http://www.codeproject.com/macro/VSNetHelp.asp
Integrate latest MSDN with VC6 and Hook functions of COM
By Chunhua Liu
Introduction
After Oct. 2001, you cannot get help by pressing F1 in VC6 with latest MSDN.
Microsoft has changed the help format from CHM to document explorer.
? Is it possible to use latest MSDN in VC6?
? The answer is YES!
Details
First, we must know how VC6 brings up the help after you press F1. This is
easy if you have a debugger such as Soft-ICE.
If you don't install MSDN, after you press F1, VC6 will popup a message box
says you haven't installed MSDN. Set a breakpoint at MessageBox. Press F1
and debugger will popup. Look at the stack. You will see this function was
called from "C:\Program Files\Common Files\Microsoft
Shared\VS98\vshelp.dll".
Then we use Dependency Walker ("depends" in Visual Studio Tools) to see
what functions are exported. We will see DllRegisterServer and
DllUnregisterServer. It's obviously a COM.
Use VC6 to create a simple console project. Add the following line to your
.cpp file.
#import "C:\Program Files\Common Files\Microsoft Shared\VS98\vshelp.dll"
And build your project.
Open the Debug directory, you will find "vshelp.tlh" and "vshelp.tli"
Open "vshelp.tlh", you will see:
struct __declspec(uuid("854d7ac0-bc3d-11d0-b421-00a0c90f9dc4"))
IVsHelpSystem : IUnknown
{
//
// Wrapper methods for error-handling
//
HRESULT KeywordSearch (
LPWSTR pszKeyword,
long dwFlags,
long dwReserved );
HRESULT ALinkSearch (
LPWSTR pszALink,
long dwFlags,
long dwReserved );
...
The function KeywordSearch was called when you press F1. So if we replace
this function and call latest MSDN's help function, it should work.
Then how to do this? Since it's a COM interface, it's easy to hook it.
Basically a COM interface is a C++ class with virtual table. It has a
pointer to a table contains all virtual functions address. And this table
is shared by all instances. So we only need change the function address in
the table. And this interface will look like:
struct _IVsHelpSystemVtbl{
HRESULT (STDMETHODCALLTYPE *QueryInterface)(IUnknown * This,
REFIID riid, void **ppvObject);
ULONG (STDMETHODCALLTYPE *AddRef)(IUnknown * This);
ULONG (STDMETHODCALLTYPE *Release)(IUnknown * This);
HRESULT (STDMETHODCALLTYPE *KeywordSearch)(IUnknown * This,
LPWSTR pszKeyword, long dwFlags, long dwReserved);
};
struct _IVsHelpSystem
{
struct _IVsHelpSystemVtbl *lpVtbl;
};
What we need to do now is create an instance of this COM. And we will get
the address of the table. Now we need to know how to bring up the help of
latest MSDN. It seems it's not documented. It's also a COM.
Add the following line to your .cpp file. You will get the COM definition.
#import "C:\Program Files\Common Files\Microsoft Shared\MSEnv\vshelp.tlb"
In "vshelp.tlh", you can find function:
HRESULT DisplayTopicFromF1Keyword ( _bstr_t pszKeyword );
Obviously, this is what we need. So in the function KeywordSearch, call
DisplayTopicFromF1Keyword will launch the latest MSDN.
Here is the code:
HRESULT hr = theHelp.CreateInstance(__uuidof(VsHelp::DExploreAppObj));
if (SUCCEEDED(hr))
{
HRESULT hr = vc6Help.CreateInstance(
__uuidof(VsHelpServices::VsHelpServices));
if (SUCCEEDED(hr))
{
iHelp = (_IVsHelpSystem *)vc6Help.GetInterfacePtr();
TRACE1("iHelp = %x\n", iHelp);
TRACE1("lpVtbl = %x\n", iHelp->lpVtbl);
TRACE1("KeywordSearch = %x\n", iHelp->lpVtbl->KeywordSearch);
OldKeywordSearch = iHelp->lpVtbl->KeywordSearch;
DWORD dwOldProtect;
if (VirtualProtect(iHelp->lpVtbl, sizeof(
_IVsHelpSystemVtbl), PAGE_READWRITE, &dwOldProtect))
iHelp->lpVtbl->KeywordSearch = MyKeywordSearch;
}
}
Easy, right? There are two things you must keep in mind. First we must
declare the vc6Help in global space and release it when program quit.
This is because the vshelp.dll will be freed if there is no more instance.
If so, then what we modified will be gone with it. The second, we must call
VirtualProtect to make the virtual table become writable, otherwise you
cannot modify the virtual table because it's read only.
How to use it?
Click VC6's menu "Tools"->"Customize"->"Add-ins and Macro Files"->"Browse".
Then choose "VSNetHelp.dll", click "Close".
Move the caret to a keyword, press F1. You got it!
