Improve link detection near timeline touch location

Riot/Modules/MatrixKit/Categories/UITextView+MatrixKit.h

@@ -1,33 +0,0 @@
-/*
- Copyright 2019 New Vector Ltd
- 
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
- 
- http://www.apache.org/licenses/LICENSE-2.0
- 
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License.
- */
-
-@import UIKit;
-
-NS_ASSUME_NONNULL_BEGIN
-
-@interface UITextView(MatrixKit)
-
-/**
- Determine if there is a link near a location point in UITextView bounds.
-
- @param point The point inside the UITextView bounds
- @return YES to indicate that a link has been detected near the location point.
- */
-- (BOOL)isThereALinkNearPoint:(CGPoint)point;
-
-@end
-
-NS_ASSUME_NONNULL_END

Riot/Modules/MatrixKit/Categories/UITextView+MatrixKit.m

@@ -1,54 +0,0 @@
-/*
- Copyright 2019 New Vector Ltd
- 
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
- 
- http://www.apache.org/licenses/LICENSE-2.0
- 
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License.
- */
-
-#import "UITextView+MatrixKit.h"
-
-@implementation UITextView(MatrixKit)
-
-- (BOOL)isThereALinkNearPoint:(CGPoint)point
-{
-    if (!CGRectContainsPoint(self.bounds, point))
-    {
-        return NO;
-    }
-    
-    UITextPosition *textPosition = [self closestPositionToPoint:point];
-    
-    if (!textPosition)
-    {
-        return NO;
-    }
-    
-    UITextRange *textRange = [self.tokenizer rangeEnclosingPosition:textPosition
-                                                    withGranularity:UITextGranularityCharacter
-                                                        inDirection:UITextLayoutDirectionLeft];
-    
-    if (!textRange)
-    {
-        return NO;
-    }
-    
-    NSInteger startIndex = [self offsetFromPosition:self.beginningOfDocument toPosition:textRange.start];
-    
-    if (startIndex < 0)
-    {
-        return NO;
-    }
-    
-    return [self.attributedText attribute:NSLinkAttributeName atIndex:startIndex effectiveRange:NULL] != nil;
-}
-
-@end

Riot/Modules/MatrixKit/Categories/UITextView+MatrixKit.swift

@@ -0,0 +1,66 @@
+// 
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import UIKit
+
+extension UITextView {
+    private enum Constants {
+        /// Distance threshold at which link can still be considered as "near" from location.
+        static let linkHorizontalDistanceThreshold: CGFloat = 16.0
+    }
+    
+    /// Determine if there is a link near a location point in UITextView bounds.
+    ///
+    /// - Parameters:
+    ///   - point: The point inside the UITextView bounds
+    /// - Returns: true to indicate that a link has been detected near the location point.
+    @objc func isThereALinkNearPoint(_ point: CGPoint) -> Bool {
+        guard bounds.contains(point),
+              let textPosition = closestPosition(to: point)
+        else {
+            return false
+        }
+
+        // Depending on cursor position on a character containing both an attachment
+        // and a link (e.g. a mention pill), a positive result can be retrieved either
+        // from textStylingAtPosition or tokenizer's rangeEnclosingPosition.
+        if let attributes = textStyling(at: textPosition, in: .forward),
+           attributes[.link] != nil {
+            // Using textStyling shouldn't provide false positives.
+            return true
+        } else if let textRange = tokenizer.rangeEnclosingPosition(textPosition,
+                                                                   with: .character,
+                                                                   inDirection: .layout(.left)) {
+            let startIndex = offset(from: beginningOfDocument, to: textRange.start)
+            if attributedText.attribute(.link, at: startIndex, effectiveRange: nil) != nil {
+                // Fix false positives from tokenizer's rangeEnclosingPosition.
+                // These occur if given point is located on the same line as a
+                // trailing character containing a mention pill. Detected link is
+                // rejected if actual distance from attachment trailing to point
+                // is greater than linkHorizontalDistanceThreshold.
+                let glyphIndex = layoutManager.glyphIndexForCharacter(at: startIndex)
+                let attachmentWidth = layoutManager.attachmentSize(forGlyphAt: glyphIndex).width
+                let glyphStartX = layoutManager.location(forGlyphAt: glyphIndex).x
+                let distance = point.x - (glyphStartX + attachmentWidth)
+
+                // TODO: improve using a range perhaps (beware of negative values when no attachment)
+                return distance < Constants.linkHorizontalDistanceThreshold
+            }
+        }
+            
+        return false
+    }
+}