C# IDeviceContext.ReleaseHdc方法代码示例

        /// <include file='doc\TextRenderer.uex' path='docs/doc[@for="TextRenderer.DrawText1"]/*' />
        public static void DrawText(IDeviceContext dc, string text, Font font, Point pt, Color foreColor, Color backColor)
        {
            if (dc == null)
            {
                throw new ArgumentNullException("dc");
            }

            WindowsFontQuality fontQuality = WindowsFont.WindowsFontQualityFromTextRenderingHint(dc as Graphics);

            IntPtr hdc = dc.GetHdc();

            try
            {
                using( WindowsGraphics wg = WindowsGraphics.FromHdc( hdc ))
                {
                    using (WindowsFont wf = WindowsGraphicsCacheManager.GetWindowsFont(font, fontQuality)) {
                        wg.DrawText(text, wf, pt, foreColor, backColor);
                    }
                }
            }
            finally
            {
                dc.ReleaseHdc();
            }
        }

 public static void DrawText(IDeviceContext dc, string text, Font font, Rectangle bounds, Color foreColor)
 {
     if (dc == null)
     {
         throw new ArgumentNullException("dc");
     }
     WindowsFontQuality fontQuality = WindowsFont.WindowsFontQualityFromTextRenderingHint(dc as Graphics);
     IntPtr hdc = dc.GetHdc();
     try
     {
         using (WindowsGraphics graphics = WindowsGraphics.FromHdc(hdc))
         {
             using (WindowsFont font2 = WindowsGraphicsCacheManager.GetWindowsFont(font, fontQuality))
             {
                 graphics.DrawText(text, font2, bounds, foreColor);
             }
         }
     }
     finally
     {
         dc.ReleaseHdc();
     }
 }

 internal static void CopyPixels(IntPtr sourceHwnd, IDeviceContext targetDC, Point sourceLocation, Point destinationLocation, Size blockRegionSize, CopyPixelOperation copyPixelOperation)
 {
     int width = blockRegionSize.Width;
     int height = blockRegionSize.Height;
     DeviceContext context = DeviceContext.FromHwnd(sourceHwnd);
     HandleRef hDC = new HandleRef(null, targetDC.GetHdc());
     HandleRef hSrcDC = new HandleRef(null, context.Hdc);
     try
     {
         if (!System.Windows.Forms.SafeNativeMethods.BitBlt(hDC, destinationLocation.X, destinationLocation.Y, width, height, hSrcDC, sourceLocation.X, sourceLocation.Y, (int) copyPixelOperation))
         {
             throw new Win32Exception();
         }
     }
     finally
     {
         targetDC.ReleaseHdc();
         context.Dispose();
     }
 }

		internal static Size MeasureTextInternal (IDeviceContext dc, string text, Font font, Size proposedSize, TextFormatFlags flags, bool useMeasureString)
		{
			if (!useMeasureString && !XplatUI.RunningOnUnix) {
				// Tell DrawText to calculate size instead of draw
				flags |= (TextFormatFlags)1024;		// DT_CALCRECT

				IntPtr hdc = dc.GetHdc ();

				XplatUIWin32.RECT r = XplatUIWin32.RECT.FromRectangle (new Rectangle (Point.Empty, proposedSize));

				IntPtr prevobj;

				if (font != null) {
					prevobj = SelectObject (hdc, font.ToHfont ());
					Win32DrawText (hdc, text, text.Length, ref r, (int)flags);
					prevobj = SelectObject (hdc, prevobj);
					DeleteObject (prevobj);
				}
				else {
					Win32DrawText (hdc, text, text.Length, ref r, (int)flags);
				}

				dc.ReleaseHdc ();

				// Really, I am just making something up here, which as far as I can tell, MS
				// just makes something up as well.  This will require lots of tweaking to match MS.  :(
				Size retval = r.ToRectangle ().Size;

				if (retval.Width > 0 && (flags & TextFormatFlags.NoPadding) == 0) {
					retval.Width += 6;
					retval.Width += (int)retval.Height / 8;
				}

				return retval;
			}
			else {
			StringFormat sf = FlagsToStringFormat (flags);

				Size retval;
				
				if (dc is Graphics)
					retval = (dc as Graphics).MeasureString (text, font, proposedSize.Width == 0 ? Int32.MaxValue : proposedSize.Width, sf).ToSize ();
				else
					retval = TextRenderer.MeasureString (text, font, proposedSize.Width == 0 ? Int32.MaxValue : proposedSize.Width, sf).ToSize ();

				if (retval.Width > 0 && (flags & TextFormatFlags.NoPadding) == 0)
					retval.Width += 9;

				return retval;
			}
		}

		internal static void DrawTextInternal (IDeviceContext dc, string text, Font font, Rectangle bounds, Color foreColor, Color backColor, TextFormatFlags flags, bool useDrawString)
		{
			if (dc == null)
				throw new ArgumentNullException ("dc");

			if (text == null || text.Length == 0)
				return;

