Merge remote-tracking branch 'origin/master' into android-text

src/Avalonia.Base/Media/GlyphRun.cs

@@ -424,13 +424,13 @@ namespace Avalonia.Media
         /// </returns>
         public CharacterHit GetPreviousCaretCharacterHit(CharacterHit characterHit)
         {
+            var previousCharacterHit = FindNearestCharacterHit(characterHit.FirstCharacterIndex - 1, out _);
+
             if (characterHit.TrailingLength != 0)
             {
-                return new CharacterHit(characterHit.FirstCharacterIndex);
+                return previousCharacterHit;
             }
 
-            var previousCharacterHit = FindNearestCharacterHit(characterHit.FirstCharacterIndex - 1, out _);
-
             return new CharacterHit(previousCharacterHit.FirstCharacterIndex);
         }
 

src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs

@@ -9,7 +9,7 @@ namespace Avalonia.Media.TextFormatting
         internal static Comparer<TextBounds> TextBoundsComparer { get; } =
             Comparer<TextBounds>.Create((x, y) => x.Rectangle.Left.CompareTo(y.Rectangle.Left));
 
-        private IReadOnlyList<IndexedTextRun>? _indexedTextRuns;
+        internal IReadOnlyList<IndexedTextRun>? _indexedTextRuns;
         private readonly TextRun[] _textRuns;
         private readonly double _paragraphWidth;
         private readonly TextParagraphProperties _paragraphProperties;
@@ -512,38 +512,45 @@ namespace Avalonia.Media.TextFormatting
         /// <inheritdoc/>
         public override CharacterHit GetNextCaretCharacterHit(CharacterHit characterHit)
         {
-            if (_textRuns.Length == 0)
+            if (_textRuns.Length == 0 || _indexedTextRuns is null)
             {
                 return new CharacterHit();
             }
 
-            if (TryFindNextCharacterHit(characterHit, out var nextCharacterHit))
-            {
-                return nextCharacterHit;
-            }
-
-            var lastTextPosition = FirstTextSourceIndex + Length;
+            var currentCharacterrHit = characterHit;
+            var characterIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
 
-            // Can't move, we're after the last character
-            var runIndex = GetRunIndexAtCharacterIndex(lastTextPosition, LogicalDirection.Forward, out var currentPosition);
+            var currentRun = GetRunAtCharacterIndex(characterIndex, LogicalDirection.Forward, out var currentPosition);
 
-            var currentRun = _textRuns[runIndex];
+            var nextCharacterHit = characterHit;
 
             switch (currentRun)
             {
                 case ShapedTextRun shapedRun:
                     {
-                        nextCharacterHit = shapedRun.GlyphRun.GetNextCaretCharacterHit(characterHit);
+                        var offset = Math.Max(0, currentPosition - shapedRun.GlyphRun.Metrics.FirstCluster - characterHit.TrailingLength);
+
+                        if (offset > 0)
+                        {
+                            currentCharacterrHit = new CharacterHit(Math.Max(0, characterHit.FirstCharacterIndex - offset), characterHit.TrailingLength);
+                        }
+
+                        nextCharacterHit = shapedRun.GlyphRun.GetNextCaretCharacterHit(currentCharacterrHit);
+
+                        if (offset > 0)
+                        {
+                            nextCharacterHit = new CharacterHit(nextCharacterHit.FirstCharacterIndex + offset, nextCharacterHit.TrailingLength);
+                        }
                         break;
                     }
-                default:
+                case TextRun:
                     {
                         nextCharacterHit = new CharacterHit(currentPosition + currentRun.Length);
                         break;
                     }
             }
 
