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How to take desktop screenshot on Mac OS X?

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #4

    The image is not accessible

    What does winId() return ?

    Interested in AI ? www.idiap.ch
    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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    • G Offline
      G Offline
      Ganster41
      wrote on last edited by
      #5

      winId() returns 4317431408.

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      • G Offline
        G Offline
        Ganster41
        wrote on last edited by
        #6

        Hmm, I check this code on Mac OS X 10.8, and it works OK. But on 10.6 it crashes :(

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #7

          If you can, could you build your application directly on 10.6 and retry ?

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • G Offline
            G Offline
            Ganster41
            wrote on last edited by
            #8

            I made all builds on same systems, where made tests. So, it crashes on 10.6 if compiled on 10.6 too.
            I can't find code for taking screenshot in Qt sources, but looks like it uses CGDisplayCreateImage() function. It's buggy on Mac OS 10.6, and crashes app if used. For now I changed code to this, and it works on both Mac OS versions:
            @#ifdef Q_OS_MAC
            // This line crashes app on 10.6, use second instead
            // CGImageRef windowImage = CGDisplayCreateImage(CGMainDisplayID());
            CGImageRef windowImage = CGWindowListCreateImage(CGRectNull, kCGWindowListOptionOnScreenOnly,
            0, kCGWindowImageBoundsIgnoreFraming);
            QPixmap screenshot = fromMacCGImageRef(windowImage);
            CGImageRelease(windowImage);
            #else
            QPixmap screenshot = mainScreen->grabWindow(QApplication::desktop()->winId());
            #endif@

            I got fromMacCGImageRef() from old revision of qtmacports.

            But now I got other issue - MyQMainWindow->showFullScreen() does't open window fullscreen. O_o

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            • G Offline
              G Offline
              Ganster41
              wrote on last edited by
              #9

              I needed to take it from my app. I know how to take it with system hotkeys.
              Now I see some critical bugs in Qt on Mac OS X, so now I trying to use Java.
              Anyway, thanks for the help!

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #10

                Can you provide a minimal compilable example that shows the crash ?

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • G Offline
                  G Offline
                  Ganster41
                  wrote on last edited by
                  #11

                  It's in first post. Just call this code on Mac OS 10.6, and app will crash.
                  I can take screenshot with Mac-specific code from my "post":http://qt-project.org/forums/viewreply/150944/ but I got two issues with fullscreen window now:

                  1. On 10.6 QMainWindow::showFullScreen() does nothing. Just shows window not fullscreen. Strange, but Java has same issue. Looks like it fixed now with "this":https://codereview.qt-project.org/#change,70543 path, but I didn't try it, because I can't install Qt 5.2 beta to Mac OS 10.6 previosly;
                  2. On 10.8 calling QMainWindow::showFullScreen() opens fullscreen window normally, but when I call QMainWindow::close() - blank frame still appears on screen. Don't know how to fix that.
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                  • V Offline
                    V Offline
                    vezprog
                    wrote on last edited by
                    #12

                    You can render a QWidget using QPixmap. This is how you would render the QWidget.
                    @
                    // render the widget to QPixmap
                    QPixmap screenshot(widget->size());
                    widget->render(&screenshot);

                    // save the screen shot
                    screenshot.save("fileName.jpg");
                    @

                    Edit: I had to change my post, I misunderstood your question...I thought you wanted to grab a screen shot of the whole screen.

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                    • G Offline
                      G Offline
                      Ganster41
                      wrote on last edited by
                      #13

                      [quote author="dvez43" date="1387217447"]You might be able to create a transparent widget to the size of the screen (using QDesktopWidget to get the dimensions), and get the screen shot.[/quote]
                      And it really will work on both systems? Looks so hacky.
                      For example, I can't open non-fullscreen window with all screen dimensions. Upper menu bar are unreachable for this windows.

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                      • V Offline
                        V Offline
                        vezprog
                        wrote on last edited by
                        #14

                        The edited code example above should work.

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                        • B Offline
                          B Offline
                          belab
                          wrote on last edited by
                          #15

                          Maybe the problem in your original code is in line 16:
                          @this->screenshot = &screenshot;@
                          You are assigning the pointer of a local object to a member. Going out of scope destroys the pixmap.

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                          • G Offline
                            G Offline
                            Ganster41
                            wrote on last edited by
                            #16

                            Yes, it was wrong, and I already changed this code. But problem are not here.

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #17

                              Did you retry with a more recent version of Qt ?

                              Interested in AI ? www.idiap.ch
                              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                              • G Offline
                                G Offline
                                Ganster41
                                wrote on last edited by
                                #18

                                I no longer have machine with Mac OS 10.6, so I can't test it anymore.
                                Now I trying to support 10.8+ only.

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