Sketcher: Constraint icons and fonts in 3D View

===============================================

Based on PRs #4146 #4155.

PR #4155 proposes a scaling factor to be used to scale up constraint icons and the subindex font of icons. The
scaling factor is a parameter.

PR #4146 proposes to derive the constraint icon size from the system font size via function of the dpi. The
constraint icon subindex is a factor of the constraint size.

Observations:
- PR #4146 identifies the need for a scaling factor too, but this is a hardcoded 1.25 factor.
- PR #4146 appears to mix font points and font pixels when deriving the sizes.
- PR #4155 deals exclusively with icon size and subindex font, not with constraint label

Useful concepts:
- Font point is a physical distance. There are 72 points in one inch.
- Monitors have pixels with varying pixel densities. The number of pixels in one point varies
with pixel density. Hence the need for a correction based on the dpi of the monitor.

API constraints:
- While QT's configuration can be obtained in points or pixels, coin3D sets the font size in points.

Solution:
- Continue relying on the local font setting from preferences for coin3d font, albeit by converting from pixels to points.
- Introduce a sketcher wide 3D view scaling factor, as per #4155. This factor is however used for geometry, not for fonts.
- Geometry is scaled to compensate for the scaling factor and the monitor pixel density (the scaling factor is the product
of both scaling factors).
- Derive the 3D view icon size to be 80% (hardcoded) of the 3D view font size. Having constraint icons proportional to contraint label
font size gives consistency to the interface, as constraint icons also have subindices. I do not think it is worth to provide this 80%
as a configurable parameter
- The constraint icon subindex, being a special case of font relative to the accompanying icon, is set to be the 80% of the
icon size (hardcoded). I think it is not worth to provide this as a configurable parameter.

Bonus:
- ViewProviderSketch implements an observer of parameter group and tracks view scaling factor parameter and marker size.
- On change of parameter the inventor nodes are updated and the 3D view redrawn.
- Size information is moved to edit structure for consistency with Marker size.

src/Mod/Sketcher/Gui/SoDatumLabel.cpp

@@ -503,7 +503,7 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
     const SbColor& t = textColor.getValue();
 
     // Set GL Properties
-    glLineWidth(2.f);
+    glLineWidth(this->lineWidth.getValue());
     glColor3f(t[0], t[1], t[2]);
 
     if (this->datumtype.getValue() == DISTANCE ||

src/Mod/Sketcher/Gui/ViewProviderSketch.cpp

@@ -188,6 +188,8 @@ struct EditData {
     PreselectCurve(-1),
     PreselectCross(-1),
     MarkerSize(7),
+    coinFontSize(11), // default of 11 points (not pixels)
+    constraintIconSize(15), // 11 points @ 96 ppi where 72 points = 1 inch
     blockedPreselection(false),
     FullyConstrained(false),
     //ActSketch(0), // if you are wondering, it went to SketchObject, accessible via getSolvedSketch() and via SketchObject interface as appropriate
@@ -208,7 +210,13 @@ struct EditData {
     textPos(0),
     constrGroup(0),
     infoGroup(0),
-    pickStyleAxes(0)
+    pickStyleAxes(0),
+    PointsDrawStyle(0),
+    CurvesDrawStyle(0),
+    RootCrossDrawStyle(0),
+    EditCurvesDrawStyle(0),
+    ConstraintDrawStyle(0),
+    InformationDrawStyle(0)
     {}
 
     // pointer to the active handler for new sketch objects
@@ -228,6 +236,9 @@ struct EditData {
     int PreselectCurve;
     int PreselectCross;
     int MarkerSize;
+    int coinFontSize;
+    int constraintIconSize;
+    double pixelScalingFactor;
     std::set<int> PreselectConstraintSet;
     bool blockedPreselection;
     bool FullyConstrained;
@@ -273,6 +284,13 @@ struct EditData {
     SmSwitchboard *constrGroup;
     SoGroup       *infoGroup;
     SoPickStyle   *pickStyleAxes;
+
+    SoDrawStyle * PointsDrawStyle;
+    SoDrawStyle * CurvesDrawStyle;
+    SoDrawStyle * RootCrossDrawStyle;
+    SoDrawStyle * EditCurvesDrawStyle;
+    SoDrawStyle * ConstraintDrawStyle;
+    SoDrawStyle * InformationDrawStyle;
 };
 
