Unable to get transparent title bar in macOS since Qt 6.4

[SGaist]

Hi,

You might want to add the macOS version as well.

[xarli]

@SGaist Sure

Can be replicated in both Big Sur and Ventura

[xarli]

Anyone can bring some light here? please.

[SGaist]

I tested your code on Monterey with 5.15.2, 6.3.2, 6.4.3 and 6.5.0 and with neither of them it worked.

Can you provide a complete minimal example ?

[xarli]

@SGaist Sorry the delay to answer, I was out, I have a CMake project so is impossible to share here, I will provide an example done in Qt Creator during the week, thank for your time!

[xarli]

@SGaist Hi,

I just uploaded an example using QMainWindow (based on mainwindow example) and QWebEngineView as CentralWidget https://we.tl/t-6Nr9CuOpxu in the order that my actual code use that.

If I execute, the title bar is not transparent

But if I move hideWindowTitleBar(*this); after setCentralWidget

It works as expected again, Im trying to understand what Im doing in my code after setting setCentralWidget because the trick doesnt behave the same that in QtCreator even hideWindowTitleBar(*this); is the last thing I do before showing the window and modifying the content

I will post here some findings, thanks for your time @SGaist.

[SGaist]

Reducing the code to something minimal, it is working setting the central widget either before or after the call to hideWindowTitleBar.
main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    MainWindow mainWin;
    mainWin.resize(800, 600);
    mainWin.show();
    return app.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "mainwindowmac.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setWindowTitle("Qt Transparent");

    QWidget *centralWidget = new QWidget();
    centralWidget->setStyleSheet("background: yellow");
    hideWindowTitleBar(this);
    setCentralWidget(centralWidget);
}

mainwindowmac.h

#ifndef MAINWINDOWMAC_H
#define MAINWINDOWMAC_H

class QMainWindow;

void hideWindowTitleBar(QMainWindow *window);

#endif // MAINWINDOWMAC_H

mainwindowmac.mm

#include "mainwindowmac.h"
#include <Cocoa/Cocoa.h>
#include <QMainWindow>

void hideWindowTitleBar(QMainWindow *window) {
    window->setUnifiedTitleAndToolBarOnMac(true);

    NSView* nativeView = reinterpret_cast<NSView*>(window->winId());
    NSWindow* nativeWindow = [nativeView window];

    [nativeWindow setStyleMask:[nativeWindow styleMask] | NSWindowStyleMaskFullSizeContentView | NSWindowTitleHidden];
    [nativeWindow setTitlebarAppearsTransparent:YES];
    [nativeWindow center];
}

[zoy_l]

#import "mac_manager.h"
#import <Cocoa/Cocoa.h>

// Declare a custom NSView subclass
@interface DraggableTitleView : NSView
@end

@implementation DraggableTitleView

// Handle mouse click events
- (void)mouseDown:(NSEvent *)event {
  // double-click to zoom
  if ([event clickCount] == 2) {
    [self.window zoom:nil];
  } else {
    // drag Window
    [self.window performWindowDragWithEvent:event];
  }
}

@end

void MacManager::removeTitleBarFromWindow() {
 // The position of the native buttons
  CGPoint nativeButtonPoint = CGPointMake(100, 7);
  
  // The height of the custom title bar, Dragging the title bar will move the window
  int titleBarViewHeight = 52;

  QWindowList windows = QGuiApplication::allWindows();

  auto item = windows.first();
  auto winId = item->winId();

  auto *nativeView = reinterpret_cast<NSView *>(winId);
  NSWindow *nativeWindow = [nativeView window];

  // Hide standard title bar
  [nativeWindow setTitlebarAppearsTransparent:YES];
  [nativeWindow setTitleVisibility:NSWindowTitleHidden];
  [nativeWindow setStyleMask:[nativeWindow styleMask] | NSWindowStyleMaskFullSizeContentView];

  // Gets the dimensions of the window contents view
  NSRect contentViewBounds = nativeWindow.contentView.bounds;

  // Create a custom Title Bar view
  DraggableTitleView *titleBarView = [[DraggableTitleView alloc] initWithFrame:NSMakeRect(0, 0, contentViewBounds.size.width, titleBarViewHeight)];
  titleBarView.autoresizingMask = NSViewWidthSizable;
  titleBarView.wantsLayer = YES;
  titleBarView.layer.backgroundColor = [[NSColor clearColor] CGColor];

  // Add a custom title bar view to the window's contents view
  [nativeWindow.contentView addSubview:titleBarView];

  // Adjust the native button positions to fit in the new title bar
  NSButton *closeButton = [nativeWindow standardWindowButton:NSWindowCloseButton];
  NSButton *minimizeButton = [nativeWindow standardWindowButton:NSWindowMiniaturizeButton];
  NSButton *zoomButton = [nativeWindow standardWindowButton:NSWindowZoomButton];

  closeButton.translatesAutoresizingMaskIntoConstraints = NO;
  minimizeButton.translatesAutoresizingMaskIntoConstraints = NO;
  zoomButton.translatesAutoresizingMaskIntoConstraints = NO;

  NSLayoutConstraint *closeButtonLeftContain = [NSLayoutConstraint constraintWithItem:closeButton attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:closeButton.superview attribute:NSLayoutAttributeLeft multiplier:1.0 constant:nativeButtonPoint.x];
  NSLayoutConstraint *closeButtonTopContain = [NSLayoutConstraint constraintWithItem:closeButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:closeButton.superview attribute:NSLayoutAttributeTop multiplier:1.0 constant:nativeButtonPoint.y];
  closeButtonLeftContain.active = YES;
  closeButtonTopContain.active = YES;
  NSLayoutConstraint *minimizeButtonLeftContain = [NSLayoutConstraint constraintWithItem:minimizeButton attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:minimizeButton.superview attribute:NSLayoutAttributeLeft multiplier:1.0 constant:20 + nativeButtonPoint.x];
  NSLayoutConstraint *minimizeButtonTopContain = [NSLayoutConstraint constraintWithItem:minimizeButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:minimizeButton.superview attribute:NSLayoutAttributeTop multiplier:1.0 constant:nativeButtonPoint.y];
  minimizeButtonLeftContain.active = YES;
  minimizeButtonTopContain.active = YES;
  NSLayoutConstraint *zoomButtonLeftContain = [NSLayoutConstraint constraintWithItem:zoomButton attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:zoomButton.superview attribute:NSLayoutAttributeLeft multiplier:1.0 constant:40 + nativeButtonPoint.x];
  NSLayoutConstraint *zoomButtonTopContain = [NSLayoutConstraint constraintWithItem:zoomButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:zoomButton.superview attribute:NSLayoutAttributeTop multiplier:1.0 constant:nativeButtonPoint.y];
  zoomButtonLeftContain.active = YES;
  zoomButtonTopContain.active = YES;
}

Help more people by implementing a fully customizable title bar here, supporting movable buttons, and retaining double-click to maximize and long-press drag events.

Have fun !

[JaxLi]

@SGaist Hello, I copied you code and run with Qt6.8.2 on OSX 14.6.1 , it seems to have no effect. Has anything changed?

[JaxLi]

After testing it with Qt6.5.3 I found that it does not work with Qt6.8.2.
https://bugreports.qt.io/browse/QTBUG-134797