I have an example of QGraphicsWidget. i want to added a tow button , a button for Zoom In , and a button for the Zoom out . the code :
#include "myGraphicsWidget.h"
int main(int argc,char* argv[])
{
QApplication app(argc,argv);
QGraphicsScene scene;
myGraphicsWidget* graphicsWidget = new myGraphicsWidget("This is My Custom\n QGraphicsWidget!!");
QGraphicsView view(&scene);
scene.addItem(graphicsWidget);
view.showFullScreen();
return app.exec
();
}
please write to me a function (slot) for Zoom .
You need to override the wheelEvent or create a button that handle the scale of the QGraphicsView:
void myGraphicsWidget::wheelEvent(QWheelEvent *event)
{
qreal zoomFactor = 1.15;
if (event->delta() > 0 && zoomLevel < 20) {
// Zoom In
scale(zoomFactor, zoomFactor);
} else if (event->delta() < 0 && zoomLevel > 0) {
// Zooming out
scale(1.0 / zoomFactor, 1.0 / zoomFactor);
}
scrollViewTo(event->pos());
}
for a Slot, that would be the same - but you would need to separate the code for zoomIn and zoomOut.
Related
I read a lot of posts/threads but I can't get it to work.
I'd like to fit every Image to a GraphicsView regardless if it is smaller or bigger then the view.
What's wrong?
void frmMain::on_btLoadImage_clicked()
{
QGraphicsScene *scene;
QPixmap image;
QString imgPath = "O:/IMG_0001.JPG";
QRectF sceneRect = ui->imgMain->sceneRect();
image.load(imgPath);
image.scaled (sceneRect.width (),sceneRect.height (), Qt::KeepAspectRatio, Qt::SmoothTransformation);
scene = new QGraphicsScene(this);
scene->addPixmap(image);
scene->setSceneRect(sceneRect); //image.rect());
//ui->imgMain->fitInView (scene->itemsBoundingRect(), Qt::KeepAspectRatio); //ui->imgMain->width (), ui->imgMain->height ());
ui->imgMain->setScene(scene);
}
Here is a basic custom QGraphicsView implementation which displays one image and keeps it sized/scaled to fit the available viewport space. Note that the image needs to be rescaled every time the viewport size changes, which is why it is simplest to reimplement the QGraphicsView itself and change the scaling in resizeEvent(). Although it could be done inside a custom QGraphicsScene instead. (Or, really, a number of other ways depending on the exact needs.)
The same technique could be used to keep a QGraphicsWidget as the root item in the scene to always take up the full space. Then a layout could be used in the widget to keep children aligned/resized/positioned/etc.
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsPixmapItem>
class GrpahicsImageView : public QGraphicsView
{
Q_OBJECT
public:
using QGraphicsView::QGraphicsView;
public slots:
void setImage(const QString &imageFile)
{
if (m_imageFile != imageFile) {
m_imageFile = imageFile;
loadImage(viewport()->contentsRect().size());
}
}
void setImageScaleMode(int mode)
{
if (m_scaleMode != Qt::AspectRatioMode(mode)) {
m_scaleMode = Qt::AspectRatioMode(mode);
if (m_item)
loadImage(viewport()->contentsRect().size());
}
}
void loadImage(const QSize &size)
{
if (!scene())
return;
if (m_imageFile.isEmpty()) {
// remove existing image, if any
removeItem();
return;
}
// Load image at original size
QPixmap pm(m_imageFile);
if (pm.isNull()) {
// file not found/other error
removeItem();
return;
}
// Resize the image here.
