I have a QListView in Icon mode with lots of icons, so that a scrollbar appears, but the scrolling is not smooth and this IMHO confuses the user since it jumps abruptly from one point to another at each scroll. I would like to make the scrolling smooth but I didn't find anything in the docs. Is it possible?
Maybe QListView.setVerticalScrollMode(QAbstractItemView::ScrollPerPixel)
If I understand your question correctly you would like to redefine the scrolling behavior of the widget. I guess what happens is that listview is getting scrolled by the item's height whenever users hits a scroll arrow (marked as b on the image below).
For a vertical scroll bar connected to a list view, scroll arrows typically move the current position one "line" up or down, and adjust the position of the slider by a small amount. I believe line in this case it is an icon's height. You can adjust items height by installing and item delegate (setItemDelegate) and overriding its sizeHint method. Though this would not help you to solve this problem. What you could try is to create a QListView descendant and override its updateGeometries method. There you can setup the vertical scrollbar step to the value you want, I guess 1 or 2 for this task. Below is an example of the custom listview:
class TestListView : public QListView
{
Q_OBJECT
public:
explicit TestListView(QWidget *parent = 0);
protected:
virtual void updateGeometries();
};
TestListView::TestListView(QWidget *parent) :
QListView(parent)
{
//???
}
void TestListView::updateGeometries()
{
QListView::updateGeometries();
verticalScrollBar()->setSingleStep(2);
}
hope this helps, regards
I have a QlistWidget* in ui->barra_scroll and I feel very smooth with this.
QScrollBar *qsb = ui->barra_scroll->verticalScrollBar();
qsb->setSingleStep(5);
Related
I have a splitview, and on the left-hand side a number of buttons. I'm putting them into a scrollbar so that they don't get squished when the container layout gets too short; but the only two options I seem to have are:
1: QScrollArea does not resize the view, so that when the window gets too short, the vertical scrollbar causes the buttons to be blocked (side-to-side) and the horizontal scrollbar also appears.
2: QScrollArea tries to resize the widget it contains (using setWidgetResizable(true)), but fits it within the same smaller size, which causes some of the text on the buttons to get clipped off the sides.
What I want is for the QScrollArea to maintain the default size of the widget (horizontally) and expand ITSELF by the size of a scrollbar when it deems one to be necessary (vertically). There's plenty of space to the right in this split view, and I would prefer if the scroll area got wider and expanded the left-hand side instead.
I had a similar situation, which was solved by overriding QScrollArea::sizeHint() in the descendant.
#include <QScrollBar>
#include <QScrollArea>
class MyScrollArea : public QScrollArea
{
Q_OBJECT
public:
QSize sizeHint() const override
{
auto newSize = QScrollArea::sizeHint();
newSize.setWidth(newSize.width()
+ verticalScrollBar()->sizeHint().width());
return newSize;
}
};
just like the title described, when i redraw the scrollbar in QTreeView which has a header(QHeaderView), but the scrollbar's height is the entire height of QTreeView, and i want to let the scrollbar's height equals the QTreeView's height minus the header's height.just like the pic below:
A solution for your problem might be setting the location of the vertical scrollbar to a constant_offset value acquired from the QHeaderView (on the y axis).
This could be done by subclassing the QTreeView like so:
class MyTreeView : public QTreeView
{
public:
MyTreeView(QWidget* parent = nullptr): QTreeView(parent){}
void updateVertScrollBar()
{
auto* ptr = verticalScrollBar();
QRect rect = ptr->geometry();
rect.setTop(header()->height());
ptr->setGeometry(rect);
}
void resizeEvent(QResizeEvent* ev) override
{
QTreeView::resizeEvent(ev);
updateVertScrollBar();
}
};
Depending on the sizePolicy the updateVertScrollBar method could be called just after data is filled or as presented in the sample implementation the update can occur for each resizeEvent - which should cover various resizing performed to the widget.
EDIT
Additionally removing the blank space left from the shrunk scrollbar would be tricky. First denote that the QTreeView is built from a viewport widget and scrollbars (among others). The issue you now see comes from the fact that viewport plus vertical scrollbar widths (if visible) should match and this is calculated internally.
I stated that it's tricky since there is a load of stuff happening when you try to force the size of these components. Some updates are called in-place some are called through the event loop. You can check this to get more detaile info about the concept. Similar approach is probably applied to QTreeView.
Basically what you would need to do is to stretch the viewport width. This should be probably done during the resizeEvent but calling from there methods like viewport()->setGeometry() might not end well - you might get caught into a loop. You might try blockSignals but I'm not sure this would help. In general if you want to mess with the internals of a given Qt widget you should go through it's implementation at least briefly.
Just as a QPushButton provides a default clicked() signal, I expected QScrollArea to have a sliderChanged() or similar signal. Interestingly, the QScrollBar does have such a signal.
All I would like to do is to know what part of the huge widget inside the scroll area is visible, whenever the user scrolls it.
