HWND chat;

chat = CreateWindowEx(WS_EX_CLIENTEDGE,RICHEDIT_CLASS,"",WS_CHILD|WS_VISIBLE|ES_DISABLENOSCROLL|ES_MULTILINE|ES_AUTOVSCROLL|WS_VSCROLL,chatposX,chatposY,chatWidth,chatHeight,hDlg,NULL,GetModuleHandle(NULL),NULL);

Und jetzt moechte ich den Text aus dieser RichEdit lesen mit

char thetext[1000],buf[1000];
GETTEXTEX get;
ZeroMemory(&get,sizeof(GETTEXTEX));	
get.cb = sizeof(GETTEXTEX);
get.codepage = CP_ACP;
get.flags = GT_DEFAULT;
get.lpDefaultChar = NULL;
get.lpUsedDefChar = NULL;

SendMessage(chat,EM_GETTEXTEX,(WPARAM)&get,(LPARAM)thetext);

sprintf(buf,"%s\n",thetext);
MessageBox(0,buf,"Buffer",MB_OK);

Die MessageBox gibt mir aber nur die ersten 21 Zeichen aus , warum ?

...
lParam
Pointer to a null-terminated string that receives the text. The size of this buffer should be placed in the cb member of the GETTEXTEX structure.

konkret:

get.cb = sizeof(thetext)-1;