pm = pm.scaled(size, m_scaleMode, Qt::SmoothTransformation);
if (createItem())
m_item->setPixmap(pm);
}
protected:
void resizeEvent(QResizeEvent *e) override
{
QGraphicsView::resizeEvent(e);
if (!scene())
return;
// Set scene size to fill the available viewport size;
const QRect sceneRect(viewport()->contentsRect());
scene()->setSceneRect(sceneRect);
// Keep the root item sized to fill the viewport and scene;
if (m_item)
loadImage(sceneRect.size());
}
private:
bool createItem() {
if (m_item)
return true;
if (!m_item && scene()) {
m_item = new QGraphicsPixmapItem();
scene()->addItem(m_item);
return true;
}
return false;
}
void removeItem()
{
if (m_item) {
if (scene())
scene()->removeItem(m_item);
delete m_item;
m_item = nullptr;
}
}
Qt::AspectRatioMode m_scaleMode = Qt::KeepAspectRatio;
QString m_imageFile;
QGraphicsPixmapItem *m_item = nullptr;
};
Usage example:
#include <QApplication>
#include <QtWidgets>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDialog d;
d.setLayout(new QVBoxLayout);
d.resize(350, 350);
GrpahicsImageView *view = new GrpahicsImageView(new QGraphicsScene, &d);
QComboBox *imgCb = new QComboBox(&d);
imgCb->addItems({
"./so-logo.png",
"./se-logo.png",
"./su-logo.png"
});
QComboBox *scaleCb = new QComboBox(&d);
scaleCb->addItems({
"IgnoreAspectRatio",
"KeepAspectRatio",
"KeepAspectRatioByExpanding"
});
QHBoxLayout *cbLayout = new QHBoxLayout;
cbLayout->setSpacing(9);
cbLayout->addWidget(imgCb);
cbLayout->addWidget(scaleCb);
d.layout()->addItem(cbLayout);
d.layout()->addWidget(view);
QObject::connect(imgCb, QOverload<const QString &>::of(&QComboBox::currentIndexChanged), view, &GrpahicsImageView::setImage);
QObject::connect(scaleCb, QOverload<int>::of(&QComboBox::currentIndexChanged), view, &GrpahicsImageView::setImageScaleMode);
view->setImageScaleMode(scaleCb->currentIndex());
view->setImage(imgCb->currentText());
return d.exec();
}
https://cdn.sstatic.net/Sites/stackoverflow/company/img/logos/so/so-logo.png
https://cdn.sstatic.net/Sites/stackoverflow/company/img/logos/so/se-logo.png
https://cdn.sstatic.net/Sites/stackoverflow/company/img/logos/so/su-logo.png
I have a window, in which is a QGraphicsView, which will be displaying an image. I have implemented the wheelEvent(). My images are mostly going to be bigger than the window, so I get scroll bars in the window.
What we normally observe when we rotate the wheel while viewing an image in Windows Photo Viewer is that when we move the wheel up (towards it's wire), the image zooms in and when we move it down (towards out body), the image zooms out.
What I am getting instead is when I move the wheel towards myself (to zoom out) the image instead of zooming out , first scrolls down, and starts zooming out only when the scroll bar touches its bottom most point.
It would be better to understand the problem by trying out the code. I am not able to explain in I guess.
I want the standard behavior. What to do?
Code
#include "viewer.h"
#include "ui_viewer.h"
#include <QGraphicsView>
#include <QGraphicsItem>
#include <QGraphicsPixmapItem>
#include <QWheelEvent>
#include <QDebug>
#include <QImage>
#include <QImageReader>
#include <QApplication>
#include <QDesktopWidget>
viewer::viewer(QWidget *parent) : QWidget(parent),ui2(new Ui::viewer)
{
ui2->setupUi(this);
}
viewer::~viewer()
{
delete ui2;
}
int viewer::show_changes(QString folder)
{
QDesktopWidget *desktop = QApplication::desktop();
int screenWidth = desktop->width();
int screenHeight = desktop->height();
QString filename = "image_bigger_than_window.jpg";
QPixmap pixmap = QPixmap(filename);
QImageReader reader(filename);
QImage image = reader.read();
QSize size = image.size();
int width = 800;
int height = (width * size.height()) / size.width();
int x = (screenWidth - width) / 2;
int y = (screenHeight - height) / 2 - 30;
setGeometry(x,y,width, height);
setWindowTitle("OUTPUT");
ui2->graphicsView->setGeometry(0,0,width,height);
QGraphicsScene* viewScene = new QGraphicsScene(QRectF(0, 0,width, height), 0);
QGraphicsPixmapItem *item = viewScene->addPixmap(pixmap.scaled(QSize((int)viewScene->width(), (int)viewScene->height()),
Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
viewScene->addItem(item);
ui2->graphicsView->fitInView(QRectF(0, 0, width, height),Qt::IgnoreAspectRatio);
ui2->graphicsView->setScene(viewScene);
ui2->graphicsView->show();
return 0;
}
void viewer::wheelEvent(QWheelEvent * event)
{
const int degrees = event->delta() / 8;
qDebug() << degrees;
int steps = degrees / 15;
double scaleFactor = 1.0;
const qreal minFactor = 1.0;
const qreal maxFactor = 10.0;
qreal h11 = 1.0, h22 = 0;
if(steps > 0)
{
h11 = (h11 >= maxFactor) ? h11 : (h11 + scaleFactor);
h22 = (h22 >= maxFactor) ? h22 : (h22 + scaleFactor);
}
else
{
h11 = (h11 <= minFactor) ? minFactor : (h11 - scaleFactor);
h22 = (h22 <= minFactor) ? minFactor : (h22 - scaleFactor);
}
ui2->graphicsView->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
ui2->graphicsView->setTransform(QTransform(h11, 0, 0,0, h22, 0, 0,0,1));
}
EDIT
1)Removed function void viewer::wheelEvent(QWheelEvent * event) from viewer.cpp
2)Put bool viewer::eventFilter(QObject *obj, QEvent *event) in its place as a protected function and void viewer::handleWheelOnGraphicsScene(QGraphicsSceneWheelEvent* scrollevent) as a public slot in viewer.h
bool viewer::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::GraphicsSceneWheel)
{
QGraphicsSceneWheelEvent *scrollevent = static_cast<QGraphicsSceneWheelEvent *>(event);
handleWheelOnGraphicsScene(scrollevent);
return true;
}
// Other events should propagate - what do you mean by propagate here?
