Problems with native Win32api RichEdit control and its IRichEditOle interface

Question

Hi All!

As part of writing custom command (COM-Visible dll with class that implements Interwoven command interface) for one of Interwoven Worksite dialog boxes,I need to extract information from RichEdit textbox.

The only connection to the existing dialog box is its HWND handle; Seemingly trivial task , but I got stuck :

Using standard win32 api functions (like GetDlgItemText) returns empty string. After using Spy++ I noticed that the dialog box gets IRichEditOle interface and seems to encapsulate the string into OLE object. Here is what I tried to do:

IRichEditOle richEditOleObj = null;
IntPtr ppv = IntPtr.Zero;
Guid guid = new Guid("00020D00-0000-0000-c000-000000000046");
Marshal.QueryInterface(pRichEdit, ref guid, out ppv);
richEditOleObj = (IRichEditOle)Marshal.GetTypedObjectForIUnknown(ppv,typeof(IRichEditOle));

judging by GetObjectCount() method of the interface there is exactly one object in the textbox - most likely the string I need to extract. I used GetObject() method and got IOleObject interface via QueryInterface :

if (richEditOleObj.GetObject(0, reObject, GetObjectOptions.REO_GETOBJ_ALL_INTERFACES) == 0) //S_OK
{
IntPtr oleObjPpv = IntPtr.Zero;
try {
IOleObject oleObject = null;
Guid objGuid = new Guid("00000112-0000-0000-C000-000000000046");
Marshal.QueryInterface(reObject.poleobj, ref objGuid, out oleObjPpv);
oleObject = (IOleObject)Marshal.GetTypedObjectForIUnknown(oleObjPpv, typeof(IOleObject));


To negate other possibilites I tried to QueryInteface IRichEditOle to ITextDocument but this also returned empty string; tried to send EM_STREAMOUT message and read buffer returned from callback - returned empty buffer.

On this point I got stuck. Googling didn't help much - couldn't find anything that was relevant to my issue - it seems that vast majority of examples on the net about IRichEditOle and RichEdit revolve around inserting bitmap into RichEdit control...

The main problem - I couldn't find a way to extract information I needed from IOleObject ihterface and didn't find any examples relevant to extracting data from the object.

Now since I know only basic stuff about COM and OLE , I guess I am missing something important here.

I would appreciate any thoughts suggestions or remarks.

Answer 1

I found the missing bit of the puzzle..Perhaps what I did will help others with similar problem : after calling IRichEditOle::GetObject I received REOBJECT structure. By using clsid field of the structure I found via registry the dll where needed interface was defined. Using explicit cast (I use C# so it is equivalent to using QueryInterface) from IOleObject to the required interface I achieved what I needed - access to the data stored in that IOleObject.