-            if (characterHit.FirstCharacterIndex + characterHit.TrailingLength == nextCharacterHit.FirstCharacterIndex + nextCharacterHit.TrailingLength)
+            if (characterIndex == nextCharacterHit.FirstCharacterIndex + nextCharacterHit.TrailingLength)
             {
                 return characterHit;
             }
@@ -554,17 +561,75 @@ namespace Avalonia.Media.TextFormatting
         /// <inheritdoc/>
         public override CharacterHit GetPreviousCaretCharacterHit(CharacterHit characterHit)
         {
-            if (TryFindPreviousCharacterHit(characterHit, out var previousCharacterHit))
+            if (_textRuns.Length == 0 || _indexedTextRuns is null)
+            {
+                return new CharacterHit();
+            }
+
+            if (characterHit.TrailingLength > 0 && characterHit.FirstCharacterIndex <= FirstTextSourceIndex)
+            {
+                return new CharacterHit(FirstTextSourceIndex);
+            }
+
+            var characterIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+
+            if (characterIndex <= FirstTextSourceIndex)
             {
-                return previousCharacterHit;
+                return new CharacterHit(FirstTextSourceIndex);
+            }
+
+            var currentCharacterrHit = characterHit;
+
+            var currentRun = GetRunAtCharacterIndex(characterIndex, LogicalDirection.Backward, out var currentPosition);
+
+            if (currentPosition == characterHit.FirstCharacterIndex)
+            {
+                currentRun = GetRunAtCharacterIndex(characterHit.FirstCharacterIndex, LogicalDirection.Backward, out currentPosition);
+            }
+
+            var previousCharacterHit = characterHit;
+
+            switch (currentRun)
+            {
+                case ShapedTextRun shapedRun:
+                    {
+                        var offset = Math.Max(0, currentPosition - shapedRun.GlyphRun.Metrics.FirstCluster);
+
+                        if (offset > 0)
+                        {
+                            currentCharacterrHit = new CharacterHit(Math.Max(0, characterHit.FirstCharacterIndex - offset), characterHit.TrailingLength);
+                        }
+
+                        previousCharacterHit = shapedRun.GlyphRun.GetPreviousCaretCharacterHit(currentCharacterrHit);
+
+                        if (offset > 0)
+                        {
+                            previousCharacterHit = new CharacterHit(previousCharacterHit.FirstCharacterIndex + offset, previousCharacterHit.TrailingLength);
+                        }
+                        break;
+                    }
+                case TextRun:
+                    {
+                        if (characterHit.TrailingLength > 0)
+                        {
+                            previousCharacterHit = new CharacterHit(currentPosition, currentRun.Length);
+
+                        }
+                        else
+                        {
+                            previousCharacterHit = new CharacterHit(currentPosition + currentRun.Length);
+                        }
+
+                        break;
+                    }
             }
 
-            if (characterHit.FirstCharacterIndex <= FirstTextSourceIndex)
+            if (characterIndex == previousCharacterHit.FirstCharacterIndex + previousCharacterHit.TrailingLength)
             {
-                characterHit = new CharacterHit(FirstTextSourceIndex);
+                return characterHit;
             }
 
-            return characterHit; // Can't move, we're before the first character
+            return previousCharacterHit;
         }
 
         /// <inheritdoc/>
@@ -1009,161 +1074,7 @@ namespace Avalonia.Media.TextFormatting
             if (_textLineBreak is null && _textRuns.Length > 1 && _textRuns[_textRuns.Length - 1] is TextEndOfLine textEndOfLine)
             {
                 _textLineBreak = new TextLineBreak(textEndOfLine);
-            }      
-        }
-
-        /// <summary>
-        /// Tries to find the next character hit.
-        /// </summary>
-        /// <param name="characterHit">The current character hit.</param>
-        /// <param name="nextCharacterHit">The next character hit.</param>
-        /// <returns></returns>
-        private bool TryFindNextCharacterHit(CharacterHit characterHit, out CharacterHit nextCharacterHit)
-        {
-            nextCharacterHit = characterHit;
-
-            var codepointIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
-            var lastCodepointIndex = FirstTextSourceIndex + Length;
-
-            if (codepointIndex >= lastCodepointIndex)
-            {
-                return false; // Cannot go forward anymore
-            }
-
-            if (codepointIndex < FirstTextSourceIndex)
-            {
-                codepointIndex = FirstTextSourceIndex;
-            }
-
-            var runIndex = GetRunIndexAtCharacterIndex(codepointIndex, LogicalDirection.Forward, out var currentPosition);
-
-            while (runIndex < _textRuns.Length)
-            {
-                var currentRun = _textRuns[runIndex];
-
-                switch (currentRun)
-                {
-                    case ShapedTextRun shapedRun:
-                        {
-                            var foundCharacterHit = shapedRun.GlyphRun.FindNearestCharacterHit(characterHit.FirstCharacterIndex + characterHit.TrailingLength, out _);
-
-                            var isAtEnd = foundCharacterHit.FirstCharacterIndex + foundCharacterHit.TrailingLength == FirstTextSourceIndex + Length;
-
-                            if (isAtEnd && !shapedRun.GlyphRun.IsLeftToRight)
-                            {
-                                nextCharacterHit = foundCharacterHit;
-
-                                return true;
-                            }
-
-                            nextCharacterHit = isAtEnd || characterHit.TrailingLength != 0 ?
-                                foundCharacterHit :
-                                new CharacterHit(foundCharacterHit.FirstCharacterIndex + foundCharacterHit.TrailingLength);
-
-                            if (isAtEnd || nextCharacterHit.FirstCharacterIndex > characterHit.FirstCharacterIndex)
-                            {
-                                return true;
-                            }
-
-                            break;
-                        }
-                    default:
-                        {
-                            var textPosition = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
-
-                            if (textPosition == currentPosition)
-                            {
-                                nextCharacterHit = new CharacterHit(currentPosition + currentRun.Length);
-
-                                return true;
-                            }
-
-                            break;
-                        }
-                }
-
-                currentPosition += currentRun.Length;
-                runIndex++;
-            }
-
-            return false;
-        }
-
-        /// <summary>
-        /// Tries to find the previous character hit.
-        /// </summary>
-        /// <param name="characterHit">The current character hit.</param>
-        /// <param name="previousCharacterHit">The previous character hit.</param>
-        /// <returns></returns>
-        private bool TryFindPreviousCharacterHit(CharacterHit characterHit, out CharacterHit previousCharacterHit)
-        {
-            var characterIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
-
-            if (characterIndex == FirstTextSourceIndex)
-            {
-                previousCharacterHit = new CharacterHit(FirstTextSourceIndex);
-
-                return true;
-            }
-
-            previousCharacterHit = characterHit;
-
-            if (characterIndex < FirstTextSourceIndex)
-            {
-                return false; // Cannot go backward anymore.
-            }
-
-            var runIndex = GetRunIndexAtCharacterIndex(characterIndex, LogicalDirection.Backward, out var currentPosition);
-
-            while (runIndex >= 0)
-            {
-                var currentRun = _textRuns[runIndex];
-
-                switch (currentRun)
-                {
-                    case ShapedTextRun shapedRun:
-                        {
-                            var foundCharacterHit = shapedRun.GlyphRun.FindNearestCharacterHit(characterHit.FirstCharacterIndex - 1, out _);
-
-                            if (foundCharacterHit.FirstCharacterIndex + foundCharacterHit.TrailingLength < characterIndex)
-                            {
-                                previousCharacterHit = foundCharacterHit;
-
-                                return true;
-                            }
-
-                            var previousPosition = foundCharacterHit.FirstCharacterIndex + foundCharacterHit.TrailingLength;
-
-                            if (foundCharacterHit.TrailingLength > 0 && previousPosition == characterIndex)
-                            {
-                                previousCharacterHit = new CharacterHit(foundCharacterHit.FirstCharacterIndex);
-                            }
-
-                            if (previousCharacterHit != characterHit)
-                            {
-                                return true;
-                            }
-
-                            break;
-                        }
-                    default:
-                        {
-                            if (characterIndex == currentPosition + currentRun.Length)
-                            {
-                                previousCharacterHit = new CharacterHit(currentPosition);
-
-                                return true;
-                            }
-
-                            break;
-                        }
-                }
-
-                currentPosition -= currentRun.Length;
-                runIndex--;
             }
-
-            return false;
         }
 
