address feedback

src/libraries/System.Drawing.Common/src/System/Drawing/GdiplusNative.Windows.cs

@@ -240,7 +240,7 @@ private static void PlatformInitialize()
             internal static extern int GdipGetImageBounds(HandleRef image, out RectangleF gprectf, out GraphicsUnit unit);
 
             [DllImport(LibraryName, ExactSpelling = true)]
-            internal static extern int GdipGetImageThumbnail(HandleRef image, int thumbWidth, int thumbHeight, out IntPtr thumbImage, Image.GetThumbnailImageAbort callback, IntPtr callbackdata);
+            internal static extern int GdipGetImageThumbnail(HandleRef image, int thumbWidth, int thumbHeight, out IntPtr thumbImage, Image.GetThumbnailImageAbort? callback, IntPtr callbackdata);
 
             [DllImport(LibraryName, ExactSpelling = true)]
             internal static extern int GdipGetImagePalette(HandleRef image, IntPtr palette, int size);

src/libraries/System.Drawing.Common/src/System/Drawing/Graphics.cs

@@ -1400,32 +1400,32 @@ public unsafe void FillClosedCurve(Brush brush, Point[] points, FillMode fillmod
         /// <summary>
         /// Draws a string with the specified font.
         /// </summary>
-        public void DrawString(string s, Font font, Brush brush, float x, float y)
+        public void DrawString(string? s, Font font, Brush brush, float x, float y)
         {
             DrawString(s, font, brush, new RectangleF(x, y, 0, 0), null);
         }
 
-        public void DrawString(string s, Font font, Brush brush, PointF point)
+        public void DrawString(string? s, Font font, Brush brush, PointF point)
         {
             DrawString(s, font, brush, new RectangleF(point.X, point.Y, 0, 0), null);
         }
 
-        public void DrawString(string s, Font font, Brush brush, float x, float y, StringFormat format)
+        public void DrawString(string? s, Font font, Brush brush, float x, float y, StringFormat? format)
         {
             DrawString(s, font, brush, new RectangleF(x, y, 0, 0), format);
         }
 
-        public void DrawString(string s, Font font, Brush brush, PointF point, StringFormat format)
+        public void DrawString(string? s, Font font, Brush brush, PointF point, StringFormat? format)
         {
             DrawString(s, font, brush, new RectangleF(point.X, point.Y, 0, 0), format);
         }
 
-        public void DrawString(string s, Font font, Brush brush, RectangleF layoutRectangle)
+        public void DrawString(string? s, Font font, Brush brush, RectangleF layoutRectangle)
         {
             DrawString(s, font, brush, layoutRectangle, null);
         }
 
-        public void DrawString(string s, Font font, Brush brush, RectangleF layoutRectangle, StringFormat? format)
+        public void DrawString(string? s, Font font, Brush brush, RectangleF layoutRectangle, StringFormat? format)
         {
             if (brush == null)
                 throw new ArgumentNullException(nameof(brush));
@@ -1445,10 +1445,10 @@ public void DrawString(string s, Font font, Brush brush, RectangleF layoutRectan
         }
 
         public SizeF MeasureString(
-            string text,
+            string? text,
             Font font,
             SizeF layoutArea,
-            StringFormat stringFormat,
+            StringFormat? stringFormat,
             out int charactersFitted,
             out int linesFilled)
         {
@@ -1479,7 +1479,7 @@ public SizeF MeasureString(
             return boundingBox.Size;
         }
 
-        public SizeF MeasureString(string text, Font font, PointF origin, StringFormat? stringFormat)
+        public SizeF MeasureString(string? text, Font font, PointF origin, StringFormat? stringFormat)
         {
             if (string.IsNullOrEmpty(text))
                 return SizeF.Empty;
@@ -1503,9 +1503,9 @@ public SizeF MeasureString(string text, Font font, PointF origin, StringFormat?
             return boundingBox.Size;
         }
 
-        public SizeF MeasureString(string text, Font font, SizeF layoutArea) => MeasureString(text, font, layoutArea, null);
+        public SizeF MeasureString(string? text, Font font, SizeF layoutArea) => MeasureString(text, font, layoutArea, null);
 
