I am trying to write a simple program to act as my desktop background in Qt, I have made it all work fine apart from making it a Desktop Widget. I have no idea on how to do this, I don't mind using XLib or Qt for doing this, but if anyone has some suggestions I would be very happy.
I have created a simple example that will fill the desktop background white. It is easy to make it draw an image.
class DesktopWidget : public QWidget
{
Q_OBJECT
public:
DesktopWidget()
{
setAttribute(Qt::WA_X11NetWmWindowTypeDesktop);
resize(QApplication::desktop()->size());
}
protected:
void paintEvent(QPaintEvent*)
{
QPainter painter(this);
painter.fillRect(geometry(), Qt::white);
}
};
The problem with this solution is that it completely paints over everything that your desktop environment draws in the background (including icons, plasmoids,...).
If you just want to set a new background image programmatically, I would check if your DE has an API for that.
Related
I'm trying to create a fullscreen window covered with an image and one entry widget in the middle of the window.
I already have the fullscreen window with the image, however, I'm struggling with positioning the entry box exactly in the middle of the window. I tried Gtk::Alignment, Gtk::VBox, Gtk::HBox, Gtk::Table
and many other containers, but to be honest, I don't really understand all the containers how do they behave. I am used to WIN32 API with absolute positioning and this is way different. I know I can use something like fixed positioning in Gtk/gtkmm, however, it does not seem like the cleanest solution to me.
class App : public Gtk::Window {
public:
[...]
App() {
fullscreen();
Gdk::Rectangle rec = get_screen()->get_monitor_workarea(get_screen()->get_primary_monitor());
set_default_size(rec.get_width(), rec.get_height());
show();
m_bgImage.set("image.jpg");
m_layout.add(m_bgImage);
m_entry.set_size_request(300, 30);
m_entry.set_opacity(0.5);
m_entry.set_visibility(false);
m_entry.signal_activate().connect(sigc::mem_fun(*this, &PadlockGui::onPasswordEntryReturn));
m_entry.set_icon_from_icon_name("edit-clear", Gtk::ENTRY_ICON_SECONDARY);
m_entry.signal_icon_press().connect(sigc::mem_fun(*this, &PadlockGui::clearPasswordEntry));
m_layout.add(m_entry);
add(m_layout);
show_all_children();
}
private:
Gtk::Layout m_layout;
Gtk::Image m_bgImage;
Gtk::Entry m_entry;
[...]
};
Here is a picture of my current situation:
Here is what I am trying to achieve:
I would suggest using CSS to create the background image rather than Gtk::Image. Then you can just put the entry directly in the window, and make sure its expand property is set to false and its halign and valign properties are centered.
I'm opening a modal window from my main window and my interest is to make the background dark so the top window is perfectly visible but the main one looks dark like in the "shade".
You can show some half-transparent widget over the mainwindow and it will create shadow effect.
For example, such widget.
class Overlay : public QWidget
{
public:
Overlay(QWidget *parent) {
setPalette(Qt::transparent);
setAttribute(Qt::WA_TransparentForMouseEvents);
}
protected:
void paintEvent(QPaintEvent *event) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
painter.setBrush(QBrush(QColor(0,0,0, 150)));
painter.setPen(Qt::NoPen);
painter.drawRect(rect());
}
};
Then create this widget, resize and show:
overlay_.reset(new Overlay(this));
overlay_->resize(size());
overlay_->setVisible(true);
You can play with the shadow color and transperancy by changing brush in paintEvent.
Hope this is the effect you wished.
This is up to the window manager to add such effect.
For example, KWin and Mutter both have their way to handle dialogs. KWin does shade the main window, and I think Mutter does it too with some additional effect.
In Mac OS, modal window are already have special properties to put it in focus on relation of it's patent window.
The way windows handle this is by forcing the focus on the modal I think. But it really is the window manager's job, and up to the user's preference to choose what effect should be active.
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.
In a standalone GUI application where I don't have a windowmanager nor a composite manager I want to display a QDialog to the user to ask for values.
The dialog is quite big, so I want to make it translucent so that the user can look through it to see what happens in the application while the dialog is shown.
The problem is that for translucency of X native windows, there needs to be a composite manager. Qt internal widgets can be painted translucent because they don't correspond to native X windows (aliens) and are completely only known to Qt.
Is there a way to make the background of a QDialog translucent without having a composite manager running? Perhaps making it a normal child widget/alien of the application's main window? Is there a better alternative to this?
