how to implement mouseEnter and mouseLeave event in QWidget?
if the mouseEnter to the QWidget then i need to set the Background color into Gray,
if the mouseLeave from the QWidget then i need to set the background color is white
i tried
void enterEvent(QEvent *);
void leaveEvent(QEvent *);
in the inside of the enter&leave event i am using bool varibale set true & false. and i am calling the QPainter event update();
the code below:
void Test::enterEvent(QEvent *)
{
_mouseMove=true;
update();
}
void Test::leaveEvent(QEvent *)
{
_mouseMove=false;
update();
}
void Test::paintEvent(QPaintEvent *)
{
QPainter painter;
painter.begin(&m_targetImage);
painter.setRenderHint(QPainter::Antialiasing);
if(_mouseMove){
painter.fillRect(QRect(0,0,width(),height()),Qt::white);}
else{
painter.fillRect(QRect(0,0,width(),height()),Qt::gray);}
painter.end();
QPainter p;
p.begin(this);
p.drawImage(0, 0, m_targetImage);
p.end();
}
i am getting following error when i am moving the mouse in the QWidget
QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::end: Painter not active, aborted
Please help me to fix this. if any one having sample code please provide me....
QWidgets also support the underMouse method which could be used instead of the StyleOption or Attribute solution:
if(underMouse()){
painter.fillRect(QRect(0,0,width(),height()),Qt::white);}
else{
painter.fillRect(QRect(0,0,width(),height()),Qt::gray);}
Use the styles.
Most widget support the :hover pseudo state, set the backgroundcolor property for your widget in the style
test->setStyleSheet(":hover {background-color: #dddddd;}");
or do it through designer, which is even more convenient, if you need to do custom drawing do it. but you don't need to do it for anything that just changes basic widget looks.
First I would use a member to save the current background color instead of a boolean. This will simplify the paintEvent code:
painter.fillRect(QRect(...), m_backColor);
I guess the errors appears for the first QPainter. Why are you using a QPainter to fill the image? If the var is a QImage you can use the fill function by example and the call drawImage as you do. You have the same kind of function for QPixmap.
Another way:
Use QStyleOption.
QStyleOption sopt;
sopt.initFrom(this);
if(sopt.state & QStyle::State_MouseOver)
{
painter.fillRect(QRect(...), m_colorHover);
}
else
{
painter.fillRect(QRect(...), m_colorNotHover);
}
Don't need use extra variable, like _mouseMove
Related
I want to draw a graph on my main form, so I figured I'd use a QLabel and Override that. Like this:
// drawlabel.h
class DrawLabel : public QLabel
{
Q_OBJECT
public:
DrawLabel(QWidget *parent = 0);
private:
void paintEvent(QPaintEvent *);
};
// drawlabel.cpp
DrawLabel::DrawLabel(QWidget *parent)
: QLabel(parent)
{
}
void DrawLabel::paintEvent(QPaintEvent *)
{
qDebug() << "paint event" ;
QPainter painter(this);
painter.setPen(QPen(QBrush(QColor(0,0,0,180)),1,Qt::DashLine));
painter.setBrush(QBrush(QColor(255,255,255,120)));
QRect selectionRect(10, 10, 100, 101);
painter.drawRect(selectionRect);
}
On my main window I droppde a QLabel, sized it to about 500x200 and promoted it to DrawLLabel. When the application is run, a dashed square is drawn on the form.
All good so far.
If I add the line:
this->setText("123456");
into the DrawLabel constructor, or add it into the paintEvent() I don't see the text. I'd also like to be able to have a border around the DrawLabel, but
this->setFrameShape(QFrame::Box);
in the constructor doesn't work either.
What should I be doing to get these to work?
Well, I think you should call paintEvent of base class. Add parameter name e to method:
void DrawLabel::paintEvent(QPaintEvent *e)
And then at end of method add
QLabel::paintEvent (e);
The second option do all painting by yourself directly at paintEvent.
