I am building an App in which I had given background to my mainWindow only and all other widgets are used without any background, but when I run the app they are not 100% transparent they are somewhat translucent, is there any way to make them 100 % transparent so that only foreground can appear with no background hint.
Could you post the code you are using to get transparancy at the moment? If you say that you get "something translucent" I think that you created a tool window which is not what you really want.
A really transparent main window could be achieved by removing the title bar (give the QWidget constructor Qt::FramelessWindowHint as second parameter - WindowFlags), draw everything in the widget that should be transparent in a uncommon color (like 255,0,255) and then cut it off.
A very primitive example of cutting off parts of a QWidget:
QBitmap b(100, 100);
b.fill(Qt::black);
setMask(b);
QBitmap must be black on that pixels that shall be visible and white on that are not. In this example just the 100,100 area starting at 0,0 will be visible, the rest of your window will be invisible.
Related
I have a transparent QGraphicsWebview inside a QGraphicsView with the following settings:
The QGraphicsView is the high level widget, and is shown in full screen mode
The graphics view uses a QGLWidget as its view port (to use opengl-es)
Alpha channel and double buffering are enabled in this QGLWidget
Transparency is achieved by graphicsView->setStyleSheet("background:transparent")
Following attributes are set for QGraphicsView and QGraphicsWebview
WA_TranslucentBackground = true
WA_NoSystemBackground = true
WA_OpaquePaintEvent = false
The QPalette::Base and QPalette::Window brushes of webview and webview->page() are set to Qt::transparent
At the beginning, the transparency works fine. But as the screen get updated (when I scroll), it looks like the new bitmap is blended on top of the existing one to get a superimposed picture. After about 5-6 screen updates, this blending causes the colors to accumulate and form an opaque rectangle (with a corrupted image). Following images show first, second and final stages of the problem.
How do I tell qt/opengl to stop blending and just draw the new image to the frame buffer?
I tried calling fillRect(boundRect(), Qt::transparent) from overridden Webview::paint and GraphicsView::paintEvent; but it didn't work except for making the updates slower.
I am new to Qt and OpenGl, so I might be missing some basic flags or settings.
I tried all the methods mentioned above. They did not work for me. I then debugged into qtbase code and found that setting the Opacity level make the top browser layer transparent.
this->setOpacity(0.1);
this pointer points to the QGraphicsWebView object.
With this method, the whole front browser contents including background will be transparent. To separate header, paragraph and background and to specify different transparent levels for them, I will have to dig into webkit code a little further to figure out the problem. But for now, setOpacity() did the trick and is good enough for what I am doing.
It turns out the problem is graphicsView->setStyleSheet("background:transparent");. Who would have guessed?!
Yeah, the line that I thought made transparency work was actually causing troubles with transparency. The application works fine without that line (or if you change it to background:none)
In short, steps to get a transparent QGraphicsWebview using QGLWidget:
Set the Base palettes of QGraphicsWebview, QWebpage and the outer QGraphicsView to Qt::transparent
scene->setBackgroundBrush(QBrush(Qt::transparent));
You should also make sure that html body background is set to transparent values:
html, body {
background-color: rgba(127, 127, 0, 0.5);
}
I want to achieve this :
Have a transparent surface of some width and height (A transparent widget)
Draw something on this surface such that only outlines of that figure are visible on the screen and nothing else (no background of the surface on which I am drawing should be there)
I made a widget and achieved to make it transparent like this :
window.setAttribute( Qt::WA_TranslucentBackground);
window.setWindowFlags (Qt::FramelessWindowHint);
window.setGeometry( 0,0,1200, 800 );
window.show();
Then I overrode the function paintEvent(QPaintEvent *); to make a ellipse using QPainter.
But still the surface is coming to be black color only. Can someone explain ?
Looks similar to what I did in a similar app, but I also did:
window.setAutoFillBackground(false);
Perhaps that's the missing piece for you?
Edit: Another idea: In your paintEvent, do you fill the widget rect() with a fully transparent color before you paint the ellipse?
I am creating a circuit schematic editor using Qt Creator. I have a QGraphicsScene/QGraphicsView canvas that I would like to drop images of circuit components onto and move them around.
I am currently using a pixmap QGraphicsItem and adding it to the canvas and making it movable. This works great when you click directly on the symbol's lines, however the symbol does not move when the transparent areas in the image are clicked.
