I want to have a QLineEdit with the specific placeholder text format: it needs to have left aligned and right aligned text. Here is an example:
Any ideas?
Unfortunately, this seems to be all hard coded in void QLineEdit::paintEvent(QPaintEvent *) as follows:
if (d->shouldShowPlaceholderText()) {
if (!d->placeholderText.isEmpty()) {
QColor col = pal.text().color();
col.setAlpha(128);
QPen oldpen = p.pen();
p.setPen(col);
QRect ph = lineRect.adjusted(minLB, 0, 0, 0);
QString elidedText = fm.elidedText(d->placeholderText, Qt::ElideRight, ph.width());
p.drawText(ph, va, elidedText);
p.setPen(oldpen);
}
}
You could reimplement this on your own in a subclass if you wish.
Naturally, you could also "cheat" with space and font sizes, but that would require a bit more work, and would be nastier in the end, too, let alone long-term reliability.
You could also contribute to the Qt Project to make this class more flexible, but they could reject it with the reason of not being common case enough. It is up to the maintainer(s).
Thanks, #lpapp ! His advice is right. Here is the code, I created from the Qt sources suggested by #lpapp :
void LineEdit::paintEvent(QPaintEvent *e) {
QLineEdit::paintEvent(e);
if (!text().isEmpty()) {
return;
}
QPainter p(this);
QStyleOptionFrameV2 panel;
initStyleOption(&panel);
QRect r = style()->subElementRect(QStyle::SE_LineEditContents, &panel, this);
r.setX(r.x() + textMargins().left());
r.setY(r.y() + textMargins().top());
r.setRight(r.right() - textMargins().right());
r.setBottom(r.bottom() - textMargins().bottom());
QFontMetrics fm = fontMetrics();
int minLB = qMax(0, -fm.minLeftBearing());
int minRB = qMax(0, -fm.minRightBearing());
int vscroll = r.y() + (r.height() - fm.height() + 1) / 2;
static const int horizontalMargin = 2; // QLineEditPrivate::horizontalMargin
QRect lineRect(r.x() + horizontalMargin, vscroll, r.width() - 2*horizontalMargin, fm.height());
QRect ph = lineRect.adjusted(minLB, 0, -minRB, 0);
QColor col = palette().text().color();
col.setAlpha(128);
p.setPen(col);
QString left = fm.elidedText("left", Qt::ElideRight, ph.width());
Qt::Alignment leftAlignment = QStyle::visualAlignment(Qt::LeftToRight, QFlag(Qt::AlignLeft));
p.drawText(ph, leftAlignment, left);
QString right = fm.elidedText("right", Qt::ElideRight, ph.width());
Qt::Alignment rightAlignment = QStyle::visualAlignment(Qt::LeftToRight, QFlag(Qt::AlignRight));
p.drawText(ph, rightAlignment, right);
}
I don't know an easy way to do this. You could try to calculate the pixel width (using QFontMetrics) of both placeholder-parts and calculate the number of spaces you need to insert between the placeholder-parts to let them appear aligned. You wuld need to set/update the calculated placeholder whenever the size of the widget changes.
Related
I have a layout that looks like this.
