WM_COMMAND unabled to fulfil request unless clicked outside of application window, - c++

Question

Currently creating an application that just outputs Physics equations + some historical and mathematical context. I've ran into this problem where I'm using WS_EX_CLIENTEDGE to sort out a list of these terms and when I click said term on the screen, expecting a definition to appear, it doesn't output anything until I've clicked outside of the application window(Visual Studio, Debug Terminal, etc)
Cursed gif
And I want to make it clear that I DON'T want to use a button due to GUI aesthetics.
Mundane WINAPI application creation
int main(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)
{
const wchar_t CLASS_NAME[] = L"Application";
WNDCLASS window = { 0 };
MSG msg = { 0 };
window.lpfnWndProc = WindowProc;
window.lpszClassName = CLASS_NAME;
window.hInstance = hInstance;
RegisterClass(&window);
HWND hWnd = CreateWindow(CLASS_NAME, L"PhysicsBox", WS_VISIBLE | WS_OVERLAPPEDWINDOW, 100, 100, 600, 500, NULL, NULL, NULL, NULL);
ShowWindow(hWnd, nCmdShow);
//aMessageBox = CreateWindowW(L"edit", L" ", WS_VISIBLE | WS_CHILD | WS_BORDER, 165, 150, 400, 300, hWnd, NULL, NULL, NULL);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}
The Juicy Window Procedure
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_CREATE:
aListBox(hWnd);
break;
case WM_COMMAND:
if (SendMessage(hList, LB_GETSEL, FORCE, 0))
{
CreateWindowW(L"static", L"Simple Text", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER, 200, 100, 100, 100, hWnd, NULL, NULL, NULL);
}
break;
case WM_DESTROY:
PostQuitMessage(0); break;
default:
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
}
The void function that creates the list
void aListBox(HWND hWnd)
{
hList = CreateWindowEx(WS_EX_CLIENTEDGE, L"ListBox", L" ", WS_CHILD | WS_VISIBLE | WS_VSCROLL | ES_AUTOVSCROLL, 3, 4, 150, 300, hWnd, (HMENU)ID_LISTBOX, 0, 0);
SendMessageW(hList, LB_ADDSTRING, FORCE, (LPARAM)L"Force");
SendMessageW(hList, LB_ADDSTRING, WORK, (LPARAM)L"Work");
SendMessageW(hList, LB_ADDSTRING, POWER, (LPARAM)L"Power");
SendMessageW(hList, LB_ADDSTRING, EFFICENCY, (LPARAM)L"Efficency");
SendMessageW(hList, LB_ADDSTRING, POTENTIALENERGY, (LPARAM)L"Potential Energy");
SendMessageW(hList, LB_ADDSTRING, HOOKESLAW, (LPARAM)L"Hooke's Law");
}
Note: the MSG('s) placed in the "aListBox(HWND hWnd)" SendMessageW parameters are numerically ordered(from 0). So FORCE = 0, WORK = 1, and so on. Also hList is a global variable if that helps :P

Answer 1

The listbox is created without the LBS_NOTIFY style and will therefore not send LBN_SELCHANGE notifications to the parent window. Changing the first line in aListBox to the following fixes this.
hList = CreateWindowEx(WS_EX_CLIENTEDGE, L"ListBox", L" ", WS_CHILD | LBS_NOTIFY | WS_VISIBLE | WS_VSCROLL | ES_AUTOVSCROLL, 3, 4, 150, 300, hWnd, (HMENU)ID_LISTBOX, 0, 0);
Also, the WindowProc does not return a result on all code paths, and does not call DefWindowProc for all messages that it does not handle. The following corrects those issues.
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_CREATE:
aListBox(hWnd);
return 0;
case WM_COMMAND:
if (SendMessage(hList, LB_GETSEL, FORCE, 0))
{
HWND hText = CreateWindowW(L"static", L"Simple Text", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER, 200, 100, 100, 100, hWnd, NULL, NULL, NULL);
ShowWindow(hText, SW_SHOW);
return 0;
}
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
Other problems remain with the code, for example the WindowProc does not check the WM_COMMAND notification code and will happily create new windows over and over, but the assumption was that this was minimal code only meant to showcase the particular issue in the question.
[ EDIT ]   The behavior described by the OP when running without the LBS_NOTIFY style bit is mostly accidental, due to WM_COMMAND not checking the WPARAM notification code. What happens is that clicking outside the app window causes the listbox to send a LBN_KILLFOCUS notification (which is being sent regardless of LBS_NOTIFY). That notification is the one which triggers the WM_COMMAND code in WindowProc that creates the static control when the FORCE item is selected.