I'm working on a program in QT Creator as well as in QT Designer. This is my first experience with the QT family, and I've been working on this for about 3 weeks now. I have to design a variety of menus for a study I've been assigned to make this thing for.
I'm using the QT Designer / QT Creator built-in drag-and-drop to make the biggest pieces and then using code to change some things during runtime (some rich text labels change after user input, for example). My problem is that I'm working on a two-monitor setup. One monitor is 1920 by 1080, and the other is 3840 by 2160. When I drag the running program from the 1920/1080 screen to the other, the sizing just goes all to hell. Text in the LineEdit gets cut off and often the labels just get screwy.
I'm using the "QT Widget Application" project as a base in QT Creator and all of the UI forms are .ui files, NOT .qml files. I have a substantial portion of this already done, so I need to either keep everything in .ui while fixing this or find an easy way to convert to a better format AND fix the problem.
What's very weird is that QT Designer's preview screen of the form looks the same on both screens. I can drag the main menu preview between the 1920/1080 screen and the 3840/2160 screen and there's only very minor changes. Meanwhile the running program in QT Creator has massive disparities in appearance depending on the screen.
Here's a picture to hopefully explain it better, visually:
These are just two print-screens, cropped down to show one of the things that's changing. The top half is the running program, and the bottom half is the preview, both on the same screen at the same screen size (maximized). I've tried changing the horizontalStretch and verticalStretch for various elements in the Designer but it's still borked.
This is probably a rookie problem, but I am in fact a rookie with QT. I'm just trying to make sure that no matter what screen size we run this thing on, it looks the same no matter what.
Looks like a problem related to widget themes in Qt.
Qt Designer shows you the form preview using the fusion style, but when you run your program Qt will select the best match for your platform. This could explain the differences that you see. You can override this behavior forcing the fusion style.
Edit: Another thing that you can try is to enable the Hi-DPI screen support for rendering, if not set yet.
Just add this line to your main function like this:
QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QApplication::setStyle(QStyleFactory::create("Fusion")); // these lines before the next
QApplication a(argc, argv);
You will need to add #include <QStyleFactory> on top to make it work.
For anyone who's facing the same issue and using PyQt. Here's the solution.
os.environ["QT_AUTO_SCREEN_SCALE_FACTOR"] = "1"
app = QtWidgets.QApplication(sys.argv)
You just need to set an environment variable :)
Related
I'm trying to get Qt and EGL to work together. I'm working on a program that uses EGL to draw, and I have to use Qt to create a GUI overlay.
The current solution was to turn a QWidget into a native window, and pass it's window handle to EGL. This works, but it's difficult to work with. Qt isn't aware that the widget is being drawn in by something else. So when another widget is overlaid, even if it's transparent, the image drawn by EGL is erased. The only way to get them to work is if I jigsaw the buttons and other GUI elements in a way that they don't overlap the parts of the native window I want to show. However this means that I can't use layouts or QML or any of the tools that would make creating different GUIs easy.
So my question is, how can I draw with EGL into Qt in a more usable way.
I'm working with Qt 5.4.2 by the way. If absolutely necessary, I might be able to upgrade to 5.5, but newer versions won't work.
I was looking into QOpenGLContext, and ways to make it use the context created by EGL, but I can't seem to find any good examples on how to actually go about doing this.
I'm new to Qt and it's quite a learning curve!
I've been search/reading/hacking and learning for most of the day on this one.
I'm working on an app that will have a image in a scroll area as it's main purpose. The image viewer example is where I started. This example appears to be "laid out by hand" if you will - i.e. there are no .ui form files for it (it's trivial so why not).
So here is the rub - I want to use designer to build a much more sophisticated app. If I start fresh with a new project and use designer the resizing doesn't work unless I add layout (used vertical, all appear to fix the resize issue) to the .ui form.
Designer creates a lot more code to do the same thing - I don't care, it is after all an IDE / code generation tool.
However it's not clear to me why the layout is required when I use designer and not if I code it by hand. I searched the code for the image viewer example and there doesn't seem to be ANY layout involved at all, just 3 or 4 nested widgits (Main/Scroll/Label).
