How to set transparency of an rectangle/screen.
I have Following code:
// main.cpp
void main(int argc, char*[] argv)
{
QApplication::setGraphicsSystem("raster");
QApplication app(argc, argv);
QDeclerativeView view;
view.setSource(QUrl::fromLocalFile("loaderTest.qml"));
view.setResizeMode(QDeclarativeView::SizeRootObjectToView);
view.showFullScreen();
//QRegion mask(10, 10, 100, 100);
//view.setMask();
view.show();
app.exec();
}
And QML file is:
//loaderTest.qml
Rectangle
{
id: mainRectangle
width: 1000
height: 700
color: "transparent"
//color: "#00000000"
Image
{
id: image1;
width: 348;
height: 155;
anchors.horizontalCenter: parent.horizontalCenter;
anchors.verticalCenter: parent.verticalCenter;
source: "test.png"
}
Loader
{
id: mainLoader
anchors.fill: parent;
source: "";
focus: true;
}
}
I have one loader and one image in this screen and background color is transparent.
When i run this application it should display transparent background with image in the center (as i have not set loader source).
but what i am getting is image in center with white background filled in the screen, I don’t know who is filling in this white background color as i have mentioned transparent color as background.
I am using QT.4.7.0 and Linux.
I have two planes on my target system one is Video plane and another is graphics plane, when i run GUI with transparent background (set transparency at video place) it should display video on Video place in above example it is showing background as white, as it should have displayed video playing on Video plane.
By default the QDeclarativeView paints a background. Maybe that's the problem in your case.
From http://doc.qt.nokia.com/4.7/qdeclarativeperformance.html
You can also prevent QDeclarativeView from painting its window background if you will provide the background of your application using QML, e.g.
QDeclarativeView window;
window.setAttribute(Qt::WA_OpaquePaintEvent);
window.setAttribute(Qt::WA_NoSystemBackground);
window.viewport()->setAttribute(Qt::WA_OpaquePaintEvent);
window.viewport()->setAttribute(Qt::WA_NoSystemBackground);
My first guess is that the background is white and your rectangle is indeed fully transparent.
What type is LoaderScreen, I guess it is some sort of QDecalarativeView, please forgive any technical misses have not coded Qt/QML for almost a year now. As I remember it the default background of the view was white and what kind of transparency are you hoping to achive anyways?
If you only set a background-color on a QPushButton, the background may not appear unless you set the border property to some value. This is because, by default, the QPushButton draws a native border which completely overlaps the background-color.
This might show a black rectangular box around QPushButton. You will face this issue especially on Linux machines. In order to avoid this you can set the border property to none
widget->setStyleSheet("border:none");
Related
I see from https://vega.github.io/vega-lite/docs/config.html that it is possible to change the background color. But i don't see any docs for adding an underlay background image.
vega-lite creates a canvas element.
So adding a background image is explained in a question about how to add a background to a canvas element.
HTML5 Canvas background image
But you can just do it with css:
canvas {
background: url("my_background.png");
}
This is just like any other background image css.
https://developer.mozilla.org/en-US/docs/Web/CSS/background-image
I have some basic styles like:
"#foo": {
backgroundColor: '#ff0000', // red
}
"#foo[if=Alloy.Globals.isSmallHeight]": {
backgroundColor: '#0000ff', // blue
}
in alloy.js I have the following:
function pxToDp(px){
return px / (Titanium.Platform.displayCaps.dpi / 160);
}
var screenWidth;
var screenHeight;
if (Ti.Platform.name == "android") {
screenWidth = pxToDp(Ti.Platform.displayCaps.platformWidth);
screenHeight = pxToDp(Ti.Platform.displayCaps.platformHeight);
} else {
screenWidth = Ti.Platform.displayCaps.platformWidth;
screenHidth = Ti.Platform.displayCaps.platformHeight;
}
Alloy.Globals.isSmallHeight= screenHeight <= 545;
This basically means the background colour of #foo is blue if the screen height is less than or equal to 545dp, and red otherwise.
This usually works fine. However, there are times when the height of the screen can change during run-time. For example:
Screen Orientation Change
Multi window (on Android)
Adjusting the splitter position while in multi window mode (Android)
The issue with this is that the styles are not re-applied to take into account the new screen width and screen height.
For example, let's say there is a screen of size 600dp x 300dp in the portrait position. #foo will correctly have a background colour of red.
However, if the orientation changes, the screen size is now: 300dp x 600dp, but the #foo does not re-check the height a background colour, and thus is still red instead of blue.
A similar issue occurs when going into split screen.
Therefore my question is, how can I reapply styles when the screen dimensions changes?
