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Rank: Newbie
Groups: Member
Joined: 6/30/2015
Posts: 8
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Hi, We purchased the EO.WebBrowser expressly for the purpose of printing html from our .net WPF application. We have a couple of problems with it.
1) If you do not dereference the WebView from the WebControl both object are not able to be GC'd due to event handlers holding references between the two objects. It would be nice if this was done with weak events so that the cleanup would be more simple.
2) More importantly the Print(x,x,x) function returns immediately with no task object to wait on completion. We need to close the view and cleanup after the printing has occurred, we cannot leave and reuse the print view. If we close the view after the print method returns the print will not complete and simply blackholes. We have tried our cleanup in the BeforePrint event but this too is too early esp in regards to network printer that may take a while to respond. We need a deterministic way to depose of the browser after the printing is completed (sent to the spooler).
We have tried to gain a deeper understanding of these issues but the library is obfuscated and is making attempts at understanding the threading model difficult.
Any help on these issues would be great.
Daniel
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Rank: Administration
Groups: Administration
Joined: 5/27/2007
Posts: 24,071
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Hi,
Thank you very much for the feedback.
As to #1, I believe if you explicitly remove the WebControl from its container, it will practically isolate the WebControl/WebView pair from anything else. After this they will be eligible for GC because they are not reachable from anywhere else within your code. It doesn't matter whether they reference each other. What matters is whether they are reachable. .NET itself has a lot of circular references (for example, parent/child controls) and they can all be GCed fine as soon as you severe the link between them and others.
As to #2, I believe we will need some kind of AfterPrint event so that you can track whether the printing is still in progress along with BeforePrint event. These two events should be sufficient for you to track the printing progress since a WebView can only have at most one printing job at the same time. We will try to implement this and update again once it's implemented.
Thanks!
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Rank: Newbie
Groups: Member
Joined: 6/30/2015
Posts: 8
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Thanks so much for your reply. #1 Even after completely dereferencing the control and indeed closing the window does not cause the WebControl or the WebView to be garbage collected. I can submit a project that demonstrates my problem if you wish. https://github.com/MemoryExpress/EOBrowserDisposePlease use your obfuscated code to reproduce these memory leaks, the process of obfuscation seem to be creating a lot of delegates which can leave object references around. Also it seems that Dispose needs to be called on the webView as the finalizers do not seem release the unmanaged resources. #2 That would be so great if you could provide an after print event. We could then close our print window and perform cleanup. Thanks, Daniel
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Rank: Administration
Groups: Administration
Joined: 5/27/2007
Posts: 24,071
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Thanks for the test project. We will look into it and get back to you as soon as possible.
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Rank: Administration
Groups: Administration
Joined: 5/27/2007
Posts: 24,071
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Hi,
We have posted a new build that added AfterPrint event. This event will be fired as soon as all the pages have been sent to the printer. Note that this is not the same as printer finishes printing. The printer may take a while to actually finishes printing.
We have also looked into the GC issue. Using your test project, sometimes we can reproduce the issue, but sometimes we can not. If you move the code that checks whether the objects are still alive in a different function and calls it from a separate button, the issue will not occur. We have also used a memory profiler to examine the heap and we do not see either object. So we believe the objects are properly disposed, it's just a matter of timing when the GC actually occurs.
Thanks!
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Rank: Newbie
Groups: Member
Joined: 6/30/2015
Posts: 8
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This is great! The new after-print method seems to be working fine and we are able to release the memory. We are implementing this build now, thanks so much.
Daniel
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Rank: Administration
Groups: Administration
Joined: 5/27/2007
Posts: 24,071
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Great. Glad to hear that it's working for you. Please feel free to let us know if there is anything else.
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