I'm using Qt6.1 and I want send my widget's pixmap when it painted.
I have similar code:
void MyWidget::paintEvent(QPaintEvent*)
{
// static bool callGrab = true;
// m_callGrab initialize with true
if (m_callGrab)
{
m_callGrab = false;
auto pixmap = grab();
m_callGrab = true;
emit widgetRepainted(pixmap);
QPainter painter(this);
painter.drawPixmap(0, 0, pixmap);
painter.end();
return;
}
QPainter painter(this);
...
painter.end();
}
I know call grab() in paintEvent() will cause recursive so I use a variable to prevent it.
it works well, but I get "QWidget::repaint: Recursive repaint detected" in console. It's too lot and scrolls my debug information up.
I have tried add DEFINES += QT_NO_WARNING_OUTPUT in my .pro file but it doesn't work.
I want to know whether can disable print the message in console.
Related
I want to use a QTimer object to control a LED indictor status. A QLed class inherited QWidget is created to control the LED indicator. Here below its two major functions relevant:
void QLed::setLEDFlashing(bool value)
{
ledStatus = value; //Boolean value to accept a user-defined LED status
m_value = ledStatus; //m_value is used in painting LED (with QtSvgRenderer)
QTimer ledTimer;
ledTimer.setInterval(300);
if(!ledTimer.isActive())
{
ledTimer.start();
}
//Here is the connection between the timer and this (i.e., QLed*) object
connect(&ledTimer, SIGNAL(timeout()), this, SLOT(setLEDFlashingTimerHandler()));
}
//I want to use this function to make LED keep flashing
void QLed::setLEDFlashingTimerHandler()
{
//qDebug()<<"setLEDFlashingTimerHandler()";
if (ledStatus)
{
m_value = TRUE;
ledStatus = FALSE;
}
else
{
m_value = FALSE;
ledStatus =TRUE;
}
}
//This is to paint the LED widget
void QLed::paintEvent(QPaintEvent *)
{
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
//based on m_value, different svg file is loaded
if(m_value)
ledShapeAndColor.append(colors[m_onColor]);
else
ledShapeAndColor.append(colors[m_offColor]);
renderer->load(ledShapeAndColor);
renderer->render(&painter);
//qDebug()<<"paintEvent m_value="<<m_value;
}
In the mainwindow.ui, I add a QLabel object (named led) and promote it to QLed, and in the mainwindow.cpp:
ui->led->setLEDFlashing(TRUE);
The above codes cannot result in a flashing LED indicator. Actually, the connection between ledTimer and setLEDFlashingTimerHandler does NOT take effect for some reason, and m_value is not updated in paintEvent. Anyone can help debug my codes? Thanks!
Edits:
I have solved the connection issue by using QTimer *ledTimer in stead of QTimer ledTimer. But the painting still not works as expected, since m_value is not updated in that function or the function is only invoked for the very first time?
In your function QLed::setLEDFlashing, you create a local instance of QTimer which will be destroyed at the end of your function.
You should declare your QTimer as an attribute of your class or use a inner timer with QObject::startTimer
I have a Window subclass in my project, and at runtime the instance is created and shown entirely on the QML side. I know that I can prevent the window from being minimized by not including the WindowMinimizeButtonHint in the flags:, but I actually need to have the minimize button present and enabled but be able to intercept the minimize button click, cancel the actual minimizing, and do something else (FYI my client is requiring this non-standard windowing behavior, not me).
So far, the only thing I've been able to achieve is to handle the onWindowStateChanged: event, check if windowState === Qt.WindowStateMinimized and call show() from a timer (calling it inside the event handler directly does nothing). This results in the window moving down to the system tray and then suddenly coming back up to normal.
Is there any way to do this, something like an OnMinimized event that can be cancelled?
Edit: based on Benjamin T's answer, I'm at least part way to a solution for OSX:
#import <AppKit/AppKit.h>
bool NativeFilter::nativeEventFilter(const QByteArray &eventType,
void *message, long *result)
{
if (eventType == "mac_generic_NSEvent") {
NSEvent *event = static_cast<NSEvent *>(message);
if ([event type] == NSKeyDown) {
return true;
}
}
return false;
}
In this example I'm able to intercept and cancel all NSKeyDown events (while leaving other events like mouse clicks etc. still working). The remaining problem is that I still don't know to intercept a minimize event - NSEvent.h doesn't seem to have anything that covers that. Perhaps I need to cast to a different type of event?
