From 6beded7b49264c509514bf2cc3b751e9b112b86e Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 18 Aug 2025 14:45:18 +0530
Subject: [PATCH] Cleanup previous PR

---
 docs/changelog.rst  |  4 +++
 glfw/cocoa_window.m | 64 +++++++++++++++++++++++++++++++--------------
 kitty/state.c       |  1 +
 3 files changed, 50 insertions(+), 19 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 54a81bf22..aee54b795 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -122,6 +122,10 @@ Detailed list of changes
 - New support for creating and switching to :doc:`sessions` easily, allowing
   users to define and use sessions/projects efficiently
 
+- macOS: Allow the window title bar to be semi-transparent when
+  :opt:`background_opacity` is less than one and :opt:`macos_titlebar_color` is
+  set to ``background`` (:pull:`8906`)
+
 - A new :opt:`cursor_trail_color` setting to independently control the color of
   cursor trails (:pull:`8830`)
 
diff --git a/glfw/cocoa_window.m b/glfw/cocoa_window.m
index d27ec2706..bd606d739 100644
--- a/glfw/cocoa_window.m
+++ b/glfw/cocoa_window.m
@@ -3168,34 +3168,60 @@ GLFWAPI GLFWcocoarenderframefun glfwCocoaSetWindowResizeCallback(GLFWwindow *w,
     return current;
 }
 
-static void setTitlebarBackgroundColor(NSWindow *window, NSColor *backgroundColor) {
-    if (!window) return;
+@implementation NSView (FindByIdentifier)
 
-    NSView *contentView = window.contentView;
-    NSView *titlebarContainer = contentView.superview;
+- (NSArray<NSView *> *)viewsWithIdentifier:(NSUserInterfaceItemIdentifier)identifier {
+    NSMutableArray<NSView *> *result = [NSMutableArray array];
+    if ([self.identifier isEqual:identifier]) {
+        [result addObject:self];
+    }
+    for (NSView *sub in self.subviews) {
+        [result addObjectsFromArray:[sub viewsWithIdentifier:identifier]];
+    }
+    return result;
+}
+
+@end
+
+static CGFloat
+title_bar_and_tool_bar_height(NSWindow *window) {
+    NSRect frame = window.frame;
+    NSRect content = [window contentRectForFrameRect:frame];
+    return NSHeight(frame) - NSHeight(content);
+}
+
+static
+void clear_title_bar_background_views(NSWindow *window) {
+#define tag @"kitty-for-transparent-titlebar"
+    NSView *contentView = window.contentView, *titlebarContainer = contentView ? contentView.superview : nil;
+    if (titlebarContainer) {
+        for (NSView *subview in [titlebarContainer viewsWithIdentifier:tag]) [subview removeFromSuperview];
+    }
+}
+
+static void
+set_title_bar_background(NSWindow *window, NSColor *backgroundColor) {
+    NSView *contentView = window.contentView, *titlebarContainer = contentView ? contentView.superview : nil;
     if (!titlebarContainer) return;
+    for (NSView *subview in [titlebarContainer viewsWithIdentifier:tag]) [subview removeFromSuperview];
+    if (!backgroundColor) return;
 
-    NSMutableArray *toRemove = [NSMutableArray array];
-    for (NSView *subview in titlebarContainer.subviews) {
-        if ([subview isKindOfClass:NSClassFromString(@"NSVisualEffectView")]) {
-            [toRemove addObject:subview];
-        }
-    }
-    for (NSView *subview in toRemove) {
-        [subview removeFromSuperview];
-    }
-
-    NSView *bgView =
-        [[NSView alloc] initWithFrame:NSMakeRect(0, titlebarContainer.bounds.size.height - 28,
-                                                 titlebarContainer.bounds.size.width, 28)];
+    const CGFloat height = title_bar_and_tool_bar_height(window);
+    NSView *bgView = [[NSView alloc] initWithFrame:NSMakeRect(
+        0, titlebarContainer.bounds.size.height - height, titlebarContainer.bounds.size.width, height)];
     bgView.autoresizingMask = NSViewWidthSizable | NSViewMinYMargin;
     bgView.wantsLayer = YES;
     bgView.layer.backgroundColor = backgroundColor.CGColor;
+    bgView.identifier = tag;
 
     NSView *containerView = [[NSView alloc] initWithFrame:window.contentView.bounds];
     containerView.autoresizingMask = NSViewWidthSizable | NSViewHeightSizable;
+    containerView.identifier = tag;
     [containerView addSubview:bgView];
+    [bgView release];
     [window.contentView addSubview:containerView];
+    [containerView release];
+#undef tag
 }
 
 GLFWAPI void glfwCocoaSetWindowChrome(GLFWwindow *w, unsigned int color, bool use_system_color, unsigned int system_color, int background_blur, unsigned int hide_window_decorations, bool show_text_in_titlebar, int color_space, float background_opacity, bool resizable) { @autoreleasepool {
@@ -3291,8 +3317,8 @@ GLFWAPI void glfwCocoaSetWindowChrome(GLFWwindow *w, unsigned int color, bool us
     [[window->ns.object standardWindowButton: NSWindowMiniaturizeButton] setHidden:hide_titlebar_buttons];
     [[window->ns.object standardWindowButton: NSWindowZoomButton] setHidden:hide_titlebar_buttons];
     if (background_opacity < 1.0 && !window->ns.titlebar_hidden && window->decorated) {
-        setTitlebarBackgroundColor(window->ns.object, [background colorUsingColorSpace:cs]);
-    }
+        set_title_bar_background(window->ns.object, [background colorUsingColorSpace:(cs ? cs : [NSColorSpace deviceRGBColorSpace])]);
+    } else clear_title_bar_background_views(window->ns.object);
     // Apple throws a hissy fit if one attempts to clear the value of NSWindowStyleMaskFullScreen outside of a full screen transition
     // event. See https://github.com/kovidgoyal/kitty/issues/7106
     NSWindowStyleMask fsmask = current_style_mask & NSWindowStyleMaskFullScreen;
diff --git a/kitty/state.c b/kitty/state.c
index 34c86a200..690d46011 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -960,6 +960,7 @@ PYWRAP1(change_background_opacity) {
     WITH_OS_WINDOW(os_window_id)
         os_window->background_opacity = opacity;
         if (!os_window->redraw_count) os_window->redraw_count++;
+        set_os_window_chrome(os_window);  // on macOS titlebar opacity can depend on background_opacity
         Py_RETURN_TRUE;
     END_WITH_OS_WINDOW
     Py_RETURN_FALSE;