Where:
Blue: rectangle it's a ScrollArea
Orange: rectangles are the widgets from that ScrollArea
My code:
#include <QtWidgets>
///////////////////////////////////////////////////////////////////////////////////////
class RoundedPolygon : public QPolygon {
public:
RoundedPolygon() { SetRadius(10); }
void SetRadius(unsigned int iRadius) { m_iRadius = iRadius; }
const QPainterPath &GetPath() {
m_path = QPainterPath();
if (count() < 3) {
qDebug() << "!! Polygon should have at least 3 points !!";
return m_path;
}
QPointF pt1;
QPointF pt2;
for (int i = 0; i < count(); i++) {
pt1 = GetLineStart(i);
if (i == 0)
m_path.moveTo(pt1);
else
m_path.quadTo(at(i), pt1);
pt2 = GetLineEnd(i);
m_path.lineTo(pt2);
}
// close the last corner
pt1 = GetLineStart(0);
m_path.quadTo(at(0), pt1);
return m_path;
}
private:
QPointF GetLineStart(int i) const {
QPointF pt;
QPoint pt1 = at(i);
QPoint pt2 = at((i + 1) % count());
float fRat = m_iRadius / GetDistance(pt1, pt2);
if (fRat > 0.5f)
fRat = 0.5f;
pt.setX((1.0f - fRat) * pt1.x() + fRat * pt2.x());
pt.setY((1.0f - fRat) * pt1.y() + fRat * pt2.y());
return pt;
}
QPointF GetLineEnd(int i) const {
QPointF pt;
QPoint pt1 = at(i);
QPoint pt2 = at((i + 1) % count());
float fRat = m_iRadius / GetDistance(pt1, pt2);
if (fRat > 0.5f)
fRat = 0.5f;
pt.setX(fRat * pt1.x() + (1.0f - fRat) * pt2.x());
pt.setY(fRat * pt1.y() + (1.0f - fRat) * pt2.y());
return pt;
}
float GetDistance(QPoint pt1, QPoint pt2) const {
int fD = (pt1.x() - pt2.x()) * (pt1.x() - pt2.x()) + (pt1.y() - pt2.y()) * (pt1.y() - pt2.y());
return sqrtf(fD);
}
private:
QPainterPath m_path;
unsigned int m_iRadius{};
};
class PolygonButtonWidget : public QWidget {
Q_OBJECT
public:
explicit PolygonButtonWidget(QWidget *parent = nullptr) : QWidget(parent) {}
~PolygonButtonWidget() override = default;
protected:
void resizeEvent(QResizeEvent *event) override {
float ratioW = 8;
float ratioH = 3;
// ui->scrollAreaWidgetContents->setFixedSize(5000, h);
float thisAspectRatio = (float) event->size().width() / event->size().height();
if (thisAspectRatio < ratioW / ratioH) {
float w = event->size().height() * ratioW / ratioH;
float h = event->size().height();
qDebug() << hasHeightForWidth() << " " << w << " " << h;
this->resize(w, h);
if (m_nrButtons != 0) {
this->move((w + 20) * m_nrButtons, this->y());
}
}
QWidget::resizeEvent(event);
}
int m_nrButtons{};
public:
void setMNrButtons(int mNrButtons) {
m_nrButtons = mNrButtons;
}
protected:
void paintEvent(QPaintEvent *event) override {
int offset = 50;
m_polygon.clear();
m_polygon.emplace_back(0, height()); //DOWN-LEFT
m_polygon.emplace_back(width() - offset, height()); //DOWN-RIGHT
m_polygon.emplace_back(width(), 0); //TOP-RIGHT
m_polygon.emplace_back(0 + offset, 0);
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
RoundedPolygon poly;
poly.SetRadius(15);
for (QPoint point: m_polygon) {
poly << point;
}
QBrush fillBrush;
fillBrush.setColor(Qt::darkBlue);
fillBrush.setStyle(Qt::SolidPattern);
QPainterPath path;
path.addPath(poly.GetPath());
painter.fillPath(path, fillBrush);
}
void mousePressEvent(QMouseEvent *event) override {
auto cursorPos = mapFromGlobal(QCursor::pos());
qDebug() << "X: " << cursorPos.x() << " Y: " << cursorPos.y();
inside(cursorPos, m_polygon);
qDebug() << "Pressed";
}
private:
std::vector<QPoint> m_polygon;
bool inside(QPoint point, std::vector<QPoint> polygon) {
auto x = point.x();
auto y = point.y();
auto inside = false;
auto i = 0;
auto j = polygon.size() - 1;
while (i < polygon.size()) {
auto xi = polygon[i].x();
auto yi = polygon[i].y();
auto xj = polygon[j].x();
auto yj = polygon[j].y();
auto intersect = ((yi > y) != (yj > y)) && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
if (intersect) inside = !inside;
j = i++;
}
qDebug() << inside;
return inside;
}
};
///////////////////////////////////////////////////////////////////////////////////////
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
QWidget root;
QHBoxLayout layout{&root};
for (int i = 0; i < 10; ++i) {
auto p = new PolygonButtonWidget();
p->setMinimumSize(100, 100);
p->setMNrButtons(i);
layout.addWidget(p);
}
root.setStyleSheet("background-color: rgb(19,19,19);");
QScrollArea view;
view.setWidget(&root);
view.show();
app.exec();
}
#include "main.moc"
The problem arises when I'm trying to resize the window. In the moment of resizing, I want my widgets to keep their aspect ratio. But that's not going to happen.