Edit 2 - working solution:
I was not able to find any way to intercept the minimize event proper and cancel it, so my workaround is to instead intercept the click on the window, determine if the click is over the minimize button (or the close or zoom buttons) and cancel the event if so (and send a notification to my qml window that the click occurred). I also handle the case of double-clicking the titlebar to zoom the window, and using the Command-M keys to minimize the window.
First step is to implement a QAbstractNativeEventFilter. In your header:
#include <QAbstractNativeEventFilter>
class NativeFilter : public QAbstractNativeEventFilter {
public:
bool nativeEventFilter(const QByteArray &eventType, void *message,
long *result);
};
The implementation:
#import <AppKit/AppKit.h>
#import <AppKit/NSWindow.h>
#import <AppKit/NSButton.h>
bool NativeFilter::nativeEventFilter(const QByteArray &eventType, void
*message, long *result)
{
if (eventType == "mac_generic_NSEvent") {
NSEvent *event = static_cast<NSEvent *>(message);
NSWindow *win = [event window];
// TODO: determine whether or not this is a window whose
// events you want to intercept. I did this by checking
// [win title] but you may want to find and use the
// window's id instead.
// Detect a double-click on the titlebar. If the zoom button
// is enabled, send the full-screen message to the window
if ([event type] == NSLeftMouseUp) {
if ([event clickCount] > 1) {
NSPoint pt = [event locationInWindow];
CGRect rect = [win frame];
// event coordinates have y going in the opposite direction from frame coordinates, very annoying
CGFloat yInverted = rect.size.height - pt.y;
if (yInverted <= 20) {
// TODO: need the proper metrics for the height of the title bar
NSButton *btn = [win standardWindowButton:NSWindowZoomButton];
if (btn.enabled) {
// notify qml of zoom button click
}
return true;
}
}
}
if ([event type] == NSKeyDown) {
// detect command-M (for minimize app)
if ([event modifierFlags] & NSCommandKeyMask) {
// M key
if ([event keyCode] == 46) {
// notify qml of miniaturize button click
return true;
}
}
// TODO: we may be requested to handle keyboard actions for close and zoom buttons. e.g. ctrl-cmd-F is zoom, I think,
// and Command-H is hide.
}
if ([event type] == NSLeftMouseDown) {
NSPoint pt = [event locationInWindow];
CGRect rect = [win frame];
// event coordinates have y going in the opposite direction from frame coordinates, very annoying
CGFloat yInverted = rect.size.height - pt.y;
NSButton *btn = [win standardWindowButton:NSWindowMiniaturizeButton];
CGRect rectButton = [btn frame];
if ((yInverted >= rectButton.origin.y) && (yInverted <= (rectButton.origin.y + rectButton.size.height))) {
if ((pt.x >= rectButton.origin.x) && (pt.x <= (rectButton.origin.x + rectButton.size.width))) {
// notify .qml of miniaturize button click
return true;
}
}
btn = [win standardWindowButton:NSWindowZoomButton];
rectButton = [btn frame];
if (btn.enabled) {
if ((yInverted >= rectButton.origin.y) && (yInverted <= (rectButton.origin.y + rectButton.size.height))) {
if ((pt.x >= rectButton.origin.x) && (pt.x <= (rectButton.origin.x + rectButton.size.width))) {
// notify qml of zoom button click
return true;
}
}
}
btn = [win standardWindowButton:NSWindowCloseButton];
rectButton = [btn frame];
if ((yInverted >= rectButton.origin.y) && (yInverted <= (rectButton.origin.y + rectButton.size.height))) {
if ((pt.x >= rectButton.origin.x) && (pt.x <= (rectButton.origin.x + rectButton.size.width))) {
// notify qml of close button click
return true;
}
}
}
return false;
}
return false;
}
Then in main.cpp:
Application app(argc, argv);
app.installNativeEventFilter(new NativeFilter());
Generally speaking, you should use the event system ans not signal/slots to intercept events and changes.