return false;
}
void viewer::handleWheelOnGraphicsScene(QGraphicsSceneWheelEvent* scrollevent)
{
const int degrees = scrollevent->delta() / 8;
qDebug() << degrees;
int steps = degrees / 15;
qDebug() << steps;
double scaleFactor = 1.0; //How fast we zoom
const qreal minFactor = 1.0;
const qreal maxFactor = 10.0;
if(steps > 0)
{
h11 = (h11 >= maxFactor) ? h11 : (h11 + scaleFactor);
h22 = (h22 >= maxFactor) ? h22 : (h22 + scaleFactor);
}
else
{
h11 = (h11 <= minFactor) ? minFactor : (h11 - scaleFactor);
h22 = (h22 <= minFactor) ? minFactor : (h22 - scaleFactor);
}
ui2->graphicsView->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
ui2->graphicsView->setTransform(QTransform(h11, 0, 0,0, h22, 0, 0,0,1));
}
The code shows that you didn't subclass QGraphicsView, but instead use one in your own widget.
The wheel event will be first sent to the actual graphics view widget. There it is handled with Qt's default behaviour, namely scrolling. Only if you scrolled to the bottom, the graphics view cannot handle the wheel event, and it is propagated to its parent, your class. That's why you only can zoom when scrolled to the border.
To fix this, you should install an event filter. That allows you to intercept the wheel event and process it in your class:
// Outline, not tested
viewer::viewer(QWidget *parent) : QWidget(parent),ui2(new Ui::viewer)
{
ui2->setupUi(this);
// Let me handle your events
ui2->graphicsView->installEventFilter(this);
}
// should be protected
bool viewer::eventFilter(QObject *obj, QEvent *event) {
if (event->type() == QEvent::GraphicsSceneWheel) {
// Your implementation.
// You can't use QWheelEvent, as Graphicscene works with its own events...
handleWheelOnGraphicsScene(static_cast<QGraphicsSceneWheelEvent*> (event));
// Don't propagate
return true;
}
// Other events should propagate
return false;
}
Update
I just figured out that the event filter will not recieve GraphicsSceneWheel events on the graphics view. Instead, you have to install the filter on the Graphics Scene. Also, you have to call event->accept() so that it will not propagated.
So Updated Code:
// In Constructor, or where appropriate
ui2->graphicsView->scene()->installEventFilter(this);
bool viewer::eventFilter(QObject *obj, QEvent *event) {
if (event->type() == QEvent::GraphicsSceneWheel) {
handleWheelOnGraphicsScene(static_cast<QGraphicsSceneWheelEvent*> (event));
// Don't propagate
event->accept();
return true;
}
return false;
}
also note that handleWheelOnGraphicsScene or whatever you want to call it, should be a private method, and doesn't have to be a slot.
I would like to programmatically scroll a scene to the left / right, but I am not sure how to do that properly. Note that I do not want to have (visible) scroll bars.
I use a standard QGraphicsView + QGraphicsScene + QGraphicsItem setup. I have downsized it to the minimum, with one single QGraphicsItem (a QGraphicsRectItem) in the scene.
I have managed to achieve programmatic scrolling by setting my view like this:
// view setup
view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
and then, in another part of the code:
// programmatic scrolling
QScrollBar* const sb = view->horizontalScrollBar();
sb->setRange(0, 1000); // some values for experimenting
sb->setValue(sb->value() + 100 or -100); // some increment for experimenting
This works, but... scrolling through invisible scrollbars doesn't feel right.
