winapi - a standard way to retrieve text from running text editor - c++

Question

Is there a standard message that can be sent to a text editor window or a certain WinApi call, that will retrieve the contents of the currently edited text?
For example, to retrieve the current contents of a Notepad window. (assumed that the most up to date text wasn't yet written to a file)
I've tried retrieving the text via SendMessage using WM_GETTEXT, WM_GETTEXTLENGTH but I was able to retrieve the title text only.

Answer 1

In general no there is no standard message for this.
But Windows' Notepad has an "Edit" child which responds to WM_GETTEXT and WM_GETTEXTLENGTH - messages normally used to retrieve text from input controls.
Here's a PoC demonstrating the idea:
#include <iostream>
#include <vector>
#include <string.h>
#include <Windows.h>
BOOL CALLBACK enumProc(HWND hwnd, LPARAM) {
std::vector<char> buf(100);
GetClassNameA(hwnd, buf.data(), 100);
if (strcmp(buf.data(), "Notepad")) return TRUE;
hwnd = FindWindowEx(hwnd, NULL, "Edit", NULL);
if (!hwnd) return TRUE;
int textLength = SendMessageA(hwnd, WM_GETTEXTLENGTH, 0, 0) + 1;
if (textLength <= 0) return TRUE;
buf.resize(textLength);
SendMessage(hwnd, WM_GETTEXT, textLength, (LPARAM)buf.data());
std::cout << buf.data() << "\n";
return TRUE;
}
int main() {
EnumWindows(&enumProc, 0);
}
Works on Windows 10: