorHtml);
//AddressChanged isn't called for failed Urls so we need to manually update the Url TextBox
this.InvokeOnUiThreadIfRequired(() => urlTextBox.Text = args.FailedUrl);
}The example projects have been updated. |
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The new extension methods are available in version 97.1.11. |
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CEF will hopefully be adding a function for displaying error pages. https://bitbucket.org/chromiumembedded/cef/issues/3265/alloy-add-better-support-for-error-pages |
After #2921 the best way to handle errors seemed to be using LoadHtml/LoadUrl the problem of this is that it creates an additional history entry that prevents the back button from properly functioning. The back button takes you to the same error site that re-triggers the error. We could work around this by not showing the error the second time but that would still require hitting the back button twice.
A temporary solution is to inject JS to call the history.go(-2) if on an error page but isn't great.
Per @amaitland suggestion created an upstream discussion thread about suggested best practice with some suggested options:
https://www.magpcss.org/ceforum/viewtopic.php?f=10&t=17250
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