I create a custom QGraphicsItem. And overwrite the boundingRect() and paint().
QRectF myTile::boundingRect() const
{
return QRectF(xPos*10, yPos*10, 10, 10);
}
void myTile::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
QRectF rec = boundingRect();
int gvi = value * 255;
QColor gv(gvi, gvi, gvi, 255);
QBrush brush(gv);
painter->fillRect(rec, brush);
painter->drawRect(rec);
}
Then I use addItem() to add a item to a scene. Now I want to get it from the scene by its position. I find the itemAt function. But the problem is I don't know what is the const QTransform & deviceTransform. What should I use for the QTransform?.
Because I didn't implement any transform in the QGraphicsItem. This confuses me.
QGraphicsItem * QGraphicsScene::itemAt ( const QPointF & position, const QTransform & deviceTransform ) const
Returns the topmost visible item at the specified position, or 0 if
there are no items at this position. deviceTransform is the
transformation that applies to the view, and needs to be provided if
the scene contains items that ignore transformations. This function
was introduced in Qt 4.6.
So I would say, if you have the need to transform some items and ignore the others, you can simply go with the default value of QTransform() or even better the QGraphicsView::transform() const.
soo long zai
Related
I am having QGraphicsView, which has multiple QGraphicsItem's. On QGraphicsView I am performing multiple transformation like zoom-in, zoom-out, Fit-in etc.
In QGraphicsItem, I am having few rectangles and some polylines Every polyline has its own name written above it.
Whenever I zoom-in or zoom-out my view, I dont want to change my text size. It should remain same. For that I applied flag QGraphicsItem::ItemIgnoresTransformations.
But after applying this flag, whenever I zoomed-in text changes its position. Means in every zoom-in it should be just above the polyline. But it is changing it's position.
I have taken a help from link but still problem persist.
myText.cpp
myText::myText(const QString &text): QGraphicsSimpleTextItem(text)
{}
QRectF myText::boundingRect() const
{
QRectF b = QGraphicsSimpleTextItem::boundingRect();
return QRectF(b.x()-b.width()/2.0, b.y()-b.height()/2.0,
b.width(), b.height());
}
void myText::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
painter->translate(boundingRect().topLeft());
QGraphicsSimpleTextItem::paint(painter, option, widget);
painter->translate(-boundingRect().topLeft());
}
myClass.cpp
void myClass:: addText()
{
QGraphicsSimpleTextItem* text= new QGraphicsSimpleTextItem("Line 1");
text->setPos(QPointF(some points );
text->setDefaultTextColor(Qt::black);
text->setFlag(QGraphicsItem::ItemIgnoresTransformations, true);
scene->addItem(text);
}
So question is :
How to ensure that text should not change its position ?
I have a large log data (100, 1000, 100000, ... records) and I want to visualize it in the following manner:
Which widget (e.g. QListView, QListWidget) should I use and how, in order to stay away from performance and memory problems?
Is it possible to add a custom widget into a QListView?
Please, read about:
How to display a scrollable list with a substantial amount of widgets as items in a Qt C++ app?
I want to show every log message in the above format
Solution
To achieve the desired result and stay away from performance issues, even with a very long data log, use a QListView with a custom delegate:
Create a subclass of QStyledItemDelegate, say Delegate
Reimplement the QStyledItemDelegate::paint method to do the custom drawing
Reimplement the QStyledItemDelegate::sizeHint to report the correct size of the items in the list
Use the custom delegate in the view by calling QAbstractItemView::setItemDelegate
Example
I have prepared a working example for you in order to demonstrate how the proposed solution could be implemented and used in an application.
The essential part of the example is the way the delegate paints the items in the list view:
void Delegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
QStyleOptionViewItem opt(option);
initStyleOption(&opt, index);
const QPalette &palette(opt.palette);
const QRect &rect(opt.rect);
const QRect &contentRect(rect.adjusted(m_ptr->margins.left(),
m_ptr->margins.top(),
-m_ptr->margins.right(),
-m_ptr->margins.bottom()));
const bool lastIndex = (index.model()->rowCount() - 1) == index.row();
const bool hasIcon = !opt.icon.isNull();
const int bottomEdge = rect.bottom();
QFont f(opt.font);
f.setPointSize(m_ptr->timestampFontPointSize(opt.font));
painter->save();
painter->setClipping(true);
painter->setClipRect(rect);
painter->setFont(opt.font);
// Draw background
painter->fillRect(rect, opt.state & QStyle::State_Selected ?
