Implement proper y-axis labeling

Change-Id: Ie2bdb4b85f168dc611a52303143a6a6fc110e3c3
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/CMakeLists.txt

@@ -649,6 +649,7 @@ extend_qtc_plugin(QmlDesigner
 extend_qtc_plugin(QmlDesigner
   SOURCES_PREFIX components/curveeditor
   SOURCES
+    curveeditor.qrc
     animationcurve.cpp animationcurve.h
     curveeditor.cpp curveeditor.h
     curveeditormodel.cpp curveeditormodel.h
@@ -656,6 +657,7 @@ extend_qtc_plugin(QmlDesigner
     curvesegment.cpp curvesegment.h
     keyframe.cpp keyframe.h
     treeitem.cpp treeitem.h
+    detail/axis.cpp detail/axis.h
     detail/colorcontrol.cpp detail/colorcontrol.h
     detail/curveeditorstyledialog.cpp detail/curveeditorstyledialog.h
     detail/curveitem.cpp detail/curveitem.h

src/plugins/qmldesigner/components/curveeditor/curveeditor.pri

@@ -44,6 +44,7 @@ SOURCES += \
     $$PWD/detail/treemodel.cpp \
     $$PWD/detail/treeview.cpp \
     $$PWD/detail/utils.cpp \
+    $$PWD/detail/axis.cpp \
     $$PWD/keyframe.cpp \
     $$PWD/treeitem.cpp
 

src/plugins/qmldesigner/components/curveeditor/curveeditorstyle.h

@@ -123,6 +123,7 @@ struct CurveEditorStyle
     double valueAxisWidth = 60.0;
     double valueOffsetTop = 10.0;
     double valueOffsetBottom = 10.0;
+    double labelDensityY = 1.5;
 
     HandleItemStyleOption handleStyle;
     KeyframeItemStyleOption keyframeStyle;