The easiest way to do so is either to subclass the object you use and reimplement the appropriate event handler, or to use an event filter.
Since you are using QML, subclassing might be difficult as you don't have access to all Qt internal classes.
Here is what the code would look like when using event filtering.
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
auto root = engine.rootObjects().first();
root->installEventFilter(new EventFilter());
return app.exec();
}
class EventFilter : public QObject
{
Q_OBJECT
public:
explicit EventFilter(QObject *parent = nullptr);
bool eventFilter(QObject *watched, QEvent *event) override;
};
bool EventFilter::eventFilter(QObject *watched, QEvent *event)
{
if (event->type() == QEvent::WindowStateChange) {
auto e = static_cast<QWindowStateChangeEvent *>(event);
auto window = static_cast<QWindow *>(watched);
if (window->windowStates().testFlag(Qt::WindowMinimized)
&& ! e->oldState().testFlag(Qt::WindowMinimized))
{
// Restore old state
window->setWindowStates(e->oldState());
return true;
}
}
// Do not filter event
return false;
}
However, you will quickly run into the same issue that when using the signal/slot mechanism: Qt only notify you when the window has already been minimized. Meaning that restoring the window at this point will make a hide/show effect.
So you need to go deeper and you a native event filter.
The following code works on Windows, you should adapt it for macOS:
class NativeFilter : public QAbstractNativeEventFilter {
public:
bool nativeEventFilter(const QByteArray &eventType, void *message, long *result);
};
bool NativeFilter::nativeEventFilter(const QByteArray &eventType, void *message, long *result)
{
/* On Windows we interceot the click in the title bar. */
/* If we wait for the minimize event, it is already too late. */
#ifdef Q_OS_WIN
auto msg = static_cast<MSG *>(message);
// Filter out the event when the minimize button is pressed.
if (msg->message == WM_NCLBUTTONDOWN && msg->wParam == HTREDUCE)
return true;
#endif
/* Example macOS code from Qt doc, adapt to your need */
#ifdef Q_OS_MACOS
if (eventType == "mac_generic_NSEvent") {
NSEvent *event = static_cast<NSEvent *>(message);
if ([event type] == NSKeyDown) {
// Handle key event
qDebug() << QString::fromNSString([event characters]);
}
}
#endif
return false;
}
In your main():
QGuiApplication app(argc, argv);
app.installNativeEventFilter(new NativeFilter());
For more info, you can read the Qt documentation about QAbstractNativeEventFilter.
You may need to use QWindow::winId() to check to which window the native events are targeted.
As I am not a macOS developer, I do not know what you can do with NSEvent.
Also it seems the NSWindowDelegate class could be useful to you: https://developer.apple.com/documentation/appkit/nswindowdelegate
If you can retrieve a NSWindow from QWindow::winId(), you should be able to use it.
I have a problem if I want to display a video using QGLWidget. With one instance it works, but it doesn't and widgets are black with multi-occurrence (usage in QGridLayout for example).
I subclass QGLWidget that way to play a video (by refreshing the QPixmap I want to show using my setCurrentImage method):
class GLWidget : public QGLWidget
{
Q_OBJECT
public:
GLWidget(QGLWidget* shareWidget = 0, QWidget* parent = 0)
: QGLWidget(parent, shareWidget)
{
//...
// I do this because the QPixmap to refresh is produced in a different thread than UI thread.
connect(this, SIGNAL(updated()), this SLOT(update()));
}
//...