If you want something custom, then implement a custom widget inheriting QWidget. Then you get to draw whatever you want and have whatever members you want.
Your problem is you have overridden the label's paint event, so the code to draw the label text is not executed.
You could call the method from QLabel as Evgeny suggested, but it is better to implement a custom widget instead.
Calling the method from the base class might for example corrupt any previous drawing, unless the method was implemented with calling form derived classes in mind. I don't expect that is the case for stock widgets. I haven't tried doing it with QLabel re-implementations in particular, but I have tried it with other stock widgets and it did not work as expected.
Is it possible to use clipping in an widgets painEvent, if the widget is using stylesheets?
The background and reason for my question is that I want to make the widget animating when it appears and disappears. (Something like a resizing circle or square, that gets bigger starting as a small area from the center).
My first (and only) thought on how to solve this, was to use the clipping of a QPainter, so that only the required area is drawn.
If I make the Background of the widget transparent and use the primitive drawing functions from QPainter it works fine. But how can I solve this, if the widget has a stylesheet applied? Is it even possible?
The used Qt version is Qt 4.8.6
My questions are:
Is it possible to achieve what I want with the mentioned strategy?
Is it possible in any way to clip all the children, too?
Is my strategy appropriate or is it a bad Idea to solve it that way?
Are there any other ideas, best practices, Qt Classes, ... that can give me what I want?
Additional Information
I haven't much code to show, because I stuck with this clipping things. But here is something to get an idea of what I have tried:
This works.
/* Shows a small red circle inside the widget as expected */
void MyAnimatingWidget::paintEvent(QPaintEvent *ev) {
QPainter painter(this);
QRect rect = this->geometry()
QStyleOption opt;
painter.setClipRegion(QRegion(rect.width()/2,
rect.height()/2,
150, 150,
QRegion::Ellipse));
painter.setPen(QColor(255, 0, 0));
painter.setBrush(QColor(255, 0, 0));
painter.setOpacity(1);
painter.drawRect(rect);
}
But the following doesn't change anything:
/* This shows the widget as usual */
void MyAnimatingWidget::paintEvent(QPaintEvent *ev) {
QPainter painter(this);
QRect rect = this->geometry();
QStyleOption opt;
painter.setClipRegion(QRegion(rect.width()/2,
rect.height()/2,
150, 150,
QRegion::Ellipse));
painter.setRenderHint(QPainter::Antialiasing);
painter.setOpacity(1);
opt.init(this);
style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
}
Moreover I have noticed, that the stylesheet is also drawn, even if I remove the style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this); line at all.
The stylesheet you apply to your widget overrides the OS-specific style(s) widgets are equipped with by default. This can even cause problems, if you want to have a, say, Windows look, but still want to use a stylesheet. Anyway, you can check what each style does in the Qt source directory: src/gui/styles. For style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);, the code reads:
case PE_Widget:
if (w && !rule.hasDrawable()) {
QWidget *container = containerWidget(w);
if (styleSheetCaches->autoFillDisabledWidgets.contains(container)
&& (container == w || !renderRule(container, opt).hasBackground())) {
//we do not have a background, but we disabled the autofillbackground anyway. so fill the background now.
// (this may happen if we have rules like :focus)
p->fillRect(opt->rect, opt->palette.brush(w->backgroundRole()));
}
break;
}
As you can see clipping is not meddled with in any way, so your idea of setting a clip region should work. Now for the painting mystery. The painting of the background happens in void QWidgetPrivate::paintBackground(QPainter *painter, const QRegion &rgn, int flags) const, which is called from void QWidgetPrivate::drawWidget(QPaintDevice *pdev, const QRegion &rgn, const QPoint &offset, int flags, QPainter *sharedPainter, QWidgetBackingStore *backingStore). You can find the code in: /src/gui/kernel/qwidget.cpp. The relevant code reads:
if (q->testAttribute(Qt::WA_StyledBackground)) {
painter->setClipRegion(rgn);
QStyleOption opt;
opt.initFrom(q);
q->style()->drawPrimitive(QStyle::PE_Widget, &opt, painter, q);
}
Maybe turning the attribute off would help? The basic lesson you should draw from my answer is to get accustomed to source diving. The idea behind Qt is nice (instantiating controls, without bothering about implementation details), but it rarely works in practice, i.e. you often need to source dive.
