I heard that qt(older versions, at least) do not use windows native API to draw its widgets. I want to know how is this possible ? how does it draw without calling functions from the native API ? is there a way through which creation of non-native widgets is possible ?if yes, then what is it?
I don't know where you heard that, but all drawing operations will at some point need to make platform API calls. Drawing anything on the screen would otherwise be impossible.
Unless by "painting" you mean the way Qt creates the image data for the widgets prior to drawing them on the screen. In that case, yes, Qt rasterizes on its own. It still gets some image data from the native API though, otherwise it wouldn't be able to produce widgets of the currently set theme.
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.
Other than trying to manually, re-write everything to mimic the tooblar graphics and the size transition animation when moving between pages, Is there a better way to do this?
Amazingly I can't find ANY resources covering this, or even someone asking for this.
http://qt-project.org/doc/qt-5.1/qtwidgets/qtwidgets-index.html#styles
The window animations may already work as is... You may want to specify Native Windowing, so that the Mac Windowing system is aware of your Qt windows:
http://qt-project.org/doc/qt-5.1/qtwidgets/qwidget.html#native-widgets-vs-alien-widgets
Native Widgets vs Alien Widgets
Introduced in Qt 4.4, alien widgets
are widgets unknown to the windowing system. They do not have a native
window handle associated with them. This feature significantly speeds
up widget painting, resizing, and removes flicker. Should you require
the old behavior with native windows, you can choose one of the
following options:
Use the QT_USE_NATIVE_WINDOWS=1 in your
environment.
Set the Qt::AA_NativeWindows attribute on your
application. All widgets will be native widgets.
Set the
Qt::WA_NativeWindow attribute on widgets: The widget itself and all of
its ancestors will become native (unless
Qt::WA_DontCreateNativeAncestors is set).
Call QWidget::winId to
enforce a native window (this implies 3).
Set the Qt::WA_PaintOnScreen
attribute to enforce a native window (this implies 3).
See also
QEvent, QPainter, QGridLayout, and QBoxLayout.
And this link has more information on the styling in Qt than I have ever seen before today!
http://qt-project.org/doc/qt-5.1/qtwidgets/style-reference.html
Hope that helps.
I'm currently trying to get Qt working with my existing program.
I'm using SFML for creating my OpenGL rendering context and creating the window. The things I tried out so far however always create a separate window by Qt instead of just rendering into the existing context.
Is there any way I can force Qt to render to an already existing OpenGL context?
I've not looked into the specifics, but this has been done for openage.
I think looking at the documentation for QQuickRenderControl might be a good place to start.
Qt wants full control over the windows and the event loop, so this will not work (unless you put a lot of effort into it). Your best bet is using a QGLWidget and emulate the event management of SFML with that, so that your application effectively runs on Qt. It is very well possible to render Qt widgets into a OpenGL window (Qt has a OpenGL widget backend) but this must be still managed by Qt itself.
I have enabled qt+OpenGl+SimpleGl on one of the ARM platform and was able to run opengl example programs.
I also has a qt+Webkit, which is working with a graphic plugin.
I wanted to use simpleGl context for every thing, instead of using the normal graphic screen. So, when I try to run Qt+Webkit with simpleGl, I just get a blank screen.
Does QT support this? If so how can we make it?
Yes, this is correct. OpenGL draws directly to the framebuffer. The simplegl driver doesn't handle what is drawn using the raster paint engine of the QWS, so you may see only black.
Using simplegl for "everything" means you want everything to be drawn using OpenGL in your EGL full-screen window? This is possible under some assumptions. You have to write all your applications to be rendered using the Qt OpenGL paint engine (using the opengl graphics system is not supported under Qt/E). This is possible also for QtWebKit, I'm doing it now. Note that this does not mean that everything is rendered using hardware acceleration. You'll have to write your applications "the right way" to get all actually hardware accelerated. Consider that you'll have to handle the mouse pointer some other way in this case.
The other way is to just modify the simplegl driver to allow for the use of Qt applications using the raster paint engine. This is possible as well with some limitations. Qt can use blit to place its own windows over OpenGL. Look for the framebuffer driver inside the Qt source tree to know how to do this. You can then have common Qt applications and OpenGL Qt applications some way. I'm doing this as well. Not everything can be done anyway.
EDIT: I'm sure you already did, but in case, give this http://doc.qt.io/qt-4.8/qt-embeddedlinux-opengl.html much attention.
Unfortunately I don't know anything about SimpleGL, but I do know that there is a way to render a standard Qt widget in a QGLWidget. Maybe have a look at this Qt Quarterly which I think is somewhat related to your question:
http://doc.qt.nokia.com/qq/qq26-openglcanvas.html
I need an appropriate rendering engine to render a 3D model into Qt, and use Qt then as an event handler to this model. Thank you.
As for the rendering engine, you can go several directions, but I'll mention two. Qt comes with an OpenGL widget. You could make use of this by either:
writing your own rendering code to render your model using OpenGL
or
making use of a rendering engine/framework which has it's own Qt Widget (possibly derived from Qt's OpenGl widget). I know OpenSceneGraph has Qt integration available. And I seem to remember Ogre does as well. This just to mention two options. Just Google for Qt and your favorite engine and you'll most likely find something suitable. And if not, it is usually not that difficult to write your own integration if you feel like it.
Whichever option is more suitable for you depends on the exact specification of what you're trying to achieve. You probably know that better than we do.
As for the event handling, you might want to be a bit more specific as to what you mean.