diff --git a/Source/Headers/vChewing-Bridging-Header.h b/Source/Headers/vChewing-Bridging-Header.h
new file mode 100644
index 00000000..e25b8a8e
--- /dev/null
+++ b/Source/Headers/vChewing-Bridging-Header.h
@@ -0,0 +1,10 @@
+#import <InputMethodKit/InputMethodKit.h>
+
+@interface IMKCandidates(vChewing) {}
+
+- (unsigned long long)windowLevel;
+- (void)setWindowLevel:(unsigned long long)level;
+- (BOOL)handleKeyboardEvent:(NSEvent *)event;
+- (void)setFontSize:(double)fontSize;
+
+@end
diff --git a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
index 204cba63..d9a9cb70 100644
--- a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
+++ b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
@@ -252,7 +252,7 @@ class ctlInputMethod: IMKInputController {
           isARepeat: event.isARepeat,
           keyCode: event.keyCode
         )
-        ctlCandidateCurrent.perform(Selector(("handleKeyboardEvent:")), with: newEvent)
+        ctlCandidateCurrent.handleKeyboardEvent(newEvent)
       }
 
       ctlCandidateCurrent.interpretKeyEvents([event])
diff --git a/Source/Modules/ControllerModules/ctlInputMethod_HandleDisplay.swift b/Source/Modules/ControllerModules/ctlInputMethod_HandleDisplay.swift
index 248e60c5..7ab40ee9 100644
--- a/Source/Modules/ControllerModules/ctlInputMethod_HandleDisplay.swift
+++ b/Source/Modules/ControllerModules/ctlInputMethod_HandleDisplay.swift
@@ -110,7 +110,9 @@ extension ctlInputMethod {
     if let ctlCandidateCurrent = ctlInputMethod.ctlCandidateCurrent as? ctlCandidateIMK,
       mgrPrefs.adjustIMKCandidateWindowLevel
     {
-      ctlCandidateCurrent.perform(Selector(("setWindowLevel:")), with: client.windowLevel() + 1000)
+      while ctlCandidateCurrent.windowLevel() <= client.windowLevel() {
+        ctlCandidateCurrent.setWindowLevel(UInt64(max(0, client.windowLevel() + 1000)))
+      }
     }
 
     ctlInputMethod.ctlCandidateCurrent.visible = true
diff --git a/Source/Modules/UIModules/CandidateUI/ctlCandidateIMK.swift b/Source/Modules/UIModules/CandidateUI/ctlCandidateIMK.swift
index ae9a8ef6..253060d9 100644
--- a/Source/Modules/UIModules/CandidateUI/ctlCandidateIMK.swift
+++ b/Source/Modules/UIModules/CandidateUI/ctlCandidateIMK.swift
@@ -50,7 +50,17 @@ public class ctlCandidateIMK: IMKCandidates, ctlCandidateProtocol {
   public var keyLabelFont: NSFont = NSFont.monospacedDigitSystemFont(
     ofSize: 14, weight: .medium
   )
-  public var candidateFont: NSFont = NSFont.systemFont(ofSize: 18)
+
+  public var candidateFont: NSFont = NSFont.systemFont(ofSize: 18) {
+    didSet {
+      setFontSize(candidateFont.pointSize)
+      var attributes = attributes()
+      // FB11300759: Set "NSAttributedString.Key.font" doesn't work.
+      attributes?[NSAttributedString.Key.font] = candidateFont
+      setAttributes(attributes)
+    }
+  }
+
   public var tooltip: String = ""
 