I have scroll list of widgets which is looking like this (if it's expended on X way too much)
If I will scale it on Y-axis it's going to look like this.
After I've changed the resizeEvent now it's going to look something like this
or like this
How can I fix this? For some reason, some of my widgets are going to disappear, what should be my approach in order to fix this issue?
The problem is caused by the assumption that there's any mechanism that will automatically resize the widgets for you. There isn't. A QScrollArea acts as a layout barrier and any layouts inside of it are isolated from its size, and thus from any resize events.
You must resize the container widget (the one with blue outline on your diagram) yourself anytime the scroll area changes size, and you need first to prepare a test case for the widgets such that their size changes are properly managed when placed in the layout of your choice, and said layout is resized.
Finally, the pet peeve of mine: It's unlikely that you actually need the QMainWindow for anything. It's just a silly Qt Creator template. But unless you want an MDI interface and docking, you shouldn't be using the QMainWindow - and especially not when making a self-contained example. All you need here is QScrollArea as a top-level widget. That's literally all. Any QWidget can be a top-level window!
For future submissions, please provide all the code needed in a single main.cpp file that begins with #include <QtWidgets> and ends with #include "main.moc". You won't need any other includes for Qt classes, and you can write class definitions Java-style, with all the methods defined within the class declaration itself. This provides for short code - after all, a SO question isn't an Enterprise project. It's supposed to be minimal, and that really means that anything not necessary must be removed. No need for header files, multiple includes, nor other fluff - i.e. use Qt containers instead of C++ STL so that you don't need more includes etc.
Your example should look roughly as follows:
#include <QtWidgets>
class PolygonButtonWidget : public QAbstractButton {
Q_OBJECT
/* without seeing the code here, your question is unanswerable */
};
int main(int argc, char* argv[]) {
QApplication app(argc, argv);
QWidget root;
QHBoxLayout layout{&root};
PolygonButtonWidget buttons[10];
for (auto &button : buttons)
layout.addWidget(&button);
QScrollArea view;
view.setWidget(&root);
view.show();
app.exec();
view.takeWidget();
}
#include "main.moc"
Without such an example, your question is hard to answer, since:
How can we debug it? Debugging means using a debugger. If your code cannot be immediately compiled, then it's quite unlikely that someone will bother debugging it, and debugging by inspection is often error-prone.
How can we provide a tested answer if we'd have to first write the entire "test case" for it?
How can we know what's inside your button widget? The behavior of that widget does affect the ultimate solution.
It'd also help if you described a few use cases that you'd expect to work. That is, mock up (with a drawing) the state of the widgets before and after the view is resized, so that we can easily see what it is that you expect to happen. A lot of it is very easy to miss when explaining your needs in words. Use cases are a lingua franca of software specifications. If you don't use them, it's highly likely that you yourself don't know what behavior you expect in all cases.
I'm creating a screen where users can add certain tiles to use in an editor, but when adding a tile the window does not correctly resize to fit the content. Except that when I drag the window or resize it even just a little then it snaps to the correct size immediately.
And when just dragging the window it snaps to the correct size.
I tried using resize(sizeHint()); which gave me an incorrect size and the following error, but the snapping to correct size still happens when resizing/dragging.
QWindowsWindow::setGeometry: Unable to set geometry 299x329+991+536 on QWidgetWindow/'TileSetterWindow'. Resulting geometry: 299x399+991+536 (frame: 8, 31, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 259x329, maximum size: 16777215x16777215).
I also tried using updateGeometry() and update(), but it didn't seem to do much if anything.