         /// <summary>
@@ -1173,15 +1084,23 @@ namespace Avalonia.Media.TextFormatting
         /// <param name="direction">The logical direction.</param>
         /// <param name="textPosition">The text position of the found run index.</param>
         /// <returns>The text run index.</returns>
-        private int GetRunIndexAtCharacterIndex(int codepointIndex, LogicalDirection direction, out int textPosition)
+        private TextRun? GetRunAtCharacterIndex(int codepointIndex, LogicalDirection direction, out int textPosition)
         {
             var runIndex = 0;
             textPosition = FirstTextSourceIndex;
+
+            if (_indexedTextRuns is null)
+            {
+                return null;
+            }
+
+            TextRun? currentRun = null;
             TextRun? previousRun = null;
 
-            while (runIndex < _textRuns.Length)
+            while (runIndex < _indexedTextRuns.Count)
             {
-                var currentRun = _textRuns[runIndex];
+                var indexedRun = _indexedTextRuns[runIndex];
+                currentRun = indexedRun.TextRun;
 
                 switch (currentRun)
                 {
@@ -1189,64 +1108,49 @@ namespace Avalonia.Media.TextFormatting
                         {
                             var firstCluster = shapedRun.GlyphRun.Metrics.FirstCluster;
 
-                            if (firstCluster > codepointIndex)
-                            {
-                                break;
-                            }
-
-                            if (previousRun is ShapedTextRun previousShaped && !previousShaped.ShapedBuffer.IsLeftToRight)
-                            {
-                                if (shapedRun.ShapedBuffer.IsLeftToRight)
-                                {
-                                    if (firstCluster >= codepointIndex)
-                                    {
-                                        return --runIndex;
-                                    }
-                                }
-                                else
-                                {
-                                    if (codepointIndex > firstCluster + currentRun.Length)
-                                    {
-                                        return --runIndex;
-                                    }
-                                }
-                            }
+                            firstCluster += Math.Max(0, indexedRun.TextSourceCharacterIndex - firstCluster);
 
                             if (direction == LogicalDirection.Forward)
                             {
-                                if (codepointIndex >= firstCluster && codepointIndex <= firstCluster + currentRun.Length)
+                                if (codepointIndex >= firstCluster && codepointIndex < firstCluster + currentRun.Length)
                                 {
-                                    return runIndex;
+                                    return currentRun;
                                 }
                             }
                             else
                             {
-                                if (codepointIndex > firstCluster &&
-                                    codepointIndex <= firstCluster + currentRun.Length)
+                                if (previousRun is not null && previousRun is not ShapedTextRun && codepointIndex == textPosition + firstCluster)
+                                {
+                                    textPosition -= previousRun.Length;
+
+                                    return previousRun;
+                                }
+
+                                if (codepointIndex > firstCluster && codepointIndex <= firstCluster + currentRun.Length)
                                 {
-                                    return runIndex;
+                                    return currentRun;
                                 }
                             }
 