   var keyCount = 0
@@ -301,7 +311,7 @@ public class ctlCandidateIMK: IMKCandidates, ctlCandidateProtocol {
               return
             }
           } else {
-            perform(Selector(("handleKeyboardEvent:")), with: newEvent)
+            handleKeyboardEvent(newEvent)
             return
           }
         }
diff --git a/vChewing.xcodeproj/project.pbxproj b/vChewing.xcodeproj/project.pbxproj
index 96a01632..5e25beef 100644
--- a/vChewing.xcodeproj/project.pbxproj
+++ b/vChewing.xcodeproj/project.pbxproj
@@ -332,6 +332,7 @@
 		5BEDB71E283B4AEA0078EB25 /* data-symbols.plist */ = {isa = PBXFileReference; lastKnownFileType = file.bplist; name = "data-symbols.plist"; path = "Data/data-symbols.plist"; sourceTree = "<group>"; };
 		5BEDB71F283B4AEA0078EB25 /* data-zhuyinwen.plist */ = {isa = PBXFileReference; lastKnownFileType = file.bplist; name = "data-zhuyinwen.plist"; path = "Data/data-zhuyinwen.plist"; sourceTree = "<group>"; };
 		5BEDB720283B4AEA0078EB25 /* data-cht.plist */ = {isa = PBXFileReference; lastKnownFileType = file.bplist; name = "data-cht.plist"; path = "Data/data-cht.plist"; sourceTree = "<group>"; };
+		5BF255CD28B2694E003ECB60 /* vChewing-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "vChewing-Bridging-Header.h"; sourceTree = "<group>"; };
 		5BF9DA2228840E6200DBD48E /* template-usersymbolphrases.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; lineEnding = 0; path = "template-usersymbolphrases.txt"; sourceTree = "<group>"; usesTabs = 0; };
 		5BF9DA2328840E6200DBD48E /* template-exclusions.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; lineEnding = 0; path = "template-exclusions.txt"; sourceTree = "<group>"; usesTabs = 0; };
 		5BF9DA2428840E6200DBD48E /* template-associatedPhrases-chs.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; lineEnding = 0; name = "template-associatedPhrases-chs.txt"; path = "../Data/components/chs/template-associatedPhrases-chs.txt"; sourceTree = "<group>"; usesTabs = 0; };
@@ -760,6 +761,14 @@
 			path = KeyboardExtension;
 			sourceTree = "<group>";
 		};
+		5BF255CC28B2690B003ECB60 /* Headers */ = {
+			isa = PBXGroup;
+			children = (
+				5BF255CD28B2694E003ECB60 /* vChewing-Bridging-Header.h */,
+			);
+			path = Headers;
+			sourceTree = "<group>";
+		};
 		6A0D4E9215FC0CFA00ABF4B3 = {
 			isa = PBXGroup;
 			children = (
@@ -793,6 +802,7 @@
 			children = (
 				5B62A35027AE7F6600A19448 /* Data */,
 				5B62A30127AE732800A19448 /* 3rdParty */,
+				5BF255CC28B2690B003ECB60 /* Headers */,
 				6A0D4F1215FC0EB100ABF4B3 /* Modules */,
 				5B62A33027AE78E500A19448 /* Resources */,
 				5B62A33A27AE7C7500A19448 /* WindowControllers */,
@@ -962,7 +972,7 @@
 						ProvisioningStyle = Automatic;
 					};
 					6A0D4EA115FC0D2D00ABF4B3 = {
-						LastSwiftMigration = 1240;
+						LastSwiftMigration = 1400;
 						ProvisioningStyle = Automatic;
 					};
 					6ACA41CA15FC1D7500935EF6 = {
@@ -1668,6 +1678,7 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CLANG_CXX_LANGUAGE_STANDARD = "c++17";
 				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_ENABLE_OBJC_WEAK = YES;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
@@ -1711,6 +1722,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = org.atelierInmu.inputmethod.vChewing;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				PROVISIONING_PROFILE_SPECIFIER = "";
+				SWIFT_OBJC_BRIDGING_HEADER = "Source/Headers/vChewing-Bridging-Header.h";
 				SWIFT_VERSION = 5.0;
 				WRAPPER_EXTENSION = app;
 			};
@@ -1723,6 +1735,7 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CLANG_CXX_LANGUAGE_STANDARD = "c++17";
 				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_ENABLE_OBJC_WEAK = YES;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
@@ -1760,6 +1773,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				PROVISIONING_PROFILE_SPECIFIER = "";
 				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_OBJC_BRIDGING_HEADER = "Source/Headers/vChewing-Bridging-Header.h";
 				SWIFT_VERSION = 5.0;
 				WRAPPER_EXTENSION = app;
 			};