QWindow::showFullScreen is buggy on Mac OS 10.8



  • I'm using Qt 5.0 on Mac OS 10.8.

    QWindow::showFullScreen() and ::showNormal() are the procedural way to enter and exit full screen mode.
    On Mac OS 10.8 (and 10.7) each window has an "expand" button that looks like two arrows pointing away from each other in the upper right of the window that gives a user interface to full screen mode.

    The bug is that with Qt 5.0 on Mac OS 10.8 if you use the expand button and then call showNormal(), it does not exit full screen mode. I conclude that the expand button is messing up some state information inside Qt. Below is a stripped down program and a script to reproduce the bug.

    Put cursor in window and type these keys --- And you'll see this

    A
    up-arrow --- enters full screen, as it should
    B
    down-arrow --- exits full screen, as it should
    C
    expand-button --- enters full screen, as it should
    D
    down-arrow --- calls showNormal, but does not exit full screen! bug!
    E
    up-arrow --- calls showFullScreen, so should do nothing, but it exits full screen! bug!
    F

    The keys A,B,C,D,E,F above simply act as markers in the history. The printout is:

    @
    Resize from -1x-1 to 200x100
    Resize from 640x480 to 200x100
    KeyPress key=0x00000041=(A) status: isFullScreen=0 windowState=0
    KeyPress key=0x01000013=()=UP
    showFullScreen - Resize from 200x100 to 1280x800
    status: isFullScreen=1 windowState=1
    KeyPress key=0x00000042=(B) status: isFullScreen=1 windowState=1
    KeyPress key=0x01000015=()=DOWN
    showNormal - status: isFullScreen=0 windowState=0
    Resize from 1280x800 to 200x100
    KeyPress key=0x00000043=(C) status: isFullScreen=0 windowState=0
    Resize from 200x100 to 1280x800
    KeyPress key=0x00000044=(D) status: isFullScreen=1 windowState=1
    KeyPress key=0x01000015=()=DOWN
    showNormal - status: isFullScreen=0 windowState=0
    KeyPress key=0x00000045=(E) status: isFullScreen=0 windowState=0
    KeyPress key=0x01000013=()=UP
    showFullScreen - status: isFullScreen=1 windowState=1
    Resize from 1280x800 to 200x100
    KeyPress key=0x00000046=(F) status: isFullScreen=0 windowState=0
    @

    Note that the first UP and DOWN keys and the expand button cause Resize events, as they should, but the DOWN that is done after D does not cause a Resize event, and the isFullScreen() values after that DOWN and at E are incorrect. So as far as I can tell, the numbers in the Resize are accurate, but isFullScreen() can't be trusted fully on 10.8, nor windowState(), nor showNormal(), nor showFullScreen().

    Is there a workaround for this until it's fully fixed?

    thanks

    fullscreen.pro:
    @
    greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
    CONFIG += release
    HEADERS = fullscreen.h
    SOURCES = fullscreen.cpp
    @

    fullscreen.h:
    @
    #include <QMainWindow>
    class QEvent;

    class TopWindow : public QMainWindow {
    Q_OBJECT
    public:
    TopWindow(); // creates subwidgets and does show()
    private:
    bool event(QEvent *event);
    };
    @

    fullscreen.cpp:
    @
    // test Qt full screen functions:
    // can we enter and exit full screen mode well?

    #include <iostream>
    #include <QApplication>
    #include <QKeyEvent>
    #include <QLabel>

    #include "fullscreen.h"

    TopWindow::TopWindow() {
    QLabel *label = new QLabel(this);
    label->setText("xyz");
    show();
    }

    bool TopWindow::event(QEvent *event) {
    switch (event->type()) {
    case QEvent::KeyPress:
    {
    QKeyEvent *key_event = static_cast<QKeyEvent *>(event);
    int key = key_event->key();
    printf(" KeyPress key=0xx=(%c)", key, key);
    switch (key) {
    case Qt::Key_Up:
    printf("=UP\nshowFullScreen - ");
    showFullScreen();
    printf("status: isFullScreen=%d windowState=%d\n", isFullScreen(),
    windowState().testFlag(Qt::WindowFullScreen));
    return true; // we handled the event
    break;
    case Qt::Key_Down:
    printf("=DOWN\nshowNormal - ");
    showNormal();
    printf("status: isFullScreen=%d windowState=%d\n", isFullScreen(),
    windowState().testFlag(Qt::WindowFullScreen));
    return true; // we handled the event
    break;
    default:
    printf(" status: isFullScreen=%d windowState=%d\n", isFullScreen(),
    windowState().testFlag(Qt::WindowFullScreen));
    break;
    }
    break;
    }
    case QEvent::Resize:
    {
    QResizeEvent *resize_event = static_cast<QResizeEvent *>(event);
    printf("Resize from %dx%d to %dx%d\n",
    resize_event->oldSize().width(), resize_event->oldSize().height(),
    resize_event->size().width(), resize_event->size().height());
    break;
    }
    default: break;
    }
    return false; // we didn't handle the event
    }

    int main(int argc, char **argv) {
    QApplication app(argc, argv);
    TopWindow top;
    app.exec();
    }
    @



  • I can confirm this problem. I think you should post it on the bug tracker.



  • I put this in bugtracker - see https://bugreports.qt-project.org/browse/QTBUG-30139 .

    Aside: the link to bugtracker from the forum's Start New Discussion page was broken, which is why I didn't post this as a bug initially!


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