                             if (runIndex + 1 >= _textRuns.Length)
                             {
-                                return runIndex;
+                                return currentRun;
                             }
 
                             textPosition += currentRun.Length;
 
                             break;
                         }
-                    default:
+                    case TextRun:
                         {
                             if (codepointIndex == textPosition)
                             {
-                                return runIndex;
+                                return currentRun;
                             }
 
                             if (runIndex + 1 >= _textRuns.Length)
                             {
-                                return runIndex;
+                                return currentRun;
                             }
 
                             textPosition += currentRun.Length;
@@ -1257,10 +1161,11 @@ namespace Avalonia.Media.TextFormatting
                 }
 
                 runIndex++;
+
                 previousRun = currentRun;
             }
 
-            return runIndex;
+            return currentRun;
         }
 
         private TextLineMetrics CreateLineMetrics()

src/Avalonia.Base/Threading/AvaloniaSynchronizationContext.cs

@@ -99,14 +99,15 @@ namespace Avalonia.Threading
             }
         }
 
-        public static RestoreContext Ensure(DispatcherPriority priority)
+        public static RestoreContext Ensure(DispatcherPriority priority) => Ensure(Dispatcher.UIThread, priority);
+        public static RestoreContext Ensure(Dispatcher dispatcher, DispatcherPriority priority)
         {
             if (Current is AvaloniaSynchronizationContext avaloniaContext 
                 && avaloniaContext.Priority == priority)
                 return default;
             var oldContext = Current;
-            Dispatcher.UIThread.VerifyAccess();
-            SetSynchronizationContext(Dispatcher.UIThread.GetContextWithPriority(priority));
+            dispatcher.VerifyAccess();
+            SetSynchronizationContext(dispatcher.GetContextWithPriority(priority));
             return new RestoreContext(oldContext);
         }
     }

src/Avalonia.Base/Threading/Dispatcher.Invoke.cs

@@ -98,7 +98,7 @@ public partial class Dispatcher
         if (timeout.TotalMilliseconds < 0 &&
             timeout != TimeSpan.FromMilliseconds(-1))
         {
-            throw new ArgumentOutOfRangeException("timeout");
+            throw new ArgumentOutOfRangeException(nameof(timeout));
         }
 
         // Fast-Path: if on the same thread, and invoking at Send priority,
@@ -106,7 +106,7 @@ public partial class Dispatcher
         // call the callback directly.
         if (!cancellationToken.IsCancellationRequested && priority == DispatcherPriority.Send && CheckAccess())
         {
-            using (AvaloniaSynchronizationContext.Ensure(priority))
+            using (AvaloniaSynchronizationContext.Ensure(this, priority))
                 callback();
             return;
         }
@@ -220,7 +220,7 @@ public partial class Dispatcher
         if (timeout.TotalMilliseconds < 0 &&
             timeout != TimeSpan.FromMilliseconds(-1))
         {
-            throw new ArgumentOutOfRangeException("timeout");
+            throw new ArgumentOutOfRangeException(nameof(timeout));
         }
 
         // Fast-Path: if on the same thread, and invoking at Send priority,
@@ -228,7 +228,7 @@ public partial class Dispatcher
         // call the callback directly.
         if (!cancellationToken.IsCancellationRequested && priority == DispatcherPriority.Send && CheckAccess())
         {
-            using (AvaloniaSynchronizationContext.Ensure(priority))
+            using (AvaloniaSynchronizationContext.Ensure(this, priority))
                 return callback();
         }
 

src/Avalonia.Base/Threading/Dispatcher.MainLoop.cs

@@ -49,7 +49,7 @@ public partial class Dispatcher
         try
         {
             _frames.Push(frame);
-            using (AvaloniaSynchronizationContext.Ensure(DispatcherPriority.Normal))
+            using (AvaloniaSynchronizationContext.Ensure(this, DispatcherPriority.Normal))
                 frame.Run(_controlledImpl);
         }
         finally

src/Avalonia.Base/Threading/Dispatcher.Queue.cs

@@ -9,7 +9,9 @@ public partial class Dispatcher
     private readonly DispatcherPriorityQueue _queue = new();
     private bool _signaled;
     private bool _explicitBackgroundProcessingRequested;
-    private const int MaximumTimeProcessingBackgroundJobs = 50;
+    private const int MaximumInputStarvationTimeInFallbackMode = 50;
+    private const int MaximumInputStarvationTimeInExplicitProcessingExplicitMode = 50;
+    private int _maximumInputStarvationTime;
     
     void RequestBackgroundProcessing()
     {
@@ -35,8 +37,8 @@ public partial class Dispatcher
         lock (InstanceLock)
         {
             _explicitBackgroundProcessingRequested = false;
-            ExecuteJobsCore();
         }
+        ExecuteJobsCore(true);
     }
 