palette.highlight().color() :
palette.light().color());
// Draw bottom line
painter->setPen(lastIndex ? palette.dark().color()
: palette.mid().color());
painter->drawLine(lastIndex ? rect.left() : m_ptr->margins.left(),
bottomEdge, rect.right(), bottomEdge);
// Draw message icon
if (hasIcon)
painter->drawPixmap(contentRect.left(), contentRect.top(),
opt.icon.pixmap(m_ptr->iconSize));
// Draw timestamp
QRect timeStampRect(m_ptr->timestampBox(opt, index));
timeStampRect.moveTo(m_ptr->margins.left() + m_ptr->iconSize.width()
+ m_ptr->spacingHorizontal, contentRect.top());
painter->setFont(f);
painter->setPen(palette.text().color());
painter->drawText(timeStampRect, Qt::TextSingleLine,
index.data(Qt::UserRole).toString());
// Draw message text
QRect messageRect(m_ptr->messageBox(opt));
messageRect.moveTo(timeStampRect.left(), timeStampRect.bottom()
+ m_ptr->spacingVertical);
painter->setFont(opt.font);
painter->setPen(palette.windowText().color());
painter->drawText(messageRect, Qt::TextSingleLine, opt.text);
painter->restore();
}
The complete code of the example is available on GitHub.
Result
As written, the given example produces the following result:
I have a QChartView which displays some 2D points which are representing each one a specific project I want to label each point with the project name AND NOT with it's x,y coordinates as the default behaviour
Is there any way to achieve override the function that creates or render the labels?
Why this could be difficult to achieve without changing the Qt source code
QXYSeries::setPointLabelsFormat wouldn't be of much help to you. It does indeed allow you to change the format of the labels, but the only variable part of it are the coordinates of the points.
All the drawing is done in the private part of the Qt classes. Here is the whole story:
The labels are drawn in the private part of QXYSeries (painter->drawText(position, pointLabel);):
void QXYSeriesPrivate::drawSeriesPointLabels(QPainter *painter, const QVector<QPointF> &points,
const int offset)
{
if (points.size() == 0)
return;
static const QString xPointTag(QLatin1String("#xPoint"));
static const QString yPointTag(QLatin1String("#yPoint"));
const int labelOffset = offset + 2;
painter->setFont(m_pointLabelsFont);
painter->setPen(QPen(m_pointLabelsColor));
QFontMetrics fm(painter->font());
// m_points is used for the label here as it has the series point information
// points variable passed is used for positioning because it has the coordinates
const int pointCount = qMin(points.size(), m_points.size());
for (int i(0); i < pointCount; i++) {
QString pointLabel = m_pointLabelsFormat;
pointLabel.replace(xPointTag, presenter()->numberToString(m_points.at(i).x()));
pointLabel.replace(yPointTag, presenter()->numberToString(m_points.at(i).y()));
// Position text in relation to the point
int pointLabelWidth = fm.width(pointLabel);
QPointF position(points.at(i));
position.setX(position.x() - pointLabelWidth / 2);
position.setY(position.y() - labelOffset);
painter->drawText(position, pointLabel);
}
}
drawSeriesPointLabels is called from the paint method of ScatterChartItem (this class is not included in the official documentation):
void ScatterChartItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
Q_UNUSED(option)
Q_UNUSED(widget)
if (m_series->useOpenGL())
return;
QRectF clipRect = QRectF(QPointF(0, 0), domain()->size());
painter->save();
painter->setClipRect(clipRect);
if (m_pointLabelsVisible) {
if (m_pointLabelsClipping)
painter->setClipping(true);
else
painter->setClipping(false);
m_series->d_func()->drawSeriesPointLabels(painter, m_points,
m_series->markerSize() / 2
+ m_series->pen().width());
}
painter->restore();
}
The ScatterChartItem in turn is created in the private part of QScatterSeries and can't be substituted with a custom class:
void QScatterSeriesPrivate::initializeGraphics(QGraphicsItem* parent)
{
Q_Q(QScatterSeries);
ScatterChartItem *scatter = new ScatterChartItem(q,parent);
m_item.reset(scatter);
QAbstractSeriesPrivate::initializeGraphics(parent);
}
What you might wanna try
Hide the original labels with setPointLabelsVisible(false); The labels will be drawn separately afterwards.
Subclass QChartView and reimplement the paintEvent, invoking first QChartView::paintEvent and then calling a custom function (lets say drawCustomLabels), which is a modified version of QXYSeriesPrivate::drawSeriesPointLabels. By calling drawCustomLabels pass:
a local painter drawing on the vieport of MyChartView,
the points as returned by QXYSeries::points,
the desired offset.
