Message queue for two cpp file with windows API - c

Question

To send the message in the Queue from one source file and get the message in another source file.I read the docs from Microsoft and try to implement as below
test2.c - post the message
main.c - get the Message
Testing1: If i execute the same code in single file that get executed and i receive the data
Testing : Same code is written in two separate file "if (msg.message == WM_YOUR_MESSAGE)" these statement does not get satisfied.
test2.h
typedef struct
{
int SomeData1;
int SomeData2;
int SomeDataN;
} MessageData;
/* Unique IDs for Window messages to exchange between the worker and the
GUI thread. */
#define WM_YOUR_MESSAGE ( WM_USER + 3 )
void __cdecl ThreadProc(void* aArg);
test2.c
#include <windows.h>
#include <process.h>
#include "malloc.h"
#include <stdio.h>
#include <test2.h>
volatile DWORD ThreadID_GUI;
void __cdecl ThreadProc(void* aArg)
{
MessageData* data;
for (;; )
{
Sleep(500);
/* Allocate memory for a new message data structure */
data = (MessageData*)malloc(sizeof(*data));
/* Initialize the message data structure with some information to transfer
to the GUI thread. */
data->SomeData1 = 1234;
data->SomeData2 = 4567;
data->SomeDataN = 7894;
PostThreadMessage(ThreadID_GUI, WM_YOUR_MESSAGE, 0, (LPARAM)data);
}
}
main.c
#include <windows.h>
#include <tchar.h>
#include <process.h>
#include "malloc.h"
#include "stdio.h"
#include<test2.h>
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
// TODO: Place code here.
ThreadID_GUI = GetCurrentThreadId();
/* Start some background thread */
_beginthread(ThreadProc, 0, 0);
// Initialize global strings
LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadStringW(hInstance, IDC_TESTMESSAGEQUEUE, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTMESSAGEQUEUE));
MSG msg;
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
/* STEP 3: React on the message sent from the foreign thread */
if (msg.message == WM_YOUR_MESSAGE)
{
MessageData* tmp = (MessageData*)msg.lParam;
if (tmp->SomeData1 == 1234) {
printf("someData\n");
}
/* Free the data structure associated to the message */
free(tmp);
}
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int) msg.wParam;
}
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEXW 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_CLIENTMQ));
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = MAKEINTRESOURCEW(IDC_CLIENTMQ);
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance,
MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassExW(&wcex);
}
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hInst = hInstance; // Store instance handle in our global variable
HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance,
nullptr);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM
lParam)
{
switch (message)
{
case WM_COMMAND:
{
int wmId = LOWORD(wParam);
// 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:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc 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;
}

Answer 1

After filling all the missing information in your source, and removing useless code, I have your code working.
main.c:
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <process.h>
#include "test2.h"
HINSTANCE hInst;
LPCWSTR szWindowClass = L"Piu";
LPCWSTR szTitle = L"Title";
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM
lParam)
{
switch (message)
{
case WM_COMMAND:
{
int wmId = LOWORD(wParam);
// 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:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc here...
EndPaint(hWnd, &ps);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEXW wcex;
ZeroMemory(&wcex, sizeof(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_CLIENTMQ));
wcex.hIconSm = LoadIcon(wcex.hInstance,
MAKEINTRESOURCE(IDI_SMALL));
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName = MAKEINTRESOURCEW(IDC_CLIENTMQ);
*/
wcex.lpszClassName = szWindowClass;
return RegisterClassExW(&wcex);
}
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hInst = hInstance; // Store instance handle in our global variable
HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, 0, 0, hInstance,
NULL);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
// TODO: Place code here.
ThreadID_GUI = GetCurrentThreadId();
/* Start some background thread */
_beginthread(ThreadProc, 0, 0);
// Initialize global strings
// LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
// LoadStringW(hInstance, IDC_TESTMESSAGEQUEUE, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance(hInstance, nCmdShow))
{
return FALSE;
}
// HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTMESSAGEQUEUE));
MSG msg;
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
/* STEP 3: React on the message sent from the foreign thread */
if (msg.message == WM_YOUR_MESSAGE)
{
MessageData* tmp = (MessageData*)msg.lParam;
if (tmp->SomeData1 == 1234) {
printf("someData\n");
}
/* Free the data structure associated to the message */
free(tmp);
}
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int)msg.wParam;
}
test2.c:
#include <Windows.h>
#include "test2.h"
volatile DWORD ThreadID_GUI;
void __cdecl ThreadProc(void* aArg)
{
MessageData* data;
for (;; )
{
Sleep(500);
/* Allocate memory for a new message data structure */
data = (MessageData*)malloc(sizeof(*data));
/* Initialize the message data structure with some information to transfer
to the GUI thread. */
data->SomeData1 = 1234;
data->SomeData2 = 4567;
data->SomeDataN = 7894;
PostThreadMessage(ThreadID_GUI, WM_YOUR_MESSAGE, 0, (LPARAM)data);
}
}
test2.h
typedef struct
{
int SomeData1;
int SomeData2;
int SomeDataN;
} MessageData;
/* Unique IDs for Window messages to exchange between the worker and the
GUI thread. */
#define WM_YOUR_MESSAGE ( WM_USER + 3 )
void __cdecl ThreadProc(void* aArg);
extern volatile DWORD ThreadID_GUI;
I removed menu and icons so there is no .rc file.