How to set int or double variable entere

Use GetWindowText() function and parse the input into an int
https://msdn.microsoft.com/en-us/library/windows/desktop/ms633520%28v=vs.85%29.aspx

And SetWindowText() to set it.
https://msdn.microsoft.com/en-us/library/windows/desktop/ms633546%28v=vs.85%29.aspx

Last edited on

I don't understand this how MSDN explain it.

Please note that I may get some TCHAR functions wrong as I don't remember the exact syntax now.

HWND someEditControl;
/*initialize control & stuff*/

/*maximum number of (w)chars you want to get from the edit box control, 
for example you can use this to round a float/double a few decimals*/
constexpr BYTE maxChars = 10; 

TCHAR * buffer = new TCHAR[maxChars]; /* buffer to hold the content you'll get */

/* get up to maxChars (w)chars from the edit control into your buffer */
int writtenChars = GetWindowText(someEditControl, buffer, maxChars); 

/* convert the buffer, but remember that the control may contain less (w)chars 
than the maximum you want, writtenChars will contain the exact number */
float editBoxContent = _tcstof(buffer, NULL);

delete[] buffer; //don't forget to delete buffer

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I would do it like this:

HWND hEdit; // your edit window
const int BUFFER_SIZE = 10;
std::string buffer(BUFFER_SIZE, 10);
int len = GetWindowTextA(hEdit, &buffer[0], BUFFER_SIZE);
if (len == 0)
{
  MessageBoxA(0, "Text was empty", "ERROR", MB_OK | MB_ICONASTERISK);
  return FALSE;          
}
buffer.resize(len);
MessageBoxA(0, buffer.c_str(), "Number as text", MB_OK);
int num = stoi(buffer);

Thank you but it does calculate.I wanted to do addition operation but it does work.
I hope any you guys can help me.

#include <Windows.h>
#define ID_CALCULATE 101

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

HWND hwnd,editnum1,editnum2,edittotal,buttoncalclulate;
WNDCLASSEX wc;
MSG msg;
HINSTANCE hinst;
int APIENTRY WinMain(HINSTANCE hinst, HINSTANCE hprev, LPSTR line, int show)
{
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.cbSize = sizeof(WNDCLASSEX);
	wc.cbClsExtra = 0;
	wc.cbWndExtra = 0;
	wc.hInstance = hinst;
	wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wc.hCursor = LoadCursor(NULL, IDI_APPLICATION);
	wc.hbrBackground = (HBRUSH)(COLOR_WINDOW );
	wc.lpszClassName = TEXT("simplecalculator");
	wc.lpszMenuName = NULL;
	wc.lpfnWndProc = WndProc;
	wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

	RegisterClassEx(&wc);
	hwnd = CreateWindowEx(NULL, TEXT("simplecalculator"), TEXT("Simple Calculator"),WS_SYSMENU|WS_MINIMIZEBOX, CW_USEDEFAULT, CW_USEDEFAULT, 790, 150, NULL, NULL, hinst, NULL);
	ShowWindow(hwnd, show);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);

	}
	return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
	

	switch (msg)
	{
	case WM_CREATE:
		editnum1 = CreateWindow(TEXT("edit"), NULL, WS_CHILD | WS_VISIBLE, 20, 20, 200, 30,hwnd, NULL, hinst, NULL);
		editnum2 = CreateWindow(TEXT("edit"), NULL, WS_CHILD | WS_VISIBLE, 230, 20, 200, 30, hwnd, NULL, hinst, NULL);
		edittotal = CreateWindow(TEXT("edit"), NULL, WS_CHILD | WS_VISIBLE, 550, 20, 200, 30, hwnd, NULL, hinst, NULL);
		buttoncalclulate = CreateWindow(TEXT("button"), "Calculate", WS_CHILD | WS_VISIBLE|BS_FLAT, 440, 20, 100, 30, hwnd, (HMENU)ID_CALCULATE, hinst, NULL);
		break;
	case WM_COMMAND:
		if (LOWORD(wparam) == ID_CALCULATE)
		{
			BYTE maxChars = 10;
			TCHAR * buffer = new TCHAR[maxChars]; 		
			int writtenChars = GetWindowText(editnum1, buffer, maxChars);
			float num1 = _tcstof(buffer, NULL);

