随机画出随机颜色的线hpen MoveToEx LineTo DeleteObject
// DEMO4_2.CPP - Line drawing demo
// INCLUDES ///////////////////////////////////////////////
#define WIN32_LEAN_AND_MEAN // just say no to MFC
#include
#include
#include
#include
#include
#include
// DEFINES ////////////////////////////////////////////////
// defines for windows
#define WINDOW_CLASS_NAME "WINCLASS1"
#define WINDOW_WIDTH 400
#define WINDOW_HEIGHT 300
// MACROS /////////////////////////////////////////////////
#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)
#define KEYUP(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)
// GLOBALS ////////////////////////////////////////////////
HWND main_window_handle = NULL; // globally track main window
HINSTANCE hinstance_app = NULL; // globally track hinstance
char buffer[80]; // general printing buffer
// FUNCTIONS //////////////////////////////////////////////
LRESULT CALLBACK WindowProc(HWND hwnd,
UINT msg,
WPARAM wparam,
LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT ps; // used in WM_PAINT
HDC hdc; // handle to a device context
char buffer[80]; // used to print strings
// what is the message
switch(msg)
{
case WM_CREATE:
{
// do initialization stuff here
// return success
return(0);
} break;
case WM_PAINT:
{
// simply validate the window
hdc = BeginPaint(hwnd,&ps);
// end painting
EndPaint(hwnd,&ps);
// return success
return(0);
} break;
case WM_DESTROY:
{
// kill the application, this sends a WM_QUIT message
PostQuitMessage(0);
// return success
return(0);
} break;
default:break;
} // end switch
// process any messages that we didn't take care of
return (DefWindowProc(hwnd, msg, wparam, lparam));
} // end WinProc
// WINMAIN ////////////////////////////////////////////////
int WINAPI WinMain( HINSTANCE hinstance,
HINSTANCE hprevinstance,
LPSTR lpcmdline,
int ncmdshow)
{
WNDCLASSEX winclass; // this will hold the class we create
HWND hwnd; // generic window handle
MSG msg; // generic message
HDC hdc; // graphics device context
// first fill in the window class stucture
winclass.cbSize = sizeof(WNDCLASSEX);
winclass.style = CS_DBLCLKS | CS_OWNDC |
CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc = WindowProc;
winclass.cbClsExtra = 0;
winclass.cbWndExtra = 0;
winclass.hInstance = hinstance;
winclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName = NULL;
winclass.lpszClassName = WINDOW_CLASS_NAME;
winclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
// save hinstance in global
hinstance_app = hinstance;
// register the window class
if (!RegisterClassEx(&winclass))
return(0);
// create the window
if (!(hwnd = CreateWindowEx(NULL, // extended style
WINDOW_CLASS_NAME, // class
"Line Drawing Demo", // title
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
0,0, // initial x,y
WINDOW_WIDTH, // initial width
WINDOW_HEIGHT,// initial height
NULL, // handle to parent
NULL, // handle to menu
hinstance,// instance of this application
NULL))) // extra creation parms
return(0);
// save main window handle
main_window_handle = hwnd;
// enter main event loop, but this time we use PeekMessage()
// instead of GetMessage() to retrieve messages
while(TRUE)
{
// test if there is a message in queue, if so get it
if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
{
// test if this is a quit
if (msg.message == WM_QUIT)
break;
// translate any accelerator keys
TranslateMessage(&msg);
// send the message to the window proc
DispatchMessage(&msg);
} // end if
// draw a random line
// get the graphics device context
hdc = GetDC(hwnd);
// create a random colored pen
HPEN hpen = CreatePen(PS_SOLID,1,RGB(rand()%256,rand()%256,rand()%256));
/*
The CreatePen function creates a logical pen that has the specified style, width, and color.
The pen can subsequently be selected into a device context and used to draw lines and curves.
参数为：样式，宽度，颜色
样式参考：ms-help://MS.MSDNQTR.v80.chs/MS.MSDN.v80/MS.WIN32COM.v10.en/gdi/pens_9wha.htm
*/
// select the pen into context
HPEN old_hpen = (HPEN)SelectObject(hdc,hpen);
/*
The SelectObject function selects an object into the specified device context (DC). The new object replaces the previous object of the same type.
Return Values 返回老的画笔
*/
// move to a random postion
MoveToEx(hdc, rand()%WINDOW_WIDTH, rand()%WINDOW_HEIGHT, NULL);
/*
The MoveToEx function updates the current position to the specified point and optionally returns the previous position
MoveToEx是用来移动当前画笔的位置，LineTo是用来画直线的函数，其实在计算机图形里的直线显示是使用光栅图形学里的原理
*/
// draw a line
LineTo(hdc,rand()%WINDOW_WIDTH, rand()%WINDOW_HEIGHT);
//The LineTo function draws a line from the current position up to, but not including, the specified point.
// now delete the pen
SelectObject(hdc,old_hpen);
//还原到原来的默认画笔
//删除画笔
DeleteObject(hpen);
// release the device context
ReleaseDC(hwnd,hdc);
//翻译HDC
// main game processing goes here
if (KEYDOWN(VK_ESCAPE))
SendMessage(hwnd, WM_CLOSE, 0,0);
} // end while
// return to Windows like this
return(msg.wParam);
} // end WinMain
///////////////////////////////////////////////////////////