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Hi,

I'm working on developing my win32 api test application.
I've done the tool bar menus. Static and button controls.

Every thing is OK, but the problem is that when I want to print a new content, I still have some stuff from the previous content.

So my question, is how to clear the window before printing new content ?


This is my code:

C++
#include <windows.h>
#include <stdint.h>

#define FILE_MENU_NEW   1   // File menu item to be used as window numbered functions
#define FILE_MENU_OPEN  2   // File menu item to be used as window numbered functions
#define FILE_MENU_EXIT  3   // File menu item to be used as window numbered functions


#define HOME_PAGE       4
#define PAGE1           5
#define PAGE2           6

LRESULT CALLBACK WindowProcedure(HWND, UINT, WPARAM, LPARAM);
void AddMenus(HWND);
void main_page(HWND hWnd);
void page1(HWND hWnd);
void page2(HWND hWnd);


HMENU hMenu;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR args, int nCmdShow){

    WNDCLASSW wc = {0};

    wc.hbrBackground = (HBRUSH)COLOR_WINDOW;    // color of the window
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);   // shape of the cursor
    wc.hInstance = hInstance;                   // pass it windows main system handler
    wc.lpszClassName = L"myWindowClass";        // name of the window class
    wc.lpfnWndProc = WindowProcedure;

    if(!RegisterClassW(&wc)){
        return -1;
    }

    CreateWindowW(L"myWindowClass", L"My Window", WS_OVERLAPPEDWINDOW | WS_VISIBLE, 1920/4, 1080/8, 320, 480,
        NULL,       // Parent window
        NULL,       // Menu
        NULL,       // Instance handle
        NULL        // Additional application data
        );

    MSG msg = {0};

    while(GetMessage(&msg, NULL, (uint64_t)NULL, (uint64_t)NULL)){
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }


    return 0;
}


LRESULT CALLBACK WindowProcedure(HWND hWnd, UINT msg, WPARAM wp, LPARAM lp){
    switch(msg){

    case WM_COMMAND:
        switch(wp){

        case FILE_MENU_NEW:
            MessageBeep(MB_ICONINFORMATION);
            break;
        case FILE_MENU_OPEN:
            MessageBeep(MB_OK);
            break;
        case FILE_MENU_EXIT:
            break;

        case HOME_PAGE:
            main_page(hWnd);
            break;

        case PAGE1:
            page1(hWnd);
            break;
        case PAGE2:
            page2(hWnd);
            break;

        }

        break;

    case WM_CREATE:
        AddMenus(hWnd);
        main_page(hWnd);

        break;

//    case WM_PAINT:
//        InvalidateRect(hWnd, NULL, TRUE);
//        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    case WM_QUIT:

        break;


    default:
        return DefWindowProcW(hWnd, msg, wp, lp);

    }
    return 0;
}

void AddMenus(HWND hWnd){

    hMenu = CreateMenu();

    HMENU hFileMenu = CreateMenu();

    AppendMenu(hMenu, MF_POPUP, (UINT_PTR)hFileMenu, "File");
    AppendMenu(hMenu, MF_STRING, (uint64_t)NULL, "Help");

    HMENU hSubMenu = CreateMenu();
    AppendMenu(hSubMenu, MF_STRING, (uint64_t)NULL, "New 1");

    AppendMenu(hFileMenu, MF_POPUP, (UINT_PTR)hSubMenu, "New");
    AppendMenu(hFileMenu, MF_SEPARATOR, (uint64_t)NULL, 0);
    AppendMenu(hFileMenu, MF_STRING, FILE_MENU_OPEN, "Open");
    AppendMenu(hFileMenu, MF_SEPARATOR, (uint64_t)NULL, 0);
    AppendMenu(hFileMenu, MF_STRING, FILE_MENU_EXIT, "Exit");

    SetMenu(hWnd, hMenu);
}

void main_page(HWND hWnd){
    CreateWindowW(L"Static", L"main page", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 10, 180, 20, hWnd, NULL, NULL, NULL);

    CreateWindowW(L"Button", L"Page1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 50, 180, 30, hWnd, (HMENU)PAGE1, NULL, NULL);
    CreateWindowW(L"Button", L"Page2", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 90, 180, 30, hWnd, (HMENU)PAGE2, NULL, NULL);
}

void page1(HWND hWnd){
    CreateWindowW(L"Static", L"Page1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 10, 180, 20, hWnd, NULL, NULL, NULL);

    CreateWindowW(L"Button", L"P1 - button1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 50, 180, 30, hWnd, NULL, NULL, NULL);
    CreateWindowW(L"Button", L"P1 - button2", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 90, 180, 30, hWnd, NULL, NULL, NULL);
    CreateWindowW(L"Button", L"P1 - button3", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 130, 180, 30, hWnd, NULL, NULL, NULL);