void setCurrentImage(const QPixmap& pixmap)
{
m_mutex.lock();
m_pixmap = pixmap;
m_mutex.unlock();
emit updated();
}
protected:
void initializeGL()
{
static const int coords[4][2] = {{ +1, -1 }, { -1, -1 }, { -1, +1 }, { +1, +1 }};
for(int j = 0; j < 4; ++j){
m_texCoords.append(QVector2D(j == 0 || j == 3, j == 0 || j == 1));
m_vertices.append(QVector2D(0.5 * coords[j][0], 0.5 * coords[j][1]));
}
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_TEXTURE_2D);
#define PROGRAM_VERTEX_ATTRIBUTE 0
#define PROGRAM_TEXCOORD_ATTRIBUTE 1
QGLShader* vShader = new QGLShader(QGLShader::Vertex, this);
const char* szVShaderCode = /*...*/;
vShader->compileSourceCode(szVShaderCode);
QGLShader *fShader = new QGLShader(QGLShader::Fragment, this);
const char* szFShaderCode = /*...*/;
fShader->compileSourceCode(szFShaderCode);
m_pProgram = new QGLShaderProgram(this);
m_pProgram->addShader(vShader);
m_pProgram->addShader(fShader);
m_pProgram->bindAttributeLocation("vertex", PROGRAM_VERTEX_ATTRIBUTE);
m_pProgram->bindAttributeLocation("texCoord", PROGRAM_TEXCOORD_ATTRIBUTE);
m_pProgram->link();
m_pProgram->bind();
m_pProgram->setUniformValue("texture", 0);
}
void paintGL()
{
qglClearColor(Qt::black);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// I use some uniform values to "modify" image
m_pProgram->setUniformValue(/*...*/);
//...
QMatrix4x4 m;
m.ortho(-0.5f, +0.5f, +0.5f, -0.5f, 4.0f, 15.0f);
m.translate(0.0f, 0.0f, -10.0f);
m_pProgram->setUniformValue("matrix", m);
m_pProgram->enableAttributeArray(PROGRAM_VERTEX_ATTRIBUTE);
m_pProgram->enableAttributeArray(PROGRAM_TEXCOORD_ATTRIBUTE);
m_pProgram->setAttributeArray(PROGRAM_VERTEX_ATTRIBUTE, m_vertices.constData());
m_pProgram->setAttributeArray(PROGRAM_TEXCOORD_ATTRIBUTE, m_texCoords.constData());
glBindTexture(GL_TEXTURE_2D, m_texture);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
void resizeGL(int iWidth, int iHeight)
{
glViewport(0, 0, iWidth, iHeight);
}
private slots:
void update()
{
QPixmap pixmap;
m_mutex.lock();
pixmap = m_pixmap;
m_mutex.unlock();
m_texture = bindTexture(pixmap, GL_TEXTURE_2D);
updateGL();
}
private:
QMutex m_mutex;
QPixmap m_pixmap;
QVector<QVector2D> m_vertices;
QVector<QVector2D> m_texCoords;
QGLShaderProgram* m_pProgram;
};
Then, to simulate a multi thread rendering (each thread produces its own video images), I wrote these little classes.
The image producer class:
class ImageProducer : public QThread
{
Q_OBJECT
public:
ImageProducer(QGLWidget* pGLWidget)
: QThread(pGLWidget), m_pGLWidget(pGLWidget)
{
m_pixmap = QPixmap("fileName.jpg");
m_bMustStop = false;
}
protected:
void run()
{
while(!m_bMustStop){
static_cast<GLWidget*>(m_pGLWidget)->setCurrentImage(m_pixmap);
// Simulate a frame rate
msleep(1000 / /*FRAME_RATE*/);
}
}
private:
QGLWidget* m_pGLWidget;
QPixmap m_pixmap;
bool m_bMustStop;
};
And the rendering class:
#define ROWS 1
#define COLS 1
class Window : public QWidget
{
public:
Window()
{
QGridLayout* pMainLayout = new QGridLayout(this);
setLayout(pMainLayout);
for(int i = 0; i < ROWS; ++i){
for(int j = 0; j < COLS; ++j){
QGLWidget* pGLWidget = new GLWidget();
pMainLayout->addWidget(pGLWidget, i, j);
ImageProducer* pImageProducer = new ImageProducer(pGLWidget);
pImageProducer->start();
}
}
}
};
Ok stop with code samples ^^ Problem is with ROWS = 1 and COLS = 1 (see Window class) it works, but I have black widgets with other values... I'm lost, what do I miss?
Thanks!