src/plugins/qmldesigner/components/curveeditor/detail/axis.cpp

@@ -0,0 +1,213 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Design Tooling
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+#include "axis.h"
+
+#include <algorithm>
+#include <assert.h>
+#include <cmath>
+#include <limits>
+
+namespace DesignTools {
+
+// The following is based on: "An Extension of Wilkinson's Algorithm for Positioning Tick Labels on Axes"
+// by Justin Talbot, Sharon Lin and Pat Hanrahan.
+// The Implementation uses the conventions and variable names found in the paper where:
+// Inputs:
+//     Q           Preference ordered list of nice steps
+//     dmin/dmax   Data range
+//     pt          Target label density
+//     fst         Target font size (currently ignored)
+//     Formats     set of label formats (currently ignored)
+// Other:
+//     q           Element of Q
+//     i           Index of q in Q
+//     j           Label skipping amount (taking only jth label into account)
+//     lmin/lmax   Labeling sequence range
+//     v           Indicator if labeling should include 0. (1 means yes / 0 no)
+
+double simplicity(int i, std::vector<double> &Q, int j, int v = 1)
+{
+    assert(Q.size() > 1);
+    return 1.0 - ((static_cast<double>(i) - 1.0) / (static_cast<double>(Q.size()) - 1.0))
+           - static_cast<double>(j) + static_cast<double>(v);
+}
+
+double coverage(double dmin, double dmax, double lmin, double lmax)
+{
+    return 1.0 - 0.5 *
+        ((std::pow(dmax - lmax, 2.0) + std::pow(dmin - lmin, 2.0)) /
+         (std::pow(0.1 * (dmax - dmin), 2.0)));
+}
+
+double coverageMax(double dmin, double dmax, double labelingRange)
+{
+    double dataRange = dmax - dmin;
+    if (labelingRange > dataRange) {
+        double range = (labelingRange - dataRange) / 2.;
+        return 1 - 0.5 * ((std::pow(range, 2.0) * 2.0) / (std::pow(0.1 * (dmax - dmin), 2.0)));
+    }
+    return 1;
+}
+
+double density(double p, double pt)
+{
+    return 2.0 - std::max(p / pt, pt / p);
+}
+
+double densityMax(double p, double pt)
+{
+    if (p >= pt)
+        return 2 - p / pt;
+    else
+        return 1;
+}
+
+namespace Legibility {
+
+class Format
+{
+public:
+    double legibility() const { return 1.0; }
+};
+
+class FontSize
+{
+public:
+    double legibility() const { return 1.0; }
+};
+
+class Orientation
+{
+public:
+    double legibility() const { return 1.0; }
+};
+
+class Overlap
+{
+public:
+    double legibility() const { return 1.0; }
+};
+
+} // End namespace Legibility.
+
+using namespace Legibility;
+
+double legibility(const Format &fmt, const FontSize &fs, const Orientation &ori, const Overlap &ovl)
+{
+    return (fmt.legibility() + fs.legibility() + ori.legibility() + ovl.legibility()) / 4.0;
+}
+
+struct LabelingInfo
+{
+    double l;
+    Format lformat;
+};
+
+LabelingInfo optLegibility(int k, double lmin, double lstep)
+{
+    std::vector<double> stepSequence;
+    for (int i = 0; i < k; ++i)
+        stepSequence.push_back(lmin + i * lstep);
+
+    Format fmt;
+    FontSize fs;
+    Orientation ori;
+    Overlap ovl;
+
+    LabelingInfo info;
+    info.l = legibility(fmt, fs, ori, ovl);
+    info.lformat = fmt;
+    return info;
+}
+
+Axis Axis::compute(double dmin, double dmax, double height, double pt)
+{
+    Axis result;
+
+    auto score = [](double a, double b, double c, double d) {
+        return a * 0.2 + b * 0.25 + c * 0.5 + d * 0.05;
+    };
+
+    std::vector<double> Q = {1., 5., 2., 2.5, 3.};
+    //std::vector<double> Q = {1., 5., 2., 2.5, 3., 4., 1.5, 7., 6., 8., 9.};
+
+    double best_score = -2.0;
+    int j = 1;
+    while (j < std::numeric_limits<int>::max()) {
+        for (int i = 0; i < static_cast<int>(Q.size()); ++i) {
+            double q = Q[i];
+
+            auto simMax = simplicity(i, Q, j);
+            if (score(simMax, 1.0, 1.0, 1.0) < best_score) {
+                j = std::numeric_limits<int>::max() - 1;
+                break;
+            }
+
+            int k = 2; // label count
+            while (k < std::numeric_limits<int>::max()) {
+                auto p = k / height;
+                auto denMax = densityMax(p, pt);
+                if (score(simMax, 1.0, denMax, 1.0) < best_score)
+                    break;
+
+                auto delta = (dmax - dmin) / (k + 1) / (j * q);
+                int z = std::ceil(std::log10(delta));
+                while (z < std::numeric_limits<int>::max()) {
+                    auto lstep = q * static_cast<double>(j) * std::pow(10, z);
+                    auto covMax = coverageMax(dmin, dmax, lstep * (k - 1));
+                    if (score(simMax, covMax, denMax, 1.0) < best_score)
+                        break;
+
+                    int start = (std::floor(dmax / lstep) - (k - 1)) * j;
+                    int end = std::ceil(dmin / lstep) * j;
+                    for (; start <= end; ++start) {
+                        double lmin = start * lstep / j;
+                        double lmax = lmin + lstep * (k - 1);
+
+                        double s = simplicity(i, Q, j);
+                        double d = density(p, pt);
+                        double c = coverage(dmin, dmax, lmin, lmax);
+
+                        if (score(s, c, d, 1.0) < best_score)
+                            continue;
+
+                        auto info = optLegibility(k, lmin, lstep);
+                        const double cscore = score(s, c, d, info.l);
+                        if (cscore > best_score) {
+                            best_score = cscore;
+                            result = {lmin, lmax, lstep};
+                        }
+                    }
+                    z++;
+                }
+                k++;
+            }
+        }
+        j++;
+    }
+    return result;
+}
+
+} // End namespace DesignTools.