I tried this more straightforward approach:
// programmatic scrolling - doesn't quite work
view->viewport()->scroll(100 or -100, 0); // some increment for experimenting
This code does scroll, but when the rectangle goes off the left edge of the view, and I reverse the scrolling direction (increment changed from 100 to -100 in the call to scroll()), the uncovered part of the rectangle is not repainted. The reason is that QGraphicsRectItem::paint() is not called in that case (it is called when using the scrollbar method).
So, is there a way to get viewport()->scroll() work? Or some other simple way to achieve programmatic scrolling? Or is the artificial scrollbar method just the way to go?
Moving the view assumes that it's smaller than its scene. If they're the same size, it won't move.
QGraphicsView can be set to centerOn any position in scene coordinates. Use a timer to call centerOn to move the view one frame at a time.
Here's a working example: -
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsRectItem>
#include <QTimer>
class MyView : public QGraphicsView
{
private:
public:
MyView(QGraphicsScene* pScene)
: QGraphicsView(pScene, NULL)
{}
void AnimateBy(int x)
{
float updateFrequency = (1000/30.0); // ~30 frames per second
QPointF currScenePos = sceneRect().center();
int curX = currScenePos.x();
int endPos = curX + x;
int distanceToAnimate = (endPos - curX);
// speed = dist / time
float updatePosInterval = (float)distanceToAnimate / updateFrequency;
printf("updatePosInterval: %f \n", updatePosInterval);
static float newXPos = sceneRect().center().x();
QTimer* pTimer = new QTimer;
QObject::connect(pTimer, &QTimer::timeout, [=](){
newXPos += updatePosInterval;
centerOn(newXPos, sceneRect().center().y());
// check for end position or time, then....
if(newXPos >= endPos)
{
pTimer->stop();
pTimer->deleteLater();
}
});
pTimer->start(updateFrequency);
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGraphicsScene scene(0, 0, 10000, 20000);
MyView* view = new MyView(&scene);
QGraphicsRectItem* pRect = new QGraphicsRectItem(0, 0, 100, 100);
pRect->setPos(scene.width()/2, scene.height()/2);
scene.addItem(pRect);
// timer to wait for the window to appear, before starting to move
QTimer* pTimer = new QTimer;
pTimer->setSingleShot(true);
QObject::connect(pTimer, &QTimer::timeout,[=](){
view->centerOn(pRect); // centre on the rectangle
view->AnimateBy(100);
pTimer->deleteLater();
});
pTimer->start(1000);
view->show();
return a.exec();
}
So, we create the animation by moving the view frame-by-frame using the call to centerOn.
For simplicity, the code just deals with moving in one axis. To move in 2 axis, use 2D vector maths to calculate the interval position.
Try to change the view transformation with the QGraphicsView::translate() or QGraphicsView::setTransform().
But keep in mind that you can't move the viewport "outside" the scene, so make sure that your scene rectangle is large enough.
If I got your question correctly, there is a dojo classes library with such class as PanWebView that allow QWebView to scroll smoothly with mouse without any scrollbars. Take a look at sources. It supports panning and can be suitable for mobile apps, but maybe it'll help you too.
