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Heath Stewart12-Jul-04 4:18

12-Jul-04 4:18

A native long is 32 bits. A managed long is 64 bits (System.Int64). This is documented in the Platform SDK (and I know from many years of experience). If you want further proof, read Platform Invoke Data Types[^] in the .NET Framework SDK.

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bouli12-Jul-04 4:22

12-Jul-04 4:22

ok for the length between Win32 and .NET.
I have written the declarations as you advised me, but I get an error when I execute the line

Graphics	gr=Graphics.FromHdc(GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN));

There is no spoon.

Heath Stewart12-Jul-04 4:24

12-Jul-04 4:24

It would help to know on which operation, which means - as I said before - you have to split them up.

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bouli12-Jul-04 4:44

12-Jul-04 4:44

I have declared the following:

private const int	DCX_WINDOW=0x0001;
private const int	DCX_INTERSECTRGN=0x0080;

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern IntPtr GetDCEx(IntPtr hWnd, IntPtr hrgnClip, int flags);

I have trapped the WM_NCPAINT in the WndProc method of my System.Windows.Forms.Form derived window:

protected override void WndProc(ref Message m)
{
	switch (m.Msg)
	{
		case WM_NCPAINT:
		{
			Debug.WriteLine("WM_NCPAINT");

			Graphics		gr=Graphics.FromHdc(GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN));

			ControlPaint.DrawButton(gr, 60, 1, 5, 5, ButtonState.Normal);

			break;
		}
	}
	
	base.WndProc(ref m);
}

and I have the message "An unhandled exception of type 'System.OutOfMemoryException' occurred in system.drawing.dll

Additional information: Out of memory.", at the line

Graphics		gr=Graphics.FromHdc(GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN));

There is no spoon.

Heath Stewart12-Jul-04 4:58

12-Jul-04 4:58

As I said before, split the line:

IntPtr hdc = GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN);
Graphics g = Graphics.FromHdc(hdc);

This is the very problem I mentioned earlier about combing such complex, compound statements together. Now which lines does the exception get thrown?

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bouli12-Jul-04 5:00

12-Jul-04 5:00

I still get the error Frown | :(

it seems the handle is null... When I call the GetDCEx I have 0x0 as result.

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Nick Parker12-Jul-04 5:09

Nick Parker

12-Jul-04 5:09

bouli wrote:
When I call the GetDCEx I have 0x0 as result

Check to make sure you have a valid handle to the window when you call GetDCEx.

- Nick Parker
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bouli12-Jul-04 5:14

12-Jul-04 5:14

I always get a null handle Confused | :confused:

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Heath Stewart12-Jul-04 5:13

12-Jul-04 5:13

And for the 3rd time, on which line do you get the error after splitting the two methods on two separate lines?

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bouli12-Jul-04 5:16

12-Jul-04 5:16

I get the error because the Handle returned by GetDCEx is null.

I can understand that the handle is null once (at initialization time), but it's always null Confused | :confused:

there is maybe something wrong in my declaration?

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Heath Stewart12-Jul-04 5:23

12-Jul-04 5:23

So the exception is being thrown on the second line? How hard is that question to answer?

You need to debug your code and find out this type of information. Is the Message.HWnd or Message.WParam NULL (IntPtr.Zero) before being passed to GetDCEx?

I never said splitting the lines would make it work - that doesn't matter when the compiler produces the IL. I said it would make things easier to debug. Put a break-point in there and step through your code to see what the inputs and outputs of the methods are. And always perform checks (like making sure that GetDCEx doesn't return IntPtr.Zero before passing it to Graphics.FromHdc) - never assume something just works (especially when dealing with interop since the callee is unmanaged by the CLR).

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bouli12-Jul-04 22:22

12-Jul-04 22:22

hi,
ok, I'm going to dig deeper.
but it was easier to draw in the NC area with MFC Frown | :(

.NET is very different... I need to check my marks.
Thanks for the help Smile | :)

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Heath Stewart13-Jul-04 3:01

Call function from pointer

13-Jul-04 3:01

Yes, of course it's very different. .NET is referred to as a "managed environment" because the Common Language Runtime (CLR) manages memory, provides garbage collection (no explicit destruction of objects like in C/C++/MFC), and many other things.

