C++: Draw a Clock

 

Task: draw a clock. More specific:

  1. Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting “one thousand and one”, anything. Only showing the seconds is required, e.g. a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn’t qualify. Both text-based and graphical drawing are OK.
  2. The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
  3. A clock is rarely (never?) a major application: don’t be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the framebuffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
  4. A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don’t write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.

Clock cpp.png

#include <windows.h>
#include <string>
#include <math.h>

//--------------------------------------------------------------------------------------------------
using namespace std;

//--------------------------------------------------------------------------------------------------
const int BMP_SIZE = 300, MY_TIMER = 987654, CENTER = BMP_SIZE >> 1, SEC_LEN = CENTER - 20,
MIN_LEN = SEC_LEN - 20, HOUR_LEN = MIN_LEN - 20;
const float PI = 3.1415926536f;

//--------------------------------------------------------------------------------------------------
class vector2
{
public:
	vector2() { x = y = 0; }
	vector2( int a, int b ) { x = a; y = b; }
	void set( int a, int b ) { x = a; y = b; }
	void rotate( float angle_r )
	{
		float _x = static_cast<float>( x ),
		_y = static_cast<float>( y ),
		s = sinf( angle_r ),
		c = cosf( angle_r ),
		a = _x * c - _y * s,
		b = _x * s + _y * c;

		x = static_cast<int>( a );
		y = static_cast<int>( b );
	}
	int x, y;
};
//--------------------------------------------------------------------------------------------------
class myBitmap
{
public:
	myBitmap() : pen( NULL ), brush( NULL ), clr( 0 ), wid( 1 ) {}
	~myBitmap()
	{
		DeleteObject( pen );
		DeleteObject( brush );
		DeleteDC( hdc );
		DeleteObject( bmp );
	}

	bool create( int w, int h )
	{
		BITMAPINFO    bi;
		ZeroMemory( &bi, sizeof( bi ) );
		bi.bmiHeader.biSize        = sizeof( bi.bmiHeader );
		bi.bmiHeader.biBitCount    = sizeof( DWORD ) * 8;
		bi.bmiHeader.biCompression = BI_RGB;
		bi.bmiHeader.biPlanes      = 1;
		bi.bmiHeader.biWidth       =  w;
		bi.bmiHeader.biHeight      = -h;

		HDC dc = GetDC( GetConsoleWindow() );
		bmp = CreateDIBSection( dc, &bi, DIB_RGB_COLORS, &pBits, NULL, 0 );
		if( !bmp ) return false;

		hdc = CreateCompatibleDC( dc );
		SelectObject( hdc, bmp );
		ReleaseDC( GetConsoleWindow(), dc );

		width = w; height = h;
		return true;
	}

	void clear( BYTE clr = 0 )
	{
		memset( pBits, clr, width * height * sizeof( DWORD ) );
	}

	void setBrushColor( DWORD bClr )
	{
		if( brush ) DeleteObject( brush );
		brush = CreateSolidBrush( bClr );
		SelectObject( hdc, brush );
	}

	void setPenColor( DWORD c )
	{
		clr = c;
		createPen();
	}

	void setPenWidth( int w )
	{
		wid = w;
		createPen();
	}

	void saveBitmap( string path )
	{
		BITMAPFILEHEADER fileheader;
		BITMAPINFO       infoheader;
		BITMAP           bitmap;
		DWORD            wb;

		GetObject( bmp, sizeof( bitmap ), &bitmap );
		DWORD* dwpBits = new DWORD[bitmap.bmWidth * bitmap.bmHeight];

		ZeroMemory( dwpBits, bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD ) );
		ZeroMemory( &infoheader, sizeof( BITMAPINFO ) );
		ZeroMemory( &fileheader, sizeof( BITMAPFILEHEADER ) );

		infoheader.bmiHeader.biBitCount = sizeof( DWORD ) * 8;
		infoheader.bmiHeader.biCompression = BI_RGB;
		infoheader.bmiHeader.biPlanes = 1;
		infoheader.bmiHeader.biSize = sizeof( infoheader.bmiHeader );
		infoheader.bmiHeader.biHeight = bitmap.bmHeight;
		infoheader.bmiHeader.biWidth = bitmap.bmWidth;
		infoheader.bmiHeader.biSizeImage = bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD );

		fileheader.bfType    = 0x4D42;
		fileheader.bfOffBits = sizeof( infoheader.bmiHeader ) + sizeof( BITMAPFILEHEADER );
		fileheader.bfSize    = fileheader.bfOffBits + infoheader.bmiHeader.biSizeImage;