Have a look at the dynamic styles section in the documentation
http://docs.appcelerator.com/platform/latest/#!/guide/Dynamic_Styling
http://docs.appcelerator.com/platform/latest/#!/guide/Dynamic_Styles
it will give you a basic idea on how to create style at runtime and apply them. You could do this inside the orientation change event
I'm trying to get something in a ScrollView to expand in width to fit the screen. The ScrollView is anchored to the main window.
For example purposes, a Rectangle:
ScrollView {
anchors.fill: parent //mainWindow
Rectangle {
color: "light grey"
height: 1000
width: mainWindow.width
}
}
But when the vertical scrollbar appears, it obscures the Rectangle. I can sort of fix it by using a magic constant:
width: mainWindow.width - 20
But what if somebody has bigger scrollbars on their computer? Also it leaves an ugly empty space on the right when the vertical scrollbar is invisible.
Is there a way to automatically learn what the available space is inside of a ScrollView?
There is no need to explicitly adjust to scroll bar. You can just make it to fill the entire available parent space or so. And if you want specify margins:
ScrollView {
id: scrollView
anchors.fill: parent // mainWindow ?
anchors.centerIn: parent // anchoring as asked
anchors.margins: 20
contentItem:
Rectangle {
id: rectScroll
width: scrollView.viewport.width // set as viewport
height: 1000 // set to what you need
}
}
The original issue was solved mainly due to the width property of Rectangle set to parent.parent.width or scrollView.viewport.width as it is more adequate. The latter is definitely better, as long as the width of precisely viewport of scroll area and not the parent width (which in general not guaranteed to contain only this ScrollView).
I am trying to use mask on my QWidget. I want to overlay existing widget with row of buttons - similar to Skype
Notice that these buttons don't have jagged edges - they are nicely antialiased and widget below them is still visible.
I tried to accomplish that using Qt Stylesheets but on pixels that should be "masked out" was just black colour - it was round button on black, rectangular background.
Then I tried to do this using QWidget::mask(). I used following code
QImage alpha_mask(QSize(50, 50), QImage::Format_ARGB32);
alpha_mask.fill(Qt::transparent);
QPainter painter(&alpha_mask);
painter.setBrush(Qt::black);
painter.setRenderHint(QPainter::Antialiasing);
painter.drawEllipse(QPoint(25,25), 24, 24);
QPixmap mask = QPixmap::fromImage(alpha_mask);
widget.setMask(mask.mask());
Sadly, it results in following effect
"Edges" are jagged, where they should be smooth. I saved generated mask so I could investigate if it was the problem
it wasn't.
I know that Linux version of Skype does use Qt so it should be possible to reproduce. But how?
One possible approach I see is the following.
Prepare a nice high resolution pixmap with the circular button icon over transparent background.
Paint the pixmap on a square widget.
Then mask the widget leaving just a little bit of margin beyond the border of the circular icon so that the widget mask jaggedness won't touch the smooth border of the icon.
I managed to get a nice circular button with not so much code.
Here is the constructor of my custom button:
Button::Button(Type t, QWidget *parent) : QPushButton(parent) {
setIcon(getIcon(t));
resize(30,30);
setMouseTracking(true);
// here I apply a centered mask and 2 pixels bigger than the button
setMask(QRegion(QRect(-1,-1,32,32),QRegion::Ellipse));
}
and in the style sheet I have the following:
Button {
border-radius: 15px;
background-color: rgb(136, 0, 170);
}
With border-radius I get the visual circle and the mask doesn't corrupt the edges because it is 1 pixel away.
You are using the wrong approach for generating masks. I would generate them from the button images themselves:
QImage image(widget.size(), QImage::Format_Alpha8);
widget.render(&image);
widget.setMask(QBitmap::fromImage(image.createMaskFromColor(qRgba(0, 0, 0, 0))));
I have come to see that Sencha Touch framework is improving noticeably. Since I couldn't see something like what I want, I wanted to ask here and see if it's possible. I would like to hear your opinion on how to do some image change animation when the image is touched. When you touch the image, another image will animate growing from the middle.
Actually I also want to detect (if possible) the location of the touch on the image (Things I could do on iOS).
Is this possible? If so, any advice is appreciated.
Thanks
Panel has some properties to find out location of the touch:
var Xscroll = somePanel.scroller.offset.x;
var Yscroll = somePanel.scroller.offset.y;
Also, for your animation, you can do something like this:
Have 1 image on your 1st panel (make that image fit to the panel and keep it to background) like this:
JS:
App.somePanel= new Ext.Panel({
cls: 'somePanel',
html: '<h1>Welcome to my app!</h1>',
//some other properties
});
CSS:
.somePanel {
background-image: url(http://somesite.com/someimage.png);
background-repeat: no-repeat;
background-size: 100% 100%;
}
Have second panel like that.
On some event on the first panel do:
Hide that panel with animation
Show the second panel with animation
The list of animations is given in Sencha Touch API