Adding a QWindow to UIKit application on iOS

[eliseev]

Hi all,

This is essentially a continuation of this topic:
https://forum.qt.io/topic/65979/calling-qt-gui-from-native-ios-gui-vice-versa

I have a requirement to embed Qt content to an iOS application written in Swift.
For testing purposes I am using Objective-C at first.

For the example below I am using RasterWindow class from here: https://github.com/msorvig/qt-and-swift/tree/master/QtApplication

I have created a single-view iOS application using XCode. Then converted it Obj-C++ by changing extensions form ".m" to ".mm". Added Qt library and header paths to the project. Added RasterWindow class. And now I am trying to instantiate and display it like this:

#include <QApplication>
#include "rasterwindow.h"

@interface ViewController ()

@end

@implementation ViewController

RasterWindow* _rwnd;

- (void)viewDidLoad {
    [super viewDidLoad];

    static int argc = 0;
    static char* argv = nullptr;
    QGuiApplication* qtAppInstance = new QGuiApplication(argc, &argv);
    
    _rwnd = new RasterWindow();
    _rwnd->show();
    self.view = (__bridge UIView*)reinterpret_cast<void*>(_rwnd->winId());

//    self.view.contentMode = UIViewContentModeScaleToFill;
//    UIView* qtView = (__bridge UIView*)reinterpret_cast<void*>(_rwnd->winId());
//    [self.view addSubview:qtView];

    NSLog(@"view did load %@", self.view);
    // Do any additional setup after loading the view, typically from a nib.
}

Execution produces following log:

virtual void RasterWindow::showEvent(QShowEvent *) QRect(0,0 0x0)
2018-09-21 06:43:08.165951+0200 QtInObjCiOS[47805:764033] view did load <QUIView: 0x7ffe72409b90; frame = (0 0; 0 0); layer = <CAEAGLLayer: 0x6000027ffb80>>
-[ViewController viewDidAppear:] QRasterWindow(0x6000003b6a60) QRect(0,0 834x1112)

Visible result is a black screen, the window is not being drawn. If I change from assigning Qt window to self.view to adding it as a subview, then behaviour changes so that RasterWindow instance will have (0,0) size, and I couldn't force it to take size.

Note, same code works for Mac Cocoa using NSView. As does this simple app

#include "rasterwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
   QApplication a(argc, argv);
   RasterWindow w;
   w.show();

   return a.exec();
}

What am I missing? How do I correctly add a QWindow to a UIViewController?

Thank you in advance!

p.s. Complete project: https://www.dropbox.com/s/mz6ty3922u6vcdp/QtInObjCiOS.zip?dl=0 Mind, you'd have to change library and header paths to match your project and Qt locations.

[eliseev]

Ok, the problem solved itself with update to Qt 5.11.2 (while running iOS12). Thanks for reading.