Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / WinForms / Managed / System / WinForms / GDI / WindowsGraphicsWrapper.cs / 1 / WindowsGraphicsWrapper.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.Windows.Forms { using System.Internal; using System; using System.Drawing; using System.Windows.Forms.Internal; using System.Diagnostics; ////// This class wrapps a WindowsGraphics and is provided to be able to manipulate WindowsGraphics objects /// created from a Graphics object in the same way as one created from any other IDeviceContext object, /// which could be a custom one. /// This class was designed to help TextRenderer determine how to create the underlying WindowsGraphics. /// internal sealed class WindowsGraphicsWrapper : IDisposable { IDeviceContext idc; WindowsGraphics wg; ////// Constructor that determines how to create the WindowsGraphics, there are three posible cases /// for the IDeviceContext object type: /// 1. It is a Graphics object: In this case we need to check the TextFormatFlags to determine whether /// we need to re-apply some of the Graphics properties to the WindowsGraphics, if so we call /// WindowsGraphics.FromGraphics passing the corresponding flags. If not, we treat it as a custom /// IDeviceContext (see below). /// 2. It is a WindowsGraphics object: /// In this case we just need to use the wg directly and be careful not to dispose of it since /// it is owned by the caller. /// 3. It is a custom IDeviceContext object: /// In this case we create the WindowsGraphics from the native DC by calling IDeviceContext.GetHdc, /// on dispose we need to call IDeviceContext.ReleaseHdc. /// public WindowsGraphicsWrapper( IDeviceContext idc, TextFormatFlags flags) { if( idc is Graphics ) { ApplyGraphicsProperties properties = ApplyGraphicsProperties.None; if( (flags & TextFormatFlags.PreserveGraphicsClipping) != 0) { properties |= ApplyGraphicsProperties.Clipping; } if( (flags & TextFormatFlags.PreserveGraphicsTranslateTransform) != 0) { properties |= ApplyGraphicsProperties.TranslateTransform; } // Create the WindowsGraphics from the Grahpics object only if Graphics properties need // to be reapplied to the DC wrapped by the WindowsGraphics. if( properties != ApplyGraphicsProperties.None ) { this.wg = WindowsGraphics.FromGraphics( idc as Graphics, properties); } } else { // If passed-in IDeviceContext object is a WindowsGraphics we can use it directly. this.wg = idc as WindowsGraphics; if( this.wg != null ) { // In this case we cache the idc to compare it against the wg in the Dispose method to avoid // disposing of the wg. this.idc = idc; } } if( this.wg == null ) { // The IDeviceContext object is not a WindowsGraphics, or it is a custom IDeviceContext, or // it is a Graphics object but we did not need to re-apply Graphics propertiesto the hdc. // So create the WindowsGraphics from the hdc directly. // Cache the IDC so the hdc can be released on dispose. this.idc = idc; this.wg = WindowsGraphics.FromHdc( idc.GetHdc() ); } // Set text padding on the WindowsGraphics (if any). if( (flags & TextFormatFlags.LeftAndRightPadding) != 0 ) { wg.TextPadding = TextPaddingOptions.LeftAndRightPadding; } else if ((flags & TextFormatFlags.NoPadding) != 0 ) { wg.TextPadding = TextPaddingOptions.NoPadding; } // else wg.TextPadding = TextPaddingOptions.GlyphOverhangPadding - the default value. } public WindowsGraphics WindowsGraphics { get { Debug.Assert( this.wg != null, "WindowsGraphics is null." ); return this.wg; } } ~WindowsGraphicsWrapper() { Dispose(false); } public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } public void Dispose( bool disposing ) { Debug.Assert( disposing, "We should always dispose of this guy and not let GC do it for us!" ); if( this.wg != null ) { // We need to dispose of the WindowsGraphics if it is created by this class only, if the IDeviceContext is // a WindowsGraphics object we must not dispose of it since it is owned by the caller. if( this.wg != this.idc ) { // resets the hdc and disposes of the internal Graphics (if inititialized from one) which releases the hdc. this.wg.Dispose(); if( this.idc != null ) // not initialized from a Graphics idc. { this.idc.ReleaseHdc(); } } this.idc = null; this.wg = null; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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