		GetDIBits( hdc, bmp, 0, height, ( LPVOID )dwpBits, &infoheader, DIB_RGB_COLORS );

		HANDLE file = CreateFile( path.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL );
		WriteFile( file, &fileheader, sizeof( BITMAPFILEHEADER ), &wb, NULL );
		WriteFile( file, &infoheader.bmiHeader, sizeof( infoheader.bmiHeader ), &wb, NULL );
		WriteFile( file, dwpBits, bitmap.bmWidth * bitmap.bmHeight * 4, &wb, NULL );
		CloseHandle( file );

		delete [] dwpBits;
	}

	HDC getDC() const     { return hdc; }
	int getWidth() const  { return width; }
	int getHeight() const { return height; }

private:
	void createPen()
	{
		if( pen ) DeleteObject( pen );
		pen = CreatePen( PS_SOLID, wid, clr );
		SelectObject( hdc, pen );
	}

	HBITMAP bmp;
	HDC     hdc;
	HPEN    pen;
	HBRUSH  brush;
	void    *pBits;
	int     width, height, wid;
	DWORD   clr;
};
//--------------------------------------------------------------------------------------------------
class clock
{
public:
	clock()  
	{
		_bmp.create( BMP_SIZE, BMP_SIZE );
		_bmp.clear( 100 );
		_bmp.setPenWidth( 2 );
		_ang = DegToRadian( 6 );
	}

	void setNow()
	{
		GetLocalTime( &_sysTime );
		draw();
	}

	float DegToRadian( float degree ) { return degree * ( PI / 180.0f ); }

	void setHWND( HWND hwnd ) { _hwnd = hwnd; }

private:
	void drawTicks( HDC dc )
	{
		vector2 line;
		_bmp.setPenWidth( 1 );
		for( int x = 0; x < 60; x++ )
		{
			line.set( 0, 50 );
			line.rotate( static_cast<float>( x + 30 ) * _ang );
			MoveToEx( dc, CENTER - static_cast<int>( 2.5f * static_cast<float>( line.x ) ), CENTER - static_cast<int>( 2.5f * static_cast<float>( line.y ) ), NULL );
			LineTo( dc, CENTER - static_cast<int>( 2.81f * static_cast<float>( line.x ) ), CENTER - static_cast<int>( 2.81f * static_cast<float>( line.y ) ) );
		}

		_bmp.setPenWidth( 3 );
		for( int x = 0; x < 60; x += 5 )
		{
			line.set( 0, 50 );
			line.rotate( static_cast<float>( x + 30 ) * _ang );
			MoveToEx( dc, CENTER - static_cast<int>( 2.5f * static_cast<float>( line.x ) ), CENTER - static_cast<int>( 2.5f * static_cast<float>( line.y ) ), NULL );
			LineTo( dc, CENTER - static_cast<int>( 2.81f * static_cast<float>( line.x ) ), CENTER - static_cast<int>( 2.81f * static_cast<float>( line.y ) ) );
		}
	}

	void drawHands( HDC dc )
	{
		float hp = DegToRadian( ( 30.0f * static_cast<float>( _sysTime.wMinute ) ) / 60.0f );
		int h = ( _sysTime.wHour > 12 ? _sysTime.wHour - 12 : _sysTime.wHour ) * 5;

		_bmp.setPenWidth( 3 );
		_bmp.setPenColor( RGB( 0, 0, 255 ) );
		drawHand( dc, HOUR_LEN, ( _ang * static_cast<float>( 30 + h ) ) + hp );

		_bmp.setPenColor( RGB( 0, 128, 0 ) );
		drawHand( dc, MIN_LEN, _ang * static_cast<float>( 30 + _sysTime.wMinute ) );