Is the default layout basically built in?
The example you linked to uses a QMainWindow. This widget has its own layout because it has built-in support for menubars, toolbars, dock widgets and a statusbar:
Main Window Framework:
Normally, the widget set as the central-widget would need to have a layout explicitly set on it in order to layout its own child widgets. However, in your linked example, the central-widget is a QScrollArea, which also happens to have a built-in layout. This is all just coincidental, though. The large majority of widgets don't have a built-in layout, so most GUIs will need to explictly add at least one layout, and several will usually be needed for more complex applications.
I would say Qt Designer is absolutely essential when it comes to experimenting with layouts (especially when you start learning Qt). Even if you don't actually use the ui file, it's still very helpful to just view the code that would be generated from it.
I'm upgrading some Qt (C++ & QML) code from Qt4.8 to Qt5.1.
The Qt4.8 code is a trivial C++ "QML viewer" app subclassing a QDeclarativeView, and a bunch of QML.
It's been easy enough to change this to use Qt5/QtQuick2's QQuickView except for one thing:
The Qt4.8 app has a method for printing to PDF:
void MyQMLViewer::printToPDF(const QString& filename) const {
QPrinter printer(QPrinter::HighResolution);
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setPageSize(QPrinter::A3);
printer.setOutputFileName(filename);
printer.setOrientation(QPrinter::Landscape);
QPainter painter(&printer);
render(&painter);
}
There were a few "environment" changes needed for Qt5.1 to get a QPrinter (ie add QT += printsupport to the project .pro file and #include <QtPrintSupport>), but there seems to be a more fundamental problem that QQuickView doesn't provide anything which is obviously compatible with the QGraphicsView/QPainter/QPaintDevice world of QPrinter (specifically, QQuickView has no render method, and all the drawing/painting/rendering-related methods it does have seem very tied up with OpenGL).
Any suggestions for how to best obtain high-quality PDF output from a QQuickView ?
(Note that I am not simply looking to screenshot the view; with QDeclarativeView, the code above generates PDFs with much better resolution even than the app fullscreened on my largest monitor).
I see the "QDeclarativeItem and QDeclarativeView" section of the "Porting QML Applications to Qt 5" guide does mention the loss of QGraphicsView-specific functionality, but doesn't offer any solutions (although it does mention workrounds for the case of items with custom QPainter-based rendering being bought into the new regime).
Update with some additional background info: an example of a PDF printed from QDeclarativeView using the above code can be found here. There's a png of the same view on a decent size monitor here. (This is actually the last slide in a series of slides; it's actually a gallery of the previous slides which bounces each slide onto the screen; if I had the time I'd look into the feasibility of the gallery being the only thing and transforming each scattered slide into view for a Prezi-style presentation; suspect QDeclarative isn't really performant enough though, which is one reason for wanting to get onto QtQuick2+Qt5.2's new scene graph stuff). Anyway, If you zoom the PDF up to 100% you'll see the text is... well it's better than anything a sanely sized image file will manage I think, although the sloping text baselines perhaps look a little uneven. There is also an issue with opacity values not being represented in the PDF (so the drop shadows and "bubbles" come out solid); another one of my motivations for trying for a QtQuick2 version was actually to see if translucent elements were dealt with any better. I assume the PDF just contains rasterized (or maybe vector outlines) of all the elements as utilities like "pdftotext" can't extract anything from it. I don't know enough about PDF tools to know how to inspect the internal structure of the thing but I assume there's some hierarchy there and the QML element tree is all laid out using a similar structure of nested transforms to the QML. Just for comparison and the sort of richness I'm potentially working towards here's a poster I did with LaTeX/Beamerposter; I find Beamerposter's rigid block structure rather limiting (and fiddly) compared with the possibilities QML seems to offer though. BTW, another thing on my wishlist/todolist is a QML element which can render LaTeX source, math and all, just to get the best of both worlds.
Update: Recent Qt blog post on all the backend changes in Qt5.8 has a comment linking to this Qt issue to use the new possibility of QPainter-rendered QtQuick scenes to render PDFs.
