diff -r 409d9c7214be -r fb0bb9a2a7e1 src/RangedSlider.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/RangedSlider.cpp	Wed Mar 30 15:31:57 2022 +0200
@@ -0,0 +1,443 @@
+/*
+ * RangedSlider.cpp is part bmsapp.
+ *
+ * Original written for Brewtarget, and is Copyright the following
+ * authors 2009-2020
+ * - Matt Young <mfsy@yahoo.com>
+ * - Mik Firestone <mikfire@gmail.com>
+ * - Philip G. Lee <rocketman768@gmail.com>
+ *
+ * bmsapp is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * bmsapp is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "RangedSlider.h"
+//#include "brewtarget.h"
+#include <QPaintEvent>
+#include <QPainter>
+#include <QColor>
+#include <QPalette>
+#include <QApplication>
+#include <QRectF>
+#include <QFont>
+#include <QFontMetrics>
+#include <QMouseEvent>
+#include <QLabel>
+#include <QToolTip>
+#include <QLinearGradient>
+#include <QPainterPath>
+
+#include <QDebug>
+
+RangedSlider::RangedSlider(QWidget* parent)
+   : QWidget(parent),
+     _min(0.0),
+     _max(1.0),
+     _prefMin(0.25),
+     _prefMax(0.75),
+     _val(0.5),
+     _valText("0.500"),
+     _prec(3),
+     _tickInterval(0),
+     _secondaryTicks(1),
+     _tooltipText(""),
+     _bgBrush(QColor(255,255,255)),
+     _prefRangeBrush(QColor(0,0,0)),
+     _prefRangePen(Qt::NoPen),
+     _markerBrush(QColor(255,255,255)),
+     _markerTextIsValue(false),
+     valueTextFont("Arial",
+                   14,             // QFonts are specified in point size, so the hard-coded number is fine here.
+                   QFont::Black),  // Note that QFont::Black is a weight (more bold than ExtraBold), not a colour.
+     indicatorTextFont("Arial",
+                       10,
+                       QFont::Normal) // Previously we just did the indicator text in 'default' font
+{
+   // Ensure this->heightInPixels is properly initialised
+   this->recalculateHeightInPixels();
+
+   // In principle we want to set our min/max sizes etc here.  However, if, say, a maximumSize property has been set
+   // for this object in a Designer UI File (eg ui/mainWindow.ui) then that setting will override this one, because it
+   // will be applied later (in fact pretty much straight after this constructor returns).  So we also make this call
+   // inside setValue(), which will be invoked _after_ the setter calls that were auto-generated from the Designer UI
+   // File.
+   this->setSizes();
+
+   // Generate mouse move events whenever mouse movers over widget.
+   this->setMouseTracking(true);
+
+   this->repaint();
+}
+
+void RangedSlider::setPreferredRange( double min, double max )
+{
+   _prefMin = min;
+   _prefMax = max;
+
+   // Only show tooltips if the range has nonzero size.
