关于线段的绘制
这里我们主要使用两个函数来完成MoveToEx函数和LineTo函数。
MoveToEx
The MoveToEx function updates the current position to the specified point and optionally returns the previous position.
BOOL MoveToEx( _In_ HDC hdc, _In_ int X, _In_ int Y, _Out_ LPPOINT lpPoint );
Parameters
- hdc [in] Handle to a device context.
- X [in] Specifies the x-coordinate, in logical units, of the new position, in logical units.
- Y [in] Specifies the y-coordinate, in logical units, of the new position, in logical units.
- lpPoint [out] Pointer to a POINT structure that receives the previous current position. If this parameter is a NULL pointer, the previous position is not returned.
Return value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero.
LineTo
The LineTo function draws a line from the current position up to, but not including, the specified point.
BOOL LineTo( _In_ HDC hdc, _In_ int nXEnd, _In_ int nYEnd );
Parameters
- hdc [in] Handle to a device context.
- nXEnd [in] Specifies the x-coordinate, in logical units, of the line's ending point.
- nYEnd [in] Specifies the y-coordinate, in logical units, of the line's ending point.
Return value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero.
下面的代码给出了绘制矩形的。起点的位置为（20，20）。代码如下：
MoveToEx(hdc, 20, 20, NULL); LineTo(hdc,200,20); LineTo(hdc,200,200); LineTo(hdc,20,200); LineTo(hdc,20,20);
下面的完整的例子给出了随机直线的绘制。
// INCLUDES /////////////////////////////////////////////// #define WIN32_LEAN_AND_MEAN // just say no to MFC #include <windows.h> // include all the windows headers #include <windowsx.h> // include useful macros #include <mmsystem.h> // very important and include WINMM.LIB too! #include <stdio.h> #include <stdlib.h> #include <math.h> // 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)); // select the pen into context HPEN old_hpen = (HPEN)SelectObject(hdc,hpen); // move to a random postion MoveToEx(hdc, rand()%WINDOW_WIDTH, rand()%WINDOW_HEIGHT, NULL); // draw a line LineTo(hdc,rand()%WINDOW_WIDTH, rand()%WINDOW_HEIGHT); // now delete the pen SelectObject(hdc,old_hpen); DeleteObject(hpen); // release the device context ReleaseDC(hwnd,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
绘制的结果如下：