		_bmp.setPenWidth( 2 );
		_bmp.setPenColor( RGB( 255, 0, 0 ) );
		drawHand( dc, SEC_LEN, _ang * static_cast<float>( 30 + _sysTime.wSecond ) );
	}

	void drawHand( HDC dc, int len, float ang )
	{
		vector2 line;
		line.set( 0, len );
		line.rotate( ang );
		MoveToEx( dc, CENTER, CENTER, NULL );
		LineTo( dc, line.x + CENTER, line.y + CENTER );
	}

	void draw()
	{
		HDC dc = _bmp.getDC();

		_bmp.setBrushColor( RGB( 250, 250, 250 ) );
		Ellipse( dc, 0, 0, BMP_SIZE, BMP_SIZE );
		_bmp.setBrushColor( RGB( 230, 230, 230 ) );
		Ellipse( dc, 10, 10, BMP_SIZE - 10, BMP_SIZE - 10 );

		drawTicks( dc );
		drawHands( dc );

		_bmp.setPenColor( 0 ); _bmp.setBrushColor( 0 );
		Ellipse( dc, CENTER - 5, CENTER - 5, CENTER + 5, CENTER + 5 );

		_wdc = GetDC( _hwnd );
		BitBlt( _wdc, 0, 0, BMP_SIZE, BMP_SIZE, dc, 0, 0, SRCCOPY );
		ReleaseDC( _hwnd, _wdc );
	}

	myBitmap   _bmp;
	HWND       _hwnd;
	HDC        _wdc;
	SYSTEMTIME _sysTime;
	float      _ang;
};
//--------------------------------------------------------------------------------------------------
class wnd
{
public:
	wnd() { _inst = this; }
	int wnd::Run( HINSTANCE hInst )
	{
		_hInst = hInst;
		_hwnd = InitAll();
		SetTimer( _hwnd, MY_TIMER, 1000, NULL );
		_clock.setHWND( _hwnd );

		ShowWindow( _hwnd, SW_SHOW );
		UpdateWindow( _hwnd );

		MSG msg;
		ZeroMemory( &msg, sizeof( msg ) );
		while( msg.message != WM_QUIT )
		{
			if( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) != 0 )
			{
				TranslateMessage( &msg );
				DispatchMessage( &msg );
			}
		}
		return UnregisterClass( "_MY_CLOCK_", _hInst );
	}
private:
	void wnd::doPaint( HDC dc ) { _clock.setNow(); }
	void wnd::doTimer()         { _clock.setNow(); }
	static int WINAPI wnd::WndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
	{
		switch( msg )
		{
		case WM_DESTROY: PostQuitMessage( 0 ); break;
		case WM_PAINT:
			{
				PAINTSTRUCT ps;
				HDC dc = BeginPaint( hWnd, &ps );
				_inst->doPaint( dc );
				EndPaint( hWnd, &ps );
				return 0;
			}
		case WM_TIMER: _inst->doTimer(); break;
		default:
			return DefWindowProc( hWnd, msg, wParam, lParam );
		}
		return 0;
	}

	HWND InitAll()
	{
		WNDCLASSEX wcex;
		ZeroMemory( &wcex, sizeof( wcex ) );
		wcex.cbSize           = sizeof( WNDCLASSEX );
		wcex.style           = CS_HREDRAW | CS_VREDRAW;
		wcex.lpfnWndProc   = ( WNDPROC )WndProc;
		wcex.hInstance     = _hInst;
		wcex.hCursor       = LoadCursor( NULL, IDC_ARROW );
		wcex.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );
		wcex.lpszClassName = "_MY_CLOCK_";

		RegisterClassEx( &wcex );

		RECT rc = { 0, 0, BMP_SIZE, BMP_SIZE };
		AdjustWindowRect( &rc, WS_SYSMENU | WS_CAPTION, FALSE );
		int w = rc.right - rc.left, h = rc.bottom - rc.top;
		return CreateWindow( "_MY_CLOCK_", ".: Clock -- PJorente :.", WS_SYSMENU, CW_USEDEFAULT, 0, w, h, NULL, NULL, _hInst, NULL );
	}

	static wnd* _inst;
	HINSTANCE  _hInst;
	HWND       _hwnd;
	clock      _clock;
};
wnd* wnd::_inst = 0;
//--------------------------------------------------------------------------------------------------
int APIENTRY _tWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow )
{
	wnd myWnd;
	return myWnd.Run( hInstance );
}
//--------------------------------------------------------------------------------------------------

SOURCE

Content is available under GNU Free Documentation License 1.2.

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