When setting the window to fixedSize it will immediately resize, but then the user cannot resize the window anymore. What am I doing wrong here and where do I start to solve it?
Edit
Minimal verifiable example and the .ui file.
selected_layout is of type Flowlayout
The flowlayout_placeholder_1 is only there because I can't place a flowlayout directly into the designer.
Edit2
Here is a minimal Visual Studio example. I use Visual Studio for Qt development. I tried creating a project in Qt Creator, but I didn't get that to work.
Edit3
Added a little video (80 KB).
Edit4
Here is the updated Visual Studio example. It has the new changes proposed by jpo38. It fixes the issue of the bad resizing. Though now trying to downsize the windows causes issues. They don't correctly fill up vertical space anymore if you try to reduce the horizontal space even though there is room for more rows.
Great MCVE, exactly what's needed to easily investigate the issue.
Looks like this FlowLayout class was not designed to have it's minimum size change on user action. Layout gets updated 'by chance' by QWidget kernel when the window is moved.
I could make it work smartly by modifying FlowLayout::minimumSize() behaviour, here are the changes I did:
Added QSize minSize; attribute to FlowLayout class
Modifed FlowLayout::minimumSize() to simply return this attribute
Added a third parameter QSize* pMinSize to doLayout function. This will be used to update this minSize attribute
Modified doLayout to save computed size to pMinSize parameter if specified
Had FlowLayout::setGeometry pass minSize attribute to doLayout and invalidate the layout if min size changed
The layout then behaves as expected.
int FlowLayout::heightForWidth(int width) const {
const int height = doLayout(QRect(0, 0, width, 0), true,NULL); // jpo38: set added parameter to NULL here
return height;
}
void FlowLayout::setGeometry(const QRect &rect) {
QLayout::setGeometry(rect);
// jpo38: update minSize from here, force layout to consider it if it changed
QSize oldSize = minSize;
doLayout(rect, false,&minSize);
if ( oldSize != minSize )
{
// force layout to consider new minimum size!
invalidate();
}
}
QSize FlowLayout::minimumSize() const {
// jpo38: Simply return computed min size
return minSize;
}
int FlowLayout::doLayout(const QRect &rect, bool testOnly,QSize* pMinSize) const {
int left, top, right, bottom;
getContentsMargins(&left, &top, &right, &bottom);
QRect effectiveRect = rect.adjusted(+left, +top, -right, -bottom);
int x = effectiveRect.x();
int y = effectiveRect.y();
int lineHeight = 0;
// jpo38: store max X
int maxX = 0;
for (auto&& item : itemList) {
QWidget *wid = item->widget();
int spaceX = horizontalSpacing();
if (spaceX == -1)
spaceX = wid->style()->layoutSpacing(QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
int spaceY = verticalSpacing();
if (spaceY == -1)
spaceY = wid->style()->layoutSpacing(QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
int nextX = x + item->sizeHint().width() + spaceX;
if (nextX - spaceX > effectiveRect.right() && lineHeight > 0) {
x = effectiveRect.x();
y = y + lineHeight + spaceY;
nextX = x + item->sizeHint().width() + spaceX;
lineHeight = 0;
}
if (!testOnly)
item->setGeometry(QRect(QPoint(x, y), item->sizeHint()));
// jpo38: update max X based on current position
maxX = qMax( maxX, x + item->sizeHint().width() - rect.x() + left );
x = nextX;
lineHeight = qMax(lineHeight, item->sizeHint().height());
}
// jpo38: save height/width as max height/xidth in pMinSize is specified
int height = y + lineHeight - rect.y() + bottom;
if ( pMinSize )
{
pMinSize->setHeight( height );
pMinSize->setWidth( maxX );
}
return height;
}
I was having the same exact issue (albeit on PySide2 rather than C++).
#jpo38's answer above did not work directly, but it un-stuck me by giving me a new approach.
What worked was storing the last geometry, and using that geometry's width to calculate the minimum height.