    CreateWindowW(L"Button", L"Main Page - P1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 310, 180, 30, hWnd, (HMENU)HOME_PAGE, NULL, NULL);
}

void page2(HWND hWnd){
    CreateWindowW(L"Static", L"Page2", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 10, 180, 20, hWnd, NULL, NULL, NULL);

    CreateWindowW(L"Button", L"P2 - button1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 50, 180, 30, hWnd, NULL, NULL, NULL);
    CreateWindowW(L"Button", L"P2 - button2", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 90, 180, 30, hWnd, NULL, NULL, NULL);
    CreateWindowW(L"Button", L"P2 - button3", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 130, 180, 30, hWnd, NULL, NULL, NULL);

    CreateWindowW(L"Button", L"Main Page - P2", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER
                  , 65, 310, 180, 30, hWnd, (HMENU)HOME_PAGE, NULL, NULL);
}


What I have tried:

Nothing actually.

I tried to create a new window, but that open a new window to the current one which is not what I want.
Posted
Updated 21-Nov-23 22:10pm
v2
Comments
Andre Oosthuizen 20-Nov-23 13:59pm    
And your code to do this where it error's is thus...
R1S8K 22-Nov-23 3:10am    
I added the code.
Richard MacCutchan 22-Nov-23 3:47am    
It is not clear what that code is supposed to do, apart from create lots of buttons, or what is has to do with your original question.
R1S8K 22-Nov-23 4:01am    
There are 3 pages: main_page, page1 and page2.

I'm simulating any system based on paging. It's like any menu contains a main system list.

Take this youtube video as an example:
https://www.youtube.com/watch?v=9Ms59ofSJIY

There are 3 buttons on the main page: distance, RGB control and a game.

So when I press one of the buttons I should transfer from the main page to the sub-page, and then I should have a button to go back to the main menu. That's my problem in win32 api, which is when I go back to the main_page, there are buttons left from page1 and page2.
Richard MacCutchan 22-Nov-23 4:22am    
Yes, because you are creating all the buttons in the same Window; that is the main window of the application. So you could change this by creating three client windows, and add each set of buttons to a different client. You then make each client visible or not visible as required. But I have to say even doing that, this is a really bad design.

1 solution

It depends where you are storing the data that you dispaly in the Window. The proper sequence of operations is to respond to the WM_PAINT message by displaying all the relevant information in the window, as controlled by any scrollbar positioning. So every time you modify the data to be displayed you should make a call to InvalidateRect function (winuser.h) - Win32 apps | Microsoft Learn[^]. This should clear the Window and post a WM_PAINT message to update the display.

If you have further detasils then please use the Improve question link above, and add them to your question.

[edit]
Here is a fairly basic sample, but it shows how to switch between the different client windows.

C++
#include <windows.h>				// general windows definitions

#pragma comment(lib, "user32")
#pragma comment(lib, "Gdi32")


#define	IDR_MAINFRAME	128
#define	ID_APP_EXIT		130
#define	GO_PAGE_1		150
#define	GO_PAGE_2		151
#define	GO_MAIN			152

HWND	hMainPage;
HWND	hPage_1;
HWND	hPage_2;

///
///
/// 
HWND CreatePage(
	HWND		hWndParent,
	PCSTR		szClassName,
	UINT		uWindowId
)
{
	HWND		hWnd;

	// create the child window
	hWnd = CreateWindowEx(
		0,			// extended window style
		szClassName,				// registered class name
		NULL,						// and window title
		WS_CHILD,		// window style
		0, 0, 0, 0,					// position and size of window
		hWndParent,					// handle to parent or owner window
		(HMENU)uWindowId,	// menu handle or child identifier
		GetModuleHandle(NULL),		// handle to application instance
		NULL						// sent with WM_CREATE message in CREATESTRUCT
	);

	return hWnd;
}


///
/// Handle the <c>WM_CREATE</c> message. Any one-time code or modifications
///
BOOL OnCreate(
	HWND			hWnd,
	LPCREATESTRUCT	pCreateStruct
)
{
	//	Register the child window class
	WNDCLASSEX	wndClassEx;	// class structure
	memset(&wndClassEx, 0, sizeof(wndClassEx));
	wndClassEx.cbSize = sizeof wndClassEx;
	wndClassEx.style = CS_HREDRAW | CS_VREDRAW;
	wndClassEx.lpfnWndProc = (WNDPROC)GetWindowLongPtr(hWnd, GWLP_WNDPROC);
	wndClassEx.hInstance = GetModuleHandle(NULL);
	wndClassEx.hIcon = NULL;
	wndClassEx.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndClassEx.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
	wndClassEx.lpszMenuName = NULL;
	wndClassEx.lpszClassName = "ChildView";
	wndClassEx.hIconSm = NULL;

