WM_ACTIVATE行为异常

问题描述

这是一个困扰我很长时间的难题.这是一个简单的小程序，可突出显示我在说什么:

Here's a puzzle that's baffled me for quite some time.  Here's a simple little program to highlight what I'm talking about:

#include <windows.h>


LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)

{

	switch(msg)

	{

		case WM_ACTIVATE:

			if(wParam == WA_INACTIVE)

				SetWindowText(hwnd, "Inactive");

			else

				SetWindowText(hwnd, "Active");

			break;

		case WM_CLOSE:

			DestroyWindow(hwnd);

			break;

		case WM_DESTROY:

			PostQuitMessage(0);

			break;

		default:

			return DefWindowProc(hwnd, msg, wParam, lParam);

	}

	return 0;

}



int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)

{

	// Delay the start of the program by five seconds to highlight odd WM_ACTIVATE behaviour.

	Sleep(5000);



	WNDCLASS wc = {0};

	wc.lpfnWndProc   = WndProc;

	wc.hInstance     = hInstance;

	wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);

	wc.hCursor       = LoadCursor(NULL, IDC_ARROW);

	wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);

	wc.lpszClassName = "myWindow";



	RegisterClass(&wc);



	HWND hwnd = CreateWindow("myWindow", "Default Title", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, 

		CW_USEDEFAULT, 500, 100, NULL, NULL, hInstance, NULL);


	ShowWindow(hwnd, nCmdShow);

	UpdateWindow(hwnd);



	MSG Msg;

	while(GetMessage(&Msg, NULL, 0, 0) > 0)

		DispatchMessage(&Msg);



	return Msg.wParam;

}

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