 
@@ -373,7 +391,8 @@ ViewProviderSketch::ViewProviderSketch()
 
     //rubberband selection
     rubberband = new Gui::Rubberband();
-    InitItemsSizes();
+
+    subscribeToParameters();
 }
 
 ViewProviderSketch::~ViewProviderSketch()
@@ -3191,11 +3210,14 @@ QString ViewProviderSketch::getPresentationString(const Constraint *constraint)
             }
         }
     }
+
     if (constraint->Type == Sketcher::Diameter){
         userStr.insert(0, QChar(8960)); // Diameter sign
-    }else if (constraint->Type == Sketcher::Radius){
+    }
+    else if (constraint->Type == Sketcher::Radius){
         userStr.insert(0, QChar(82)); // Capital letter R
     }
+
     return userStr;
 }
 
@@ -3652,10 +3674,10 @@ QImage ViewProviderSketch::renderConstrIcon(const QString &type,
     // Constants to help create constraint icons
     QString joinStr = QString::fromLatin1(", ");
 
-    QImage icon = Gui::BitmapFactory().pixmapFromSvg(type.toLatin1().data(),QSizeF(constraintIconSize,constraintIconSize)).toImage();
+    QImage icon = Gui::BitmapFactory().pixmapFromSvg(type.toLatin1().data(),QSizeF(edit->constraintIconSize,edit->constraintIconSize)).toImage();
 
     QFont font = QApplication::font();
-    font.setPixelSize(static_cast<int>(0.8 * constraintIconSize));
+    font.setPixelSize(static_cast<int>(0.8 * edit->constraintIconSize));
     font.setBold(true);
     QFontMetrics qfm = QFontMetrics(font);
 
@@ -3754,23 +3776,97 @@ float ViewProviderSketch::getScaleFactor()
     }
 }
 
-void ViewProviderSketch::InitItemsSizes()
+void ViewProviderSketch::OnChange(Base::Subject<const char*> &rCaller, const char * sReason)
+{
+    (void) rCaller;
+    //ParameterGrp& rclGrp = ((ParameterGrp&)rCaller);
+    if (strcmp(sReason, "ViewScalingFactor") == 0   ||
+        strcmp(sReason, "MarkerSize") == 0          ||
+        strcmp(sReason, "EditSketcherFontSize") == 0 ) {
+        if(edit) { // only if in edit mode, if not it gets updated when entering edit mode
+            initItemsSizes();
+            updateInventorNodeSizes();
+            rebuildConstraintsVisual();
+            draw();
+        }
+    }
+}
+
+void ViewProviderSketch::subscribeToParameters()
+{
+     ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
+     hGrp->Attach(this);
+}
+
+void ViewProviderSketch::updateInventorNodeSizes()
+{
+    assert(edit);
+    edit->PointsDrawStyle->pointSize = std::lround(8 * edit->pixelScalingFactor);
+    edit->PointSet->markerIndex = Gui::Inventor::MarkerBitmaps::getMarkerIndex("CIRCLE_FILLED", edit->MarkerSize);
+    edit->CurvesDrawStyle->lineWidth = std::lround(3 * edit->pixelScalingFactor);
+    edit->RootCrossDrawStyle->lineWidth = std::lround(2 * edit->pixelScalingFactor);
+    edit->EditCurvesDrawStyle->lineWidth = std::lround(3 * edit->pixelScalingFactor);
+    edit->ConstraintDrawStyle->lineWidth = std::lround(1 * edit->pixelScalingFactor);
+    edit->InformationDrawStyle->lineWidth = std::lround(1 * edit->pixelScalingFactor);
+}
+
+void ViewProviderSketch::initItemsSizes()
 {
     //Add scaling to Constraint icons
-    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/Mod/Sketcher/General");
-    double viewScalingFactor = hGrp->GetFloat("ViewScalingFactor", 1.25);
+    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
+    double viewScalingFactor = hGrp->GetFloat("ViewScalingFactor", 1.0);
     viewScalingFactor = Base::clamp<double>(viewScalingFactor, 0.5, 5.0);
+    int markersize = hGrp->GetInt("MarkerSize", 7);
+
+    int defaultFontSizePixels = QApplication::fontMetrics().height(); // returns height in pixels, not points
+    int sketcherfontSize = hGrp->GetInt("EditSketcherFontSize", defaultFontSizePixels);
+
+    auto pixelsToPoints = [](int pixels, int dpi) {
+        return pixels*72/dpi; // definition of point, 72 points = 1 inch
+    };
+
+    // coin takes the font size in points, not pixels
+    // the coin FontSize in points from the system font, taking into account the application scaling factor is:
+    // -> pixelsToPoints(defaultFontSizePixels * viewScalingFactor, dpi)
+
+    int dpi = QApplication::desktop()->logicalDpiX();
+
+    if(edit) {
+        // simple scaling factor for hardcoded pixel values in the Sketcher
+        edit->pixelScalingFactor = viewScalingFactor * dpi / 96; // 96 ppi is the standard pixel density for which pixel quantities were calculated
 
