win32 窗口 绘制椭圆

win32 窗口 绘制椭圆

测试环境: win7 64 位 vs2013

建立一个 win32 应用程序 ，空项目，名称是 HelloPaintEllipse,

在项目中添加源文件 HelloPaintEllipse.cpp :

#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <tchar.h>

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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("HelloWin");
HWND         hwnd;
MSG          msg;
WNDCLASS     wndclass;

wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;

if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("This program requires Windows NT!"),
szAppName, MB_ICONERROR);
return 0;
}

hwnd = CreateWindow(szAppName,                  // window class name
TEXT("The Hello Program"), // window caption
WS_OVERLAPPEDWINDOW,        // window style
CW_USEDEFAULT,              // initial x position
CW_USEDEFAULT,              // initial y position
CW_USEDEFAULT,              // initial x size
CW_USEDEFAULT,              // initial y size
NULL,                       // parent window handle
NULL,                       // window menu handle
hInstance,                  // program instance handle
NULL);                     // creation parameters

ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);

while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC         hdc;
PAINTSTRUCT ps;

switch (message)
{
case WM_CLOSE:
DestroyWindow(hwnd);
break;

case WM_DESTROY:
PostQuitMessage(0);
break;

case WM_PAINT:

hdc = BeginPaint(hwnd, &ps);                         // 1

Rectangle(hdc, 50, 50, 200, 200);                    // 2

Rectangle(hdc, 300, 50, 500, 200);                   // 3

Ellipse(hdc, 50, 50, 200, 200);                      // 4

Ellipse(hdc, 300, 200, 500, 50);                     // 5

EndPaint(hwnd, &ps);                                 // 6

break;

default:
return DefWindowProc(hwnd, message, wParam, lParam);

}

return 0;
}

显示效果如下:



坐标标注:



绘制椭圆是使用的

矩形的对角的两点的坐标，该坐标可以是左上角和右下角，也可以是左下角和右上角

绘制的椭圆是对应矩形的内切椭圆