Some Windows messages have a pointer to a structure as the lParam. How do I "follow" this pointer and get the data it points to? I need to be able to read the contents of the structure. I have no idea what to do with the pointer (it's a number).

Thanks!

I think this is an example of the kind of thing you want...

code:

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//Show color picker common dialog

    //Create our CHOOSECOLOR data block
    var CHOOSECOLOR = Interop.Allocate(36);
    CHOOSECOLOR.WriteDWORD(0, 36); //DWORD lStructSize
    CHOOSECOLOR.WriteDWORD(4, 0); //HWND hwndOwner
    CHOOSECOLOR.WriteDWORD(8, 0); //HWND hInstance
    CHOOSECOLOR.WriteDWORD(12, 0x000000FF); //COLORREF rgbResult (COLORREF = 0x00bbggrr)
    var CustColors = Interop.Allocate(64); //Create an array of 16 COLORREFs for CustColors
    CHOOSECOLOR.WriteDWORD(16, CustColors.DataPtr); //COLORREF *lpCustColors (pointer to our array)
    CHOOSECOLOR.WriteDWORD(20, 3); //DWORD Flags (3 = 2 (CC_FULLOPEN) + 1 (CC_RGBINIT) )
    CHOOSECOLOR.WriteDWORD(24, 0); //LPARAM lCustData
    CHOOSECOLOR.WriteDWORD(28, 0); //LPCCHOOKPROC lpfnHook
    CHOOSECOLOR.WriteDWORD(32, 0); //LPCTSTR lpTemplateName

    //Open the dialog box
    var result = Interop.Call('comdlg32.dll', 'ChooseColorA', CHOOSECOLOR);
    //If the user pressed ok convert it to hex
    if(result == 1){
      //Get decimal values
      var r = CHOOSECOLOR.ReadDWORD(12) & 0xFF;
      var g = (CHOOSECOLOR.ReadDWORD(12) / 0x100) & 0xFF;
      var b = (CHOOSECOLOR.ReadDWORD(12) / 0x10000) & 0xFF;
      Debug.Trace('RGB: ' + r + ',' + g + ',' + b)
      //Get hex values
      var hexchars="0123456789ABCDEF";
      var r = hexchars.charAt((r >> 4) & 0xf) + hexchars.charAt(r & 0xF);
      var g = hexchars.charAt((g >> 4) & 0xf) + hexchars.charAt(g & 0xF);
      var b = hexchars.charAt((b >> 4) & 0xf) + hexchars.charAt(b & 0xF);
      Debug.Trace('HEX: ' + r + g + b);
    }

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No. That's making a pointer to my own data, I know how to do that

I need to get data from a pointer given to me by Windows.

Don't you still have to specify the pointer? if you do that then can't you still use

code:

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lpointer.ReadDWORD

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heres an example of WM_COPYDATA

code:

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/*
        typedef struct {
           DWORD dwData; 4
           DWORD cbData; 4
           PVOID lpData; 4
        } COPYDATASTRUCT; 12
        */
       
        var struct = Interop.Allocate(12);
        Interop.Call('Kernel32','RtlMoveMemory', struct, lParam,12);
       
        var dwData = struct.ReadDWORD(0);
        var cbData = struct.ReadDWORD(4);
        var lpData = struct.ReadDWORD(8);

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Thanks! That worked