Here is an untested C++ implementation based on the code in jpo38's answer (I don't code much in C++ so apologies in advance if some syntax is wrong):
int FlowLayout::heightForWidth(int width) const {
const int height = doLayout(QRect(0, 0, width, 0), true);
return height;
}
void FlowLayout::setGeometry(const QRect &rect) {
QLayout::setGeometry(rect);
// e-l: update lastSize from here
lastSize = rect.size();
doLayout(rect, false);
}
QSize FlowLayout::minimumSize() const {
// e-l: Call heightForWidth from here, my doLayout is doing things a bit differently with regards to margins, so might have to add or not add the margins here to the height
QSize size;
for (const QLayoutItem *item : qAsConst(itemList))
size = size.expandedTo(item->minimumSize());
const QMargins margins = contentsMargins();
size += QSize(margins.left() + margins.right(), margins.top() + margins.bottom());
size.setHeight(heightForWidth(qMax(lastSize.width(), size.width())));
return size;
}
int FlowLayout::doLayout(const QRect &rect, bool testOnly) const {
int left, top, right, bottom;
getContentsMargins(&left, &top, &right, &bottom);
QRect effectiveRect = rect.adjusted(+left, +top, -right, -bottom);
int x = effectiveRect.x();
int y = effectiveRect.y();
int lineHeight = 0;
for (auto&& item : itemList) {
QWidget *wid = item->widget();
int spaceX = horizontalSpacing();
if (spaceX == -1)
spaceX = wid->style()->layoutSpacing(QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
int spaceY = verticalSpacing();
if (spaceY == -1)
spaceY = wid->style()->layoutSpacing(QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
int nextX = x + item->sizeHint().width() + spaceX;
if (nextX - spaceX > effectiveRect.right() && lineHeight > 0) {
x = effectiveRect.x();
y = y + lineHeight + spaceY;
nextX = x + item->sizeHint().width() + spaceX;
lineHeight = 0;
}
if (!testOnly)
item->setGeometry(QRect(QPoint(x, y), item->sizeHint()));
x = nextX;
lineHeight = qMax(lineHeight, item->sizeHint().height());
}
int height = y + lineHeight - rect.y() + bottom;
return height;
}
I have managed to generate bar-code on a QLabel. I have tried QPainter and I could not get properly aligned output. My label size is 50*25 mm for a label ,one row contain two label.
This is my code for printing label.
I want to know that, is there any solution to print label using html. So that I can design very well.
QPrinter printer1;
QList<QPrinterInfo> printerList = QPrinterInfo::availablePrinters() ;
for(int r=0; r<printerList.size();++r)
{
if(printerList[r].printerName() == "TSC TE200")
{
QPageSize pageSize(QSizeF(45.0,70.0),QPageSize::Millimeter,"",QPageSize::ExactMatch);
QPrinter PRINTER(printerList[r],QPrinter::PrinterResolution);
PRINTER.setOrientation(QPrinter::Portrait);
PRINTER.setPageSize(pageSize);
PRINTER.setFullPage(true);
PRINTER.setOutputFormat(QPrinter::NativeFormat);
// int id = QFontDatabase::addApplicationFont("/Applications/untitledfolder/free3of9.ttf");
// QFontDatabase::applicationFontFamilies(id).at(0);
QFont barcodefont;
barcodefont.setFamily("Code 128");
barcodefont.setWeight(QFont::Normal);
barcodefont.setPointSize(60);
QFontMetrics fntm(barcodefont);
QPainter painter2;
if(!painter2.begin(&PRINTER))
return;
int x1 = printer1.paperRect().x() + printer1.width()/2 -
fntm.width("123456789")/2;enter code here
int y1 = printer1.paperRect().y();
int w1 = fntm.width("123456789");
int h1 = fntm.height()/4;
int x11 = printer1.paperRect().x() + printer1.width() - fntm.width("123456789")/2;
int y11 = printer1.paperRect().y();
int w11 = fntm.width("123456789");
int h11 = fntm.height()/4;
QRect rect10 = QRect(x1,y1,w1,h1);
QRect rect20 = QRect(x11,y11,w11,h11);
painter2.setFont(barcodefont);
painter2.drawText(rect10,Qt::AlignLeft,"123456789");
painter2.end();
break;
}
}
Sorry about my English. I'm not fluent in English.Thanks in advance.
