Fix: text color of the last event description was incorrect.

Riot/Managers/Theme/ThemeIdentifier.swift

@@ -16,7 +16,7 @@
 
 import Foundation
 
-enum ThemeIdentifier: String, RawRepresentable {
+enum ThemeIdentifier: String, RawRepresentable, CaseIterable {
     case light = "default"
     case dark = "dark"
     case black = "black"

Riot/Managers/Theme/ThemeService.swift

@@ -23,5 +23,5 @@ extension ThemeService {
             return nil
         }        
         return ThemeIdentifier(rawValue: themeId)
-    }    
+    }
 }

Riot/Modules/Common/Recents/Views/RecentTableViewCell.m

@@ -81,7 +81,29 @@ - (void)render:(MXKCellData *)cellData
         // Manage lastEventAttributedTextMessage optional property
         if (!roomCellData.roomSummary.spaceChildInfo && [roomCellData respondsToSelector:@selector(lastEventAttributedTextMessage)])
         {
-            self.lastEventDescription.attributedText = roomCellData.lastEventAttributedTextMessage;
+            // Attempt to correct the attributed string colors to match the current theme
+            NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] initWithAttributedString:roomCellData.lastEventAttributedTextMessage];
+            [attributedText enumerateAttribute:NSForegroundColorAttributeName
+                                       inRange:NSMakeRange(0, attributedText.length)
+                                       options:0
+                                    usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop) {
+                if ([value isKindOfClass:UIColor.class])
+                {
+                    UIColor *color = (UIColor*)value;
+                    if (color)
+                    {
+                        UIColor *correctedColor = [color convertToCurrentTheme];
+                        if (![color isEqual:correctedColor])
+                        {
+                            [attributedText addAttribute:NSForegroundColorAttributeName
+                                                   value:correctedColor
+                                                   range:range];
+                        }
+                    }
+                }
+            }];
+
+            self.lastEventDescription.attributedText = attributedText;
         }
         else
         {

Riot/Utils/ThemeColorConverter.swift

@@ -0,0 +1,88 @@
+// 
+// Copyright 2023 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 Foundation
+
+/// Utility struct to convert a color to its equivalent in a given theme
+struct ThemeColorConverter {
+    private static var conversionTable: [String: UIColor] = [:]
+    private static let conversionTableQueue = DispatchQueue(label: "io.element.ThemeColorConverter.queue", qos: .userInteractive)
+
+    /// Tries to convert a color to its equivalent in the given theme
+    /// - Parameters:
+    ///   - color: the color to convert
+    ///   - targetTheme: destination theme
+    /// - Returns: the converted color or the original one if no match is found
+    static func convertColor(_ color: UIColor, to targetTheme: Theme) -> UIColor {
+        let conversionTableKey = computeColorConversionTableKey(color: color, theme: targetTheme)
+        if let cachedColor = conversionTable[conversionTableKey] {
+            return cachedColor
+        }
+
+        var resultColor = color
+
+        defer {
+            // Store the resulting color in the conversion table
+            conversionTableQueue.sync {
+                conversionTable[conversionTableKey] = resultColor
+            }
+        }
+
+        for themeIdentifier in ThemeIdentifier.allCases {
+            if themeIdentifier.rawValue == targetTheme.identifier {
+                continue
+            }
+            if let convertedColor = convertColor(color, from: ThemeService.shared().theme(withThemeId: themeIdentifier.rawValue), to: targetTheme) {
+                resultColor = convertedColor
+                break
+            }
+        }
+
+        return resultColor
+    }
+
+    /// Attempts to convert a color from one theme to another
+    /// - Parameters:
+    ///   - color: the color to convert
+    ///   - source: source Theme
+    ///   - destination: destination Theme
+    /// - Returns: corresponding color or nil if not found
+    private static func convertColor(_ color: UIColor, from source: Theme, to destination: Theme) -> UIColor? {
+        let mirror = Mirror(reflecting: source.colors)
+        // If the source theme contains the same color value for several colors, the first one will be used.
+        if let colorName = mirror.children.first(where: {($0.value as? UIColor) == color})?.label {
+            return destination.colors.value(forKey: colorName) as? UIColor
+        }
+
+        return nil
+    }
+
+    private static func computeColorConversionTableKey(color: UIColor, theme: Theme) -> String {
+        var r: CGFloat = 0
+        var g: CGFloat = 0
+        var b: CGFloat = 0
+        var a: CGFloat = 0
+        color.getRed(&r, green: &g, blue: &b, alpha: &a)
+        let hexValue = Int(r * 255) << 24 | Int(g * 255) << 16 | Int(b * 255) << 8 | Int(a * 255) << 0
+        return "\(theme.identifier)-\(String(format: "#%08x", hexValue))"
+    }
+}
+
+extension UIColor {
+    @objc func convertToCurrentTheme() -> UIColor {
+        return ThemeColorConverter.convertColor(self, to: ThemeService.shared().theme)
+    }
+}

changelog.d/pr-7545.bugfix

@@ -0,0 +1 @@
+Fix: The last event description text color now matches the active theme.