To clip widget's children to arbitrary clip regions, you can capture them into a pixmap, example:
QPixmap pixmap(widget->size());
widget->render(&pixmap);
And then draw the pixmap manually. You might also be able to prevent them repainting automatically (via setUpdatesEnabled() or by hiding them) and then calling their render in you paintEvent handler manually.
I am working on QT v5.2
I need to hide the blinking cursor (caret) of QLineEdit permanently.
But at the same time, I want the QLineEdit to be editable (so readOnly and/or setting editable false is not an option for me).
I am already changing the Background color of the QLineEdit when it is in focus, so I will know which QLineEdit widget is getting edited.
For my requirement, cursor (the blinking text cursor) display should not be there.
I have tried styleSheets, but I can't get the cursor hidden ( {color:transparent; text-shadow:0px 0px 0px black;} )
Can someone please let me know how can I achieve this?
There is no standard way to do that, but you can use setReadOnly method which hides the cursor. When you call this method it disables processing of keys so you'll need to force it.
Inherit from QLineEdit and reimplement keyPressEvent.
LineEdit::LineEdit(QWidget* parent)
: QLineEdit(parent)
{
setReadOnly(true);
}
void LineEdit::keyPressEvent(QKeyEvent* e)
{
setReadOnly(false);
__super::keyPressEvent(e);
setReadOnly(true);
}
As a workaround you can create a single line QTextEdit and set the width of the cursor to zero by setCursorWidth.
For a single line QTextEdit you should subclass QTextEdit and do the following:
Disable word wrap.
Disable the scroll bars (AlwaysOff).
setTabChangesFocus(true).
Set the sizePolicy to (QSizePolicy::Expanding, QSizePolicy::Fixed)
Reimplement keyPressEvent() to ignore the event when Enter/Return is hit
Reimplement sizeHint to return size depending on the font.
The implementation is :
#include <QTextEdit>
#include <QKeyEvent>
#include <QStyleOption>
#include <QApplication>
class TextEdit : public QTextEdit
{
public:
TextEdit()
{
setTabChangesFocus(true);
setWordWrapMode(QTextOption::NoWrap);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed);
setFixedHeight(sizeHint().height());
}
void keyPressEvent(QKeyEvent *event)
{
if (event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter)
event->ignore();
else
QTextEdit::keyPressEvent(event);
}
QSize sizeHint() const
{
QFontMetrics fm(font());
int h = qMax(fm.height(), 14) + 4;
int w = fm.width(QLatin1Char('x')) * 17 + 4;
QStyleOptionFrameV2 opt;
opt.initFrom(this);
return (style()->sizeFromContents(QStyle::CT_LineEdit, &opt, QSize(w, h).
expandedTo(QApplication::globalStrut()), this));
}
};
Now you can create an instance of TextEdit and set the cursor width to zero :
textEdit->setCursorWidth(0);
Most straight forward thing I found was stolen from this github repo:
https://github.com/igogo/qt5noblink/blob/master/qt5noblink.cpp
Basically you just want to disable the internal "blink timer" Qt thinks is somehow good UX (hint blinking cursors never were good UX and never will be - maybe try color or highlighting there eh design peeps).
So the code is pretty simple:
from PyQt5 import QtGui
app = QtGui.QApplication.instance()
app.setCursorFlashTime(0)
voilà.
