MeasurementDCInfo.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Misc / GDI / MeasurementDCInfo.cs / 1 / MeasurementDCInfo.cs
                        

                        
                            #if OPTIMIZED_MEASUREMENTDC 
#if WGCM_TEST_SUITE // Enable tracking when built for the test suites.
#define TRACK_HDC
#define GDI_FONT_CACHE_TRACK
#endif 

#if WINFORMS_NAMESPACE 
namespace System.Windows.Forms.Internal { 
#elif DRAWING_NAMESPACE
namespace System.Drawing.Internal { 
#else
namespace System.Experimental.Gdi {
#endif
#if WINFORMS_PUBLIC_GRAPHICS_LIBRARY 
    public
#else 
    internal 
#endif
    static class MeasurementDCInfo { 

        /// MeasurementDCInfo
        /// This class optimizes the MeasurmentGraphics as it caches in the last used font and TextMargins used.
        /// This prevents unnecessary p/invoke calls to GetCurrentObject, etc 
        /// It has been found to give close to 2x performance when drawing lots of text in rapid succession
        /// DataGridView with lots of text, etc. 
        /// To turn it on for your DLL, use the OPTIMIZED_MEASUREMENTDC compiler switch and add this class to the sources. 

       [ThreadStatic] 
       private static CachedInfo cachedMeasurementDCInfo;

       /// IsMeasurementDC
       ///  Returns whether the IDeviceContext passed in is our static MeasurementDC. 
       ///  If it is, we know a bit more information about it.
       internal static bool IsMeasurementDC(DeviceContext dc) 
       { 
            WindowsGraphics sharedGraphics = WindowsGraphicsCacheManager.GetCurrentMeasurementGraphics();
            return sharedGraphics != null && sharedGraphics.DeviceContext != null && sharedGraphics.DeviceContext.Hdc == dc.Hdc; 
       }

       /// LastUsedFont -
       ///  Returns the font we think was last selected into the MeasurementGraphics. 
       ///
       internal static WindowsFont LastUsedFont 
       { 
          get
          { 
             return (cachedMeasurementDCInfo == null) ? null : cachedMeasurementDCInfo.LastUsedFont;
          }
          set
          { 
             if (cachedMeasurementDCInfo == null)
             { 
                cachedMeasurementDCInfo = new CachedInfo(); 
             }
             cachedMeasurementDCInfo.UpdateFont(value); 
          }
       }

 
       /// GetTextMargins - checks to see if we have cached information about the current font,
       /// returns info about it. 
       /// An MRU of Font margins was considered, but seems like overhead. 
       internal static IntNativeMethods.DRAWTEXTPARAMS GetTextMargins(WindowsGraphics wg, WindowsFont font) {
 
            // PERF: operate on a local reference rather than party directly on the thread static one.
            CachedInfo currentCachedInfo = cachedMeasurementDCInfo;

            if (currentCachedInfo != null && currentCachedInfo.LeftTextMargin >0 && currentCachedInfo.RightTextMargin >0 && font == currentCachedInfo.LastUsedFont) 
            {
                // we have to return clones as DrawTextEx will modify this struct 
                return new IntNativeMethods.DRAWTEXTPARAMS(currentCachedInfo.LeftTextMargin,currentCachedInfo.RightTextMargin); 
            }
            else if (currentCachedInfo == null) 
            {
                currentCachedInfo = new CachedInfo();
                cachedMeasurementDCInfo = currentCachedInfo;
            } 
            IntNativeMethods.DRAWTEXTPARAMS drawTextParams = wg.GetTextMargins(font);
            currentCachedInfo.LeftTextMargin = drawTextParams.iLeftMargin; 
            currentCachedInfo.RightTextMargin = drawTextParams.iRightMargin; 

            // returning a copy here to be consistent with the return value from the cache. 
            return new IntNativeMethods.DRAWTEXTPARAMS(currentCachedInfo.LeftTextMargin,currentCachedInfo.RightTextMargin);

       }
 
        internal static void ResetIfIsMeasurementDC(IntPtr hdc) {
           WindowsGraphics sharedGraphics = WindowsGraphicsCacheManager.GetCurrentMeasurementGraphics(); 
           if (sharedGraphics != null && sharedGraphics.DeviceContext != null && sharedGraphics.DeviceContext.Hdc == hdc) { 
               CachedInfo currentCachedInfo = cachedMeasurementDCInfo;
               if (currentCachedInfo != null) 
               {
                    currentCachedInfo.UpdateFont(null);
               }
           } 
       }
       /// Reset 
       ///  clear the current cached information about the measurement dc. 
       internal static void Reset() {
           CachedInfo currentCachedInfo = cachedMeasurementDCInfo; 
           if (currentCachedInfo != null)
           {
                currentCachedInfo.UpdateFont(null);
           } 
       }
       /// CachedInfo 
       ///  store all the thread statics together so we dont have to fetch individual fields out of TLS 
       private sealed class CachedInfo
       { 
            public WindowsFont LastUsedFont;
            public int LeftTextMargin;
            public int RightTextMargin;
 
            internal void UpdateFont(WindowsFont font)
            { 
                if (LastUsedFont != font) 
                {
                    LastUsedFont = font; 
                    LeftTextMargin = -1;
                    RightTextMargin = -1;
                }
            } 
       }
    } 
} 
#endif // OPTIMIZED_MEASUREMENTDC

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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