I have this example code:
QDialog *dialog = new QDialog(this);
QPoint dialogPos = dialog->mapToGlobal(dialog->pos());
QPoint thisPos = mapToGlobal(this->pos());
dialog->exec();
But the Dialog is not centered on his parent. Thanks in advance.
UPDATE:
I'm calling Dialog from constructor in MainWindow:
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
this->panelInferior = new WidgetTabsInferior;
this->acciones = new Acciones(this);
crearAcciones();
crearBarraMenu();
crearToolbar();
crearTabsEditor();
crearArbolDir();
crearDockWindows();
crearStatusBar();
setWindowIcon(QIcon(":imgs/logo.png"));
connect(this->pestanasEditor , SIGNAL(currentChanged(int)),this,SLOT(cambioTab(int)));
this->dialogo = new AcercaDe(this);
this->dialogo->move(x() + (width() - dialogo->width()) / 2,
y() + (height() - dialogo->height()) / 2);
this->dialogo->show();
this->dialogo->raise();
this->dialogo->activateWindow();
}
But I get is:
I have this code in github
inline void CenterWidgets(QWidget *widget, QWidget *host = 0) {
if (!host)
host = widget->parentWidget();
if (host) {
auto hostRect = host->geometry();
widget->move(hostRect.center() - widget->rect().center());
}
else {
QRect screenGeometry = QApplication::desktop()->screenGeometry();
int x = (screenGeometry.width() - widget->width()) / 2;
int y = (screenGeometry.height() - widget->height()) / 2;
widget->move(x, y);
}
}
Hope it helps
edit
fix the deprecation warning issued from recent Qt versions:
#include <QScreen>
#include <QWidget>
#include <QGuiApplication>
inline void CenterWidgets(QWidget *widget, QWidget *host = Q_NULLPTR) {
if (!host)
host = widget->parentWidget();
if (host) {
auto hostRect = host->geometry();
widget->move(hostRect.center() - widget->rect().center());
}
else {
QRect screenGeometry = QGuiApplication::screens()[0]->geometry();
int x = (screenGeometry.width() - widget->width()) / 2;
int y = (screenGeometry.height() - widget->height()) / 2;
widget->move(x, y);
}
}
Thought I would post my own solution here. #CapelliC's solution works, but is deprecated since Qt5.11. Infact, the documentation says the QDesktopWidget class is obsolete.
Solution (which is a litte crude) is to use the QGuiApplication::screenAt()
Context: class inheriting QMainWindow, but can can extend for any QWidget
// Get current screen size
QRect rec = QGuiApplication::screenAt(this->pos())->geometry();
// Using minimum size of window
QSize size = this->minimumSize();
// Set top left point
QPoint topLeft = QPoint((rec.width() / 2) - (size.width() / 2), (rec.height() / 2) - (size.height() / 2));
// set window position
setGeometry(QRect(topLeft, size));
Hope it helps.
You have to change the geometry of the QDialog:
dialog->move(x() + (width() - dialog->width()) / 2,
y() + (height() - dialog->height()) / 2);
The move() function moves respect the parent, so it is not necessary to map to global.
On constructor the position and size of parent are not set yet. You can try executing the dialog in a separate method or, if needed on constructor, try with something like
QTimer::singleShot(0, [=]() {
// ... your dialog code
});
It will be shown on the next iteration of the event loop.
I think it's a Qt4 bug. I used Qt4 on Ubuntu and it doesn't respect the parent widget center.
However, when I use Qt5, It seems to work fine.
You can also use move() to arrive to your position.
I'm trying to make an horizontal layout with 3 QLabel scale use all its available space. More specifically, this is what I have
this is what I am aiming for
At the moment, the second image is achieved by changing the stylesheet of the qlabels with a slider. Additionally, since I have the the three labels in a layout inside a groupbox, the groupbox resizes to fit its contents, cool.
Now I wanted to drop the slider approach and instead autofit the space available when moving the splitters. In this question, OP reimplements the resizeEvent, and I've seen other posts suggesting the same, changing point by point with this while( !doesFit ) or something similar.