Is there a way to expand the hitbox/mouse area to make these transparent regions respond the same as the other regions do on the symbol? Below is how I am adding the image. (I need the image transparent so that other symbols are visible behind/infront of it)
QGraphicsItem* b = canvas.addPixmap(QPixmap(":/images/ground2.gif"));
b->setFlag(QGraphicsItem::ItemIsMovable);
b->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
All help is much appreciated! Thanks!
Josh
You can call QGraphicsPixmapItem::setShapeMode( QGraphicsPixmapItem::BoundingRectShape ) to have the item treated a rectangle.
I have a full size QGLWidget which paints the application background using QPainter (might change to native openGL commands in the future).
On top of this QGLWidget I use QWidgets (non-GL) for the user interface elements. These are, for example, QLineEdits and QPushButtons. I put them into a custom painted QWidget which uses semi-transparent background painting. The paintEvents of the QLineEdit and QPushButton are overwritten and use semi-transparent backgrounds, too.
The whole UI should look like the following (This is a screenshot where I disabled OpenGL and used QWidget instead of QGLWidget for the background. Note the semi-transparent top bar which also draws a shadow (within its own region)):
When the QLineEdit has the focus, it should have a higher opacity but still not fully opaque:
So now, with OpenGL enabled (The background then is a QGLWidget), the semi-transparent widgets above don't paint on top of the background but on (it seems to be) uninitialized data. The image shining through the top bar is sometimes the whole window itself and sometimes other windows currently being on my desktop.
This currently looks like the following (In this screenshot, the data on which the semi-transparent painting operations are painted on seems to be an image of the widget itself, having an offset.):
When I wrote text into the line edit (here: "This is some text which has been there before!"), removed it and set the focus back to the background widget (so the magnifier icon and the placeholder text appear), the previously painted things still shine through (Note that the visible border should not be visible anymore, but also still shines through):
So the problem is: Instead of being painted on top of the underlying widgets, the semi-transparent widget is painted on top of the old results, initially being something like "uninitialized memory".
Why does this happen? How can I solve the problem?
Things you should know before answering:
The background scene is a composition of tiles which are rendered off-screen. So it can be painted very fast and repainting of the background for every little change of the overlay isn't problematic.
The top bar is a custom QWidget with manual painting and arrangement of the contained two widgets (the button and line edit).
The two widgets overwrite the paintEvent, only draw their own (semi-transparent) background when they have focus and don't use frames already provided by Qt. So the white border in the second screenshot is drawn in my custom paintEvent.
I want the background and the composition of overlay widgets to be separately implementable. The background is an AbstractMapView which has some concrete map view classes. The whole window is an AbstractView (there are multiple concrete views, too), which contains both a concrete map view and the overlay widgets, composed in a way itself decides. Therefore, I don't want the logic of the overlay widgets to be part of the underlying map view. (I hope you understood this, as it is a bit complicated.)
This sounds like an issue where the GL content (i.e. your background aka the QGLWidget) is not in the Qt context. While I'm not a pro on GL painting with Qt, you may want to look at this discussion regarding GL painting and a QLabel for some direction/potential hints.
http://www.qtcentre.org/threads/40335-QLabel-on-top-of-a-QGLWidget-background-issue
In short, we here at the office use OpenGL painting and offscreen rendering of maps and it's very important to make sure Qt is aware of the pixels so your foreground widgets can have the semi-transparency applied to their backgrounds.
The particular product we use also renders the map in tiles and supports providing the GL output in a buffer (i.e. it's call a snapshot and is provided as a bitmap) at which point we use the paintEvent of a regular QWidget to paint the buffer so that the painted pixels are in Qt context.
You can define a Qframe with Qt::SplashScreen flag as the search box and set its opacity. Put your widgets inside it such as the search textbox and positon it where it should appear on the mainwindow. It will also be a good idea to reposition it as the mainwindow is moved or resized overriding its moveEvent.
I have a QLabel, and I put an image on it using setpixmap(). That image has alpha channel.
The QLabel is on a QWidget which has a border-image specified by an image (so that the image is rescaled to fill the QWidget).
On the transparent parts of the QLabel, the result is not the image specified on the QWidget, but a gray color characteristic of "no color" Widget.
My question is how do I make this in such a way that the transparent part of the QLabel shows the border-image of the QWidget?
I've tried canceling autofillbackground, changing the background color of the QLabel to white transparent, but none helped.
You need to set the Widget Attributes and Window Flags appropriately:
Using QWidget::setAttribute() and Qt::WidgetAttribute...
Qt::WA_TranslucentBackground needs to be set to true.
Along with learning the Window Flags Example should help a lot.
If you are just looking for a single widget that paints a frameless image...
Here is a perfect example:
QSplashScreen Replacement