Here is an example of how the drawCustomLabels might look like:
void MyChartView::drawCustomLabels(QPainter *painter, const QVector<QPointF> &points, const int offset)
{
if (points.count() == 0)
return;
QFontMetrics fm(painter->font());
const int labelOffset = offset + 2;
painter->setFont(m_pointLabelsFont); // Use QXYSeries::pointLabelsFont() to access m_pointLabelsFont
painter->setPen(QPen(m_pointLabelsColor)); // Use QXYSeries::pointLabelsColor() to access m_pointLabelsColor
for (int n(0); n < points.count(); n++) {
QString pointLabel = "..."; // Set the desired label for the n-th point of the series
// Position text in relation to the point
int pointLabelWidth = fm.width(pointLabel);
QPointF position(points.at(n));
position.setX(position.x() - pointLabelWidth / 2);
position.setY(position.y() - labelOffset);
painter->drawText(position, pointLabel);
}
}
I'm trying to create customObject (rectangle and it inherit from QGraphicsItem) that will be painted on scene with ceratin text(stored in attribute), but when I scale it - i wish to keep same size of text. Here is my over. paint function:
void CustomRectangle::paint(QPainter *painter, const QStyleOptionGraphicsItem *options, QWidget *widget)
{
QColor currentColor = get_ColorByCurrentState();
QRectF rect = boundingRect();
QPen pen(currentColor, Own_LineWidith);
painter->setPen(pen);
painter->drawRect(rect);
QRectF rect_text(rect.x(), rect.y(),100,100);
painter->drawText(rect_text,this->getText() );
}
and my two scaling functions:
void CustomObject::scaleUp()
{
scale(ScaleFactor_X,ScaleFactor_Y);
}
void CustomObject::scaleDown()
{
scale(1/ScaleFactor_X,1/ScaleFactor_Y);
}
But text still keep scaling along with rectangle.
EDIT 1
I tried adding it another way, i nfucntion that creates and adds my rectangle to scene (here - named "newObject"), but result is still the same.
QGraphicsTextItem* GTI = new QGraphicsTextItem(newObject->toStringForScene(), newObject);
I'm beginign to think that I shoud create each text object as separeted object and save it different list. Ofcours, i would have to update it then, whenever it's object moved.
Try this:
QGraphicsTextItem* gti = new QgraphicsTextItem("text");
gti->setFont(QFont("Arial", 18));
// this is important
gti->setFlag(QGraphicsTextItem::ItemIgnoresTransformations, true);
scene->addItem(gti);
The QGraphicsItem::ItemIgnoresTransformations flag prevents your graphics item to be scaled when you scale your view (QGraphicsView).
That means that you need a separated item for rendering text. But it can be a child item of your rectangle item.
I resolved this with QGraphicsTextItem's poitner as class's attribute.
QGraphicsTextItem* GTI;
I initialzie it in constructor:
GTI_Description = new QGraphicsTextItem(this->toStringForScene());
and then I call function to updated it's X and Y:
void updateTextPosition()
{
GTI->setX( this->x() );
GTI->setY( this->y() );
}
and to add it to the scene:
addTextToScene(DragScene* _scene)
{
updateDescriptionPosition();
_scene->addItem(GTI_GTI);
_scene->update();
}
Then i just call updateTextPosition() whenerver I change positions (in my mouseRelease event's handler).
I'm looking for the most effective way to size a QGraphicsItem based on the length of a given QString, so that the text is always contained within the QGraphicsItem's boundaries. The idea is to keep the QGraphicsItem as small as possible, while still containing the text at a legible size. Wrapping onto multiple lines at a certain width threshold would be ideal as well. For example,
TestModule::TestModule(QGraphicsItem *parent, QString name) : QGraphicsPolygonItem(parent)
{
modName = name;
// what would be the best way to set these values?
qreal w = 80.0;
qreal h = 80.0;
QVector<QPointF> points = { QPointF(0.0, 0.0),
QPointF(w, 0.0),
QPointF(w, h),
QPointF(0.0, h) };
baseShape = QPolygonF(points);
setPolygon(baseShape);
}
void TestModule::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
QBrush *brush = new QBrush(Qt::gray, Qt::SolidPattern);
painter->setBrush(*brush);
painter->drawPolygon(baseShape);
painter->drawText(QPointF(0.0, 40.0), modName);
}
what code could I add to the constructor to make my requirement work? Setting the width based on the total length of the string, making assumptions for how much pixel space each character takes up is the most obvious solution, but I'm looking for something a little more elegant. Any ideas? Thank you in advance for any help.
The QFontMetrics class has a function called boundingRect which takes the string that you're wanting to print and returns the QRect for the string, based on the QFont that you used to initalise QFontMetrics.
If you want to wrap, then you'd need to work out the maximum number of words in your string that will allow boundingRect to return a QRect that fits within your QGraphicsItem's boundingRect.
Take a look to QFontMetrics
You can ask your widget for the font
And check this snippet from QFontMetrics docs
QFont font("times", 24);
QFontMetrics fm(font);
int pixelsWide = fm.width("What's the width of this text?");
int pixelsHigh = fm.height();
Edit: As Merlin said in comment, use
QRect QFontMetrics::boundingRect ( const QString & text ) const
So:
int pixelsWide = fm.boundingRect("What's the width of this text?").width();