Getting a list of all open windows in c++ and storing them - c++

Question

I'm currently trying to get a list of all opened windows and storing them inside a vector. I've been looking at the code so much that the solution could be very easy but I don't seem to get it done without a global variable (which I want to avoid).
Here is the code:
#include "stdafx.h"
#include "json.h"
#include <algorithm>
using namespace std;
vector<string> vec;
BOOL CALLBACK speichereFenster(HWND hwnd, LPARAM substring){
const DWORD TITLE_SIZE = 1024;
TCHAR windowTitle[TITLE_SIZE];
GetWindowText(hwnd, windowTitle, TITLE_SIZE);
int length = ::GetWindowTextLength(hwnd);
wstring temp(&windowTitle[0]);
string title(temp.begin(), temp.end());
if (!IsWindowVisible(hwnd) || length == 0 || title == "Program Manager") {
return TRUE;
}
vec.push_back(title);
return TRUE;
}
int main() {
EnumWindows(speichereFenster, NULL);
cin.get();
return 0;
}
I want to store all titles in the vector but I don't know how as I can't pass the vector into the function...
Thanks!!!

Answer 1

The second parameter (lParam) to EnumWindows is documented as:
An application-defined value to be passed to the callback function.
Just pass your container to the API call:
int main() {
std::vector<std::wstring> titles;
EnumWindows(speichereFenster, reinterpret_cast<LPARAM>(&titles));
// At this point, titles if fully populated and could be displayed, e.g.:
for ( const auto& title : titles )
std::wcout << L"Title: " << title << std::endl;
cin.get();
return 0;
}
And use it in your callback:
BOOL CALLBACK speichereFenster(HWND hwnd, LPARAM lParam){
const DWORD TITLE_SIZE = 1024;
WCHAR windowTitle[TITLE_SIZE];
GetWindowTextW(hwnd, windowTitle, TITLE_SIZE);
int length = ::GetWindowTextLength(hwnd);
wstring title(&windowTitle[0]);
if (!IsWindowVisible(hwnd) || length == 0 || title == L"Program Manager") {
return TRUE;
}
// Retrieve the pointer passed into this callback, and re-'type' it.
// The only way for a C API to pass arbitrary data is by means of a void*.
std::vector<std::wstring>& titles =
*reinterpret_cast<std::vector<std::wstring>*>(lParam);
titles.push_back(title);
return TRUE;
}
Notes:
The code presented uses a std::wstring in place of std::string. This is necessary so that the entire character set can be represented.
As written, the code isn't correct. There are (invisible) code paths, that have no well-defined meaning. The Windows API is strictly exposed as a C interface. As such, it doesn't understand C++ exceptions. Particularly with callbacks it is vital to never let C++ exceptions travel across unknown stack frames. To fix the code apply the following changes:
[C++11 only] Mark the callback noexcept.
Wrap the entire callback inside a try-catch block, and handle any exceptions appropriately.
[C++11 only] With C++11 you can pass C++ exceptions across unknown stack frames, by passing a std::exception_ptr, and calling std::rethrow_exception at the call site.

Answer 2

Simple code to get all visible windows with non empty title
for (HWND hwnd = GetTopWindow(NULL); hwnd != NULL; hwnd = GetNextWindow(hwnd, GW_HWNDNEXT))
{
if (!IsWindowVisible(hwnd))
continue;
int length = GetWindowTextLength(hwnd);
if (length == 0)
continue;
char* title = new char[length+1];
GetWindowText(hwnd, title, length+1);
if (title == "Program Manager")
continue;
std::cout << "HWND: " << hwnd << " Title: " << title << std::endl;
}