Solution in python:
# somelibraries
class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.layout = QVBoxLayout()
self.setFocus() # this is what you need!!!
container = QWidget()
container.setLayout(self.layout)
# Set the central widget of the Window.
self.setCentralWidget(container)
app = QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec()
I ran into the same problem but setReadOnly is not a viable option because it alters the UI behavior in other places too.
Somewhere in a Qt-forum I found the following solution that actually solves the problem exactly where it occurs without having impact on other parts.
In the first step you need to derive from QProxyStyle and overwrite the pixelMetric member function:
class CustomLineEditProxyStyle : public QProxyStyle
{
public:
virtual int pixelMetric(PixelMetric metric, const QStyleOption* option = 0, const QWidget* widget = 0) const
{
if (metric == QStyle::PM_TextCursorWidth)
return 0;
return QProxyStyle::pixelMetric(metric, option, widget);
}
};
The custom function simply handles QStyle::PM_TextCursorWidth and forwards otherwise.
In your custom LineEdit class constructor you can then use the new Style like this:
m_pCustomLineEditStyle = new CustomLineEditProxyStyle();
setStyle(m_pCustomLineEditStyle);
And don't forget to delete it in the destructor since the ownership of the style is not transferred (see documentation). You can, of course, hand the style form outside to your LineEdit instance if you wish.
Don't get complicated:
In QtDesigner ,
1.Go the the lineEdit 's property tab
2.Change focusPolicy to ClickFocus
That's it...
Maybe someone can help me with the following problem:
I want to draw the content of a QImage in a QGLWidget, but the widget is painted in black.
class QGLCanvas {
public:
QGLCanvas(QWidget* parent) : QGLWidget(parent) {
}
void setImage(const QImage* image) {
img = image;
}
void paintEvent(QPaintEvent*) {
// From Painter Documentation Qt
QPainter p(this);
p.setRenderHint(QPainter::SmoothPixmapTransform, 1);
p.drawImage(this->rect(), *img);
p.end();
}
public slots:
void rgb_data(const void *data) {
memcpy((void *)img->bits(), data, img->byteCount()); // data will be copied (sizes are known)
// img.save("text.png"); // saves right image
this->update(); // calls repaint, but does not draw the image.
}
private:
QImage *img;
}
The Bug:
When the slot is called, the memory is copied to the image. If the image is saved, the content is correct. But the repaint method just draws black content to the widget.
The Fix:
If the memcpy line is implemented outside the slot, the image content is drawn to the widget. This fix increased code complexity a lot. Thus, i've got the following question:
The Question:
Why does the memcpy not work within the slot? Is this a general problem with Qt?
There's nothing special about a slot which would stop your code from working.
What's probably the issue is that when you call update(), a repaint is scheduled but happens asynchronously. From the code you've provided the most likely cause is img being modified between the calls to rbg_data and paintEvent
You want to be sure about the format of the QImage. When you call bits and are expecting it to be RGB, you need to check the format.
if( img->format() != QImage::Format_RGB888 )
{
// convert the image format to RGB888
*img = img->convertToFormat(QImage::Format_RGB888);
}
This way, Qt will know the image format when trying to paint it. If you fill it with RGB data but the QImage is "formatted" as ARGB, you will get some painting errors.
In a graphical qt application,
i can learn if my object that inherits from QGraphicsItem is focused in paint method:
Qt Code:
void MyQGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
{
if (option->state & QStyle::State_HasFocus) {
//if focus some shape
} else {
//if no focus another shape
}
}
but i must click it and the shape must change whether it is focused or not.
how can i get if focused information in
Qt Code:
QPainterPath QGraphicsItem::shape() const
method in an appropriate way?
I think to declare a global variable but i do not like this idea.
thanks
Use QGraphicsItem::hasFocus() :
Returns true if this item is active, and it or its focus proxy has
keyboard input focus; otherwise, returns false.
Incidentally, if you want the shape to change when you focus the item, you will need to override focusInEvent() and focusOutEvent() and remember to call prepareGeometryChange() before the shape changes.