			// We use MS GDI API's unless told not to, or we aren't on Windows
			if (!useDrawString && !XplatUI.RunningOnUnix) {
				if ((flags & TextFormatFlags.VerticalCenter) == TextFormatFlags.VerticalCenter || (flags & TextFormatFlags.Bottom) == TextFormatFlags.Bottom)
					flags |= TextFormatFlags.SingleLine;

				// Calculate the text bounds (there is often padding added)
				Rectangle new_bounds = PadRectangle (bounds, flags);
				new_bounds.Offset ((int)(dc as Graphics).Transform.OffsetX, (int)(dc as Graphics).Transform.OffsetY);

				IntPtr hdc = IntPtr.Zero;
				bool clear_clip_region = false;
				
				// If we need to use the graphics clipping region, add it to our hdc
				if ((flags & TextFormatFlags.PreserveGraphicsClipping) == TextFormatFlags.PreserveGraphicsClipping) {
					Graphics graphics = (Graphics)dc;
					Region clip_region = graphics.Clip;
					
					if (!clip_region.IsInfinite (graphics)) {
						IntPtr hrgn = clip_region.GetHrgn (graphics);
						hdc = dc.GetHdc ();
						SelectClipRgn (hdc, hrgn);
						DeleteObject (hrgn);
						
						clear_clip_region = true;
					}
				}
				
				if (hdc == IntPtr.Zero)
					hdc = dc.GetHdc ();
					
				// Set the fore color
				if (foreColor != Color.Empty)
					SetTextColor (hdc, ColorTranslator.ToWin32 (foreColor));

				// Set the back color
				if (backColor != Color.Transparent && backColor != Color.Empty) {
					SetBkMode (hdc, 2);	//1-Transparent, 2-Opaque
					SetBkColor (hdc, ColorTranslator.ToWin32 (backColor));
				}
				else {
					SetBkMode (hdc, 1);	//1-Transparent, 2-Opaque
				}

				XplatUIWin32.RECT r = XplatUIWin32.RECT.FromRectangle (new_bounds);

				IntPtr prevobj;

				if (font != null) {
					prevobj = SelectObject (hdc, font.ToHfont ());
					Win32DrawText (hdc, text, text.Length, ref r, (int)flags);
					prevobj = SelectObject (hdc, prevobj);
					DeleteObject (prevobj);
				}
				else {
					Win32DrawText (hdc, text, text.Length, ref r, (int)flags);
				}

				if (clear_clip_region)
					SelectClipRgn (hdc, IntPtr.Zero);

				dc.ReleaseHdc ();
			}
			// Use Graphics.DrawString as a fallback method
			else {
				Graphics g;
				IntPtr hdc = IntPtr.Zero;
				
				if (dc is Graphics)
					g = (Graphics)dc;
				else {
					hdc = dc.GetHdc ();
					g = Graphics.FromHdc (hdc);
				}

				StringFormat sf = FlagsToStringFormat (flags);

				Rectangle new_bounds = PadDrawStringRectangle (bounds, flags);

				g.DrawString (text, font, ThemeEngine.Current.ResPool.GetSolidBrush (foreColor), new_bounds, sf);

				if (!(dc is Graphics)) {
					g.Dispose ();
					dc.ReleaseHdc ();
				}
			}
		}

 private Padding GetThemeMargins(IDeviceContext dc, MarginTypes marginType)
 {
     MARGINS margins;
     try
     {
         IntPtr hDC = dc.GetHdc();
         if (0 == GetThemeMargins(_renderer.Handle, hDC, _renderer.Part, _renderer.State, (int) marginType, IntPtr.Zero, out margins))
             return new Padding(margins.cxLeftWidth, margins.cyTopHeight, margins.cxRightWidth, margins.cyBottomHeight);
         return new Padding(0);
     }
     finally
     {
         dc.ReleaseHdc();
     }
 }

 private Padding GetThemeMargins(IDeviceContext dc,
                                 MarginProperty marginType)
 {
   NativeMethods.MARGINS margins;
   try {
     var hDC = dc.GetHdc();
     var rv = NativeMethods.GetThemeMargins(
       renderer.Handle,
       hDC,
       renderer.Part,
       renderer.State,
       (int)marginType,
       IntPtr.Zero,
       out margins);
     if (rv == 0) {
       return new Padding(
         margins.cxLeftWidth,
         margins.cyTopHeight,
         margins.cxRightWidth,
         margins.cyBottomHeight);
     }
     return new Padding(0);
   }
   catch (Exception) {
     return renderer.GetMargins(dc, marginType);
   }
   finally {
     dc.ReleaseHdc();
   }
 }

