mouseReleaseEvent is not called - c++

Question

I tried to implement a way for changing the background when an SVG button is pressed and reseting when it is released. My problem is that the mouseReleaseEvent is not called when I hide the QSvgWidget on which the mousePressEvent was called.
Here is my code:
SvgButton.cpp
#include "SvgButton.h"
SVGButton::SVGButton(QByteArray backgroundImage, QWidget *parent) :
QPushButton(parent)
{
this->init(backgroundImage);
}
SVGButton::SVGButton(QString backgroundImagePath, QWidget *parent) : QPushButton(parent)
{
SVGDom normalBackgroundImage(backgroundImagePath);
this->init(normalBackgroundImage.byteArray());
}
void SVGButton::init(QByteArray backgroundImage)
{
setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
_backgroundImageWidget = new QSvgWidget();
_backgroundImageWidget->load(backgroundImage);
setLayout(new QHBoxLayout(this));
layout()->addWidget(_backgroundImageWidget);
this->setFlat(true);
}
void SVGButton::select()
{
this -> setStyleSheet("background-color:rgba(0, 0, 0, 10);");
}
void SVGButton::deselect()
{
this -> setStyleSheet("background-color:rgba(0, 0, 0, 0)");
}
int SVGButton::tag()
{
return _tag;
}
void SVGButton::setTag(int tag)
{
_tag = tag;
}
void SVGButton::paintEvent(QPaintEvent *)
{
QStyleOption opt;
opt.init(this);
QPainter p(this);
style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
}
SVGButton::~SVGButton()
{
delete _backgroundImageWidget;
}
and BaseNavigationButton.cpp
#include "BaseNavigationButton.h"
const int kButtonWidth = 140;
const int kButtonHeight = 70;
BaseNavigationButton::BaseNavigationButton(QString backgroundImagePath, QString pressedBackgroundImagePath, QWidget *parent)
: SVGButton(backgroundImagePath, parent)
{
this->setMinimumSize(kButtonWidth, kButtonHeight);
if (!pressedBackgroundImagePath.isNull())
{
SVGDom pressedBackgroundImage(pressedBackgroundImagePath);
_pressedBackgroundImageWidget = new QSvgWidget();
_pressedBackgroundImageWidget->load(pressedBackgroundImage.byteArray());
layout()->addWidget(_pressedBackgroundImageWidget);
_pressedBackgroundImageWidget->hide();
}
else
{
_pressedBackgroundImageWidget = NULL;
}
}
void BaseNavigationButton::mouseReleaseEvent(QMouseEvent * event)
{
qDebug() << "SVGButton::mouseReleaseEvent";
if (_pressedBackgroundImageWidget) {
_backgroundImageWidget->setVisible(false);
_pressedBackgroundImageWidget->setVisible(true);
//_backgroundImageWidget->show();
//_pressedBackgroundImageWidget->hide();
}
QPushButton::mouseReleaseEvent(event);
//emit released();
}
void BaseNavigationButton::mousePressEvent(QMouseEvent *event)
{
qDebug() << "SVGButton::mousePressEvent";
if(_pressedBackgroundImageWidget)
{
_backgroundImageWidget->setVisible(true);
_pressedBackgroundImageWidget->setVisible(false);
}
QPushButton::mousePressEvent(event);
// emit pressed();
}
BaseNavigationButton::~BaseNavigationButton()
{
if (_pressedBackgroundImageWidget)
{
delete _pressedBackgroundImageWidget;
}
}
The SVGDom basically just create a ByteArray from the SVG images. The code works, it is relatively correct, the only problem is that I described above.

Answer 1

When you hide a QWidget, it lose the focus, and a Widget --or some child widget-- must have the focus in order to the events work on it.
Try this simple example:
Press the mouse button when the cursor is over a button.
Move the pointer out of the button without release the mouse button.
Release the mouse button.
As you will see, this not will trigger the button clicked --clicked is a mousePressEvent followed by a mouseReleaseEvent-- event.
Hence, you cannot receive mouse buttons events from hidden objects.
What can I do to implement the "mouse pressed" style behaviour?
If by "mouse pressed style behaviour" you mean: "I want my widget style change when I press the mouse button".
Well, you can use the setStyleSheet function and applpy a CSS style to your widget. See Qt Style Sheets Examples