I tried using this approach, both on the resize event and on the splitterMoved event. However, this approach is way prone to feedback loops and other display errors caused. In the other question, they suggest enabling ignoreSizePolicy to prevent the size policy retriggering the sizeevent, but I like how qt handles the size of the layout, how it keeps a minimum size and then it folds the widget if the user insists. Maybe it would work if the HLayout would ignore the resize events triggered by the QLabels, still IMHO unclean thought.
I was wondering if that's the recommended way of achieving this, and wether a less unstable solution exists, maybe using using stylesheets. There are some behaviours that I could also drop, the minimum size limit (so the user could potentially hide the groupbox).
If that's the recommended way of doing it, how should I use the fontmetrics if I have three separate labels, one of which (the number) changes its text dynamically and rapidly? It should not have an impact on performance, and that while loop makes me wary.
It doesn't sound like the while(!fit) approach is going to cut it. Or does it?
--- Edit regarding the duplicate question
Another post creates an event filter, which might also work if reworked to deal with a layout with 3 labels. I finally used a version of the first mentioned post with the variation of the post mentioned in the comments. I'll post the answer if the question is reopened.
One could apply the Newton's method approach from this answer to work on all widgets in a given layout. It will work on any widget with a settable font, not only on a QLabel.
The Newton's algorithm converges reasonably quickly when given a good starting point, e.g. when resizing interactively. It's not atypical to have the loop execute only once. On the other hand, QWidget::sizeHint is integer-valued and and widgets may round fractional font sizes, thus sometimes the iteration is a bit slower than one would expect. The number of iterations is capped to ensure decent performance.
A custom replacement for the label, that provided a QSizeF sizeHintF(), would work better here.
The minimum sizing for the widgets is a bit of a stretch, as the size is not updated as the widget contents change. This could be remedied easily, though.
// https://github.com/KubaO/stackoverflown/tree/master/questions/label-text-size-vert-40861305
#include <QtWidgets>
class LabelStretcher : public QObject {
Q_OBJECT
static constexpr const char kMinimumsAcquired[] = "ls_minimumsAcquired";
static constexpr const char kStretcherManaged[] = "ls_stretcherManaged";
public:
LabelStretcher(QObject *parent = 0) : QObject(parent) {
apply(qobject_cast<QWidget*>(parent));
}
void apply(QWidget *widget) {
if (!widget) return;
setManaged(widget);
setMinimumSize(widget);
widget->installEventFilter(this);
}
void setManaged(QWidget *w, bool managed = true) {
w->setProperty(kStretcherManaged, managed);
}
protected:
bool eventFilter(QObject * obj, QEvent * ev) override {
auto widget = qobject_cast<QWidget*>(obj);
if (widget && ev->type() == QEvent::Resize)
resized(widget);
return false;
}
private:
void onLayout(QLayout *layout, const std::function<void(QWidget*)> &onWidget) {
if (!layout) return;
auto N = layout->count();
for (int i = 0; i < N; ++i) {
auto item = layout->itemAt(i);
onWidget(item->widget());
onLayout(item->layout(), onWidget);
}
}
void setFont(QLayout *layout, const QFont &font) {
onLayout(layout, [&](QWidget *widget){ setFont(widget, font); });
}
void setFont(QWidget *widget, const QFont &font) {
if (!widget || !widget->property(kStretcherManaged).toBool()) return;
widget->setFont(font);
setFont(widget->layout(), font);
}
void setMinimumSize(QWidget *widget) {
if (widget->layout()) return;
widget->setMinimumSize(widget->minimumSizeHint());
}
static int dSize(const QSizeF & inner, const QSizeF & outer) {
auto dy = inner.height() - outer.height();
