Add setting for whether to show document icon at title bar

Don't automatically hide the icon while in transparent title bar mode,
since it's a little confusing to the user. Instead, just use an extra
setting for that.

Also, when hiding the icon, properly hide it now by clearing it.
Previously it was just making an invisible icon which was still
draggable and didn't behave properly. Make sure after we set the setting
it's refreshed correctly.

Fix #1503

src/MacVim/MMAppController.m

@@ -217,6 +217,7 @@ + (void)registerDefaults
         [NSNumber numberWithInt:0],       MMAppearanceModeSelectionKey,
         [NSNumber numberWithBool:NO],     MMNoTitleBarWindowKey,
         [NSNumber numberWithBool:NO],     MMTitlebarAppearsTransparentKey,
+        [NSNumber numberWithBool:YES],    MMTitlebarShowsDocumentIconKey,
         [NSNumber numberWithBool:NO],     MMZoomBothKey,
         @"",                              MMLoginShellCommandKey,
         @"",                              MMLoginShellArgumentKey,

src/MacVim/MMWindowController.h

@@ -42,6 +42,7 @@
     NSRect              preFullScreenFrame;
     MMWindow            *decoratedWindow;
     NSString            *lastSetTitle;
+    NSString            *documentFilename; ///< File name of document being edited, used for the icon at the title bar.
     int                 userRows;
     int                 userCols;
     NSPoint             userTopLeft;
@@ -72,6 +73,7 @@
 - (void)zoomWithRows:(int)rows columns:(int)cols state:(int)state;
 - (void)setTitle:(NSString *)title;
 - (void)setDocumentFilename:(NSString *)filename;
+- (void)updateDocumentFilename;
 - (void)setToolbar:(NSToolbar *)toolbar;
 - (void)createScrollbarWithIdentifier:(int32_t)ident type:(int)type;
 - (BOOL)destroyScrollbarWithIdentifier:(int32_t)ident;

src/MacVim/MMWindowController.m

@@ -268,6 +268,7 @@ - (void)dealloc
     // in case processAfterWindowPresentedQueue wasn't called
     [afterWindowPresentedQueue release];  afterWindowPresentedQueue = nil;
     [lastSetTitle release]; lastSetTitle = nil;
+    [documentFilename release]; documentFilename = nil;
 
     [super dealloc];
 }
@@ -503,6 +504,8 @@ - (void)setTitle:(NSString *)title
     }
 }
 
+/// Set the currently edited document's file path, passed in from Vim. Buffers with
+/// no file paths will be passed in as empty strings.
 - (void)setDocumentFilename:(NSString *)filename
 {
     if (!filename)
@@ -513,15 +516,22 @@ - (void)setDocumentFilename:(NSString *)filename
     if (![[NSFileManager defaultManager] fileExistsAtPath:filename])
         filename = @"";
 
+    [filename retain];
+    [documentFilename release];
+    documentFilename = filename;
+
+    [self updateDocumentFilename];
+}
+
+- (void)updateDocumentFilename
+{
+    if (documentFilename == nil)
+        return;
+    const bool showDocumentIcon = [[NSUserDefaults standardUserDefaults] boolForKey:MMTitlebarShowsDocumentIconKey];
+    NSString *filename = showDocumentIcon ? documentFilename : @"";
     [decoratedWindow setRepresentedFilename:filename];
     [fullScreenWindow setRepresentedFilename:filename];
 
-    if ([[NSUserDefaults standardUserDefaults] boolForKey:MMTitlebarAppearsTransparentKey]) {
-        // Remove the draggable file icon in the title bar for a clean look
-        // when we are in transparent titlebar mode.
-        [[decoratedWindow standardWindowButton:NSWindowDocumentIconButton] setImage: nil];
-        [[fullScreenWindow standardWindowButton:NSWindowDocumentIconButton] setImage: nil];
-    }
 }
 
 - (void)setToolbar:(NSToolbar *)theToolbar
@@ -613,6 +623,7 @@ - (void)refreshApperanceMode
 
     // Title may have been lost if we hid the title-bar. Reset it.
     [self setTitle:lastSetTitle];
+    [self updateDocumentFilename];
 
     // Dark mode only works on 10.14+ because that's when dark mode was
     // introduced.

src/MacVim/Miscellaneous.h

@@ -37,6 +37,7 @@ extern NSString *MMFontPreserveLineSpacingKey;
 extern NSString *MMAppearanceModeSelectionKey;
 extern NSString *MMNoTitleBarWindowKey;
 extern NSString *MMTitlebarAppearsTransparentKey;
+extern NSString *MMTitlebarShowsDocumentIconKey;
 extern NSString *MMNoWindowShadowKey;
 extern NSString *MMDisableLaunchAnimationKey;
 extern NSString *MMLoginShellKey;

src/MacVim/Miscellaneous.m

@@ -33,6 +33,7 @@
 NSString *MMAppearanceModeSelectionKey    = @"MMAppearanceModeSelection";
 NSString *MMNoTitleBarWindowKey           = @"MMNoTitleBarWindow";
 NSString *MMTitlebarAppearsTransparentKey = @"MMTitlebarAppearsTransparent";
+NSString *MMTitlebarShowsDocumentIconKey  = @"MMTitlebarShowsDocumentIcon";
 NSString *MMNoWindowShadowKey             = @"MMNoWindowShadow";
 NSString *MMDisableLaunchAnimationKey     = @"MMDisableLaunchAnimation";
 NSString *MMLoginShellKey                 = @"MMLoginShell";