+   setMouseTracking(min < max);
+
+   _tooltipText = QString("%1 - %2").arg(min, 0, 'f', _prec).arg(max, 0, 'f', _prec);
+
+   update();
+}
+
+void RangedSlider::setPreferredRange(QPair<double,double> minmax)
+{
+   setPreferredRange( minmax.first, minmax.second );
+}
+
+void RangedSlider::setRange( double min, double max )
+{
+   _min = min;
+   _max = max;
+   update();
+}
+
+void RangedSlider::setRange(QPair<double,double> minmax)
+{
+   setRange( minmax.first, minmax.second );
+}
+
+void RangedSlider::setValue(double value)
+{
+   _val = value;
+   _valText = QString("%1").arg(_val, 0, 'f', _prec);
+   update();
+
+   // See comment in constructor for why we call this here
+   this->setSizes();
+   return;
+}
+
+void RangedSlider::setPrecision(int precision)
+{
+   _prec = precision;
+   update();
+}
+
+void RangedSlider::setBackgroundBrush( QBrush const& brush )
+{
+   _bgBrush = brush;
+   update();
+}
+
+void RangedSlider::setPreferredRangeBrush( QBrush const& brush )
+{
+   _prefRangeBrush = brush;
+   update();
+}
+
+void RangedSlider::setPreferredRangePen( QPen const& pen )
+{
+   _prefRangePen = pen;
+   update();
+}
+
+void RangedSlider::setMarkerBrush( QBrush const& brush )
+{
+   _markerBrush = brush;
+   update();
+}
+
+void RangedSlider::setMarkerText( QString const& text )
+{
+   _markerText = text;
+   update();
+}
+
+void RangedSlider::setMarkerTextIsValue(bool val)
+{
+   _markerTextIsValue = val;
+   update();
+}
+
+void RangedSlider::setTickMarks( double primaryInterval, int secondaryTicks )
+{
+   _secondaryTicks = (secondaryTicks<1)? 1 : secondaryTicks;
+   _tickInterval = primaryInterval/_secondaryTicks;
+
+   update();
+}
+
+void RangedSlider::recalculateHeightInPixels() const {
+   //
+   // We need to be able to tell Qt about our minimum and preferred size in pixels.  This is something that's going
+   // to depend on the dots-per-inch (DPI) resolution of the monitor we're being displayed on.  Advice at
+   // https://doc.qt.io/qt-5/highdpi.html is that, for best High DPI display support, we should replace hard-coded
+   // sizes in layouts and drawing code with values calculated from font metrics or screen size.  For this widget, we
+   // use font sizes (as described in more detail later in this comment) as it seems simpler and the height of the
+   // widget really is determined by the size of the text it contains.
+   //
+   // In theory, someone might be running the app on a system with multiple screens with different DPI resolutions,
+   // so, in principle we ought to do redo size calculations every time the widget is moved, in case it moves from one
+   // screen to another and the resolution changes.  In practice, I'm not sure how big a requirement this is.  So, for
+   // now, have just tried to organise things so that it would, in principle, be possible to implement such behaviour
+   // in future.
+   //
+   // We want height to be fixed, as the slider does not get more readable if you make it taller.  So minimum and
+   // preferred height are the same.
+   //
+   // For width, We are OK for them to expand and contract horizontally, within reason, as the size of the main window
+   // changes.  Minimum and preferred widths are a bit of a rule-of-thumb, but 2× and 4× height are a sensible stab.
+   //
+   // Firstly we have to determine what the fixed height is.  We could query the DPI resolution and size of the current
+   // screen, but the simplest thing is to use font sizes.  The slider is basically two lines of characters high.  Top
+   // line is the "indicator" text that sits above the slider visual in the middle of the "preferred range".  Bottom
+   // line is the slider visual and the "value" text that sits to the right of the slider visual.  The fonts for both
+   // bits of text are set in device-independent points in the constructor, and we can just query their height etc in
+   // pixels.
+   //
+   // Secondly, the way we tell Qt about minimum and preferred sizes is slightly different:
+   //  • setMinimumSize() tells Qt not to make us smaller than the specified size when resizing windows etc, HOWEVER
+   //    it does not determine what size we are initially drawn
+   //  • instead, Qt calls sizeHint() when doing initial layout, and we must override this to supply our desired
+   //    initial dimensions.  NB: Although it makes no sense, there is nothing to stop this method returning dimensions
+   //    below the minimums already set via setMinimumSize().  (AIUI, sizeHint() is also called on resize events to
+   //    find our preferred dimensions.)
+   //
+   // The final wrinkle is that the height of the font sort of depends what you mean.  Strictly, using the inter-line
+   // spacing (= height plus leading, though the latter is often 0) gives you enough space to show any character of the
+   // font.  It is helpful for the indicator text to have a bit of space below it before we draw the graphical bit, and
+   // it's not a large font in any case.  However, for large value text font we don't necessarily need all this space
+   // because we currently only show digits and decimal points, which don't require space below the baseline.  However,
+   // assumptions about space below the baseline are locale-specific, so, say, using ascent() instead of lineSpacing()
+   // could end up painting us into a corner.
