Webbrowser control problem

minor28 · May 07, 2013, 06:00:22 AM

I am using the iefram.dll webbrowser control. I can navigate to different url with the IWebBrowser2.Navigate2 function. Even the "about:blank" is working. Now I want to write to the document from memory.

With the "about:blank" document I retrieve the document object with IWebBrowser2.Document function.

Now my problem starts.

MSDN say that IHTMLDocument.Write parameter should be a safe array.

pHtmlText is a BSTR

Code Select


invoke SafeArrayCreateVector,VT_VARIANT,0,1
mov pSafeArray,eax
invoke SafeArrayAccessData,pSafeArray,addr pData
mov ebx,pData
mov word ptr [ebx].VARIANT.vt,VT_BSTR
mov eax,pHtmlText
mov dword ptr [ebx].VARIANT.bstrVal,eax
invoke SafeArrayUnaccessData,pSafeArray

invoke VariantInit,addr var1
mov var1.vt,VT_SAFEARRAY
mov eax,pSafeArray
mov var1.parray,eax

IHTMLDocument.Write(addr var1)

This will be a blank page totally empty not even <html></html>. Changing the parameter to pSafeArray result in "NULL" on the page. As I can see the safe array has no NULL string.

Now I use the BSTR as parameter

Code Select


invoke VariantInit,addr var1
mov var1.vt,VT_BSTR
mov eax,pHtmlText
mov var1.bstrVal,eax

IHTMLDocument.Write(addr var1)

This will aleast give a result. If the html code i a short text strings it works well but if it is a longer htmlcode the text string is truncated and it is also in some extent not written as I wrote it.

Any idea how to solve this problem

Antariy · May 07, 2013, 12:10:00 PM

How defined pHtmlText variable?
BSTR datatype uses a DWORD with a length of the string, which lies 4 bytes above the pointer to the string.
I.e., proper pre-initialized BSTR should look like:

.data

dd sizeof pHtmlText
pHtmlText dw "<","h","t","m","l" ... and so on ... ; dw is because BSTR is usually Unicode string

minor28 · May 07, 2013, 04:30:25 PM

pHtmlText is a pointer to a unicode string preseeded whith the length of the string, i.e. a BSTR string. I'm sure of that.

qWord · May 07, 2013, 10:02:42 PM

the method write() expects the type SAFEARRAY* whereas your code passes a VARIANTARG* -> you might try it with using pSafeArray instead.

minor28 · May 08, 2013, 01:47:18 AM

Code Select


invoke SafeArrayCreateVector,VT_VARIANT,0,1
mov pSafeArray,eax
mov ebx,eax
mov word ptr [ebx].SAFEARRAY.fFeatures,100h ;FADF_BSTR
invoke SafeArrayAccessData,pSafeArray,addr pData
mov ebx,pData
mov word ptr [ebx].VARIANT.vt,VT_BSTR
mov eax,pHtmlText
mov dword ptr [ebx].VARIANT.bstrVal,eax
invoke SafeArrayUnaccessData,pSafeArray

lea edi,dp ;dispparams sturcture
mov eax,pSafeArray
mov dword ptr [edi].DISPPARAMS.rgvarg,eax
mov dispidNamed,DISPID_VALUE
lea eax,dispidNamed ;default handle!
mov dword ptr [edi].DISPPARAMS.rgdispidNamedArgs,eax
mov dword ptr [edi].DISPPARAMS.cArgs,1
mov dword ptr [edi].DISPPARAMS.cNamedArgs,0

invoke VariantInit,addr RetVal

push 0
push 0
lea eax,RetValue
push eax
lea eax,dp
push eax
push DISPATCH_METHOD
push lcid
push offset NullCLSCID
push memid

mov eax,ppHtmlDocument
mov edx,dword ptr [eax]
push ppHtmlDocument
add edx,offs ;offs = IDispatch.Invoke
call dword ptr [edx]

No error in execution. Result page showing "null" with page code = "null" nothing more.

If I make a temporary file and navigate to this file correct page is visible.

minor28 · June 06, 2013, 07:16:08 AM

My project is to calculate the sun's position at any selected time and at any selected
location on earth. I use Google maps and Google timezone api to select locations. There
are some drawings with Gdip flat apis. The ClientSite of the webbrowser control was a
tricky item to solve. I have written more clientsite methods than is used i this project.

For those who are interested the application can be downloaded and you can read the code
here (http://minor28.divdev.se/)

How hard I tried I could not get the Write and Close methods to write to the about:blank
document. By contrast, I could create a temporary file to navigate to. The file could be
deleted after the page load was completed. A solution without creating a temporary file
was to stream text using the interface IPersistStreamInit. This became the solution.

Code Select


;Implement IPersistStreamInit on the document to init stream persistance
invoke Set_Interface,ppIHTMLDocument2,WSTR("{7FD52380-4E07-101B-AE2D-08002B2EC713}"),
		1,addr ppIPersistStreamInit

;Create the stream from resource html code
invoke FindResource,hInstance,RES_MAP,RT_RCDATA
.if eax
	mov hResinfo,eax
	invoke LoadResource,hInstance,hResinfo
	.if eax
		push esi	;preserve
		mov esi,eax
		push eax
		invoke SizeofResource,hInstance,hResinfo
		invoke GlobalAlloc,GMEM_MOVEABLE or GMEM_NODISCARD,eax
		.if eax
			push edi	;preserve
			mov hMem,eax
			invoke GlobalLock,eax
			mov edi,eax
			push edi
			xor ecx,ecx
			.while byte ptr [esi]!=0
				movsb
				inc ecx
			.endw
			pop edi
			invoke CreateStreamOnHGlobal,edi,TRUE,addr ppIStream
			.if eax==S_OK
				;Load the stream
				invoke RunInterfaceMethod,ppIPersistStreamInit,IPersistStreamInit.Load,
						1,ppIStream
				.if eax==S_OK
					;Make the browser connectable
					invoke AdviseEvent,ppIWebBrowser2,offset DIID_DWebBrowserEvents2
					invoke Release_Object,ppIPersistStreamInit
				.endif
				invoke Release_Object,ppIStream
			.endif
			invoke GlobalFree,hMem
			pop edi	;restore
		.endif
		pop esi	;restore
	.endif
.endif

dedndave · June 06, 2013, 08:03:12 AM

for older versions of internet explorer (and other browsers, i suspect), blank.html was a real physical file
newer versions, however, seem to have eliminated the file and use internal data
i am guessing it was for security reasons :P

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Webbrowser control problem

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