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copied!<p>The <code>windowOpacity</code> property only applies to top level windows so it won't help you with animating transparency on child widgets unfortunately.</p> <p>Standard controls are a bit problematic as well as there are many considerations contributing to their final appearance. There are many approaches you could take but they will all involve a certain amount of coding. There is no easy way :)</p> <p>To set the transparency of a <code>QPushButton</code>, you would need to either set a stylesheet for it, or change some of the properties of the palette. Since neither of these options are directly usable by a <code>QPropertyAnimation</code>, you can create your own custom property and animate that.</p> <p>Below is some code that specifies a custom property for a <code>MainWindow</code> called <code>alpha</code>. The alpha value is used to set the alpha portion of the button color. With this property in place, we can use <code>QPropertyAnimation</code> to animate it. The result is a button that fades in and out. This only handles the buttons background and not the text but it should provide a starting point for you.</p> <p><strong>MainWindow.h:</strong></p> <pre><code>#ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QWidget> #include <QPushButton> class MainWindow : public QWidget { Q_OBJECT Q_PROPERTY(int alpha READ alpha WRITE setAlpha); public: MainWindow(); virtual ~MainWindow(); private: int m_alpha; QPushButton * m_button1, *m_button2; int alpha() const; void setAlpha(const int a_alpha); }; #endif /* MAINWINDOW_H */ </code></pre> <p><strong>MainWindow.cpp:</strong> <em>(Updated to include stylesheet transparency example)</em></p> <pre><code>#include <QPlastiqueStyle> #include <QPropertyAnimation> #include "MainWindow.h" MainWindow::MainWindow() : m_button1(0), m_button2(0), m_alpha(255) { resize(200, 200); QPalette windowPalette(palette()); windowPalette.setBrush(QPalette::Background, QBrush(QColor(200, 0, 0))); setPalette(windowPalette); m_button1 = new QPushButton(this); m_button1->setText("Palette Transparency"); m_button1->setAutoFillBackground(false); // NOTE: Changing the button background color does not work with XP Styles // so we need to use a style that allows it. m_button1->setStyle(new QPlastiqueStyle()); m_button2 = new QPushButton(this); m_button2->move(0, 50); m_button2->setText("Stylesheet Transparency"); m_button2->setAutoFillBackground(false); m_button2->setStyle(new QPlastiqueStyle()); QPropertyAnimation *animation = new QPropertyAnimation(this, "alpha"); animation->setDuration(1000); animation->setKeyValueAt(0, 255); animation->setKeyValueAt(0.5, 100); animation->setKeyValueAt(1, 255); animation->setLoopCount(-1); animation->start(); } MainWindow::~MainWindow() { } int MainWindow::alpha() const { return m_alpha; } void MainWindow::setAlpha(const int a_alpha) { m_alpha = a_alpha; QPalette buttonPalette(m_button1->palette()); QColor buttonColor(buttonPalette.button().color()); buttonColor.setAlpha(m_alpha); buttonPalette.setBrush(QPalette::Button, QBrush(buttonColor)); m_button1->setPalette(buttonPalette); QString stylesheet("background-color: rgba(0,200,0," + QString::number(m_alpha) + ");"); m_button2->setStyleSheet(stylesheet); } </code></pre> <p><strong>main.cpp:</strong></p> <pre><code>#include <QtGui/QApplication> #include "MainWindow.h" int main(int argc, char *argv[]) { QApplication app(argc, argv); MainWindow m; m.show(); return app.exec(); } </code></pre>

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