Convert WinApi type to Qt type

[lolopolosko]

Hi
This code is working fine, but in ending I got error (debug) "Exception at 0x5313a407, code: 0xc0000005: read access violation at: 0x0, flags=0x0"
@ HWND activeWindow;
activeWindow = GetForegroundWindow();
LPWSTR l_windowTitle;
SetWindowText(activeWindow,L"Hi!");
GetWindowText(activeWindow,l_windowTitle,256);
QString wchr = QString::fromWCharArray(l_windowTitle);
qDebug()<<wchr;@
Why?

[lolopolosko]

Edit code
@ HWND activeWindow;
activeWindow = GetForegroundWindow();
LPWSTR l_windowTitle = L"";
LPWSTR l_windowTitle2;
GetWindowText(activeWindow,l_windowTitle,256);
GetWindowText(activeWindow,l_windowTitle2,256);

qDebug()<<QString::fromWCharArray(l_windowTitle);
qDebug()<<QString::fromWCharArray(l_windowTitle2);@

output without error
""
""

---

@ HWND activeWindow;
activeWindow = GetForegroundWindow();
LPWSTR l_windowTitle;
GetWindowText(activeWindow,l_windowTitle,256);

qDebug()<<QString::fromWCharArray(l_windowTitle);

@

output with error
"Title message"

[lolopolosko]

And now I am editing my code and this work perfectly. But why? ^_^

@ HWND activeWindow;
activeWindow = GetForegroundWindow();
char testVar[256];
GetWindowTextA(activeWindow,testVar,sizeof testVar);

qDebug()<<testVar;@

[AcerExtensa]

How should it work if you didn't initialized your wchar_t variables?
LPWSTR is simple pointer in memory of wchar_t type:
@
// LPWSTR l_windowTitle is the same as
wchar_t * windowTitle;
@

And after what you are trying to get 256 bytes to this uninitialized place in memory, of cause it will fail!

@
//
HWND activeWindow = GetForegroundWindow();
LPWSTR l_windowTitle = new wchar_t[256]; // or better use winapi memory initialization functions if you use wrappers for wchar_t type
GetWindowText(activeWindow,l_windowTitle,255);// let 1 byte for \0
qDebug()<<QString::fromWCharArray(l_windowTitle);
// free memory after you don't need it anymore
delete [] l_windowTitle;
@

[lolopolosko]

Thanks ^_^

[AcerExtensa]

Please add "[SOLVED]" prefix left to the subject topic. And have fun with coding!