src/plugins/qmldesigner/components/curveeditor/detail/axis.h

@@ -0,0 +1,42 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Design Tooling
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QToolBar>
+#include <QWidget>
+
+namespace DesignTools {
+
+struct Axis
+{
+    static Axis compute(double dmin, double dmax, double height, double pt);
+
+    double lmin;
+    double lmax;
+    double lstep;
+};
+
+} // End namespace DesignTools.

src/plugins/qmldesigner/components/curveeditor/detail/graphicsview.cpp

@@ -24,6 +24,7 @@
 ****************************************************************************/
 
 #include "graphicsview.h"
+#include "axis.h"
 #include "curveeditormodel.h"
 #include "curveitem.h"
 #include "treeitem.h"
@@ -35,6 +36,8 @@
 #include <QScrollBar>
 
 #include <cmath>
+#include <iomanip>
+#include <sstream>
 
 namespace DesignTools {
 
@@ -361,15 +364,15 @@ void GraphicsView::drawForeground(QPainter *painter, const QRectF &rect)
     if (abscissa.isValid())
         drawTimeScale(painter, abscissa);
 
+    painter->fillRect(QRectF(rect.topLeft(), abscissa.bottomLeft()),
+                      m_style.backgroundAlternateBrush);
+
     auto ordinate = valueScaleRect();
     if (ordinate.isValid())
         drawValueScale(painter, ordinate);
 
     m_playhead.paint(painter, this);
 
-    painter->fillRect(QRectF(rect.topLeft(), abscissa.bottomLeft()),
-                      m_style.backgroundAlternateBrush);
-
     m_selector.paint(painter);
 }
 
@@ -460,7 +463,8 @@ void GraphicsView::applyZoom(double x, double y, const QPoint &pivot)
 
 void GraphicsView::drawGrid(QPainter *painter, const QRectF &rect)
 {
-    QRectF gridRect = rect.adjusted(m_style.valueAxisWidth + m_style.canvasMargin,
+    QRectF gridRect = rect.adjusted(
+        m_style.valueAxisWidth + m_style.canvasMargin,
         m_style.timeAxisHeight + m_style.canvasMargin,
         -m_style.canvasMargin,
         -m_style.canvasMargin);
@@ -586,17 +590,24 @@ void GraphicsView::drawValueScale(QPainter *painter, const QRectF &rect)
 
     QFontMetrics fm(painter->font());
     auto paintLabeledTick = [this, painter, rect, fm](double value) {
+        std::stringstream sstr;
+        sstr << std::fixed << std::setprecision(10) << value;
+        sstr >> value;
+
         QString valueText = QString("%1").arg(value);
-
         int position = mapValueToY(value);
-
         QRect textRect = fm.boundingRect(valueText);
         textRect.moveCenter(QPoint(rect.center().x(), position));
+
         painter->drawText(textRect, Qt::AlignCenter, valueText);
     };
 
-    paintLabeledTick(minimumValue());
+    double density = 1. / (static_cast<double>(fm.height()) * m_style.labelDensityY);
-    paintLabeledTick(maximumValue());
+    Axis axis = Axis::compute(minimumValue(), maximumValue(), rect.height(), density);
+    const double eps = 1.0e-10;
+    for (double i = axis.lmin; i <= axis.lmax + eps; i += axis.lstep)
+        paintLabeledTick(i);
+
     painter->restore();
 }
 

src/plugins/qmldesigner/qmldesignerplugin.qbs

@@ -715,6 +715,8 @@ Project {
                 "curveeditor/keyframe.h",
                 "curveeditor/treeitem.cpp",
                 "curveeditor/treeitem.h",
+                "curveeditor/detail/axis.cpp",
+                "curveeditor/detail/axis.h",
                 "curveeditor/detail/colorcontrol.cpp",
                 "curveeditor/detail/colorcontrol.h",
                 "curveeditor/detail/curveeditorstyledialog.cpp",