Win32 API VS C++; Text Box Content to String - c++

Question

I am new with programming Win32 applications. I have programmed a text box where the user can enter text. The problem is that I don't know how to get the input of the box into a string, which is necessary to process the input. For testing purposes, I tried to give out the entered text through the output text box, which I had to program anyway.
Googling, I found out that GetWindowTextA(hInput, input, length); should do the trick. However, I am not sure how to get the input into a variable using this method.
So, my question is, how do I get a text, entered by a user into a text box, into a string?
In case this does matter: I am not using the free version of Visual Studio, as I have free access to Microsoft software through my university. And at the moment I am using Visual Studio 2015 Ultimate Preview anyway. To answer the question in advance, this is NO homework or other work for my university, for a job or anything commercially. I have taught myself C++, which has become my favorite programming language, and I want to be able to program graphical interfaces with it.
Here is Visual Studio's standard code with some modifications, most notably the addition of two text boxes and a button (which does nothing at the moment and is of no importance for this question):
Includes, globals, forward declarations
#include "stdafx.h"
#include "WilliTeX.h"
#include <iostream>;
using namespace std;
#define MAX_LOADSTRING 100
//custom defines
#define TEXT_INPUT_BOX 1
#define TEXT_OUTPUT_BOX 2
#define BUTTON 3
HWND hInput;
HWND hOutput;
HWND hButton;
int length;
LPSTR input;
// Global Variables:
HINSTANCE hInst; // current instance
TCHAR szTitle[MAX_LOADSTRING]; // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING]; // the main window class name
// Forward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);
_tWinMain
int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
MSG msg;
HACCEL hAccelTable;
// Initialize global strings
LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadString(hInstance, IDC_WILLITEX, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WILLITEX));
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
MyRegisterClass
//
// FUNCTION: MyRegisterClass()
//
// PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_WILLITEX));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = MAKEINTRESOURCE(IDC_WILLITEX);
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassEx(&wcex);
}
Rest of Code
//
// FUNCTION: InitInstance(HINSTANCE, int)
//
// PURPOSE: Saves instance handle and creates main window
//
// COMMENTS:
//
// In this function, we save the instance handle in a global variable and
// create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
HWND hWnd;
hInst = hInstance; // Store instance handle in our global variable
hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
//
// FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
// PURPOSE: Processes messages for the main window.
//
// WM_COMMAND - process the application menu
// WM_PAINT - Paint the main window
// WM_DESTROY - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_CREATE:
{
//This is the input box, where the user enters the text
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"EDIT",
"",
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
10, //moving up/down the box
1300, //length
350, //height
hWnd,
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
//This is the output text box, that will display the convertion
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"Edit",
"test",
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
200, //moving up/down the box
1300, //length
450, //height
hWnd,
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
hButton = CreateWindowExA(NULL,
"BUTTON",
"OK",
WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,
3, //moving left/right
10, //moving up/down
48, //length
50, //height
hWnd,
(HMENU) BUTTON,
GetModuleHandle(NULL),
NULL);
break;
}
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
switch (LOWORD(wParam)) {
//refreshing the output box whenever the user is giving an input
case TEXT_INPUT_BOX:
{
length = GetWindowTextLengthA(hInput);
GetWindowTextA(hInput, input, length);
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"Edit",
input,
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
200, //moving up/down the box
1300, //length
450, //height
hWnd,
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
break;
}
case BUTTON:
{
break;
}
}
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
break;
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code here...
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
}
P.S. I am aware that using namespace std; is bad coding practice but for this learning program I don't really care.

Answer 1

You seem to be creating the input text box (again) when you get a message from it. That doesn't make sense. ANd your GetWindowTextA call is using a variable 'input' that you have not defined. Allocate a character array for that variable.