How to take desktop screenshot on Mac OS X?
-
Hello!
I need to take screenshot inside my app, but when I trying to do it, like in example, application crashed with EXC_BAD_ACCESS error. It's bug? What else I can use? Now I use Qt 5.1.1
Code to take screenshot:
@QPixmap screenshot = QPixmap::grabWindow(QApplication::desktop()->winId());@
Thanks! -
Hi and welcome to devnet,
Can you check what does QApplication::desktop() returns ?
-
I don't know it's correct or not, but not NULL. There is "screenshot":https://www.dropbox.com/s/qqpm45xsn0idyaa/debug.png (image are to large for attach to post) of debug window with all values.
-
The image is not accessible
What does winId() return ?
-
If you can, could you build your application directly on 10.6 and retry ?
-
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
-
Can you provide a minimal compilable example that shows the crash ?
-
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:- 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;
- 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.
-
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.
-
[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. -
Did you retry with a more recent version of Qt ?