+   //
+   QFontMetrics indicatorTextFontMetrics(this->indicatorTextFont);
+   QFontMetrics valueTextFontMetrics(this->valueTextFont);
+   this->heightInPixels = indicatorTextFontMetrics.lineSpacing() + valueTextFontMetrics.lineSpacing();
+   return;
+}
+
+void RangedSlider::setSizes() {
+   // Caller's responsibility to have recently called this->recalculateHeightInPixels().  (See comment in that function
+   // for how we choose minimum width.)
+   this->setMinimumSize(2 * this->heightInPixels, this->heightInPixels);
+
+   this->setSizePolicy( QSizePolicy::MinimumExpanding, QSizePolicy::Fixed );
+
+   // There no particular reason to limit our horizontal size, so, in principle, this call asks that there be no such
+   // (practical) limit.
+   this->setMaximumWidth(QWIDGETSIZE_MAX);
+
+   return;
+}
+
+QSize RangedSlider::sizeHint() const
+{
+   this->recalculateHeightInPixels();
+   return QSize(4 * this->heightInPixels, this->heightInPixels);
+}
+
+void RangedSlider::mouseMoveEvent(QMouseEvent* event)
+{
+   event->accept();
+
+   QPoint tipPoint( mapToGlobal(QPoint(0,0)) );
+   QToolTip::showText( tipPoint, _tooltipText, this );
+}
+
+void RangedSlider::paintEvent(QPaintEvent* event)
+{
+   //
+   // Simplistically, the high-level layout of the slider is:
+   //
+   //    |-------------------------------------------------------------|
+   //    |                   Indicator text               | B L A N K  |
+   //    |------------------------------------------------+------------|
+   //    | <--------------- Graphical Area -------------> | Value text |
+   //    |-------------------------------------------------------------|
+   //
+   // The graphical area has:
+   //  - a background rectangle of the full width of the area, representing the range from this->_min to this->_max
+   //  - a foreground rectangle showing the sub-range of this background from this->_prefMin to this->_prefMax
+   //  - a line ("the indicator") showing where this->_val lies in the (this->_min to this->_max) range
+   //
+   // The indicator text sits above the indicator line and shows either its value (this->_valText) or some textual
+   // description (eg "Slightly Malty" on the IBU/GU scale) which comes from this->_markerText.
+   //
+   // In principle, we could have the value text a slightly different height than the graphical area - eg to help
+   // squeeze into smaller available vertical space on small screens (as we know there is blank space of
+   // indicatorTextHeight pixels above the space for the value text).
+   //
+   // The value text also shows this->_valText.
+   //
+
+   QFontMetrics indicatorTextFontMetrics(this->indicatorTextFont);
+   int indicatorTextHeight = indicatorTextFontMetrics.lineSpacing();
+
+   // The heights of the slider graphic and the value text are usually the same, but we calculate them differently in
+   // case, in future, we want to squeeze things up a bit.
+   QFontMetrics valueTextFontMetrics(this->valueTextFont);
+   int valueTextHeight = valueTextFontMetrics.lineSpacing();
+
+   int graphicalAreaHeight = this->height() - indicatorTextHeight;
+
+   // Although the Qt calls take an x- and a y- radius, we want the radius on the rectangle corners to be the same
+   // vertically and horizontally, so only define one measure here.
+   int rectangleCornerRadius = graphicalAreaHeight / 4;
+
+   static const QPalette palette(QApplication::palette());
+   static const int indicatorLineWidth   = 4;
+   static const QColor fgRectColor(0,127,0);
+   static const QColor indicatorTextColor(0,0,0);
+   static const QColor valueTextColor(0,127,0);
+
+   // We need to allow for the width of the text that displays to the right of the slider showing the current value.