-        public SizeF MeasureString(string text, Font font, SizeF layoutArea, StringFormat? stringFormat)
+        public SizeF MeasureString(string? text, Font font, SizeF layoutArea, StringFormat? stringFormat)
         {
             if (string.IsNullOrEmpty(text))
                 return SizeF.Empty;
@@ -1529,22 +1529,22 @@ public SizeF MeasureString(string text, Font font, SizeF layoutArea, StringForma
             return boundingBox.Size;
         }
 
-        public SizeF MeasureString(string text, Font font)
+        public SizeF MeasureString(string? text, Font font)
         {
             return MeasureString(text, font, new SizeF(0, 0));
         }
 
-        public SizeF MeasureString(string text, Font font, int width)
+        public SizeF MeasureString(string? text, Font font, int width)
         {
             return MeasureString(text, font, new SizeF(width, 999999));
         }
 
-        public SizeF MeasureString(string text, Font font, int width, StringFormat format)
+        public SizeF MeasureString(string? text, Font font, int width, StringFormat? format)
         {
             return MeasureString(text, font, new SizeF(width, 999999), format);
         }
 
-        public Region[] MeasureCharacterRanges(string text, Font font, RectangleF layoutRect, StringFormat stringFormat)
+        public Region[] MeasureCharacterRanges(string? text, Font font, RectangleF layoutRect, StringFormat? stringFormat)
         {
             if (string.IsNullOrEmpty(text))
                 return Array.Empty<Region>();

src/libraries/System.Drawing.Common/src/System/Drawing/Image.Unix.cs

@@ -126,7 +126,7 @@ public PropertyItem GetPropertyItem(int propid)
             return item;
         }
 
-        public Image GetThumbnailImage(int thumbWidth, int thumbHeight, Image.GetThumbnailImageAbort callback, IntPtr callbackData)
+        public Image GetThumbnailImage(int thumbWidth, int thumbHeight, Image.GetThumbnailImageAbort? callback, IntPtr callbackData)
         {
             if ((thumbWidth <= 0) || (thumbHeight <= 0))
                 throw new OutOfMemoryException(SR.InvalidThumbnailSize);

src/libraries/System.Drawing.Common/src/System/Drawing/Image.Windows.cs

@@ -258,7 +258,7 @@ public void Save(Stream stream, ImageCodecInfo encoder, EncoderParameters? encod
         /// <summary>
         /// Adds an <see cref='EncoderParameters'/> to this <see cref='Image'/>.
         /// </summary>
-        public void SaveAdd(EncoderParameters encoderParams)
+        public void SaveAdd(EncoderParameters? encoderParams)
         {
             IntPtr encoder = IntPtr.Zero;
             if (encoderParams != null)
@@ -282,7 +282,7 @@ public void SaveAdd(EncoderParameters encoderParams)
         /// <summary>
         /// Adds an <see cref='EncoderParameters'/> to the specified <see cref='Image'/>.
         /// </summary>
-        public void SaveAdd(Image image, EncoderParameters encoderParams)
+        public void SaveAdd(Image image, EncoderParameters? encoderParams)
         {
             IntPtr encoder = IntPtr.Zero;
 
@@ -374,7 +374,7 @@ public ColorPalette Palette
         /// <summary>
         /// Returns the thumbnail for this <see cref='Image'/>.
         /// </summary>
-        public Image GetThumbnailImage(int thumbWidth, int thumbHeight, GetThumbnailImageAbort callback, IntPtr callbackData)
+        public Image GetThumbnailImage(int thumbWidth, int thumbHeight, GetThumbnailImageAbort? callback, IntPtr callbackData)
         {
             IntPtr thumbImage = IntPtr.Zero;
 

src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Unix.cs

@@ -105,7 +105,7 @@ public static void Animate(Image image, EventHandler onFrameChangedHandler)
             thread.Start();
         }
 
-        public static bool CanAnimate(Image image)
+        public static bool CanAnimate(Image? image)
         {
             if (image == null)
                 return false;
@@ -144,7 +144,7 @@ public static void UpdateFrames()
         }
 