     /// <summary>
@@ -130,10 +132,10 @@ public partial class Dispatcher
         lock (InstanceLock)
             _signaled = false;
 
-        ExecuteJobsCore();
+        ExecuteJobsCore(false);
     }
 
-    void ExecuteJobsCore()
+    void ExecuteJobsCore(bool fromExplicitBackgroundProcessingCallback)
     {
         long? backgroundJobExecutionStartedAt = null;
         while (true)
@@ -151,7 +153,6 @@ public partial class Dispatcher
             if (job.Priority > DispatcherPriority.Input)
             {
                 ExecuteJob(job);
-                backgroundJobExecutionStartedAt = null;
             }
             // If platform supports pending input query, ask the platform if we can continue running low priority jobs
             else if (_pendingInputImpl?.CanQueryPendingInput == true)
@@ -164,6 +165,13 @@ public partial class Dispatcher
                     return;
                 }
             }
+            // We can't ask if the implementation has pending input, so we should let it to call us back
+            // Once it thinks that input is handled
+            else if (_backgroundProcessingImpl != null && !fromExplicitBackgroundProcessingCallback)
+            {
+                RequestBackgroundProcessing();
+                return;
+            }
             // We can't check if there is pending input, but still need to enforce interactivity
             // so we stop processing background jobs after some timeout and start a timer to continue later
             else
@@ -171,7 +179,7 @@ public partial class Dispatcher
                 if (backgroundJobExecutionStartedAt == null)
                     backgroundJobExecutionStartedAt = Now;
                 
-                if (Now - backgroundJobExecutionStartedAt.Value > MaximumTimeProcessingBackgroundJobs)
+                if (Now - backgroundJobExecutionStartedAt.Value > _maximumInputStarvationTime)
                 {
                     _signaled = true;
                     RequestBackgroundProcessing();

src/Avalonia.Base/Threading/Dispatcher.Timers.cs

@@ -127,7 +127,7 @@ public partial class Dispatcher
         if (needToPromoteTimers)
             PromoteTimers();
         if (needToProcessQueue)
-            ExecuteJobsCore();
+            ExecuteJobsCore(false);
         UpdateOSTimer();
     }
     

src/Avalonia.Base/Threading/Dispatcher.cs

@@ -34,6 +34,9 @@ public partial class Dispatcher : IDispatcher
         _controlledImpl = _impl as IControlledDispatcherImpl;
         _pendingInputImpl = _impl as IDispatcherImplWithPendingInput;
         _backgroundProcessingImpl = _impl as IDispatcherImplWithExplicitBackgroundProcessing;
+        _maximumInputStarvationTime = _backgroundProcessingImpl == null ?
+            MaximumInputStarvationTimeInFallbackMode :
+            MaximumInputStarvationTimeInExplicitProcessingExplicitMode;
         if (_backgroundProcessingImpl != null)
             _backgroundProcessingImpl.ReadyForBackgroundProcessing += OnReadyForExplicitBackgroundProcessing;
     }

src/Avalonia.Base/Threading/DispatcherFrame.cs

@@ -38,10 +38,14 @@ public class DispatcherFrame
     ///        for their important criteria to be met.  These frames
     ///        should have a timeout associated with them.
     /// </param>
-    public DispatcherFrame(bool exitWhenRequested)
+    public DispatcherFrame(bool exitWhenRequested) : this(Dispatcher.UIThread, exitWhenRequested)
     {
-        Dispatcher = Dispatcher.UIThread;
         Dispatcher.VerifyAccess();
+    }
+
+    internal DispatcherFrame(Dispatcher dispatcher, bool exitWhenRequested)
+    {
+        Dispatcher = dispatcher;
         _exitWhenRequested = exitWhenRequested;
         _continue = true;
     }

src/Avalonia.Base/Threading/DispatcherOperation.cs

@@ -258,7 +258,7 @@ public class DispatcherOperation
 
         try
         {
-            using (AvaloniaSynchronizationContext.Ensure(Priority))
+            using (AvaloniaSynchronizationContext.Ensure(Dispatcher, Priority))
                 InvokeCore();
         }
         finally

src/Avalonia.Base/Threading/DispatcherTimer.cs

@@ -112,11 +112,11 @@ public partial class DispatcherTimer
             bool updateOSTimer = false;
 
             if (value.TotalMilliseconds < 0)
-                throw new ArgumentOutOfRangeException("value",
+                throw new ArgumentOutOfRangeException(nameof(value),
                     "TimeSpan period must be greater than or equal to zero.");
 