-    int defaultFontSize = QApplication::fontMetrics().height();
-    int ldpi = QApplication::desktop()->logicalDpiX();
-    float virtualdpi = 96.;
-    float QtPixelRatio = virtualdpi/ldpi;
-    float coinFontPixelRatio = QtPixelRatio; // this is not absolute exactly, but the ratio is correct
+        edit->coinFontSize = pixelsToPoints(sketcherfontSize, dpi);
+        edit->constraintIconSize = std::lround(0.8 * sketcherfontSize);
 
-    hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
-    coinFontSize = hGrp->GetInt("EditSketcherFontSize", defaultFontSize * QtPixelRatio * coinFontPixelRatio * viewScalingFactor);
-    constraintIconSize = coinFontSize / coinFontPixelRatio;
-    return;
+        // The global default is used.
+        //
+        // Rationale:
+        // -> Other WBs use the default value as is
+        // -> If a user has a HDPI, he will eventually change the value for the other WBs
+        // -> If we correct the value here in addition, we would get two times a resize
+
+        edit->MarkerSize = markersize;
+
+        // This commented code would find a the closest supported marker value to a provided value.
+        // It may be useful if a different global marker size implementation is provided.
+        //
+        // Here marker size is used as a ratio to the default of 7 px (as a second scaling factor)
+        // the default marker size is 30% of the view3dFontPixels
+        // NOTE: Not all marker sizes are supported, grab the closest supported one.
+        /*
+        std::vector<int> supportedsizes {5, 7, 9, 11, 13, 15};
+        int calculatedmarker = std::lround(0.3*view3dFontPixels*markersize/7.0);
+
+        auto pos = std::upper_bound(supportedsizes.begin(), supportedsizes.end(), calculatedmarker);
+
+        if(pos == supportedsizes.end())
+            edit->MarkerSize = *std::prev(supportedsizes.end());
+        else if(pos == supportedsizes.begin())
+            edit->MarkerSize = *supportedsizes.begin();
+        else
+            edit->MarkerSize = (*pos - calculatedmarker > calculatedmarker - *std::prev(pos))?*std::prev(pos):*pos;
+        */
+    }
 }
 
 void ViewProviderSketch::draw(bool temp /*=false*/, bool rebuildinformationlayer /*=true*/)
@@ -4251,7 +4347,7 @@ void ViewProviderSketch::draw(bool temp /*=false*/, bool rebuildinformationlayer
 
             SoFont *font = new SoFont;
             font->name.setValue("Helvetica");
-            font->size.setValue(coinFontSize);
+            font->size.setValue(edit->coinFontSize);
 
             SoText2 *degreetext = new SoText2;
             degreetext->string = SbString(spline->getDegree());
@@ -4530,7 +4626,7 @@ void ViewProviderSketch::draw(bool temp /*=false*/, bool rebuildinformationlayer
 