+   // If there were just one slider, we might ask Qt for the width of this text with one of the following calls:
+   //    const int valueTextWidth = valueTextFontMetrics.width(_valText);              // Pre Qt 5.13
+   //    const int valueTextWidth = valueTextFontMetrics.horizontalAdvance(_valText);  // Since Qt 5.13
+   // However, we want all the sliders to have exact same width, so we choose some representative text to measure the
+   // width of.  We assume that all sliders show no more than 4 digits and a decimal point, and then add a space to
+   // ensure a gap between the value text and the graphical area.  (Note that digits are all the same width in the font
+   // we are using.
+   int valueTextWidth =
+#if QT_VERSION < QT_VERSION_CHECK(5,13,0)
+      valueTextFontMetrics.width(" 1.000");
+#else
+      valueTextFontMetrics.horizontalAdvance(" 1.000");
+#endif
+
+   QLinearGradient glassGrad( QPointF(0,0), QPointF(0,graphicalAreaHeight) );
+   glassGrad.setColorAt( 0, QColor(255,255,255,127) );
+   glassGrad.setColorAt( 1, QColor(255,255,255,0) );
+   QBrush glassBrush(glassGrad);
+
+   // Per https://doc.qt.io/qt-5/highdpi.html, for best High DPI display support, we need to:
+   //  • Always use the qreal versions of the QPainter drawing API
+   //  • Size windows and dialogs in relation to the corresponding screen size
+   //  • Replace hard-coded sizes in layouts and drawing code with values calculated from font metrics or screen size
+   QPainter painter(this);
+
+   // Work out the left-to-right (ie x-coordinate) positions of things in the graphical area
+   double graphicalAreaWidth  = this->width() - valueTextWidth;
+   double range               = this->_max - this->_min;
+   double fgRectLeft          = graphicalAreaWidth * ((this->_prefMin - this->_min    )/range);
+   double fgRectWidth         = graphicalAreaWidth * ((this->_prefMax - this->_prefMin)/range);
+   double indicatorLineMiddle = graphicalAreaWidth * ((this->_val     - this->_min    )/range);
+   double indicatorLineLeft   = indicatorLineMiddle - (indicatorLineWidth / 2);
+
+   // Make sure all coordinates are valid.
+   fgRectLeft          = qBound(0.0, fgRectLeft,          graphicalAreaWidth);
+   fgRectWidth         = qBound(0.0, fgRectWidth,         graphicalAreaWidth - fgRectLeft);
+   indicatorLineMiddle = qBound(0.0, indicatorLineMiddle, graphicalAreaWidth - (indicatorLineWidth / 2));
+   indicatorLineLeft   = qBound(0.0, indicatorLineLeft,   graphicalAreaWidth - indicatorLineWidth);
+
+   // The left-to-right position of the indicator text (also known as marker text) depends on where the slider is.
+   // First we ask the painter what size rectangle it will need to display this text
+   painter.setPen(indicatorTextColor);
+   painter.setFont(this->indicatorTextFont);
+   QRectF indicatorTextRect = painter.boundingRect(QRectF(),
+                                                   Qt::AlignCenter | Qt::AlignBottom,
+                                                   this->_markerTextIsValue ? this->_valText : this->_markerText);
+
+   // Then we use the size of this rectangle to try to make the middle of the text sit over the indicator marker on
+   // the slider - but bounding things so that the text doesn't go off the edge of the slider.
+   double indicatorTextLeft = qBound(0.0,
+                                    indicatorLineMiddle - (indicatorTextRect.width() / 2),
+                                    graphicalAreaWidth - indicatorTextRect.width());
+
+   // Now we can draw the indicator text
+   painter.drawText(
+      indicatorTextLeft, 0,
+      indicatorTextRect.width(), indicatorTextRect.height(),
+      Qt::AlignCenter | Qt::AlignBottom,
+      this->_markerTextIsValue ? this->_valText : this->_markerText
+   );
+
+   // Next draw the value text
+   // We work out its vertical position relative to the bottom of the graphical area in case (in future) we want to be
+   // able to use some of the blank space above it (to the right of the indicator text).