There are many solutions, none of which seem elegant to me:
subclass QScrollArea
subclass the widget inside the scroll area, and re-implement its paint event.
create a custom veiwport, using QScrollBar
periodically poll the position of the widget inside the scroll area. This seems to be the worst solution.
Is there a way without subclassing?
There is QAbstractSlider::valueChanged() signal that is emitted when the slider value has changed, with the new slider value as argument. This will notify you as soon as you scroll your view.
WRT the second problem, neither of mentioned points necessary. You need to:
1) Get the position of inner widget (if any) related to the scroll area:
QPoint p = scrollArea->widget()->pos();
It use to be a negative coordinates if you scrolled your view down/right or null without scrolling.
2) Get the size of the visible area
QSize s = scrollArea->viewport()->size();
With these two values you can construct a QRect that will represent the visible area of your inner widget.
I'm fairly new to Qt's method of stylesheets and I am looking to adjust the spacing between the icon and text on a QPushButton.
This is the gap I'm referring to: http://imageshack.us/scaled/thumb/593/4kem.png (stackoverflow won't let me post pics yet)
QPushButton {
qproperty-icon: theme_url("/button_action/add");
qproperty-iconSize: 14px;
}
Is there a parameter I can use to adjust this space? I've tried margin, padding, spacing? Perhaps there is a different selector that I can use to just grab the icon?
Actually with QPushButton you are out of luck. You can find a complete list of working options for styling push buttons in the qt documentation ( I am assuming you use qt5, but it is available for other versions as well).
What is often recommended if you want more control over the icon is to exchange your QPushButtons with QToolButtons wich are exactly the same except that they have extra features to make them compatible with toolbars -and- they have more options for icon placement. But this might not work for you because as you can see they are styled the exact same way as QPushButtons. But do look into the "toolButtonStyle" parameter which allows you to move the icon around.
Next on the list comes changing the artwork. If all you want is more space then just add the extra empty pixels to the artwork. This really hurts the perfectionist's mind but is effective.
Next on the list comes subclassing QPushButton and overriding the paint yourself. Sounds more daunting than it is. Subclassing in Qt has become a habit already and it works great. Here is a tutorial i googled in a jiffie (for 4.8 but should be about the same for 5) on the matter of subclassing. It even covers overriding the paint event.
Hope this was helpful.
At least with Qt5.5 (this may change in the future, I hope), besides overriding the paint event, which is complex and in my opinion messy for just a simple thing, there's no inherent Qt way to move that icon a few pixels here or there (small adjustments). If you remove the icon and use a stylesheet to set the background to your icon in your resource URL, you can use background-position property in the stylesheet, but unfortunately it only accepts words like center, left, etc., not pixel adjustments.
Here's how I resolved this problem. I created transparent PNGs that were slightly larger than I needed, where I had like a 4px margin around the icon itself inside the PNG. Then, I just moved the icon inside that canvas and reloaded it into the project resources file, and then mapped it again with the icon property in the designer for the QPushButton, and that worked. I now have icons that line up properly on the left with the text beside it. I can even widen the gap between icon and text.
As of Qt5.7 I don't know of any built-in functionality for the icon/text spacing.
What I usually do is give the image some more space to the right and set the icon size of the button accordingly.
Solution:
Resize your icon file to 32*16 px but leave its content as is.
Call setIconSize(QSize(32, 16)) on your button.
Result: Now there's 16 pixel empty space between its icon and text. 32 pixel is just my example, you can of course set the additional size to something that suites your style.
If you want to apply that on all your button elements simply create a tiny subclass that does it automatically in the constructor. There's really no need to override the paintEvent method for this.
Here is a workaround way to achieve that 'space between text and image':
QPushButton{
border:0px;
image: /*your url*/;
padding-top:16px;
image-position:top;
text-align:bottom;
padding-bottom:10px;
}
since qss doesn't support relative size, you need to implement resize() to change stylesheet when size changing to get a fixed space between text and image.
Here's an opportunistic approach to customize the spacing between text and icon. There's currently no regular way to change the width, so we need to add a transparent area to the right of the icon which is applied to paint device.
Firstly, add a new member variable "m_spacing"(double) and initialize it to 0.0 in constructor, as a factor of expanding the width.
Then, override the "paintEvent", "sizeHint" and "minimumSizeHint".
class CPushButton : public QPushButton {
Q_OBJECT
public:
double spaceRatio() const;
void setSpaceRatio(double ratio);
protected:
double m_spacing;
void paintEvent(QPaintEvent *event) override;
......
