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.