	if (RegisterClassEx(&wndClassEx))
	{
		hMainPage = CreatePage(hWnd, wndClassEx.lpszClassName, IDR_MAINFRAME + 1);
		CreateWindow("Button", "Main Window", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER,
			65, 50, 180, 30, hMainPage, (HMENU)GO_PAGE_1, NULL, NULL);
		hPage_1 = CreatePage(hWnd, wndClassEx.lpszClassName, IDR_MAINFRAME + 2);
		CreateWindow("Button", "Page 1", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER,
			65, 100, 180, 30, hPage_1, (HMENU)GO_PAGE_2, NULL, NULL);
		hPage_2 = CreatePage(hWnd, wndClassEx.lpszClassName, IDR_MAINFRAME + 3);
		CreateWindow("Button", "Second page", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER,
			65, 150, 180, 30, hPage_2, (HMENU)GO_MAIN, NULL, NULL);
		DWORD dwStyle = GetWindowLongPtr(hMainPage, GWL_STYLE);
		dwStyle |= WS_VISIBLE;
		SetWindowLongPtr(hMainPage, GWL_STYLE, dwStyle);
	}

	return TRUE;		// done!
}

///
/// handle the WM_SIZE message, to ensure the child window gets resized properly
///
void OnSize(
	HWND		hWnd,
	UINT		uState,
	int			nWidth,
	int			nHeight
)
{
	if (nWidth == 0)
		return;
	// resize the child window(s)
	MoveWindow(hMainPage, 0, 0, nWidth, nHeight, TRUE);
	MoveWindow(hPage_1, 0, 0, nWidth, nHeight, TRUE);
	MoveWindow(hPage_2, 0, 0, nWidth, nHeight, TRUE);
}


/// Handle the <c>WM_COMMAND</c> message.
/// Process user commands, as implemented by this application.
int OnCommand(
	HWND	hWnd,
	int		nCmdId,		// LOWORD(wParam)  Menu_ID,  Accelerator_ID,  Control_ID
	HWND	hWndCtl,	// (HWND)lParam    0         0                HWND of control
	UINT	codeNotify	//  HIWORD(wParam) 0 = Menu, 1 = Accelerator, X = notification code
)
{
	// Take action according to nCmdId
	switch (nCmdId)
	{
	case GO_PAGE_1:
	case GO_PAGE_2:
	case GO_MAIN:
	{
		HWND hWndFrom = nCmdId == GO_PAGE_1 ? hMainPage : nCmdId == GO_PAGE_2 ? hPage_1 : hPage_2;
		HWND hWndTo = nCmdId == GO_PAGE_1 ? hPage_1 : nCmdId == GO_PAGE_2 ? hPage_2 : hMainPage;
		ShowWindow(hWndFrom, SW_HIDE);
		ShowWindow(hWndTo, SW_NORMAL);
	}
		break;

	case ID_APP_EXIT:
		SendMessage(hWnd, WM_CLOSE, 0, 0);
		break;

	default:
		return 1;	// not handled
	}

	return 0;	// we did it
}


/// Dispatcher for the <c>WM_xxx</c> Windows messages.
/// Called to action the messages generated
/// in response to user actions on the main window.
LRESULT CALLBACK WindowProc(
	HWND	hWnd,
	UINT	uMessage,
	WPARAM	wParam,
	LPARAM	lParam
)
{
	switch (uMessage)
	{
	case WM_CREATE:
		return OnCreate(hWnd, (LPCREATESTRUCT)lParam);

	case WM_COMMAND:
		return OnCommand(hWnd, LOWORD(wParam), (HWND)lParam, HIWORD(wParam));

	case WM_SIZE:
		OnSize(hWnd, wParam, LOWORD(lParam), HIWORD(lParam));
		break;

	case WM_DESTROY:
		PostQuitMessage(0);	// application exit code 0
		break;

	default:
		return DefWindowProc(hWnd, uMessage, wParam, lParam);
	}

	return 0;	// the message was handled in the switch block
}


/// <summary>
/// Main function of the windows application.
/// 
int APIENTRY wWinMain(
	_In_		HINSTANCE	hInstance,
	_In_opt_	HINSTANCE	hPrevInstance,
	_In_		LPWSTR		lpCmdLine,
	_In_		int			nShowCmd
)
{
	int			nAppResult = -1;	// just in case something fails at initialisation


	WNDCLASSEX	wndClassEx;	// class structure
	HWND		hWnd = NULL;

