Error on LoadURL with TChromium

Question

I found the brilliant Delphi Chromium project for embedding Chrome in a Delphi form. It works well in Delphi7 after a bit of hacking and I can get the demo app running.

However when I do my own app with the component, I can't load my own url. I get a access violation.

Chromium2.Browser.MainFrame.LoadUrl('http://www.example.com');

The TChromium component is working and I have all the DLLs in the right place, since if I set DefaultUrl it works fine.

I have Chromium2 in a TPageControl page and with the OnClick event of a button I call the above code. I get an AccessViolation. Mainframe is nil.

I can't find a way around this, has anyone got this to work?

Have you looked at the source? Where is MainFrame meant to be created? — David Heffernan, Sep 17 '11 at 12:01
You don't have to create it manually.. and as he gets the AV on a button's click (so, not in the formcreate...), I'm 99% sure this is linked to the missing DLL ;o) — Whiler, Sep 17 '11 at 12:04
@Whiler, I don't think I'm missing DLLs. It works with defaultUrl property. — Toby Allen, Sep 17 '11 at 13:46
I have AVs in almost every URL i try to open. I'm using Delphi 2007, all dlls in the right place. TChromium generates cascade AVs and crashes the app. Any ideas ? — delphirules, Dec 21 '15 at 11:26
I asked on http://stackoverflow.com/questions/34199324/delphi-tchromium-dcef3-constant-access-violations?noredirect=1#comment56165145_34199324 — delphirules, Dec 21 '15 at 11:28

score 4 · Accepted Answer · answered Sep 17 '11 at 13:44

4

I still haven't found a resolution but I found the following work around

procedure TForm1.lblWebsiteClick(Sender: TObject);
var MainFrame : ICefFrame;
begin
  MainFrame := Chromium2.Browser.GetMainFrame;
  MainFrame.LoadUrl('http://www.cookingisfun.ie');
end;

answered Sep 17 '11 at 13:44

Toby Allen

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That does not look like a workaround. That looks like how it is meant to be used. Front page of documentation says "CefFrame represents a single frame in the browser window. Each browser window also has a top-level main frame that can be accessed via the CefBrowser::GetMainFrame() method." – David Heffernan Sep 17 '11 at 13:46
@David, the code in the Demo apps uses the code in the structure I origionally tried `Chromium2.Browser.MainFrame.LoadUrl('http://www.example.com');` so presumably the author felt this was the way it was meant to be used. – Toby Allen Sep 17 '11 at 13:48
You've got the source. I don't. It should be easy to see where MainFrame gets allocated (or not). – David Heffernan Sep 17 '11 at 13:49
I don't need this workaround in my own project. `Chromium2.Browser.MainFrame.LoadUrl('http://www.example.com');` works as expected with mine. I have no `DefaultUrl` defined.. that's maybe the difference. – Whiler Sep 17 '11 at 14:52
Its fairly odd alright. It may be something to do with running Delphi 7 on a Windows 7 machine. – Toby Allen Sep 19 '11 at 13:48

score 3 · Answer 2 · answered Sep 17 '11 at 16:32

3

The problem is that mainframe only loads after the page has loaded.

For one thing, you need to do:

if Assigned(Chromium2.Browser.MainFrame)
    then  Chromium2.Browser.MainFrame...

However, that is not the preferred way to navigate, but instead you should do:

Chromium1.Load( theUrl );

If you still want to use MainFrame, do it in OnLoadEnd event.

answered Sep 17 '11 at 16:32

Christian

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Chromium1.Load does the same as above. It just fails silently when MainFrame is nil. – migajek Sep 27 '11 at 12:00

score 2 · Answer 3 · edited Mar 06 '13 at 12:40

Had similar problems and after quite a few hours located the problem:

If TChromium is on the main form of the application then ok.
If TChromium is not on main form (or on a frame) then:
1. Open cef.inc and remove the dot to define:
```
{.$DEFINE CEF_MULTI_THREADED_MESSAGE_LOOP} 
```
2. Remove DefaultURL value so it is an empty string.

I googled CEF_MULTI_THREADED_MESSAGE_LOOP but it didn't come up with much at all.

Lastly, had resizing/refreshing problems (even with alignment set to alClient). Short term fix is within
crmLoadEnd event do something like:

     if crm.Height < panclient.Height then
        crm.Height := panclient.Height;

score 0 · Answer 4 · answered Jul 07 '14 at 07:58

Had this problem as well. It seems the MainFrame is first created when the frame/window gets visible. But there is an easy way around it. Just call .Load('about:blank') directly on your TChromium object. This will initialize the missing frame earlier.

Whiler · Answer 5 · 2011-09-17T09:42:09.103

0

Do you have alll the required DLL in the folder where your application is built?

You need: libcef.dll, icudt.dll, ...

Check this thread on their support group.

When you build/run the demos, they are built in this subfolder (*DCC_ExeOutput*): DCEF\bin\ which is why it works with them...

edited Sep 17 '11 at 09:42

answered Sep 17 '11 at 09:21

Whiler

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@David: if they are loaded dynamically and GetProcAddress returns nil, it could. – Rudy Velthuis Sep 17 '11 at 11:16
@Rudy `GetProcAddress` returning `nil` seems unlikely to lead to `MainFrame` being `nil`. `MainFrame` sounds like a component to me rather than a procedure address. What makes you think it is a procedure address? What am I missing? – David Heffernan Sep 17 '11 at 12:02
I use this component and if I remove the DLL from my executable folder, I have this behaviour... so, I think this is the reason why he gets this AV... – Whiler Sep 17 '11 at 12:02
MainFrame is set to `nil` when DLLs are missing, but is assigned if they are there? Really? – David Heffernan Sep 17 '11 at 12:06
I **think** that `MainFrame` is not instanciate when dll are missing... and if DLL are present, it is automatically instanciate... BTW, my code is always prefix with `if (chrm1.Browser <> nil) then` before each method calls... – Whiler Sep 17 '11 at 12:13
I'll take your word for it but it seems unusual. Binding errors usually result in bind time errors. – David Heffernan Sep 17 '11 at 12:42
1

All the dlls are in place, the exe is built to the bin directory with the dlls. If I set DefaultUrl it works and loads the url, but I cant set my own url. Browser isnt nil, mainframe is. – Toby Allen Sep 17 '11 at 13:35
@Toby: That's weird... See my other comment in your answer – Whiler Sep 17 '11 at 14:51

Error on LoadURL with TChromium

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