EDIT: (context is always multi-GLWidget instance, all works fine with only one)
Strange thing I just discover: I overrode QGLWidget's mouseMoveEvent (so, in my GLWidget class) which simply calls updateGL();. And fact is when I press and move the mouse with the current code nothing happens. But if I replace (in my ImageProducer's run() method):
static_cast<GLWidget*>(m_pGLWidget)->setCurrentImage(m_pixmap);
By
static_cast<GLWidget*>(m_pGLWidget)->setCurrentImage(QPixmap("fileName.jpg"));
The image is refreshed in the current component as long as I move the mouse. When I release it, or do it in an other components, the background become black again.
I am writing down the answer after a chat with the OP, for the benefit of others. Here are the main topics that lead to a resolution of the issue.
Note: At the time of writing, the Qt OpenGL module is deprecated and its usage is discouraged. According to the official documentation the suggested approach is to use the OpenGL* classes in the GUI module.
Textures
The main issue with the code above is essentially due to the way the textures are handled.
First of all, the bindTexture() method does not bind in OpenGL terms, but actually create the OpenGL texture and upload the data passed as argument to it (QImage or QPixmap). That is confusing and can lead to serious issues. In the code posted by the OP, he is essentially leaking memory allocating a new texture at each frame update.
To ensure you are not leaking memory, you should at the least release the previously allocated texture, calling QGLWidget::deleteTexture.
However, it is worth to note that there are better approaches to avoid unnecessary memory fragmentation and inefficiency. In this case, the best approach is to allocate the texture once and simply update its content when necessary. This may not be possible directly with the API offered by the old Qt OpenGL module, but you can always mix Qt and native OpenGL code.
Context handling
Another issue is the way OpenGL context is handled. As a rule of thumb, one should always ensure the correct context is current before issuing commands to the OpenGL implementation. Sometimes, Qt does this for you automatically (i.e. before calling the paintGL() method).
In this case, we need to explicitly make the QGLWidget's context the current context before calling the bindTexture method, otherwise it will effect the last context that was made current. That is why only the last widget was showing something untill somewhone was triggering a makeCurrent call by interacting with the other widgets.
Threading
There are a couple of issues here. First of all, it is not safe to use a QPixmap object in a thread other than the GUI thread. QPixmap is designed to optimize pixmap blitting on screen. In this case, the pixmap is really just the frame to be uploaded to the OpenGL implementation, which handles all the rendering. So it is safe to use a QImage instead.
The other issue is that the GLWidget::setCurrentImage() and thus, the bindTexture method, are called directly from the run() method of the ImageProducer thread. This can't be because we need to make the widget context current, but it is not possible to call makeCurrent() from a thread other than the GUI thread (more details here).
A possible approach to solve this issue is to add a signal to ImageProducer to notify the frame has been updated, and connect this signal to the setCurrentImage() slot. Qt's signal-slot mechanism will ensure that the setCurrentImage is executed in the GLWidget thread, that is the GUI thread.
Code
Here are the suggested (and tested) modifications to the code posted above.
ImageProduer class
add the signal:
void imageUpdated(const QImage &image);
and emit it when the frame is updated:
void ImageProducer::run()
{
while(!m_bMustStop){
QImage frame(m_pixmap.width(), m_pixmap.height(), m_pixmap.format());
QPainter painter(&frame);
painter.drawImage(QPoint(), m_pixmap);
painter.setFont(QFont("sans-serif", 22));
painter.setPen(Qt::white);
painter.drawText(20, 50, QString("Frame: %1").arg(QString::number(_frameCount)));
painter.end();
emit imageUpdated(frame);
msleep(1000 / FRAME_RATE);
_frameCount++;
}
}
GLWidget class
ensure the setCurrentImage method handle the OpenGL context and destroy the old texture:
void GLWidget::setCurrentImage(const QImage& pixmap)
{
m_mutex.lock();
m_pixmap = pixmap;
m_mutex.unlock();
makeCurrent();
deleteTexture(m_texture);
m_texture = bindTexture(pixmap, GL_TEXTURE_2D);
doneCurrent();
emit updated();
}
I am starting a QT5 application with a rather complex design based on Qt Widgets. It runs on Beagleboard with a touchscreen. I will have a rather weird local invention instead of the LCD display. It's a laser painting on acrylic plate. It has no driver yet. To actually update a screen I must create a screenshot of the window as bitmap, turn it to grayscale and feed to a proprietary library, which will handle the laser. It should look cute, when ready. Unfortunately, the laser blinks on update, so I cannot just make screenshots on timer, or it will be jerky like hell.