             if (value.TotalMilliseconds > Int32.MaxValue)
-                throw new ArgumentOutOfRangeException("value",
+                throw new ArgumentOutOfRangeException(nameof(value),
                     "TimeSpan period must be less than or equal to Int32.MaxValue.");
 
             lock (_instanceLock)
@@ -259,14 +259,14 @@ public partial class DispatcherTimer
         DispatcherPriority.Validate(priority, "priority");
         if (priority == DispatcherPriority.Inactive)
         {
-            throw new ArgumentException("Specified priority is not valid.", "priority");
+            throw new ArgumentException("Specified priority is not valid.", nameof(priority));
         }
 
         if (interval.TotalMilliseconds < 0)
-            throw new ArgumentOutOfRangeException("interval", "TimeSpan period must be greater than or equal to zero.");
+            throw new ArgumentOutOfRangeException(nameof(interval), "TimeSpan period must be greater than or equal to zero.");
 
         if (interval.TotalMilliseconds > Int32.MaxValue)
-            throw new ArgumentOutOfRangeException("interval",
+            throw new ArgumentOutOfRangeException(nameof(interval),
                 "TimeSpan period must be less than or equal to Int32.MaxValue.");
 
 
@@ -349,4 +349,4 @@ public partial class DispatcherTimer
 
     // used by Dispatcher
     internal long DueTimeInMs { get; private set; }
-}
+}

src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs

@@ -807,7 +807,7 @@ namespace Avalonia.Collections
             {
                 if (value < 0)
                 {
-                    throw new ArgumentOutOfRangeException("PageSize cannot have a negative value.");
+                    throw new ArgumentOutOfRangeException(nameof(value), "PageSize cannot have a negative value.");
                 }
 
                 // if the Refresh is currently deferred, cache the desired PageSize
@@ -1954,7 +1954,7 @@ namespace Avalonia.Collections
             // for indices larger than the count
             if (index >= Count || index < 0)
             {
-                throw new ArgumentOutOfRangeException("index");
+                throw new ArgumentOutOfRangeException(nameof(index));
             }
 
             if (IsGrouping)

src/Avalonia.Controls/Automation/Peers/ScrollViewerAutomationPeer.cs

@@ -146,12 +146,12 @@ namespace Avalonia.Automation.Peers
 
             if (scrollHorizontally && (horizontalPercent < 0.0) || (horizontalPercent > 100.0))
             {
-                throw new ArgumentOutOfRangeException("horizontalPercent");
+                throw new ArgumentOutOfRangeException(nameof(horizontalPercent));
             }
 
             if (scrollVertically && (verticalPercent < 0.0) || (verticalPercent > 100.0))
             {
-                throw new ArgumentOutOfRangeException("verticalPercent");
+                throw new ArgumentOutOfRangeException(nameof(verticalPercent));
             }
 
             var offset = Owner.Offset;

src/Avalonia.Controls/DateTimePickers/DateTimePickerPanel.cs

@@ -165,7 +165,7 @@ namespace Avalonia.Controls.Primitives
             set
             {
                 if (value > MaximumValue || value < MinimumValue)
-                    throw new ArgumentOutOfRangeException("SelectedValue");
+                    throw new ArgumentOutOfRangeException(nameof(value));
 
                 var sel = CoerceSelected(value);
                 _selectedValue = sel;
@@ -195,7 +195,7 @@ namespace Avalonia.Controls.Primitives
             set
             {
                 if (value <= 0 || value > _range)
-                    throw new ArgumentOutOfRangeException("Increment");
+                    throw new ArgumentOutOfRangeException(nameof(value));
                 _increment = value;
                 UpdateHelperInfo();
                 var sel = CoerceSelected(SelectedValue);

src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs

@@ -1113,11 +1113,11 @@ namespace Avalonia.Controls
             }
             if (value < Minimum)
             {
-                throw new ArgumentOutOfRangeException(nameof(value), string.Format("Value must be greater than Minimum value of {0}", Minimum));
+                throw new ArgumentOutOfRangeException(nameof(value), $"Value must be greater than Minimum value of {Minimum}");
             }
             else if (value > Maximum)
             {
-                throw new ArgumentOutOfRangeException(nameof(value), string.Format("Value must be less than Maximum value of {0}", Maximum));
+                throw new ArgumentOutOfRangeException(nameof(value), $"Value must be less than Maximum value of {Maximum}");
             }
         }
 

src/Avalonia.Controls/PullToRefresh/ScrollViewerIRefreshInfoProviderAdapter.cs

@@ -98,14 +98,14 @@ namespace Avalonia.Controls.PullToRefresh
 
             if (_scrollViewer.Content == null)
             {
-                throw new ArgumentException(nameof(adaptee), "Adaptee's content property cannot be null.");
+                throw new ArgumentException("Adaptee's content property cannot be null.", nameof(adaptee));
             }
 