 
-        public static void UpdateFrames(Image? image)
+        public static void UpdateFrames(Image image)
         {
             if (image == null)
                 return;

src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Windows.cs

@@ -93,7 +93,7 @@ private ImageAnimator()
         /// <summary>
         ///     Advances the frame in the specified image. The new frame is drawn the next time the image is rendered.
         /// </summary>
-        public static void UpdateFrames(Image? image)
+        public static void UpdateFrames(Image image)
         {
             if (!s_anyFrameDirty || image == null || s_imageInfoList == null)
             {
@@ -194,7 +194,7 @@ public static void UpdateFrames()
         ///     Adds an image to the image manager.  If the image does not support animation this method does nothing.
         ///     This method creates the image list and spawns the animation thread the first time it is called.
         /// </summary>
-        public static void Animate(Image? image, EventHandler onFrameChangedHandler)
+        public static void Animate(Image image, EventHandler onFrameChangedHandler)
         {
             if (image == null)
             {
@@ -315,7 +315,7 @@ public static bool CanAnimate(Image? image)
         /// <summary>
         ///     Removes an image from the image manager so it is no longer animated.
         /// </summary>
-        public static void StopAnimate(Image? image, EventHandler onFrameChangedHandler)
+        public static void StopAnimate(Image image, EventHandler onFrameChangedHandler)
         {
             // Make sure we have a list of images
             if (image == null || s_imageInfoList == null)

src/libraries/System.Drawing.Common/src/System/Drawing/ImageInfo.cs

@@ -26,13 +26,14 @@ private class ImageInfo
             private bool _frameDirty;
             private readonly bool _animated;
             private EventHandler? _onFrameChangedHandler;
-            private readonly int[]? _frameDelay;
+            private readonly int[] _frameDelay;
             private int _frameTimer;
 
             public ImageInfo(Image image)
             {
                 _image = image;
                 _animated = ImageAnimator.CanAnimate(image);
+                _frameDelay = null!; // guaranteed to be initialized by the final check
 
                 if (_animated)
                 {

src/libraries/System.Drawing.Common/src/System/Drawing/Imaging/ImageAttributes.cs

@@ -200,17 +200,17 @@ public void ClearColorMatrix(ColorAdjustType type)
         /// <summary>
         /// Sets a color adjust matrix for image colors and a separate gray scale adjust matrix for gray scale values.
         /// </summary>
-        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix grayMatrix)
+        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix? grayMatrix)
         {
             SetColorMatrices(newColorMatrix, grayMatrix, ColorMatrixFlag.Default, ColorAdjustType.Default);
         }
 
-        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix grayMatrix, ColorMatrixFlag flags)
+        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix? grayMatrix, ColorMatrixFlag flags)
         {
             SetColorMatrices(newColorMatrix, grayMatrix, flags, ColorAdjustType.Default);
         }
 
-        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix grayMatrix, ColorMatrixFlag mode,
+        public void SetColorMatrices(ColorMatrix newColorMatrix, ColorMatrix? grayMatrix, ColorMatrixFlag mode,
                                      ColorAdjustType type)
         {
             int status = Gdip.GdipSetImageAttributesColorMatrix(

src/libraries/System.Drawing.Common/src/System/Drawing/Imaging/Metafile.cs

@@ -174,7 +174,7 @@ public Metafile(string fileName, IntPtr referenceHdc, RectangleF frameRect, Meta
         /// <summary>
         /// Initializes a new instance of the <see cref='Metafile'/> class with the specified filename.
         /// </summary>
-        public Metafile(string fileName, IntPtr referenceHdc, RectangleF frameRect, MetafileFrameUnit frameUnit, string desc) :
+        public Metafile(string fileName, IntPtr referenceHdc, RectangleF frameRect, MetafileFrameUnit frameUnit, string? desc) :
             this(fileName, referenceHdc, frameRect, frameUnit, EmfType.EmfPlusDual, desc)
         {
         }
@@ -230,7 +230,7 @@ public Metafile(string fileName, IntPtr referenceHdc, Rectangle frameRect, Metaf
         /// <summary>
         /// Initializes a new instance of the <see cref='Metafile'/> class with the specified filename.
         /// </summary>
-        public Metafile(string fileName, IntPtr referenceHdc, Rectangle frameRect, MetafileFrameUnit frameUnit, string description) :
+        public Metafile(string fileName, IntPtr referenceHdc, Rectangle frameRect, MetafileFrameUnit frameUnit, string? description) :
             this(fileName, referenceHdc, frameRect, frameUnit, EmfType.EmfPlusDual, description)
         {
         }

