有人可以解释为什么使用DefWindowProc一切正常,但如果我删除它,字符串"Hello windows"出现在屏幕上没有窗口和任何按钮？"UpdateWindow"发送到窗口过程WM_PAINT消息,那么为什么显示文本但是跳过了窗口的创建？
#include <windows.h>
LRESULT CALLBACK proc1 (HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("Program");
HWND hwnd1;
MSG msg1;
WNDCLASS wndclass1;
wndclass1.style = CS_HREDRAW | CS_VREDRAW;
wndclass1.lpfnWndProc = proc1;
wndclass1.cbClsExtra = 0;
wndclass1.cbWndExtra = 0;
wndclass1.hInstance = hInstance;
wndclass1.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wndclass1.hCursor = LoadCursor (NULL, IDC_ARROW);
wndclass1.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH);
wndclass1.lpszMenuName = NULL;
wndclass1.lpszClassName = szAppName;
RegisterClass (&wndclass1);
hwnd1 = CreateWindow ( szAppName, …