Setup NSTextAttachmentViewProvider

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

@@ -18,8 +18,8 @@ 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
+        /// Distance threshold at which linkified text attachment can still be considered as "near" location.
+        static let attachmentLinkHorizontalDistanceThreshold: CGFloat = 16.0
     }
     
     /// Determine if there is a link near a location point in UITextView bounds.
@@ -27,40 +27,63 @@ extension UITextView {
     /// - 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 {
+    @objc func isThereALinkNearLocation(_ point: CGPoint) -> Bool {
+        return urlForLinkAtLocation(point) != nil
+    }
+    
+    /// Detect link near a location point in UITextView bounds.
+    ///
+    /// - Parameter point: The point inside the UITextView bounds
+    /// - Returns: link detected at given location
+    @objc func urlForLinkAtLocation(_ point: CGPoint) -> URL? {
         guard bounds.contains(point),
               let textPosition = closestPosition(to: point)
         else {
-            return false
+            return nil
         }
-
+        
+        // The value of `NSLinkAttributeName` attribute could be an URL or a String object.
+        func attributeToLink(_ attribute: Any) -> URL? {
+            if let link = attribute as? URL {
+                return link
+            } else if let stringURL = attribute as? String {
+                return URL(string: stringURL)
+            } else {
+                return nil
+            }
+        }
+        
         // 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 {
+           let linkAttribute = attributes[.link] {
             // Using textStyling shouldn't provide false positives.
-            return true
+            return attributeToLink(linkAttribute)
         } 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 {
+            if let linkAttribute = attributedText.attribute(.link, at: startIndex, effectiveRange: 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
+                // trailing linkified text attachment. 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
+                // Width is -1 when there is no attachment.
+                if attachmentWidth > 0 {
+                    let glyphStartX = layoutManager.location(forGlyphAt: glyphIndex).x
+                    let start = glyphStartX - Constants.attachmentLinkHorizontalDistanceThreshold
+                    let end = glyphStartX + attachmentWidth + Constants.attachmentLinkHorizontalDistanceThreshold
+                    let range = (start...end)
+                    
+                    return range.contains(point.x) ? attributeToLink(linkAttribute) : nil
+                }
             }
         }
             
-        return false
+        return nil
     }
 }