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/DefaultPrintController.cs

@@ -58,7 +58,7 @@ public override void OnStartPrint(PrintDocument document, PrintEventArgs e)
         /// <summary>
         /// Implements StartPage for printing to a physical printer.
         /// </summary>
-        public override Graphics? OnStartPage(PrintDocument document, PrintPageEventArgs e)
+        public override Graphics OnStartPage(PrintDocument document, PrintPageEventArgs e)
         {
             Debug.Assert(_dc != null && _graphics == null, "PrintController methods called in the wrong order?");
             Debug.Assert(_modeHandle != null);
@@ -78,7 +78,7 @@ public override void OnStartPrint(PrintDocument document, PrintEventArgs e)
 
             _graphics = Graphics.FromHdcInternal(_dc.Hdc);
 
-            if (_graphics != null && document.OriginAtMargins)
+            if (document.OriginAtMargins)
             {
                 // Adjust the origin of the graphics object to be at the
                 // user-specified margin location

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/Margins.cs

@@ -215,7 +215,7 @@ public override bool Equals(object? obj)
         /// <summary>
         /// Tests whether two <see cref='Margins'/> objects are identical.
         /// </summary>
-        public static bool operator ==(Margins m1, Margins m2)
+        public static bool operator ==(Margins? m1, Margins? m2)
         {
             if (m1 is null)
             {
@@ -232,7 +232,7 @@ public override bool Equals(object? obj)
         /// <summary>
         /// Tests whether two <see cref='Margins'/> objects are different.
         /// </summary>
-        public static bool operator !=(Margins m1, Margins m2) => !(m1 == m2);
+        public static bool operator !=(Margins? m1, Margins? m2) => !(m1 == m2);
 
         /// <summary>
         /// Provides some interesting information for the Margins in String form.

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/PreviewPrintController.Windows.cs

@@ -69,7 +69,7 @@ public override Graphics OnStartPage(PrintDocument document, PrintPageEventArgs
             PrintPreviewGraphics printGraphics = new PrintPreviewGraphics(document, e);
             _graphics = Graphics.FromImage(metafile);
 
-            if (_graphics != null && document.OriginAtMargins)
+            if (document.OriginAtMargins)
             {
                 // Adjust the origin of the graphics object to be at the
                 // user-specified margin location
@@ -84,7 +84,7 @@ public override Graphics OnStartPage(PrintDocument document, PrintPageEventArgs
                 _graphics.TranslateTransform(document.DefaultPageSettings.Margins.Left, document.DefaultPageSettings.Margins.Top);
             }
 
-            _graphics!.PrintingHelper = printGraphics;
+            _graphics.PrintingHelper = printGraphics;
 
             if (UseAntiAlias)
             {

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/PrinterSettings.Unix.cs

@@ -221,8 +221,7 @@ public PrinterSettings.PaperSourceCollection? PaperSources
                 return paper_sources;
             }
         }
-        public
-        string? PrintFileName
+        public string? PrintFileName
         {
             get { return print_filename; }
             set { print_filename = value; }
@@ -525,9 +524,9 @@ public StringCollection(string[] array)
             bool ICollection.IsSynchronized { get { return false; } }
             object ICollection.SyncRoot { get { return this; } }
 
-            public virtual string? this[int index]
+            public virtual string this[int index]
             {
-                get { return _Strings[index] as string; }
+                get { return (_Strings[index] as string)!; }
             }
             [EditorBrowsable(EditorBrowsableState.Never)]
             public int Add(string value) { return _Strings.Add(value); }