+   painter.setPen(valueTextColor);
+   painter.setFont(this->valueTextFont);
+   painter.drawText(graphicalAreaWidth, this->height() - valueTextHeight,
+                    valueTextWidth, valueTextHeight,
+                    Qt::AlignRight | Qt::AlignVCenter,
+                    this->_valText );
+
+   // All the rest of what we need to do is inside the graphical area, so move the origin to the top-left corner of it
+   painter.translate(0, indicatorTextRect.height());
+   painter.setPen(Qt::NoPen);
+
+   // Make sure anything we draw "inside" the "glass rectangle" stays inside.
+   QPainterPath clipRect;
+   clipRect.addRoundedRect( QRectF(0, 0, graphicalAreaWidth, graphicalAreaHeight),
+                            rectangleCornerRadius,
+                            rectangleCornerRadius );
+   painter.setClipPath(clipRect);
+
+   // Draw the background rectangle.
+   painter.setBrush(_bgBrush);
+   painter.setRenderHint(QPainter::Antialiasing);
+   painter.drawRoundedRect( QRectF(0, 0, graphicalAreaWidth, graphicalAreaHeight),
+                            rectangleCornerRadius,
+                            rectangleCornerRadius );
+   painter.setRenderHint(QPainter::Antialiasing, false);
+
+   // Draw the style "foreground" rectangle.
+   painter.save();
+      painter.setBrush(_prefRangeBrush);
+      painter.setPen(_prefRangePen);
+      painter.setRenderHint(QPainter::Antialiasing);
+      painter.drawRoundedRect( QRectF(fgRectLeft, 0, fgRectWidth, graphicalAreaHeight),
+                               rectangleCornerRadius,
+                               rectangleCornerRadius );
+   painter.restore();
+
+   // Draw the indicator.
+   painter.setBrush(_markerBrush);
+   painter.drawRect( QRectF(indicatorLineLeft, 0, indicatorLineWidth, graphicalAreaHeight) );
+
+   // Draw a white-to-clear gradient to suggest "glassy."
+   painter.setBrush(glassBrush);
+   painter.setRenderHint(QPainter::Antialiasing);
+   painter.drawRoundedRect( QRectF(0, 0, graphicalAreaWidth, graphicalAreaHeight),
+                            rectangleCornerRadius,
+                            rectangleCornerRadius );
+   painter.setRenderHint(QPainter::Antialiasing, false);
+
+   // Draw the ticks.
+   painter.setPen(Qt::black);
+   if( _tickInterval > 0.0 )
+   {
+      int secTick = 1;
+      for( double currentTick = _min+_tickInterval; _max - currentTick > _tickInterval-1e-6; currentTick += _tickInterval )
+      {
+         painter.translate( graphicalAreaWidth/(_max-_min) * _tickInterval, 0);
+         if( secTick == _secondaryTicks )
+         {
+            painter.drawLine( QPointF(0,0.25*graphicalAreaHeight), QPointF(0,0.75*graphicalAreaHeight) );
+            secTick = 1;
+         }
+         else
+         {
+            painter.drawLine( QPointF(0,0.333*graphicalAreaHeight), QPointF(0,0.666*graphicalAreaHeight) );
+            ++secTick;
+         }
+      }
+   }
+
+   return;
+}
+
+
+void RangedSlider::moveEvent(QMoveEvent *event) {
+   // If we've moved, we might be on a new screen with a different DPI resolution...
+   // .:TBD:. This almost certainly needs further work and further testing.  It's far from clear whether our font size
+   //         querying will give different answers just because the app has been moved from one screen to another.
+   this->recalculateHeightInPixels();
+
+   QWidget::moveEvent(event);
+   return;
+}