fix: move window buttons in-place on macOS (#30322)

shell/browser/ui/cocoa/window_buttons_proxy.mm

@@ -0,0 +1,200 @@
+// Copyright (c) 2021 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "shell/browser/ui/cocoa/window_buttons_proxy.h"
+
+#include "base/i18n/rtl.h"
+#include "base/notreached.h"
+
+@implementation ButtonsAreaHoverView : NSView
+
+- (id)initWithProxy:(WindowButtonsProxy*)proxy {
+  if ((self = [super init])) {
+    proxy_ = proxy;
+  }
+  return self;
+}
+
+// Ignore all mouse events.
+- (NSView*)hitTest:(NSPoint)aPoint {
+  return nil;
+}
+
+- (void)updateTrackingAreas {
+  [proxy_ updateTrackingAreas];
+}
+
+@end
+
+@implementation WindowButtonsProxy
+
+- (id)initWithWindow:(NSWindow*)window {
+  window_ = window;
+  show_on_hover_ = NO;
+  mouse_inside_ = NO;
+
+  // Save the sequence of the buttons for later computation.
+  if (base::i18n::IsRTL()) {
+    left_ = [window_ standardWindowButton:NSWindowZoomButton];
+    right_ = [window_ standardWindowButton:NSWindowCloseButton];
+  } else {
+    left_ = [window_ standardWindowButton:NSWindowCloseButton];
+    right_ = [window_ standardWindowButton:NSWindowZoomButton];
+  }
+  middle_ = [window_ standardWindowButton:NSWindowMiniaturizeButton];
+
+  // Safety check just in case Apple changes the view structure in a macOS
+  // upgrade.
+  if (!left_.superview || !left_.superview.superview) {
+    NOTREACHED() << "macOS has changed its window buttons view structure.";
+    titlebar_container_ = nullptr;
+    return self;
+  }
+  titlebar_container_ = left_.superview.superview;
+
+  // Remember the default margin.
+  margin_ = default_margin_ = [self getCurrentMargin];
+
+  return self;
+}
+
+- (void)dealloc {
+  if (hover_view_)
+    [hover_view_ removeFromSuperview];
+  [super dealloc];
+}
+
+- (void)setVisible:(BOOL)visible {
+  if (!titlebar_container_)
+    return;
+  [titlebar_container_ setHidden:!visible];
+}
+
+- (BOOL)isVisible {
+  if (!titlebar_container_)
+    return YES;
+  return ![titlebar_container_ isHidden];
+}
+
+- (void)setShowOnHover:(BOOL)yes {
+  if (!titlebar_container_)
+    return;
+  show_on_hover_ = yes;
+  // Put a transparent view above the window buttons so we can track mouse
+  // events when mouse enter/leave the window buttons.
+  if (show_on_hover_) {
+    hover_view_.reset([[ButtonsAreaHoverView alloc] initWithProxy:self]);
+    [hover_view_ setFrame:[self getButtonsBounds]];
+    [titlebar_container_ addSubview:hover_view_.get()];
+  } else {
+    [hover_view_ removeFromSuperview];
+    hover_view_.reset();
+  }
+  [self updateButtonsVisibility];
+}
+
+- (void)setMargin:(const absl::optional<gfx::Point>&)margin {
+  if (margin)
+    margin_ = *margin;
+  else
+    margin_ = default_margin_;
+  [self redraw];
+}
+
+- (NSRect)getButtonsContainerBounds {
+  return NSInsetRect([self getButtonsBounds], -margin_.x(), -margin_.y());
+}
+
+- (void)redraw {
+  if (!titlebar_container_)
+    return;
+
+  float button_width = NSWidth(left_.frame);
+  float button_height = NSHeight(left_.frame);
+  float padding = NSMinX(middle_.frame) - NSMaxX(left_.frame);
+  float start;
+  if (base::i18n::IsRTL())
+    start =
+        NSWidth(window_.frame) - 3 * button_width - 2 * padding - margin_.x();
+  else
+    start = margin_.x();
+
+  NSRect cbounds = titlebar_container_.frame;
+  cbounds.size.height = button_height + 2 * margin_.y();
+  cbounds.origin.y = NSHeight(window_.frame) - NSHeight(cbounds);
+  [titlebar_container_ setFrame:cbounds];
+
+  [left_ setFrameOrigin:NSMakePoint(start, margin_.y())];
+  start += button_width + padding;
+  [middle_ setFrameOrigin:NSMakePoint(start, margin_.y())];
+  start += button_width + padding;
+  [right_ setFrameOrigin:NSMakePoint(start, margin_.y())];
+
+  if (hover_view_)
+    [hover_view_ setFrame:[self getButtonsBounds]];
+}
+
+- (void)updateTrackingAreas {
+  if (tracking_area_)
+    [hover_view_ removeTrackingArea:tracking_area_.get()];
+  tracking_area_.reset([[NSTrackingArea alloc]
+      initWithRect:NSZeroRect
+           options:NSTrackingMouseEnteredAndExited | NSTrackingActiveAlways |
+                   NSTrackingInVisibleRect
+             owner:self
+          userInfo:nil]);
+  [hover_view_ addTrackingArea:tracking_area_.get()];
+}
+
+- (void)mouseEntered:(NSEvent*)event {
+  mouse_inside_ = YES;
+  [self updateButtonsVisibility];
+}
+
+- (void)mouseExited:(NSEvent*)event {
+  mouse_inside_ = NO;
+  [self updateButtonsVisibility];
+}
+
+- (void)updateButtonsVisibility {
+  NSArray* buttons = @[
+    [window_ standardWindowButton:NSWindowCloseButton],
+    [window_ standardWindowButton:NSWindowMiniaturizeButton],
+    [window_ standardWindowButton:NSWindowZoomButton],
+  ];
+  // Show buttons when mouse hovers above them.
+  BOOL hidden = show_on_hover_ && !mouse_inside_;
+  // Always show buttons under fullscreen.
+  if ([window_ styleMask] & NSWindowStyleMaskFullScreen)
+    hidden = NO;
+  for (NSView* button in buttons) {
+    [button setHidden:hidden];
+    [button setNeedsDisplay:YES];
+  }
+}
+
+// Return the bounds of all 3 buttons.
+- (NSRect)getButtonsBounds {
+  return NSMakeRect(NSMinX(left_.frame), NSMinY(left_.frame),
+                    NSMaxX(right_.frame) - NSMinX(left_.frame),
+                    NSHeight(left_.frame));
+}
+
+// Compute margin from position of current buttons.
+- (gfx::Point)getCurrentMargin {
+  gfx::Point result;
+  if (!titlebar_container_)
+    return result;
+
+  result.set_y((NSHeight(titlebar_container_.frame) - NSHeight(left_.frame)) /
+               2);
+
+  if (base::i18n::IsRTL())
+    result.set_x(NSWidth(window_.frame) - NSMaxX(right_.frame));
+  else
+    result.set_x(NSMinX(left_.frame));
+  return result;
+}
+
+@end