             var content = adaptee.Content as Visual;
 
             if (content == null)
             {
-                throw new ArgumentException(nameof(adaptee), "Adaptee's content property must be a Visual");
+                throw new ArgumentException("Adaptee's content property must be a Visual", nameof(adaptee));
             }
 
             if (content.GetVisualParent() == null)
@@ -118,7 +118,7 @@ namespace Avalonia.Controls.PullToRefresh
 
                 if (content.Parent is not InputElement)
                 {
-                    throw new ArgumentException(nameof(adaptee), "Adaptee's content's parent must be a InputElement");
+                    throw new ArgumentException("Adaptee's content's parent must be a InputElement", nameof(adaptee));
                 }
             }
 
@@ -194,12 +194,12 @@ namespace Avalonia.Controls.PullToRefresh
             var content = _scrollViewer?.Content as Visual;
             if (content == null)
             {
-                throw new ArgumentException(nameof(_scrollViewer), "Adaptee's content property must be a Visual");
+                throw new ArgumentException("Adaptee's content property must be a Visual", nameof(_scrollViewer));
             }
 
             if (content.Parent is not InputElement parent)
             {
-                throw new ArgumentException(nameof(_scrollViewer), "Adaptee's content parent must be an InputElement");
+                throw new ArgumentException("Adaptee's content parent must be an InputElement", nameof(_scrollViewer));
             }
 
             MakeInteractionSource(parent);

src/Avalonia.Controls/Utils/VirtualizingSnapPointsList.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Controls.Utils
             get
             {
                 if(index < 0 || index >= Count)
-                    throw new ArgumentOutOfRangeException("index");
+                    throw new ArgumentOutOfRangeException(nameof(index));
 
                 index += _start;
 

src/Avalonia.Remote.Protocol/MetsysBson.cs

@@ -752,7 +752,7 @@ namespace Metsys.Bson
 
                         if (memberExpression.Expression.NodeType != ExpressionType.Parameter && memberExpression.Expression.NodeType != ExpressionType.Convert)
                         {
-                            throw new ArgumentException(string.Format("Expression '{0}' must resolve to top-level member.", lambdaExpression), nameof(lambdaExpression));
+                            throw new ArgumentException($"Expression '{lambdaExpression}' must resolve to top-level member.", nameof(lambdaExpression));
                         }
                         return memberExpression.Member.Name;
                     default:
@@ -942,7 +942,7 @@ namespace Metsys.Bson
                     return new ListWrapper();
                 }
             }
-            throw new BsonException(string.Format("Collection of type {0} cannot be deserialized", type.FullName));
+            throw new BsonException($"Collection of type {type.FullName} cannot be deserialized");
         }
 
         public abstract void Add(object value);
@@ -1514,7 +1514,7 @@ namespace Metsys.Bson.Configuration
                     result = Visit((MemberExpression)expression.Left);
                 }
                 var index = Expression.Lambda(expression.Right).Compile().DynamicInvoke();
-                return result + string.Format("[{0}]", index);
+                return result + $"[{index}]";
             }
 
             private string Visit(MemberExpression expression)
@@ -1540,7 +1540,7 @@ namespace Metsys.Bson.Configuration
                 if (expression.Method.Name == "get_Item" && expression.Arguments.Count == 1)
                 {
                     var index = Expression.Lambda(expression.Arguments[0]).Compile().DynamicInvoke();
-                    name += string.Format("[{0}]", index);
+                    name += $"[{index}]";
                 }
                 return name;
             }

src/Avalonia.X11/X11Structs.cs

@@ -1109,7 +1109,7 @@ namespace Avalonia.X11 {
 
 		public override string ToString ()
 		{
-			return string.Format("MotifWmHints <flags={0}, functions={1}, decorations={2}, input_mode={3}, status={4}", (MotifFlags) flags.ToInt32 (), (MotifFunctions) functions.ToInt32 (), (MotifDecorations) decorations.ToInt32 (), (MotifInputMode) input_mode.ToInt32 (), status.ToInt32 ());
+			return $"MotifWmHints <flags={(MotifFlags)flags.ToInt32()}, functions={(MotifFunctions)functions.ToInt32()}, decorations={(MotifDecorations)decorations.ToInt32()}, input_mode={(MotifInputMode)input_mode.ToInt32()}, status={status.ToInt32()}";
 		}
 	}
 
