SendMessage and Handles

  • Thread starter Thread starter Steve Barnett
  • Start date Start date
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Steve Barnett

I have an app that includes two side by side Rich Text controls. What I need
to do is keep both controls synchronised, such that if I scroll the left rtb
up or down then the right one scrolls by the same amount in the same
direction.

In my simplistic mind, I believe that this can be achieved by sending an
EM_GetScrollPos message to the left rtb and using the results to send an
EM_SetScrollPos message to the right one. Problem is that I'm converting
over from VB6 and have no idea how to

a) Call the SendMessage API,
b) Code a "POINT" structure in C# for use in the call, or
c) Find the windows handle of the Rich Text box.

All of which means that I have a very long way to go to achieve a very
simple function. Can anyone please point me at some code that does this
please? Better still, can I achieve this in native C# code?

Thanks
Steve
 
Steve,
a) Call the SendMessage API,
Click to expand...

You first declare it like this

[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, uint msg, IntPtr wParam,
ref Point lParam);

then call it like any other method.

b) Code a "POINT" structure in C# for use in the call, or
Click to expand...

You can use System.Drawing.Point in its place.

c) Find the windows handle of the Rich Text box.
Click to expand...

Each control has a Handle property that returns it.


Mattias
 
Steve,

See inline:
a) Call the SendMessage API,
Click to expand...

Check out http://www.pinvoke.net. It will have the declaration of
SendMessage. You might have to tweak it for your specific message. In the
case of SetScrollPos, you will want to use this:

[DllImport("user32.dll", CharSet = CharSet.Auto, EntryPoint = "SendMessage",
ExactSpelling = false)]
static extern int SendEmSetScrollPosMessage(
IntPtr hWnd,
[MarshalAs(UnmanagedType.U4)]
int Msg,
IntPtr wParam,
ref System.Drawing.Point lParam);
b) Code a "POINT" structure in C# for use in the call, or
Click to expand...

You can use System.Drawing.Point. It will marshal correctly.
c) Find the windows handle of the Rich Text box.
Click to expand...

The RichTextBox control exposes a Handle property which you can use to
get the handle. Actually, the Control class exposes it, so all controls
expose their handle.

Hope this helps.
 
Much appreciated guys.

Steve

Nicholas Paldino said:
Steve,

See inline:
a) Call the SendMessage API,
Click to expand...

Check out http://www.pinvoke.net. It will have the declaration of
SendMessage. You might have to tweak it for your specific message. In
the case of SetScrollPos, you will want to use this:

[DllImport("user32.dll", CharSet = CharSet.Auto, EntryPoint =
"SendMessage", ExactSpelling = false)]
static extern int SendEmSetScrollPosMessage(
IntPtr hWnd,
[MarshalAs(UnmanagedType.U4)]
int Msg,
IntPtr wParam,
ref System.Drawing.Point lParam);
b) Code a "POINT" structure in C# for use in the call, or
Click to expand...

You can use System.Drawing.Point. It will marshal correctly.
c) Find the windows handle of the Rich Text box.
Click to expand...

The RichTextBox control exposes a Handle property which you can use to
get the handle. Actually, the Control class exposes it, so all controls
expose their handle.

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)
All of which means that I have a very long way to go to achieve a very
simple function. Can anyone please point me at some code that does this
please? Better still, can I achieve this in native C# code?

Thanks
Steve
Click to expand...
Click to expand...
 
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