I have a custom QGraphicsView class where I try to set the background color in its constructor.
These work in non-OpenGL mode:
QColor backgroundColor(50,50,50,255);
setBackGroundBrush(backgroundColor)
and
QPalette myPal = this->palette();
myPal.setColor(this->backgroundRole(), backgroundColor);
this->setPalette(myPal);
However in OpenGL mode the first produces a white screen clearing, while the second clears the widget with the given color. I can also see for a few milliseconds the actual item ought to be drawn in between repaints.
If I don't set the background color at all a white background is set, and everything functions just fine.
Related
How can I get the pressed background color of a QPushButton?
if (isDown())
_BGColor = <pressed background color>; // how to get this???
else
_BGColor = palette().color(QPalette::Background); // this is to get the idle backcolor
Thanks in advance!!!
It's very difficult (if not impossible) to find a way to get the backgound color of a button when it's pressed, because it depends on the style, and it's not guaranteed that the style respects the palette.
However I suggest two different approaches:
You can set you own background color using style sheets (simpler) or implement the painting of the button yourself, using styles or reimplementing paintEvent(). See Customizing QPushButton
To paint over the button with the inverse color, you can set a composition mode to the painter in order to get the inverse color.
For example:
painter.setPen(QColor(255, 255, 255));
painter.setCompositionMode(QPainter::RasterOp_SourceAndNotDestination);
(note that using this example, the inverse color of middle grey (128, 128, 128) is exactly the same color)
See QPainter::CompositionMode
I have a widget as on overlay for another widget. The transparency works fine, as long as I don't clear the background of the overlay.
But I have to clear the widget to acutalize the displayed "effects". I tried to solve the inital problem (the background getting the default color) like described in 20848594, but except changing the color to black it had no effect...
Has anyone an idea why the widget which should be transparent does not display the underlaying widget(s)?
Here the code:
SudokuMarkerOverlayWidget::SudokuMarkerOverlayWidget(QWidget* parent, uint const fieldSize) : QWidget(parent)
{
// Translucent should be the correct one
setAttribute(Qt::WA_TranslucentBackground);
//setAttribute(Qt::WA_NoSystemBackground);
setAttribute(Qt::WA_TransparentForMouseEvents);
...
}
void SudokuMarkerOverlayWidget::paintEvent(QPaintEvent*)
{
QPainter painter(this);
painter.setRenderHint( QPainter::Antialiasing );
// Tried this too, no difference
// painter.setCompositionMode(QPainter::CompositionMode_Source);
// painter.fillRect( this->rect(), Qt::transparent );
painter.setCompositionMode(QPainter::CompositionMode_Clear);
painter.eraseRect( this->rect() );
painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
...
}
EDIT:
Just noticed, using CompositionMode Source instead of SourceOver for my semi-transparent painting (gradient seen in first image) also causes them to be a red-to-black-gradient instead of red-to-transparent.
That means every transparency except the inital by WA_TranslucentBackground or WA_NoSystemBackground isn't working.
Widgets in Qt can be either a 'native' or 'alien' type. In one case they're a separate operating system window. In some operating systems a transparent window isn't supported.
You might want to consider using QML if you're after fancy visual effects. That's what it was designed for.
The question is in bold at the end so please read this as a whole.
I have a QAbstractScrollArea widget that I manually and completely render in the OnPaint() event.
In its constructor I set
setAttribute( Qt::WA_OpaquePaintEvent, true );
setAttribute( Qt::WA_NoSystemBackground, true );
setStyleSheet( "QWidget { background-color: rgb(0,0,77); }" );
and the paint event looks like this:
void MyArea::paintEvent (QPaintEvent *event) {
QPainter view(viewport());
view.fillRect(rect(), backgroundBrush);
renderedPixmap = heavyAndSlowRenderingOnAPixmap();
view.drawPixmap(viewRect, renderedPixmap, pixmapRect);
}
as you can see there's a "slow" function involved to render stuff into a pixmap.
The problem is: when I resize the window, I can see for a moment a white flickering in the area not yet redrawn
I know I can't avoid the white region until the viewport has been redrawn, but I'd like to draw that white region with the background color immediately.
So here's the question: can I display a background color immediately before the heavy-pixmap rendering?
I can't seem to find a way to achieve this.. it seems all graphics operations are buffered and then immediately bit-blitted to the screen together. I'm using Windows 8.1 x64 and Qt5. Any way to immediately draw the background color and then proceed with the rest of the rendering?
The best solution would be to move the expensive rendering out of the paintEvent(), potentially into another thread. You'll want to cache the rendered pixmap anyway. Update that pixmap when really needed and then call update() to trigger a repaint.
I have the following question.
My QTableView has background color set to black and color (of contents) to white. So, white text appears on a black background - everything seems to be correct. However, when editing (typing in editing mode) content color is changed to black and it becomes completely invisible due to black background, but editing works fine. After confirming - color reverts back to white. How to set color of currently-being-edited text to white (preferably via stylesheets) or stop such change in this case?
You have to use the :edit-focus and/or :focus states in your stylesheet.
QTableView:edit-focus {
// style here
}
For a list of all available states have a look here
Setting palette worked finally.
QPalette palette;
palette.setColor(QPalette::Text, Qt::white);
qApp->setPalette(palette);
wattron and a color pair only sets the background color of text when it is printed inside a window. What is the best way to set the background color of the entire window without filling it with spaces (i.e. a title or status bar)?
A call to wbkgd with a pointer to a WINDOW object and a color pair sets the background color of the window.