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/PrinterSettings.Windows.cs

@@ -614,10 +614,10 @@ public Graphics CreateMeasurementGraphics()
         }
 
         //whatever the call stack calling HardMarginX and HardMarginY here is safe
-        public Graphics? CreateMeasurementGraphics(bool honorOriginAtMargins)
+        public Graphics CreateMeasurementGraphics(bool honorOriginAtMargins)
         {
             Graphics g = CreateMeasurementGraphics();
-            if (g != null && honorOriginAtMargins)
+            if (honorOriginAtMargins)
             {
                 g.TranslateTransform(-_defaultPageSettings.HardMarginX, -_defaultPageSettings.HardMarginY);
                 g.TranslateTransform(_defaultPageSettings.Margins.Left, _defaultPageSettings.Margins.Top);
@@ -635,10 +635,10 @@ public Graphics CreateMeasurementGraphics(PageSettings pageSettings)
         }
 
         //whatever the call stack calling HardMarginX and HardMarginY here is safe
-        public Graphics? CreateMeasurementGraphics(PageSettings pageSettings, bool honorOriginAtMargins)
+        public Graphics CreateMeasurementGraphics(PageSettings pageSettings, bool honorOriginAtMargins)
         {
             Graphics g = CreateMeasurementGraphics();
-            if (g != null && honorOriginAtMargins)
+            if (honorOriginAtMargins)
             {
                 g.TranslateTransform(-pageSettings.HardMarginX, -pageSettings.HardMarginY);
                 g.TranslateTransform(pageSettings.Margins.Left, pageSettings.Margins.Top);

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/PrintingServices.Unix.cs

@@ -664,9 +664,11 @@ internal static void GetPrintDialogInfo(string printer, ref string port, ref str
                 NameValueCollection options = LoadPrinterOptions(cups_dests.options, cups_dests.num_options);
 
                 if (options["printer-state"] != null)
+                    // TODO-NULLABLE dotnet/roslyn#34644
                     state = int.Parse(options["printer-state"]!);
 
                 if (options["printer-comment"] != null)
+                    // TODO-NULLABLE dotnet/roslyn#34644
                     comment = options["printer-state"]!;
 
                 switch (state)

src/libraries/System.Drawing.Common/src/System/Drawing/Region.cs

@@ -346,7 +346,7 @@ public bool Equals(Region region, Graphics g)
 
         public bool IsVisible(PointF point) => IsVisible(point, null);
 
-        public bool IsVisible(float x, float y, Graphics g) => IsVisible(new PointF(x, y), g);
+        public bool IsVisible(float x, float y, Graphics? g) => IsVisible(new PointF(x, y), g);
 
         public bool IsVisible(PointF point, Graphics? g)
         {
@@ -363,7 +363,7 @@ public bool IsVisible(PointF point, Graphics? g)
 
         public bool IsVisible(RectangleF rect) => IsVisible(rect, null);
 
-        public bool IsVisible(float x, float y, float width, float height, Graphics g) => IsVisible(new RectangleF(x, y, width, height), g);
+        public bool IsVisible(float x, float y, float width, float height, Graphics? g) => IsVisible(new RectangleF(x, y, width, height), g);
 
         public bool IsVisible(RectangleF rect, Graphics? g)
         {
@@ -376,7 +376,7 @@ public bool IsVisible(RectangleF rect, Graphics? g)
             return isVisible != 0;
         }
 
-        public bool IsVisible(int x, int y, Graphics g) => IsVisible(new Point(x, y), g);
+        public bool IsVisible(int x, int y, Graphics? g) => IsVisible(new Point(x, y), g);
 
         public bool IsVisible(Point point) => IsVisible(point, null);
 
@@ -395,7 +395,7 @@ public bool IsVisible(Point point, Graphics? g)
 
         public bool IsVisible(Rectangle rect) => IsVisible(rect, null);
 
-        public bool IsVisible(int x, int y, int width, int height, Graphics g) => IsVisible(new Rectangle(x, y, width, height), g);
+        public bool IsVisible(int x, int y, int width, int height, Graphics? g) => IsVisible(new Rectangle(x, y, width, height), g);
 
         public bool IsVisible(Rectangle rect, Graphics? g)
         {