	//	Initialise the window class structure
	memset(&wndClassEx, 0, sizeof(wndClassEx));
	wndClassEx.cbSize = sizeof wndClassEx;
	wndClassEx.style = CS_HREDRAW | CS_VREDRAW;
	wndClassEx.lpfnWndProc = WindowProc;
	wndClassEx.cbClsExtra = 0;
	wndClassEx.cbWndExtra = 0;
	wndClassEx.hInstance = hInstance;
	wndClassEx.hIcon = LoadIcon(hInstance, NULL);
	wndClassEx.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndClassEx.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
	wndClassEx.lpszMenuName = NULL;
	wndClassEx.lpszClassName = "SampleApp";
	wndClassEx.hIconSm = NULL;

	if (RegisterClassEx(&wndClassEx))
	{
		// create the main frame window
		hWnd = CreateWindowEx(
			WS_EX_CLIENTEDGE,			// extended window style
			wndClassEx.lpszClassName,	// registered class name
			wndClassEx.lpszClassName,	// and window title
			WS_OVERLAPPEDWINDOW,		// window style
			CW_USEDEFAULT,				// horizontal position of window
			0,							// vertical position of window
			800,						// window width
			500,						// window height
			NULL,						// handle to parent or owner window
			NULL,						// menu handle or child identifier
			hInstance,					// handle to application instance
			NULL						// object pointer sent with WM_CREATE message in CREATESTRUCT
		);
		// display the main frame window
		ShowWindow(hWnd, SW_SHOWNORMAL);	// show the window frame and
		UpdateWindow(hWnd);					// update the client area
		MSG		msg;

		// Main message loop:
		while (GetMessage(&msg, NULL, 0, 0) > 0)
		{
			// returns when a WM_QUIT message appears
			TranslateMessage(&msg);
			DispatchMessage(&msg);	// calls the static WindowProc function
		}
		nAppResult = msg.wParam;
	}

	return nAppResult;
}


[/edit]
 
Share this answer
 
v3
Comments
Maciej Los 20-Nov-23 13:05pm    
5ed!
R1S8K 23-Nov-23 4:08am    
I got these errors:


-------------- Build: Release in code_project_example (compiler: GNU GCC Compiler)---------------

gcc.exe -Wall -O2  -c "D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c" -o obj\Release\main.o
gcc.exe  -o bin\Release\code_project_example.exe obj\Release\main.o  -s  
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c: In function 'CreatePage':
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:32:3: error: 'reinterpret_cast' undeclared (first use in this function)
   reinterpret_cast<hmenu>(uWindowId), // menu handle or child identifier
   ^~~~~~~~~~~~~~~~
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:32:3: note: each undeclared identifier is reported only once for each function it appears in
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:32:20: error: expected expression before 'HMENU'
   reinterpret_cast<hmenu>(uWindowId), // menu handle or child identifier
                    ^~~~~
In file included from D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/winnt.h:9,
                 from D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/minwindef.h:163,
                 from D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/windef.h:8,
                 from D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/windows.h:69,
                 from D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:1:
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:25:9: error: too few arguments to function 'CreateWindowExA'
  hWnd = CreateWindowEx(
         ^~~~~~~~~~~~~~
In file included from D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/windows.h:72,
                 from D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:1:
D:/Program_Files/CodeBlocks/MinGW/x86_64-w64-mingw32/include/winuser.h:2137:26: note: declared here
   WINUSERAPI HWND WINAPI CreateWindowExA(DWORD dwExStyle,LPCSTR lpClassName,LPCSTR lpWindowName,DWORD dwStyle,int X,int Y,int nWidth,int nHeight,HWND hWndParent,HMENU hMenu,HINSTANCE hInstance,LPVOID lpParam);
                          ^~~~~~~~~~~~~~~
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c: In function 'OnCreate':
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:50:23: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
  WNDCLASSEX wndClassEx{}; // class structure
                       ^
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:51:2: error: 'wndClassEx' undeclared (first use in this function); did you mean 'ReadClassStm'?
  wndClassEx.cbSize = sizeof wndClassEx;
  ^~~~~~~~~~
  ReadClassStm
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:53:27: error: 'reinterpret_cast' undeclared (first use in this function)
  wndClassEx.lpfnWndProc = reinterpret_cast<wndproc>(GetWindowLongPtr(hWnd, GWLP_WNDPROC));
                           ^~~~~~~~~~~~~~~~
D:\Programming\desktop_programming\C\windows api programming\code_project_example\code_project_example\main.c:53:44: error: expected expression before 'WNDPROC'
  wndClassEx.lpfnWndProc = reinterpret_cast<wndproc>(GetWindowLongPtr(hWnd, GWLP_WNDPROC));
                                            ^~~~~~~
... 
R1S8K 23-Nov-23 4:11am    
OK, I think your code is in C++
R1S8K 23-Nov-23 4:17am    
OK, I ran the code in C++ and changed the wWINMAIN to this one:
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR args, int nCmdShow)


and it's working, the example runs smoothly and I got the idea. Now I need just to get the grasp on the example and embed it in my code.
Richard MacCutchan 23-Nov-23 4:38am    
Yes, I convedrted it from C++ and forgot about the cast. My apologies.

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