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 ?
Related
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'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 made a small 2D level editor where you can create 2D tile based maps..however, the performance inside my application is really really bad. I am currently thinking to start all over again.
The Problem is, I currently use QGraphicsItem's to represent a single tile inside a QGraphicsScene. A tile has some properties..including an image. When a map is created, I create an item for each tile which draws an image for each tile..which basically is a lot of graphicitems and it slows down the whole application. This is the function that populates a map once it is created :
for(int i=0;i<map->m_rows;i++)
{
for(int j=0;j<map->m_cols;j++)
{
Tile* thetile=map->getAt(i,j);
if(thetile)
{
if(map->getType()==twoditor::RECTANGLETILE)
{
QGraphicsItem* item= new TileGraphicsItem(thetile);
m_scene->addItem(item);
}
else if(map->getType()==twoditor::HEXAGONTILE)
{
QGraphicsItem* item= new HexagonGraphicsItem(thetile);
m_scene->addItem(item);
}
}
}
}
This works for a map with 100x100 Tiles. But if i want to create even larger maps..the loading time is really unbearable..
Can someone give me advice for a better representation of a tile map? Are there other convenient ways to show a map and edit cells(tiles) inside it?
EDIT: TileGraphicItem paint function:
void TileGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget){
setZValue(0);
if(!m_thetile->getImage().isNull())
{
painter->drawImage(0,0,m_thetile->getImage());
}
QPainterPath circle_path;
QRect duwagrect(boundingRect().x(),boundingRect().y(),boundingRect().width(),boundingRect().height());
circle_path.addRect(duwagrect);
m_pen.setStyle(Qt::SolidLine);
m_pen.setColor(Qt::black);
m_pen.setWidth(1);
painter->setPen(m_pen);
painter->drawPath(circle_path);
if(m_thetile->getProperty()->getBlocks())
{
QPainterPath circle_path;
QRect duwagrect(boundingRect().x()+2,boundingRect().y()+2,boundingRect().width()-3,boundingRect().height()-3);
circle_path.addRect(duwagrect);
m_pen.setStyle(Qt::DotLine);
m_pen.setColor(Qt::red);
m_pen.setWidth(2);
painter->setPen(m_pen);
painter->drawPath(circle_path);
}
if(this->isSelected())
{
QPainterPath circle_path;
QRect duwagrect(boundingRect().x()+2,boundingRect().y()+2,boundingRect().width()-3,boundingRect().height()-3);
circle_path.addRect(duwagrect);
m_pen.setStyle(Qt::SolidLine);
m_pen.setColor(Qt::green);
m_pen.setWidth(3);
painter->setPen(m_pen);
painter->drawPath(circle_path);
}
if(option->state & QStyle::State_MouseOver)
{
QPainterPath circle_path;
QRect duwagrect(boundingRect().x()+2,boundingRect().y()+2,boundingRect().width()-3,boundingRect().height()-3);
circle_path.addRect(duwagrect);
m_pen.setStyle(Qt::SolidLine);
m_pen.setColor(Qt::cyan);
m_pen.setWidth(2);
painter->setPen(m_pen);
painter->drawPath(circle_path);
}
}
Problem is that you are showing everything even things not needed.
You should create only visible items (items in some visible region).
Another faster approach is to create custom QGraphicsItem which paints hole map, and paint only visible tiles (no tiles as sub items).
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
I am working with a QT GUI. I am implementing a simple hex edit control using a QTableView. My initial idea is to use a table with seventeen columns. Each row of the table will have 16 hex bytes and then an ASCII representation of that data in the seventeenth column. Ideally, I would like to edit/set the style of the seventeenth column to have no lines on the top and bottom of each cell to give the text a free flowing appearance. What is the best way to approach this using the QTableView?
I could think about a couple of ways of doing what you need; both would include drawing custom grid as it looks like there is no straight forward way of hooking into the grid painting routine of QTableView class:
1.Switch off the standard grid for your treeview grid by calling setShowGrid(false) and draw grid lines for cells which need them using item delegate. Below is an example:
// custom item delegate to draw grid lines around cells
class CustomDelegate : public QStyledItemDelegate
{
public:
CustomDelegate(QTableView* tableView);
protected:
void paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const;
private:
QPen _gridPen;
};
CustomDelegate::CustomDelegate(QTableView* tableView)
{
// create grid pen
int gridHint = tableView->style()->styleHint(QStyle::SH_Table_GridLineColor, new QStyleOptionViewItemV4());
QColor gridColor = static_cast<QRgb>(gridHint);
_gridPen = QPen(gridColor, 0, tableView->gridStyle());
}
void CustomDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
QStyledItemDelegate::paint(painter, option, index);
QPen oldPen = painter->pen();
painter->setPen(_gridPen);
// paint vertical lines
painter->drawLine(option.rect.topRight(), option.rect.bottomRight());
// paint horizontal lines
if (index.column()!=1) //<-- check if column need horizontal grid lines
painter->drawLine(option.rect.bottomLeft(), option.rect.bottomRight());
painter->setPen(oldPen);
}
// set up for your tree view:
ui->tableView->setShowGrid(false);
ui->tableView->setItemDelegate(new CustomDelegate(ui->tableView));
2.Create a QTableView descendant and override the paintEvent method. There you could either draw your own grid or let base class to draw it and then paint horizontal lines on top of the grid with using tableview's background color.
hope this helps, regards