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POProblem with WH_CALLWNDPROCRET
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  1. POProblem with WH_CALLWNDPROCRET
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    copied!<p>I am trying to catch messages from an application for which I have no source code.<br> I install a Windows hook like this:</p> <pre><code>hhk = SetWindowsHookEx(WH_CALLWNDPROCRET, HookProcSetTextRet, hinst, threadID); </code></pre> <p>(The hhk variable is in shared data.)<br> I don't understand some of the behavior, though, specifically:</p> <pre><code>LRESULT CALLBACK HookProcSetTextRet(int code,WPARAM wParam,LPARAM lParam) { PCWPRETSTRUCT st = (PCWPRETSTRUCT)lParam; switch (HIWORD(st-&gt;wParam)) { case WM_COMMAND: { /* For lbn_xxx: wParam The low-order word is the list box identifier. The high-order word is the notification message. lParam Handle to the list box. */ switch (HIWORD(st-&gt;wParam)) { case LBN_DBLCLK: { log &lt;&lt; L"\tWM_COMMAND --- LBN_DBLCLK" &lt;&lt; endl; } break; case LBN_SELCHANGE: { log &lt;&lt; L"\t+++ WM_COMMAND -LBN_SELCHANGE" &lt;&lt; endl; log &lt;&lt; L"\t\tHandle to list box : " &lt;&lt; st-&gt;lParam &lt;&lt; endl; HWND lbHwnd = (HWND) st-&gt;lParam; res = SendMessage(lbHwnd, LB_GETCOUNT, 0, 0); curSel = SendMessage(lbHwnd, LB_GETCURSEL, 0, 0); log &lt;&lt; L"\t\t\tLB_GETCURSEL returned : " &lt;&lt; curSel &lt;&lt; endl; if (LB_ERR != curSel) { res = SendMessage(lbHwnd, LB_GETTEXT, curSel, (LPARAM)(LPTSTR) szBuf); log &lt;&lt; L"\t\tLB_GETTEXT returned : " &lt;&lt; res &lt;&lt; L"\t\tszBuf: " &lt;&lt; szBuf &lt;&lt; endl; } } break; default: break; } } // WM_COMMAND /* snip */ } return CallNextHookEx(0, code, wParam, lParam); } </code></pre> <p>LBN_SELCHANGE is caught, but the value returned by LB_GETCURSEL and LB_GETTEXT is always the same.<br> LBN_DBLCLK is never caught. </p> <p>There is similar inconsistnecy with other WM_ messages, as well. Is the app itself somehow eating these messages?<br> Thanks for any ideas...</p> <p>UPDATE:<br> Following a suggestion made below, I implemented a WH_GETMESSAGE hook. It appears to be getting the doubleclick message from the listbox.<br> Unfortunately, LB_GETCOUNT returns the correct number, but LB_GETCURSEL always returns 0, and LB_GETTEXT still returns nothing...</p> <pre><code> case WM_LBUTTONDBLCLK: { const unsigned int BUFFER_SIZE = 1024; wchar_t titleBuffer[BUFFER_SIZE]; UINT curSel = LB_ERR; LRESULT res = LB_ERR; MSG * pMsg = (MSG *) lParam; HWND lbHwnd = pMsg-&gt;hwnd; log &lt;&lt; L"\tGetMsgProc\t\tWM_LBUTTONDBLCLK" &lt;&lt; endl; // Sanity check HWND parent = GetParent(lbHwnd); GetWindowText(parent, titleBuffer, BUFFER_SIZE - 1); log &lt;&lt; L"\t\tParent Title : " &lt;&lt; titleBuffer &lt;&lt; L"\tParent HWND : " &lt;&lt; parent &lt;&lt; endl; // Sanity check GetClassName(lbHwnd, titleBuffer, BUFFER_SIZE - 1); log &lt;&lt; L"\t\tList box class name: " &lt;&lt; titleBuffer &lt;&lt; L"\tList box hwnd: " &lt;&lt; pMsg-&gt;hwnd &lt;&lt; endl; res = SendMessage(lbHwnd, LB_GETCOUNT, 0, 0); if (LB_ERR != res) { log &lt;&lt; L"\t\t\tLB_GETCOUNT : " &lt;&lt; res &lt;&lt; endl; } curSel = SendMessage(lbHwnd, LB_GETCURSEL, 0, 0); log &lt;&lt; L"\t\t\tLB_GETCURSEL returned : " &lt;&lt; curSel &lt;&lt; endl; if (LB_ERR != curSel) { res = SendMessage(lbHwnd, LB_GETTEXT, curSel, (LPARAM)(LPTSTR) titleBuffer); if (LB_ERR == res ) { log &lt;&lt; L"\t\t\tLB_GETTEXT Error -- invalid index" &lt;&lt; endl; } else { log &lt;&lt; L"\t\tLB_GETTEXT returned : " &lt;&lt; res &lt;&lt; L"\t\tszBuf: " &lt;&lt; titleBuffer &lt;&lt; endl; } } else { log &lt;&lt; L"\t\tLB_GETCURSEL returned LB_ERR" &lt;&lt; endl; } } </code></pre>
 

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