At the moment, there is no code in Qt that supports rendering of a scene graph to a pdf. The underlying data that is used to render Qt Quick 2 is held in the scene graph. As Laszlo suggests, you'd need to iterate the scene graph and generate PDF primitives. There's some impedance mismatch there, but it should be doable with some sweat. I think a proof of concept could be small enough to fit here, so I'll see how easy it could be :)
If you really want a PDF, you currently have no choice but to render it to a large image at 300dpi and wrap that in a PDF. The image doesn't have to be large if the poster has large areas of solid color. PDF can do do TIFF encoding and also JPEG encoding.
I am not an expert but I have been using Qt/QtEmbedded for sometime now, for SBC 6845. I have created a few applications and have successfully run them on my device.
Now I want all of those applications to appear on a home screen. I understand that using QML/Qt Quick this might be achieved, but I don't have any idea on how to proceed with it. I have gone through some links and tutorials but most of them show how to create buttons and all that with Qt Quick, but not much than that. I am yet to find some tutorial/docs which can point me how to proceed with all applications on my home-screen. I need some directions, any links, advice on docs/books is welcome.
[While cross-compiling the QtEmbedded 4.6.2 libraries for my SBC I encountered problems with enabling opengl support. And, I am unaware of the other methods for using QtQuick2 without opengl.
The applications (5-6 of them) are QWidgets and linking icons require to stay in the home screen. I want to keep them as simple as possible without any effects for the icons.
Plainly speaking, I am trying to create a bunch of icons displayed on the home screen linked to those applications. The applications if launched in windows style application, (or like a popup QDialog) will also serve my purpose.]
Thanks.
"I have gone through some links and tutorials but most of them show
how to create buttons and all that with Qt Quick, but not much than
that"
For this part of the question, I'd advise you to download QtCreator
and start playing with the demos (using more than just some buttons:
you have demos for ListViews, GridViews, Delegates, Animations,
Particles, QtQuick Layouts (Qt5.1 only), QtQuick Controls (Qt5.1
only).
There's also the rather complete :
http://qt.gitorious.org/qt-labs/qt5-everywhere-demo
I'm completely unfamiliar with all the embedded/cross-compiling
aspects of your question.
About OpenGL/QtQuick2 : http://qt-project.org/forums/viewthread/30483
http://qt-project.org/forums/viewthread/17201
Also note that you can embed QtQuick2 scenes into a QWidget, but not
the other way around (no QtWidget inside the scenegraph).
So maybe the easiest/fastest way to go for you would be to stick with Qt4 or Qt5 declarative/QtQuick1 module (might be deprecated/removed starting with Qt 5.2). In this setup, there is no scenegraph/mandatory need for OpenGL. And you can embed QWidgets into your qml scene (no scenegraph: it uses the QGraphicsView backend) via QGraphicsProxyWidget.
You'd then have some GridView (you also could use some Grid with a Repeater) filled with models and delegates (= a delegate acts as a template item to be filled with the model).
Your delegates would have states/maybe Loader(s) (for on-demand loading) : icon state and when clicked, some maximized state containing a loader, loading your widget through QGraphicsProxyWidget.
You already have half of this presented in this example (a grid + 2 states : small icons grid and maximized view, you only need to implement the delegate/loading/model/QGraphicsProxyWidget things):
http://developer.nokia.com/Community/Wiki/Implementing_parent_change_animation_with_QML
I have a Qt 4.8 application for both Win and Mac that captures the screen.
I have a QT widget on my desktop (always on top) that shouldn't be captured during my capture. Instead of the QT widget, the application/desktop running behind the QWidget should be captured. My QT application's UI should be masked from capturing.
Is there any way i can do this?
The main question is: are you in control of taking the screenshot or not? If you're taking the screenshot, it'd be doable but platform specific. You'd need to get the contents of all of the windows on the screen except the one you don't want to see, and build up a screenshot from those.
If it's a third party screen grabber, like Ctrl-PrtSc on Windows or Grab on OS-X, then you're out of luck unless the OS provides some APIs that would enable you to hide the widget.
The functionality you desire isn't exactly commonplace so I'm doubtful there's any portable, or even sane, way of achieving what you want.