OpenEuphoria

Re: How to write graphics to MS Windows clipboard

• Posted by DB James <larches at comcast.net> May 17, 2007
• 872 views

CChris wrote:
> 
> DB James wrote:
> > 
> > CChris wrote:
> > > A way nicer version using a Pixmap:
<SNIP>
> > Thanks, that works like a charm.
> > 
> > Do you think a bitmap-in-memory can be sent (with OLE or DDE or whatever) to
> > be pasted into some other program?  It isn't uncommon to see programs do
> > this, such as IrfanView's send of an image that does not exist as a disk
> > file
> > to some other graphic editor.
> > 
> > --Quark
> 
> There is a dedicated Windows message for that, which is WM_COPYDATA.
> The trick there is that the data you pass must be accessible from the
> process you are sending this message to, so it must not contain private
> pointers. Here is the reference for this message:
> <quote>
> WM_COPYDATA 
> wParam = (WPARAM) (HWND) hwnd;            // handle of sending window 
> lParam = (LPARAM) (PCOPYDATASTRUCT) pcds; // pointer to structure with data
> 
>  
> The WM_COPYDATA message is sent when an application passes data to another
> application. 
> 
> Parameters
> hwnd:
>   Identifies the window passing the data. 
> pcds:
>    Points to a COPYDATASTRUCT structure that contains the data to be passed.
> 
> 
> Return Value
> 
> If the receiving application processes this message, it should return TRUE;
> otherwise, it should return FALSE. 
> 
> Remarks
> 
> An application must use the SendMessage function to send this message, not
> the PostMessage function. 
> The data being passed must not contain pointers or other references to
> objects not accessible to the application receiving the data. 
> While this message is being sent, the referenced data must not be changed by
> another thread of the sending process. 
> The receiving application should consider the data read-only. The pcds
> parameter is valid only during the processing of the message. The receiving
> application should not free the memory referenced by pcds. If the receiving
> application must access the data after SendMessage returns, it must copy the
> data into a local buffer. 
> </quote>
> 
> The COPYDATASTRUCT referred here is very simple:
>     DWORD dwData -- single dword to pass: used only if lpData is 0 
>     DWORD cbData -- number of bytes pointed by lpData 
>     PVOID lpData -- pointer to data
> 
> The constant WM_COPYDATA is #004A.
> The copying of data must take place inside the raw message handler you'll
> set for WM_COPYDATA.
> Google for the WM_COPYDATA for more articles on using this message for
> interprocess communication.
> 
> CChris

Thanks for that information.  After I sent my message I rooted around on the
MS site and, among many other things, saw the SendMessage and WM_COPYDATA
and wondered if that was a way to go.  Now that I know you think so, I'll
poke into it and do some testing.  Hold not thy breath,though.

Thanks again,

--Quark