PanWebView class looks like this
#include <QWebView>
#include <QWebFrame>
#include <QMouseEvent>
#include <QApplication>
class PanWebView : public QWebView
{
Q_OBJECT
private:
bool pressed;
bool scrolling;
QPoint position;
QPoint offset;
QList<QEvent*> ignored;
public:
PanWebView(QWidget *parent = 0): QWebView(parent), pressed(false), scrolling(false) {
QWebFrame *frame = page()->mainFrame();
frame->setScrollBarPolicy(Qt::Vertical, Qt::ScrollBarAlwaysOff);
frame->setScrollBarPolicy(Qt::Horizontal, Qt::ScrollBarAlwaysOff);
}
protected:
void mousePressEvent(QMouseEvent *mouseEvent) {
if (ignored.removeAll(mouseEvent))
return QWebView::mousePressEvent(mouseEvent);
if (!pressed && !scrolling && mouseEvent->modifiers() == Qt::NoModifier)
if (mouseEvent->buttons() == Qt::LeftButton) {
pressed = true;
scrolling = false;
position = mouseEvent->pos();
QWebFrame *frame = page()->mainFrame();
int x = frame->evaluateJavaScript("window.scrollX").toInt();
int y = frame->evaluateJavaScript("window.scrollY").toInt();
offset = QPoint(x, y);
QApplication::setOverrideCursor(Qt::OpenHandCursor);
return;
}
return QWebView::mousePressEvent(mouseEvent);
}
void mouseReleaseEvent(QMouseEvent *mouseEvent) {
if (ignored.removeAll(mouseEvent))
return QWebView::mouseReleaseEvent(mouseEvent);
if (scrolling) {
pressed = false;
scrolling = false;
QApplication::restoreOverrideCursor();
return;
}
if (pressed) {
pressed = false;
scrolling = false;
QMouseEvent *event1 = new QMouseEvent(QEvent::MouseButtonPress,
position, Qt::LeftButton,
Qt::LeftButton, Qt::NoModifier);
QMouseEvent *event2 = new QMouseEvent(*mouseEvent);
ignored << event1;
ignored << event2;
QApplication::postEvent(this, event1);
QApplication::postEvent(this, event2);
QApplication::restoreOverrideCursor();
return;
}
return QWebView::mouseReleaseEvent(mouseEvent);
}
void mouseMoveEvent(QMouseEvent *mouseEvent) {
if (scrolling) {
QPoint delta = mouseEvent->pos() - position;
QPoint p = offset - delta;
QWebFrame *frame = page()->mainFrame();
frame- >evaluateJavaScript(QString("window.scrollTo(%1,%2);").arg(p.x()).arg(p.y()));
return;
}
if (pressed) {
pressed = false;
scrolling = true;
return;
}
return QWebView::mouseMoveEvent(mouseEvent);
}
};
And usage:
PanWebView web;
web.setUrl(QUrl("http://news.google.com"));
web.setWindowTitle("Web View - use mouse to drag and pan around");
web.show();
Also did you check this and this topics? I think it can be usefull.
I would like to create coordinate points on a QGraphicsView. When the mouse hovers over the point, the coordinate will be shown.
I draw the coordinates by QGraphicsEllipseItem. In order to enable the hover event, I need to re-implement the QGraphicsEllipseItem. However, because the size of the QGraphicsEllipseItem is fixed when it was constructed, the hover text is not shown properly. How can I deal with this?
Here is my code:
The MainWindow:
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
view = new QGraphicsView(this);
view->setRenderHint(QPainter::Antialiasing);
scene = new QGraphicsScene(this);
view->fitInView(scene->sceneRect(), Qt::KeepAspectRatio);
view->setScene(scene);
setCentralWidget(view);
for (int y = 0; y < 900; y += 100)
for(int x = 0; x < 1400; x += 100)
drawPoint(x, y);
}
void MainWindow::drawPoint(int x, int y)
{
CoordinatePoint* point = new CoordinatePoint();
point->setRect(QRect(x, y, 3, 3));
point->setPen(QPen(Qt::red, 3, Qt::SolidLine));
point->setBrush(Qt::red);
scene->addItem(point);
}
The re-implement QGraphicsEllipseItem:
CoordinatePoint::CoordinatePoint(QGraphicsItem* parent)
:QGraphicsEllipseItem(parent)
{
setAcceptHoverEvents(true);
}
void CoordinatePoint::hoverEnterEvent(QGraphicsSceneHoverEvent* event)
{
hover = true;
mx = event->pos().x();
my = event->pos().y();
update();
}
void CoordinatePoint::hoverLeaveEvent(QGraphicsSceneHoverEvent* event)
{
hover = false;
update();
}
void CoordinatePoint::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget)
{
QGraphicsEllipseItem::paint(painter, option, widget);
if (hover)
{
painter->save();
painter->setPen(Qt::black);
painter->setBrush(Qt::black);
painter->drawText(mx + 2, my + 2,
"(" + QString::number(mx) + "," +
QString::number(my) + ")");
painter->restore();
}
}
I think that using a separate child item for the text will make your life a lot easier:
#include <QtWidgets>
class CoordinatePoint : public QGraphicsEllipseItem
{
public:
CoordinatePoint(QGraphicsItem* parent = Q_NULLPTR) :
QGraphicsEllipseItem(parent),
coordinateText(Q_NULLPTR)
{
setAcceptHoverEvents(true);
}
void hoverEnterEvent(QGraphicsSceneHoverEvent*)
{
if (!coordinateText) {
coordinateText = new QGraphicsTextItem(this);
coordinateText->setPlainText("(" + QString::number(x())
+ "," + QString::number(y()) + ")");
coordinateText->setX(2);
coordinateText->setY(2);
}
coordinateText->setVisible(true);
}
void hoverLeaveEvent(QGraphicsSceneHoverEvent*)
{
if (coordinateText) {
coordinateText->setVisible(false);
}
}
private:
QGraphicsTextItem *coordinateText;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow window;
QGraphicsView *view = new QGraphicsView(&window);
view->setRenderHint(QPainter::Antialiasing);
QGraphicsScene *scene = new QGraphicsScene(&window);
view->fitInView(scene->sceneRect(), Qt::KeepAspectRatio);
view->setScene(scene);
window.setCentralWidget(view);
for (int y = 0; y < 900; y += 100) {
for(int x = 0; x < 1400; x += 100) {
CoordinatePoint* point = new CoordinatePoint();
point->setRect(QRect(0, 0, 3, 3));
point->setX(x);
point->setY(y);
point->setPen(QPen(Qt::red, 3, Qt::SolidLine));
point->setBrush(Qt::red);
scene->addItem(point);
}
}
window.show();
return a.exec();
}
If having an extra QGraphicsTextItem for each coordinate worries you, you could construct one of them and just share it amongst them all, reparenting it as each one is hovered. This should work fine, as there can only ever be one coordinate hovered at a time.