        /// <summary>
        /// Draws composited text onto the glass area of a form.
        /// </summary>
        /// <param name="dc">The <see cref="IDeviceContext"/> onto which the composited text should be drawn.</param>
        /// <param name="text">The text to draw.</param>
        /// <param name="font">The <see cref="Font"/> to apply to the drawn text.</param>
        /// <param name="bounds">The <see cref="Rectangle" /> that represents the bounds of the text.</param>
        /// <param name="padding">The <see cref="Padding"/> around the text; necessary to allow space for the glow effect.</param>
        /// <param name="foreColor">The <see cref="Color" /> to apply to the drawn text.</param>
        /// <param name="textFormat">A bitwise combination of the <see cref="TextFormatFlags" /> values.</param>
        /// <param name="glowSize">Specifies the size of a glow that will be drawn on the background prior to any text being drawn.</param>
        /// <remarks>
        /// <para>
        ///   Do not use this method to draw text on non-glass areas of a form.
        /// </para>
        /// </remarks>
        /// <exception cref="NotSupportedException">The current operating system does not support glass, or the Desktop Window Manager is not enabled.</exception>
        /// <exception cref="ArgumentNullException"><paramref name="dc"/>, <paramref name="text"/> or <paramref name="font"/> is <see langword="null"/>.</exception>
        public static void DrawCompositedText(IDeviceContext dc, string text, Font font, Rectangle bounds, Padding padding, Color foreColor, int glowSize, TextFormatFlags textFormat)
        {
            if( !IsDwmCompositionEnabled )
                throw new NotSupportedException(Properties.Resources.GlassNotSupportedError);

            if( dc == null )
                throw new ArgumentNullException("dc");
            if( text == null )
                throw new ArgumentNullException("text");
            if( font == null )
                throw new ArgumentNullException("font");

            IntPtr primaryHdc = dc.GetHdc();
            try
            {
                using( SafeDeviceHandle memoryHdc = NativeMethods.CreateCompatibleDC(primaryHdc) )
                using( SafeGDIHandle fontHandle = new SafeGDIHandle(font.ToHfont(), true) )
                using( SafeGDIHandle dib = NativeMethods.CreateDib(bounds, primaryHdc, memoryHdc) )
                {
                    NativeMethods.SelectObject(memoryHdc, fontHandle);

                    // Draw glowing text
                    System.Windows.Forms.VisualStyles.VisualStyleRenderer renderer = new System.Windows.Forms.VisualStyles.VisualStyleRenderer(System.Windows.Forms.VisualStyles.VisualStyleElement.Window.Caption.Active);
                    NativeMethods.DTTOPTS dttOpts = new NativeMethods.DTTOPTS();
                    dttOpts.dwSize = Marshal.SizeOf(typeof(NativeMethods.DTTOPTS));
                    dttOpts.dwFlags = NativeMethods.DrawThemeTextFlags.Composited | NativeMethods.DrawThemeTextFlags.GlowSize | NativeMethods.DrawThemeTextFlags.TextColor;
                    dttOpts.crText = ColorTranslator.ToWin32(foreColor);
                    dttOpts.iGlowSize = glowSize;
                    NativeMethods.RECT textBounds = new NativeMethods.RECT(padding.Left, padding.Top, bounds.Width - padding.Right, bounds.Height - padding.Bottom);
                    NativeMethods.DrawThemeTextEx(renderer.Handle, memoryHdc, 0, 0, text, text.Length, (int)textFormat, ref textBounds, ref dttOpts);

                    // Copy to foreground
                    const int SRCCOPY = 0x00CC0020;
                    NativeMethods.BitBlt(primaryHdc, bounds.Left, bounds.Top, bounds.Width, bounds.Height, memoryHdc, 0, 0, SRCCOPY);
                }
            }
            finally
            {
                dc.ReleaseHdc();
            }
        }