@@ -1707,8 +1707,7 @@ namespace Avalonia.X11 {
 
 		public override string ToString ()
 		{
-			return string.Format ("XCursorImage (version: {0}, size: {1}, width: {2}, height: {3}, xhot: {4}, yhot: {5}, delay: {6}, pixels: {7}", 
-				version, size, width, height, xhot, yhot, delay, pixels);
+			return $"XCursorImage (version: {version}, size: {size}, width: {width}, height: {height}, xhot: {xhot}, yhot: {yhot}, delay: {delay}, pixels: {pixels}";
 		}
 	} ;
 

src/Windows/Avalonia.Win32/Automation/RootAutomationNode.cs

@@ -33,8 +33,7 @@ namespace Avalonia.Win32.Automation
                 return null;
 
             var p = WindowImpl.PointToClient(new PixelPoint((int)x, (int)y));
-            var peer = (WindowBaseAutomationPeer)Peer;
-            var found = InvokeSync(() => peer.GetPeerFromPoint(p));
+            var found = InvokeSync(() => Peer.GetPeerFromPoint(p));
             var result = GetOrCreate(found) as IRawElementProviderFragment;
             return result;
         }

tests/Avalonia.Base.UnitTests/Media/GlyphRunTests.cs

@@ -111,7 +111,7 @@ namespace Avalonia.Base.UnitTests.Media
             using(UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
             using (var glyphRun = CreateGlyphRun(advances, clusters, bidiLevel))
             {
-                var characterHit = glyphRun.GetPreviousCaretCharacterHit(new CharacterHit(currentIndex, currentLength));
+                var characterHit = glyphRun.GetPreviousCaretCharacterHit(new CharacterHit(currentIndex + currentLength));
 
                 Assert.Equal(previousIndex, characterHit.FirstCharacterIndex);
 

tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs

@@ -194,7 +194,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 for (var i = 0; i < clusters.Count; i++)
                 {
                     var expectedCluster = clusters[i];
-                    var actualCluster = nextCharacterHit.FirstCharacterIndex;
+                    var actualCluster = nextCharacterHit.FirstCharacterIndex + nextCharacterHit.TrailingLength;
 
                     Assert.Equal(expectedCluster, actualCluster);
 
@@ -278,16 +278,6 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                     Assert.Equal(clusters[i],
                         previousCharacterHit.FirstCharacterIndex + previousCharacterHit.TrailingLength);
                 }
-
-                firstCharacterHit = previousCharacterHit;
-
-                firstCharacterHit = textLine.GetPreviousCaretCharacterHit(firstCharacterHit);
-
-                previousCharacterHit = textLine.GetPreviousCaretCharacterHit(firstCharacterHit);
-
-                Assert.Equal(firstCharacterHit.FirstCharacterIndex, previousCharacterHit.FirstCharacterIndex);
-
-                Assert.Equal(0, previousCharacterHit.TrailingLength);
             }
         }
 
@@ -728,6 +718,110 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+        [Fact]
+        public void Should_GetNextCaretCharacterHit_From_Mixed_TextBuffer()
+        {
+            using (Start())
+            {
+                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
+                var textSource = new MixedTextBufferTextSource();
+
+                var formatter = new TextFormatterImpl();
+
+                var textLine =
+                    formatter.FormatLine(textSource, 0, double.PositiveInfinity,
+                        new GenericTextParagraphProperties(defaultProperties));
+
+                var characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(9, 1));
+
+                Assert.Equal(10, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetNextCaretCharacterHit(characterHit);
+
+                Assert.Equal(11, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(19, 1));
+
+                Assert.Equal(20, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(10));
+
+                Assert.Equal(11, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+
+                characterHit = textLine.GetNextCaretCharacterHit(characterHit);
+
+                Assert.Equal(12, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+
+                characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(20));
+
+                Assert.Equal(21, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+            }
+        }
+
+        [Fact]
+        public void Should_GetPreviousCaretCharacterHit_From_Mixed_TextBuffer()
+        {
+            using (Start())
+            {
+                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
+                var textSource = new MixedTextBufferTextSource();
+
+                var formatter = new TextFormatterImpl();
+
+                var textLine =
+                    formatter.FormatLine(textSource, 0, double.PositiveInfinity,
+                        new GenericTextParagraphProperties(defaultProperties));
+
+                var characterHit = textLine.GetPreviousCaretCharacterHit(new CharacterHit(20, 1));
+
+                Assert.Equal(19, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetPreviousCaretCharacterHit(new CharacterHit(10, 1));
+
+                Assert.Equal(9, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetPreviousCaretCharacterHit(characterHit);
+
+                Assert.Equal(8, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(1, characterHit.TrailingLength);
+
+                characterHit = textLine.GetPreviousCaretCharacterHit(new CharacterHit(21));
+
+                Assert.Equal(20, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+
+                characterHit = textLine.GetPreviousCaretCharacterHit(new CharacterHit(11));
+
+                Assert.Equal(10, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+
+                characterHit = textLine.GetPreviousCaretCharacterHit(characterHit);
+
+                Assert.Equal(9, characterHit.FirstCharacterIndex);
+
+                Assert.Equal(0, characterHit.TrailingLength);
+            }
+        }
+
         private class MixedTextBufferTextSource : ITextSource
         {
             public TextRun? GetTextRun(int textSourceIndex)