			BYTE maxChars2 = 10;
			TCHAR * buffer2 = new TCHAR[maxChars2];
			int writtenChars2 = GetWindowText(editnum1, buffer2, maxChars2);
			float num2 = _tcstof(buffer2, NULL);

			float total = num1 + num2;
			char display[1];
			_itoa(total, display, 100000);

			SetWindowTextA(edittotal, display);
         }
		break;
	case WM_DESTROY:
		PostQuitMessage(0);
		break;
	default:
		return DefWindowProc(hwnd, msg, wparam, lparam);
		break;
	}
	return 0;
}

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char display[1];
How many digits do you think you can store in it ?

does matter how much i set on the braket it still doesn't work.

Last edited on

What do you mean it doesn't work?
Any more crashes, wrong result, no output ????

i mean if i input 1 in first edit box and 5 in second editbox and i click calculate button which should do 1+5 but the result i got in third editbox is 2.

Yes, it does work fine, only that you read the same control box twice, so it's 1 + 1 = 2.


			BYTE maxChars = 10;
			TCHAR * buffer = new TCHAR[maxChars]; 		
			int writtenChars = GetWindowText(editnum1, buffer, maxChars);
			float num1 = _tcstof(buffer, NULL);

			BYTE maxChars2 = 10;
			TCHAR * buffer2 = new TCHAR[maxChars2];
			int writtenChars2 = GetWindowText(editnum1, buffer2, maxChars2);
			float num2 = _tcstof(buffer2, NULL);

			float total = num1 + num2;
			char display[1];
			_itoa(total, display, 100000);

			SetWindowTextA(edittotal, display);

Also some more flaws in your code:

Too many global variables:

HWND hwnd,editnum1,editnum2,edittotal,buttoncalclulate;
WNDCLASSEX wc;
MSG msg;
HINSTANCE hinst;

You never delete the buffers you put on the heap.

1
2

TCHAR * buffer = new TCHAR[maxChars];
// you should use delete[] buffer or just allocate it on the stack

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oh no didn't realize my mistake until you highlight both of the editnum1.This going to be a valuable lesson so i can pay more attention to the code.Thank you very much Golden Lizard and
Thomas 1965.

But if num1+num2=>10 it shows alphabet

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You never delete the buffers you put on the heap.

@Golden Lizard,
what do you expect ? He is using your code.

that's just a snippet, I thought deleting buffers would be a no brainer as he said he had "good knowledge of c++"

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BYTE maxChars = 1000000;
			TCHAR * buffer = new TCHAR[maxChars]; 		
			int writtenChars = GetWindowText(editnum1, buffer, maxChars);
			float num1 = _tcstof(buffer, NULL);

			BYTE maxChars2 = 100000;
			TCHAR * buffer2 = new TCHAR[maxChars2];
			int writtenChars2 = GetWindowText(editnum2, buffer2, maxChars2);
			float num2 = _tcstof(buffer2, NULL);

			float total = num1 + num2;
			char display[10];
			_itoa(total, display, 10);

			SetWindowTextA(edittotal, display);

I did some change to the code now it does't show alphabet anymore.

Thank you very much for your guide.

I'm sorry for anything you don't like from me.

Now I understand why video games are so expansive.

No need for 2 variables if you use the same length twice. Also 100000 is way too much and pretty wasteful in your context.

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Well this winapi programming is so complicated.Can you recommend any good book about it.

The unofficial Windows "Bible" is:
https://www.amazon.com/Programming-Windows%C2%AE-Fifth-Developer-Reference/dp/157231995X/ref=sr_1_1?ie=UTF8&qid=1507301248&sr=8-1&keywords=Programming+Windows

A good reference books with useful examples:
https://www.amazon.com/Windows-Win32-SuperBible-Other-Sams/dp/1571690891/ref=pd_rhf_dp_16?_encoding=UTF8&pd_rd_i=1571690891&pd_rd_r=98H52JAWW0KC6RBZ7XB9&pd_rd_w=3O6rY&pd_rd_wg=bZ7SJ&psc=1&refRID=98H52JAWW0KC6RBZ7XB9

which one is better