        /// <summary>
        /// Provides the size, in pixels, of the specified text.
        /// </summary>
        /// <param name="dc">The device context in which to measure the text.</param>
        /// <param name="text">The text to measure.</param>
        /// <param name="font">The <see cref="Font"/> to apply to the measured text.</param>
        /// <param name="textFormat">A bitwise combination of the <see cref="TextFormatFlags" /> values.</param>
        /// <returns>The <see cref="Size"/>, in pixels, of <paramref name="text"/> drawn with the specified <paramref name="font"/> and format.</returns>
        /// <exception cref="NotSupportedException">The current operating system does not support glass, or the Desktop Window Manager is not enabled.</exception>
        /// <exception cref="ArgumentNullException"><paramref name="dc"/>, <paramref name="text"/> or <paramref name="font"/> is <see langword="null"/>.</exception>
        public static Size MeasureCompositedText(IDeviceContext dc, string text, Font font, TextFormatFlags textFormat)
        {
            if( !IsDwmCompositionEnabled )
                throw new NotSupportedException(Properties.Resources.GlassNotSupportedError);

            if( dc == null )
                throw new ArgumentNullException("dc");
            if( text == null )
                throw new ArgumentNullException("text");
            if( font == null )
                throw new ArgumentNullException("font");

            IntPtr primaryHdc = dc.GetHdc();
            try
            {
                Rectangle bounds = new Rectangle(0, 0, int.MaxValue, int.MaxValue);

                using( SafeDeviceHandle memoryHdc = NativeMethods.CreateCompatibleDC(primaryHdc) )
                using( SafeGDIHandle fontHandle = new SafeGDIHandle(font.ToHfont(), true) )
                using( SafeGDIHandle dib = NativeMethods.CreateDib(bounds, primaryHdc, memoryHdc) )
                {
                    NativeMethods.SelectObject(memoryHdc, fontHandle);

                    System.Windows.Forms.VisualStyles.VisualStyleRenderer renderer = new System.Windows.Forms.VisualStyles.VisualStyleRenderer(System.Windows.Forms.VisualStyles.VisualStyleElement.Window.Caption.Active);
                    NativeMethods.RECT bounds2 = new NativeMethods.RECT(bounds);
                    NativeMethods.RECT rect;
                    NativeMethods.GetThemeTextExtent(renderer.Handle, memoryHdc, 0, 0, text, text.Length, (int)textFormat, ref bounds2, out rect);
                    return new Size(rect.Right - rect.Left, rect.Bottom - rect.Top);
                }
            }
            finally
            {
                dc.ReleaseHdc();
            }
        }

		private Padding GetThemeMargins(IDeviceContext dc, MarginTypes marginType) {
			Padding padding;
			try {
				NativeMethods.MARGINS margins;
				IntPtr hdc = dc.GetHdc();
				if (
					NativeMethods.GetThemeMargins(renderer.Handle, hdc, renderer.Part, renderer.State, (int) marginType, IntPtr.Zero,
					                              out margins) == 0) {
					return new Padding(margins.cxLeftWidth, margins.cyTopHeight, margins.cxRightWidth, margins.cyBottomHeight);
				}
				padding = new Padding(0);
			}
			finally {
				dc.ReleaseHdc();
			}
			return padding;
		}

 public static Size MeasureText(IDeviceContext dc, string text, Font font, Size proposedSize)
 {
     Size size;
     if (dc == null)
     {
         throw new ArgumentNullException("dc");
     }
     if (string.IsNullOrEmpty(text))
     {
         return Size.Empty;
     }
     WindowsFontQuality fontQuality = WindowsFont.WindowsFontQualityFromTextRenderingHint(dc as Graphics);
     IntPtr hdc = dc.GetHdc();
     try
     {
         using (WindowsGraphics graphics = WindowsGraphics.FromHdc(hdc))
         {
             using (WindowsFont font2 = WindowsGraphicsCacheManager.GetWindowsFont(font, fontQuality))
             {
                 size = graphics.MeasureText(text, font2, proposedSize);
             }
         }
     }
     finally
     {
         dc.ReleaseHdc();
     }
     return size;
 }

        // roughly the same code as in Graphics.cs
        internal static void CopyPixels(IntPtr sourceHwnd, IDeviceContext targetDC, Point sourceLocation, Point destinationLocation, Size blockRegionSize, CopyPixelOperation copyPixelOperation) {
            int destWidth = blockRegionSize.Width;
            int destHeight = blockRegionSize.Height;

            DeviceContext dc = DeviceContext.FromHwnd(sourceHwnd);
            HandleRef targetHDC = new HandleRef( null, targetDC.GetHdc());
            HandleRef screenHDC = new HandleRef( null, dc.Hdc );
            
            try {
                bool result = SafeNativeMethods.BitBlt(targetHDC, destinationLocation.X, destinationLocation.Y, destWidth, destHeight, 
                                                      screenHDC,
                                                      sourceLocation.X, sourceLocation.Y, (int) copyPixelOperation);
                
                //a zero result indicates a win32 exception has been thrown
                if (!result) {
                    throw new Win32Exception();
                }
            }
            finally {
                targetDC.ReleaseHdc();
                dc.Dispose();
            }
        }