The important thing to remember is that Windows Forms controls encapsulates the Windows APIs, so everything possible in MFC would be possible in .NET, but you have to P/Invoke native APIs (and don't P/Invoke those that are already covered in .NET APIs), define structs and consts, etc. You can't simply call native APIs like you could in MFC, unless you were to use a Managed C++ assembly in a mixed-mode compilation.

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SNTP Client

don7cry11-Jul-04 22:45

don7cry

11-Jul-04 22:45

how to get all TimeZone and send it to Time Server, recieved Time Server reply and add it to database
thanks.

Nho'c Ti`

Re: SNTP Client

Dave Kreskowiak12-Jul-04 1:04

Dave Kreskowiak

12-Jul-04 1:04

What??????????????????????????????

This doesn't make any sense whatsoever. What do you mean by "get all TimeZone" and "send it to Time Server"? What are you trying to do with this information? Are you trying to get a Time value from a server localized to your time zone?

And what's with the database?

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Re: SNTP Client

Steven Campbell12-Jul-04 3:40

Steven Campbell

12-Jul-04 3:40

The RFC for SNTP is located at http://www.faqs.org/rfcs/rfc2030.html. If you do a google search for "sntp component" you will find some 3rd party components that do the dirty work for you.

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joeyespo11-Jul-04 22:45

joeyespo

11-Jul-04 22:45

Hi,

I've searched everywhere! Does anyone here know how to call a function from C# from an IntPtr? I know how to obtain the function pointer:

IntPtr ptr = (typeof(SOMECLASS).GetMethod("SomeMethodName").MethodHandle.GetFunctionPointer())

Now I just need a way to call it ..
The reason I need this is because in MSHTML, there is an interface called IHTMLElementRender, and the function 'DrawToDC' (useful for capturing HTML documents as an image) takes the argument HDC, but is implemented to take a reference variable of an unrelated structure. Therefore I need to call the function by the pointer, as in C++.

Thanks!

- Joe Esposito

Mike Dimmick12-Jul-04 0:37

Mike Dimmick

12-Jul-04 0:37

You've run into one of the limitations of IDL: it was originally for describing structures to be marshalled across processes, but some things we'd like to describe in IDL - handles to GDI and USER objects - are process-relative and have no meaning in another process. So the IDL contains a fake definition.

I've browsed Google Groups for _RemotableHandle. The recommended answer is apparently to use ILDASM to generate IL code for the interface, change the declaration to take an IntPtr, then recompile it. Not nice.

I'd actually recommend using Managed C++ to wrap the interface as declared in mshtml.h.

Stability. What an interesting concept. -- Chris Maunder

Heath Stewart12-Jul-04 3:55

12-Jul-04 3:55

Instead of wrapping this with an MC++ assembly as the first reply states, just interop the interface yourself. Such it's such a simple interface, it won't be hard:

[ComImport, Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"),
  InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IHTMLElementRender
{
  void DrawToDc(IntPtr hdc);
  void SetDocumentPrinter(
    [MarshalAs(UnmanagedType.BStr)] string printerName, IntPtr hdc);
}

You could then use Marshal.GetComInterfaceForObject to get a pointer to this interface. You then call Marshal.GetObjectForIUnknown and cast to the interface like so:

IntPtr ptr = Marshal.GetComInterfaceForObject(element,
  typeof(IHTMLElementRender)); // Interface type from above
IHTMLElementRender render = (IHTMLElementRender)Marshal.GetObjectForIUnknown(
  ptr);
render.DrawToDc(hdc);
// IUknown::Release will be called when 'render' is GC'd, but you must
// release the IntPtr from GetComInterfaceForObject.
Marshal.Release(ptr);

Please note that this is untested but I've used similar code with different interfaces before with success.

I hope this helps.

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joeyespo12-Jul-04 8:34

joeyespo

12-Jul-04 8:34

Thanks! That did exactly what I needed it to!
I did consider using this method, however all of my attempts failed and left me clueless.

It seems that this attribute really makes the difference:
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)

Without it, the program simply crashes when you try to use it.

Also, I have been using type-casts where QueryInterface would be required. It also worked in this case:

IHTMLElementRender render = (IHTMLElementRender)element;
render.DrawToDc(hdc);

Thanks again for your reply Smile | :)

- Joe

Heath Stewart12-Jul-04 9:11