If you try to draw the text as part of the ellipse item, you'd have to:
Increase the size of the item so that it's large enough to contain the text, which means overriding boundingRect().
Only draw the ellipse within a certain part of that area.
In hoverEnterEvent(), check that the mouse cursor is within the ellipse's area.
A bunch of other stuff, probably.
I need to create an alpha transparent widget, it's basically a navigation bar with a shadow and the widgets below need to be partially visible through the shadow. The widget loads a PNG then draws it on the paint event. The problem is that the shadow is all black and is not alpha-transparent.
This is the code I'm currently using:
NavigationBar::NavigationBar(QWidget *parent) : XQWidget(parent) {
backgroundPixmap_ = new QPixmap();
backgroundPixmap_->load(FilePaths::skinFile("NavigationBarBackground.png"), "png");
setAttribute(Qt::WA_NoBackground, true); // This is supposed to remove the background but there's still a (black) background
}
void NavigationBar::paintEvent(QPaintEvent* event) {
QWidget::paintEvent(event);
QPainter painter(this);
int x = 0;
while (x < width()) {
painter.drawPixmap(x, 0, backgroundPixmap_->width(), backgroundPixmap_->height(), *backgroundPixmap_);
x += backgroundPixmap_->width();
}
}
Does anybody know what I need to change to make sure the widget is really transparent?
You're doing too much work :-)
The setAttribute call is not necessary. By default, a widget will not draw anything on its background (assuming Qt >= 4.1). Calling QWidget::paintEvent is also unnecessary - you don't want it to do anything.
Rather than doing the pattern fill yourself, let Qt do it with a QBrush:
NavigationBar::NavigationBar(QWidget *parent) : XQWidget(parent) {
backgroundPixmap_ = new QPixmap();
backgroundPixmap_->load(FilePaths::skinFile("NavigationBarBackground.png"), "png");
// debug check here:
if (!backgroundPixmap_->hasAlphaChannel()) {
// won't work
}
}
void NavigationBar::paintEvent(QPaintEvent* event) {
QPainter painter(this);
painter.fillRect(0, 0, width(), height(), QBrush(*backgroundPixmap));
}
Adjust the height parameter if you don't want the pattern to repeat vertically.
Are you sure your PNG file is actually transparent? The following (which is essentially what you are doing) is working for me. If this fails on your machine, perhaps include what version of Qt you are using, and what platform.
#include <QtGui>
class TransparentWidget : public QWidget {
public:
TransparentWidget()
: QWidget(),
background_pixmap_(":/semi_transparent.png") {
setFixedSize(400, 100);
}
protected:
void paintEvent(QPaintEvent *) {
QPainter painter(this);
int x = 0;
while (x < width()) {
painter.drawPixmap(x, 0, background_pixmap_);
x += background_pixmap_.width();
}
}
private:
QPixmap background_pixmap_;
};
class ParentWidget : public QWidget {
public:
ParentWidget() : QWidget() {
QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(new TransparentWidget);
layout->addWidget(new QPushButton("Button"));
setLayout(layout);
setBackgroundRole(QPalette::Dark);
setAutoFillBackground(true);
}
};
int main(int argc, char **argv) {
QApplication app(argc, argv);
ParentWidget w;
w.show();
return app.exec();
}