I need to run a function every time a meaningful update of GUI happens, while preferably ignore things like button being pressed and released. Is there some way to create a hook without subclassing every single Qt Widget I will use? The only way to do this I know is to override paintEvent of everything. I want a simpler solution.
Possible assumptions are: the application will be running under X server with dummy display, will be the only GUI app running. Some updates happen without user input.
The code below does it. It doesn't dig too deeply into the internals of Qt, it merely leverages the fact that backing store devices are usually QImages. It could be modified to accommodate OpenGL-based backing stores as well.
The WidgetMonitor class is used to monitor the widgets for content changes. An entire top-level window is monitored no matter which particular widget is passed to the monitor(QWidget*) method. You only need to call the monitor method for one widget in the window you intend to monitor - any widget will do. The changes are sent out as a QImage of window contents.
The implementation installs itself as an event filter in the target window widget and all of its children, and monitors the repaint events. It attempts to coalesce the repaint notifications by using the zero-length timer. The additions and removals of children are tracked automagically.
When you run the example, it creates two windows: a source window, and a destination window. They may be overlapped so you need to separate them. As you resize the source window, the size of the destination's rendition of it will also change appropriately. Any changes to the source children (time label, button state) propagate automatically to the destination.
In your application, the destination could be an object that takes the QImage contents, converts them to grayscale, resizes appropriately, and passes them to your device.
I do not quite understand how your laser device works if it can't gracefully handle updates. I presume that it is a raster-scanning laser that runs continuously in a loop that looks roughly like this:
while (1) {
for (line = 0; line < nLines; ++line) {
drawLine();
}
}
You need to modify this loop so that it works as follows:
newImage = true;
QImage localImage;
while (1) {
if (newImage) localImage = newImage;
for (line = 0; line < localImage.height(); ++line) {
drawLine(line, localImage);
}
}
You'd be flipping the newImage flag from the notification slot connected to the WidgetMonitor. You may well find out that leveraging QImage, and Qt's functionality in general, in your device driver code, will make it much easier to develop. Qt provides portable timers, threads, collections, etc. I presume that your "driver" is completely userspace, and communicates via a serial port or ethernet to the micro controller that actually controls the laser device.
If you will be writing a kernel driver for the laser device, then the interface would be probably very similar, except that you end up writing the image bitmap to an open device handle.
// https://github.com/KubaO/stackoverflown/tree/master/questions/surface-20737882
#include <QtWidgets>
#include <array>
const char kFiltered[] = "WidgetMonitor_filtered";
class WidgetMonitor : public QObject {
Q_OBJECT
QVector<QPointer<QWidget>> m_awake;
QBasicTimer m_timer;
int m_counter = 0;
void queue(QWidget *window) {
Q_ASSERT(window && window->isWindow());
if (!m_awake.contains(window)) m_awake << window;
if (!m_timer.isActive()) m_timer.start(0, this);
}
void filter(QObject *obj) {
if (obj->isWidgetType() && !obj->property(kFiltered).toBool()) {
obj->installEventFilter(this);
obj->setProperty(kFiltered, true);
}
}
void unfilter(QObject *obj) {
if (obj->isWidgetType() && obj->property(kFiltered).toBool()) {
obj->removeEventFilter(this);
obj->setProperty(kFiltered, false);
}
}
bool eventFilter(QObject *obj, QEvent *ev) override {
switch (ev->type()) {
case QEvent::Paint: {
if (!obj->isWidgetType()) break;
if (auto *window = static_cast<QWidget *>(obj)->window()) queue(window);
break;
}
case QEvent::ChildAdded: {