I don't know of any way of turning a QDialog into a normal child widget. Looking at the Qt for X11 code, I can't figure out a way of not setting the Qt::WindowFlags passed to the QWidget (parent) constructor so that it would be a plain widget and not a window of its own (but I could be wrong, didn't spend a lot of time on that).
A simple alternative is to use a plain QWidget as your container, instead of a QDialog. Here's a sample "PopupWidget" that paints a half-transparent-red background.
#include <QtGui>
class PopupWidget: public QWidget
{
Q_OBJECT
public:
PopupWidget(QWidget *parent): QWidget(parent)
{
QVBoxLayout *vl = new QVBoxLayout;
QPushButton *pb = new QPushButton("on top!", this);
vl->addWidget(pb);
connect(pb, SIGNAL(clicked()), this, SLOT(hide()));
}
public slots:
void popup() {
setGeometry(0, 0, parentWidget()->width(), parentWidget()->height());
raise();
show();
}
protected:
void paintEvent(QPaintEvent *)
{
QPainter p(this);
QBrush b(QColor(255,0,0,128));
p.fillRect(0, 0, width(), height(), b);
}
};
To show it, call it's popup() slot which will raise it to the top of the widget stack, make it as large as its parent, and show it. This will mask all the widgets behind it (you can't interact with them with the mouse). It hides itself when you click on that button.
Caveats:
this doesn't prevent the user from using Tab to reach the widgets underneath. This could be fixed by toggling the enabled property on your "normal" widget container for example. (But don't disable the PopupWidget's parent: that would disable the popup widget itself.)
this doesn't allow for a blocking call like QDialog::exec
the widgets in that popup won't be transparent, you'd have to create custom transparent-background versions for all the widget types you need AFAIK.
But that's probably less of a hassel than integarting a compositing manager in your environment.
I created a very simple GUI that has a push button and a "Graphics View" widget from Display Widgets. On pushing the button I want a line to be drawn across the "Graphics View" widget. I have changed the name of the "Graphics View" widget to gv by right-clicking the widget in design view and then selecting change objectName. I am not able to understand how should the line be drawn. I read various texts on Qt that provided information about QPainter, PaintEvent etc. But I got more confused.
Kindly help me with this. A small sample code shall be really helpful for me as I am new to Qt.
A QGraphicsView is meant for displaying instances of QGraphicsItem that are managed by a component called QGraphicsScene. In your case, you'd create a QGraphicsLineItem and add it to the scene, or directly create it as an item of the scene by calling the addLine member function of your QGraphicsScene instance.
All drawing will be done by Qt itself, assuming that you did connect your graphics view and scene properly. Be sure to read The Graphics View Framework, which gives you an overview over how these components work.
You will find code examples of how to manage and display a scene using the graphics view framework here: http://doc.trolltech.com/4.6/examples-graphicsview.html
You can paint into a QPainter
Either override the paintevent and draw there
void MyDisplayWidget::paintEvent(QPaintEvent*)
{
QPainter p(this);
p.setPen(Qt::green);
p.drawText(10,10,"hello");
}
Or draw into a QImage and display that
QImage image = QImage(size);
QPainter p(&image);
p.drawText(10,10,"hello");
// draw or save QImage
You can even use the same draw function taking a QPainter * to draw either direct to the screen or to an image.
first you must knew some information about QPainter to have benefit of it.
QPainter provides highly optimized functions to do most of the drawing GUI programs require. It can draw everything from simple graphical primitives (represented by the QPoint, QLine, QRect, QRegion and QPolygon classes) to complex shapes like vector paths .and we use it to draw on paint devices
then render it to view,and we have alot of qpaint devices like : QWidget, QImage, QPixmap, QPicture, QPrinter, and QOpenGLPaintDevice you can use any one of them depending on your requirements then create QGraphic scene and add you paint device as qgraphic scene item to be shown in qgraphic view.
here is simple code:
Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
scene=new QGraphicsScene(this); //allocate your scene to your main widget
view=new QGraphicsView(scene,this);//here is your view
pixmap=new QPixmap(QSize(700,700));// paint device
view->resize(700,700);
}
Widget::~Widget()
{
delete ui;
}
void Widget::paintEvent(QPaintEvent *e)
{
painter=new QPainter;// create your painter
painter->begin(pixmap);//add painter to your paint device
painter->fillRect(0,0,300,300,Qt::red);//draw rect
painter->setPen(Qt::yellow);
painter->drawLine(0,0,700,700);//draw line
painter->end();
scene->addPixmap(*pixmap);// add your paint device to your scene
view->show();//then show your view
}