auto dx = inner.width() - outer.width();
return std::max(dx, dy);
}
qreal f(qreal fontSize, QWidget *widget) {
auto font = widget->font();
font.setPointSizeF(fontSize);
setFont(widget, font);
auto d = dSize(widget->sizeHint(), widget->size());
qDebug() << "f:" << fontSize << "d" << d;
return d;
}
qreal df(qreal fontSize, qreal dStep, QWidget *widget) {
fontSize = std::max(dStep + 1.0, fontSize);
return (f(fontSize + dStep, widget) - f(fontSize - dStep, widget)) / dStep;
}
void resized(QWidget *widget) {
qDebug() << "pre: " << widget->minimumSizeHint() << widget->sizeHint() << widget->size();
if (!widget->property(kMinimumsAcquired).toBool()) {
onLayout(widget->layout(), [=](QWidget *widget){ setMinimumSize(widget); });
widget->setProperty(kMinimumsAcquired, true);
}
// Newton's method
auto font = widget->font();
auto fontSize = font.pointSizeF();
qreal dStep = 1.0;
int i;
for (i = 0; i < 10; ++i) {
auto prevFontSize = fontSize;
auto d = df(fontSize, dStep, widget);
if (d == 0) {
dStep *= 2.0;
continue;
}
fontSize -= f(fontSize, widget)/d;
fontSize = std::max(dStep + 1.0, fontSize);
auto change = fabs(prevFontSize - fontSize)/fontSize;
qDebug() << "d:" << d << " delta" << change;
if (change < 0.01) break; // we're within 1% of target
}
font.setPointSizeF(fontSize);
setFont(widget, font);
qDebug() << "post:" << i << widget->minimumSizeHint() << widget->sizeHint() << widget->size();
}
};
constexpr const char LabelStretcher::kMinimumsAcquired[];
constexpr const char LabelStretcher::kStretcherManaged[];
int main(int argc, char ** argv) {
QApplication app{argc, argv};
QWidget w;
QGridLayout layout{&w};
LabelStretcher stretch{&w};
QLabel labels[6];
QString texts[6] = {"V", "30.0", "kts", "H", "400.0", "ft"};
int i = 0, j = 0, k = 0;
for (auto & label : labels) {
stretch.setManaged(&label);
label.setFrameStyle(QFrame::Box);
label.setText(texts[k++]);
if (j == 0) label.setAlignment(Qt::AlignRight | Qt::AlignVCenter);
else if (j == 1) label.setAlignment(Qt::AlignCenter);
layout.addWidget(&label, i, j++);
if (j >= 3) { i++; j=0; }
}
w.show();
return app.exec();
}
#include "main.moc"
Althought I consider KubaOber's answer better, I'll post this in case it's helpful to someone who wants a solution in the line of the answers mentioned in the post.
Note that the sampletext could be retrieved from the labels as well, the font from the stylesheet, and the code could potentially be placed on a resizeEvent of the groupbox or layout. It wouldn't work on the resizeEvent of the labels since they would compete for the space.
That is one reason why KubaOber answer is superior. Other reasons I can think of is stability given that the 3 labels space differs from the sampletext, thus the font size is not as accurate as it could be. Therefore a resize event could potentially be triggered again by the font change.
static void fitGroupBoxLabels(QGroupBox* groupbox, const QFont &samplefont, const QLayout* const samplelayout)
{
groupbox->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
QString sampletext = "V 1000.0 kts";
QRect availablerect = samplelayout->contentsRect();
if(samplefont.pointSizeF() <= 0) return; //not initalized yet, return
QRect textrect = QFontMetrics(samplefont).boundingRect(sampletext);
if(!textrect.isValid() || !availablerect.isValid()) return; //not initalized yet, return
float factorh = availablerect.width() / (float)textrect.width();
float factorw = availablerect.height() / (float)textrect.height();
float factor = std::min(factorh, factorw);
if (factor < 0.95 || factor > 1.05)
{
float fontSize = samplefont.pointSizeF()*factor;
QString groupBoxStyle = QString("QGroupBox{font-size:8pt} QLabel{font-size:%1pt}").arg(fontSize);
groupbox->setStyleSheet(groupBoxStyle);
}
}
After struggling with this issue, I create DynamicFontSizeLabel and DynamicFontSizePushButton widgets. Hope it helps.
https://github.com/jonaias/DynamicFontSizeWidgets/