auto *cev = static_cast<QChildEvent *>(ev);
if (auto *child = qobject_cast<QWidget *>(cev->child())) monitor(child);
break;
}
default:
break;
}
return false;
}
void timerEvent(QTimerEvent *ev) override {
if (ev->timerId() != m_timer.timerId()) return;
qDebug() << "painting: " << m_counter++ << m_awake;
for (auto w : m_awake)
if (auto *img = dynamic_cast<QImage *>(w->backingStore()->paintDevice()))
emit newContents(*img, w);
m_awake.clear();
m_timer.stop();
}
public:
explicit WidgetMonitor(QObject *parent = nullptr) : QObject{parent} {}
explicit WidgetMonitor(QWidget *w, QObject *parent = nullptr) : QObject{parent} {
monitor(w);
}
Q_SLOT void monitor(QWidget *w) {
w = w->window();
if (!w) return;
filter(w);
for (auto *obj : w->findChildren<QWidget *>()) filter(obj);
queue(w);
}
Q_SLOT void unMonitor(QWidget *w) {
w = w->window();
if (!w) return;
unfilter(w);
for (auto *obj : w->findChildren<QWidget *>()) unfilter(obj);
m_awake.removeAll(w);
}
Q_SIGNAL void newContents(const QImage &, QWidget *w);
};
class TestWidget : public QWidget {
QVBoxLayout m_layout{this};
QLabel m_time;
QBasicTimer m_timer;
void timerEvent(QTimerEvent *ev) override {
if (ev->timerId() != m_timer.timerId()) return;
m_time.setText(QTime::currentTime().toString());
}
public:
explicit TestWidget(QWidget *parent = nullptr) : QWidget{parent} {
m_layout.addWidget(&m_time);
m_layout.addWidget(new QLabel{"Static Label"});
m_layout.addWidget(new QPushButton{"A Button"});
m_timer.start(1000, this);
}
};
int main(int argc, char **argv) {
QApplication app{argc, argv};
TestWidget src;
QLabel dst;
dst.setFrameShape(QFrame::Box);
for (auto *w : std::array<QWidget *, 2>{&dst, &src}) {
w->show();
w->raise();
}
QMetaObject::invokeMethod(&dst, [&] { dst.move(src.frameGeometry().topRight()); },
Qt::QueuedConnection);
WidgetMonitor mon(&src);
src.setWindowTitle("Source");
dst.setWindowTitle("Destination");
QObject::connect(&mon, &WidgetMonitor::newContents, [&](const QImage &img) {
dst.resize(img.size());
dst.setPixmap(QPixmap::fromImage(img));
});
return app.exec();
}
#include "main.moc"
I have a custom QWidget (actually, derived from QAbstractButton) for which I have to implement my own paintEvent. How to I use the style sheet information?
For example, suppose someone defines the following stylesheet that applies (directly or via inheritance) to my custom class:
QAbstractButton { font-weight: bold; background-color: red }
QAbstractButton:checked { background-color: blue }
In my paintEvent method, how do I get the correct background color to show up for the checked state?
void MyButton::paintEvent(QPaintEvent */*event*/) {
ensurePolished(); // Don't think this is necessary...
qDebug() << Q_FUNC_INFO << isChecked(); // This is showing the right value
QStylePainter painter(this);
painter.fillRect(rect(), painter.background()); // always red, even if checked
}
I assume I have to something like:
if (isChecked()) {
// painter.fillRect(rect(), ???);
//
// style()->drawPrimitive(???, ...);
//
// QStyleOptionButton opt;
// opt.initFrom(this);
// QBrush bg_brush = opt.???
// painter.fillRect(rect(), bg_brush);
//
// ???
} else {
painter.fillRect(rect(), painter.background());
}
How do I get the brush to use for the checked-state background that Qt resolved from the style sheets?
I never could find out how to get the resolved color (and padding) information, but was able to work around it by painting sub-elements of other widgets into mine. This isn't exactly what I was trying to do, and may not work in other cases (if your widget can't be composed by mashing together stuff that Qt does know how to draw).
void MyButton::paintEvent(QPaintEvent */*event*/) {
QStylePainter painter(this);
QStyleOptionButton opt;
opt.initFrom(this);
opt.state |= isChecked() ? QStyle::State_On : QStyle::State_Off;
opt.text = text();
painter.drawPrimitive(QStyle::PE_Widget, opt);
QStyleOptionButton label_opt = opt;
label_opt.rect =
style()->subElementRect(QStyle::SE_CheckBoxContents, &opt, this);
painter.drawControl(QStyle::CE_CheckBoxLabel, label_opt);
// ... etc.
}
I still think there has to be a better way.