Integration 3rd party application into Qt form

[Guess11]

I am trying to integrate some application that installed in my operation system to the Qt from. What I already read is this topic(https://forum.qt.io/topic/44091/embed-an-application-inside-a-qt-window-solved/7) but I am still have a problem with getting WinID of the application that I try to integrate. For example I am trying to catch Google Chrome WinID.
What I am Allready write is

    QString n1="Google_Chrome";
    LPCWSTR name=n1.utf16();
    HWND hwnd_1 = ::FindWindow(name, NULL);
    LONG retVal = GetWindowLongA(hwnd_1, GWL_STYLE);

But I am getting "cannot convert const unshort to LPCWSTR" error. If somebody can help me, I will be really thankful. I am using Windows 10 and Qt 5.5.1.

[kshegunov]

@Guess11

Q_ASSERT(sizeof(TCHAR) == sizeof(wchar_t));

int size = n1.size();

LPCTSTR name = new T‌CHAR[size + 1];
name[size] = 0;

n1.toWCharArray(name);
HWND hwnd_1 = ::FindWindow(name, NULL);

delete [] name;

One can't help it, but be inspired by MS's approach to designing an "usable" API.

[Guess11]

@kshegunov
Thank you for your reply and help. Unfortunately now I have almost the same problem: "cannot convert from LPCTSTR to wchar_t". Indeed Microsoft has "usable" API. Probably it is impossible to nicely integrate 3rd party app to Qt form.

[Gerd]

LPCTSTR is a const Pointer, not usable for toWCharArray.
Change it to LPTSTR and it should work.

Regards
Gerd

[kshegunov]

@Guess11
See @Gerd's comment. There's indeed a typo in the example, so changing to LPTSTR (or simply to TCHAR * what LPTSTR stands for) should fix it.

[Guess11]

@kshegunov said:

Q_ASSERT(sizeof(TCHAR) == sizeof(wchar_t));

int size = n1.size();

LPCTSTR name = new T‌CHAR[size + 1];
name[size] = 0;

n1.toWCharArray(name);
HWND hwnd_1 = ::FindWindow(name, NULL);

delete [] name;
Now I need to convert from *LPTSTR to LPCWSTR. My code look like this :

    QString n1="Google_Chrome";

    Q_ASSERT(sizeof(TCHAR) == sizeof(wchar_t));

    int size = n1.size();
    size=size+1;
    LPTSTR * name = new LPTSTR [size];
    name[size]=0;
    HWND hwnd_1 = ::FindWindow(name, NULL);
    LONG retVal = GetWindowLongA(hwnd_1, GWL_STYLE);
    qDebug()<<"Chrome id " <<hwnd_1;

if I put

 HWND hwnd_1 = ::FindWindow(*name, NULL);

I get unresolved externals from linker. Other way(without pointer) it is just problem to convert from *LPCTSTR to LPCWSTR. If some one has better idea how I can catсh winId of some external program please tell me.

[kshegunov]

@Guess11
Your code is wrong.

Why are you doing this:

 size=size+1;

Then the allocation looks a bit iffy:

LPTSTR * name = new LPTSTR [size];

LPTSTR is a typedef for TCHAR * so this line looks like TCHAR * name = new TCHAR * [size] which is wrong syntactically as well as semantically. You want to create an array of wide characters, not an array of pointers to wide characters. You'd do it like this:

TCHAR * name = new TCHAR[size + 1]; //< Don't modify the size variable

Then:

name[size]=0;

leads to a buffer overflow (writing beyond allocated space). And finally you didn't copy the QString object's contents into your array. This line n1.toWCharArray(name); I can't see in your code.

[Guess11]

@kshegunov
Fix that, but still problem is the same converting wchar_t to LPTSTR. this is the only one compilation error in the line:

n1.toWCharArray(name);

[kshegunov]

@Guess11

Just reinterpret cast the hell out of it ;)

n1.toWCharArray(reinterpret_cast<wchar_t *>(name));

PS.
Keep the Q_ASSERT on top, so you're sure that TCHAR is the size of wchar_t.

[Guess11]

Ok. Thank you. All responses was very helpfull. It's work. I end up with this code:

#include <Windows.h>
#include <atlbase.h>

    Q_ASSERT(sizeof(TCHAR) == sizeof(wchar_t));

    QString n1="Google_Chrome";
    int size = n1.size();

    LPTSTR * name = new LPTSTR [size+1];
    name[size]=0;
    n1.toWCharArray(reinterpret_cast<wchar_t *>(name));
    LPCWSTR newname= reinterpret_cast<LPCWSTR> (name);
    //HWND hwnd_1 = ::FindWindow(name, NULL);
    HWND hwnd_1 = ::FindWindow(newname, NULL);
    LONG retVal = GetWindowLongA(hwnd_1, GWL_STYLE);

    qDebug()<<"Chrome id " <<hwnd_1;
    qDebug()<<"Long " <<retVal;

    delete [] name;

I am wondering why program crashes after each time I closed it, But now I need to figure out why winId 0. Again thank you.

[kshegunov]

@Guess11
This code is hanging by a thread, it works more as a coincidence than anything. As I said LPTSTR is a pointer!

LPTSTR * name = new LPTSTR [size+1];

should simply be:

TCHAR * name = new TCHAR[size + 1];

And this:

LPCWSTR newname= reinterpret_cast<LPCWSTR> (name);

is not needed.