QSize CPushButton::sizeHint() const {
QSize sz = QPushButton::sizeHint();
int offset = iconSize().width() * m_spacing;
return QSize(sz.width() + offset, sz.height());
}
QSize CPushButton::minimumSizeHint() const {
QSize sz = QPushButton::minimumSizeHint();
int offset = iconSize().width() * m_spacing;
return QSize(sz.width() + offset, sz.height());
}
void CPushButton::paintEvent(QPaintEvent *event) {
QSize sz = iconSize();
QPixmap tmp = icon().pixmap(sz); // Get the pixmap to apply with right size
sz.rwidth() *= 1 + m_spacing; // Multiply width
QPixmap exp(sz); // Expended
exp.fill(Qt::transparent);
QPainter painter(&exp);
painter.drawPixmap(QRect(QPoint(), tmp.size()), tmp);
QStylePainter p(this); // From Qt source
QStyleOptionButton option; // From Qt source
initStyleOption(&option); // From Qt source
option.icon = QIcon(exp); // Change to real icon
option.iconSize = sz; // Change to real size
p.drawControl(QStyle::CE_PushButton, option); // From Qt source
Q_UNUSED(event)
}
Now you can create a CPushButton instance and set the spacingRatio to 0.1 or other positive real. Visually, it does increase the spacing between text and icon.
The simplest way to go for it is to create your own class inheriting from the QPushButton and override the PaintEvent and then manually place the pixmap of the icon where ever you want.
Best way to solve this problem is adding some blank space in the beginning of QPushButton text. it works well for me!
See here
I am trying to use a QTextEdit widget inside of a form containing several QT widgets. The form itself sits inside a QScrollArea that is the central widget for a window. My intent is that any necessary scrolling will take place in the main QScrollArea (rather than inside any widgets), and any widgets inside will automatically resize their height to hold their contents.
I have tried to implement the automatic resizing of height with a QTextEdit, but have run into an odd issue. I created a sub-class of QTextEdit and reimplemented sizeHint() like this:
QSize OperationEditor::sizeHint() const {
QSize sizehint = QTextBrowser::sizeHint();
sizehint.setHeight(this->fitted_height);
return sizehint;
}
this->fitted_height is kept up-to-date via this slot that is wired to the QTextEdit's "contentsChanged()" signal:
void OperationEditor::fitHeightToDocument() {
this->document()->setTextWidth(this->viewport()->width());
QSize document_size(this->document()->size().toSize());
this->fitted_height = document_size.height();
this->updateGeometry();
}
The size policy of the QTextEdit sub-class is:
this->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Preferred);
I took this approach after reading this post.
Here is my problem:
As the QTextEdit gradually resizes to fill the window, it stops getting larger and starts scrolling within the QTextEdit, no matter what height is returned from sizeHint(). If I initially have sizeHint() return some large constant number, then the QTextEdit is very big and is contained nicely within the outer QScrollArea, as one would expect. However, if sizeHint gradually adjusts the size of the QTextEdit rather than just making it really big to start, then it tops out when it fills the current window and starts scrolling instead of growing.
I have traced this problem to be that, no matter what my sizeHint() returns, it will never resize the QTextEdit larger than the value returned from maximumViewportSize(), which is inherited from QAbstractScrollArea. Note that this is not the same number as viewport()->maximumSize(). I am unable to figure out how to set that value.
Looking at QT's source code, maximumViewportSize() is returning "the size of the viewport as if the scroll bars had no valid scrolling range." This value is basically computed as the current size of the widget minus (2 * frameWidth + margins) plus any scrollbar widths/heights. This does not make a lot of sense to me, and it's not clear to me why that number would be used anywhere in a way that supercede's the sub-class's sizeHint() implementation. Also, it does seem odd that the single "frameWidth" integer is used in computing both the width and the height.
Can anyone please shed some light on this? I suspect that my poor understanding of QT's layout engine is to blame here.
Edit: after initially posting this, I had the idea to reimplement maximumViewportSize() to return the same thing as sizeHint(). Unfortunately, this did not work as I still have the same problem.
I have solved this issue. There were 2 things that I had to do to get it to work:
Walk up the widget hierarchy and make sure all the size policies made sense to ensure that if any child widget wanted to be big/small, then the parent widget would want to be the same thing.
This is the main source of the fix. It turns out that since the QTextEdit is inside a QFrame that is the main widget in a QScrollArea, the QScrollArea has a constraint that it will not resize the internal widget unless the "widgetResizable" property is true. The documentation for that is here: http://doc.qt.io/qt-4.8/qscrollarea.html#widgetResizable-prop. The documentation was not clear to me until I played around with this setting and got it to work. From the docs, it seems that this property only deals with times where the main scroll area wants to resize a widget (i.e. from parent to child). It actually means that if the main widget in the scroll area wants to ever resize (i.e. child to parent), then this setting has to be set to true.
So, the moral of the story is that the QTextEdit code was correct in overriding sizeHint, but the QScrollArea was ignoring the value returned from the main frame's sizeHint.
Yay! It Works!
You may try setting minimumSize property of the QTextEdit to see if that force the layout to grow.
I don't understand most of Qt's layout scheme but setting minimum and maximum size pretty much does what I want it to do. Well, most of the time anyways.