                 SoFont *font = new SoFont;
                 font->name.setValue("Helvetica");
-                font->size.setValue(coinFontSize);
+                font->size.setValue(edit->coinFontSize);
 
                 SoText2 *degreetext = new SoText2;
                 degreetext->string = SbString("(") + SbString(*itm) + SbString(")");
@@ -4597,7 +4693,7 @@ void ViewProviderSketch::draw(bool temp /*=false*/, bool rebuildinformationlayer
 
                 SoFont* font = new SoFont;
                 font->name.setValue("Helvetica");
-                font->size.setValue(coinFontSize);
+                font->size.setValue(edit->coinFontSize);
 
                 translate->translation.setValue(poleposition.x, poleposition.y, zInfo);
 
@@ -5815,7 +5911,8 @@ void ViewProviderSketch::rebuildConstraintsVisual(void)
                                             ConstrDimColor
                                             :NonDrivingConstrDimColor)
                                         :DeactivatedConstrDimColor;
-                text->size.setValue(coinFontSize);
+                text->size.setValue(edit->coinFontSize);
+                text->lineWidth = std::lround(2 * edit->pixelScalingFactor);
                 text->useAntialiasing = false;
                 SoAnnotation *anno = new SoAnnotation();
                 anno->renderCaching = SoSeparator::OFF;
@@ -5918,6 +6015,7 @@ void ViewProviderSketch::rebuildConstraintsVisual(void)
                 arrows->norm.setValue(norm);
                 arrows->string = "";
                 arrows->textColor = ConstrDimColor;
+                arrows->lineWidth = std::lround(2 * edit->pixelScalingFactor);
 
                 // #define CONSTRAINT_SEPARATOR_INDEX_MATERIAL_OR_DATUMLABEL 0
                 sep->addChild(arrows);
@@ -6105,8 +6203,8 @@ bool ViewProviderSketch::setEdit(int ModNum)
     assert(!edit);
     edit = new EditData();
 
-    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
-    edit->MarkerSize = hGrp->GetInt("MarkerSize", 7);
+    // Init icon, font and marker sizes
+    initItemsSizes();
 
     ParameterGrp::handle hSketch = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/Mod/Sketcher");
     edit->handleEscapeButton = !hSketch->GetBool("LeaveSketchWithEscape", true);
@@ -6161,6 +6259,7 @@ bool ViewProviderSketch::setEdit(int ModNum)
 
     float transparency;
 
+    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
     // set the point color
     unsigned long color = (unsigned long)(VertexColor.getPackedValue());
     color = hGrp->GetUnsigned("EditedVertexColor", color);
@@ -6424,10 +6523,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     edit->PointsCoordinate->setName("PointsCoordinate");
     pointsRoot->addChild(edit->PointsCoordinate);
 
-    SoDrawStyle *drawStyle = new SoDrawStyle;
-    drawStyle->setName("PointsDrawStyle");
-    drawStyle->pointSize = 8;
-    pointsRoot->addChild(drawStyle);
+    edit->PointsDrawStyle = new SoDrawStyle;
+    edit->PointsDrawStyle->setName("PointsDrawStyle");
+    edit->PointsDrawStyle->pointSize = std::lround(8 * edit->pixelScalingFactor);
+    pointsRoot->addChild(edit->PointsDrawStyle);
 
     edit->PointSet = new SoMarkerSet;
     edit->PointSet->setName("PointSet");
@@ -6450,10 +6549,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     edit->CurvesCoordinate->setName("CurvesCoordinate");
     curvesRoot->addChild(edit->CurvesCoordinate);
 
-    drawStyle = new SoDrawStyle;
-    drawStyle->setName("CurvesDrawStyle");
-    drawStyle->lineWidth = 3;
-    curvesRoot->addChild(drawStyle);
+    edit->CurvesDrawStyle = new SoDrawStyle;
+    edit->CurvesDrawStyle->setName("CurvesDrawStyle");
+    edit->CurvesDrawStyle->lineWidth = std::lround(3 * edit->pixelScalingFactor);
+    curvesRoot->addChild(edit->CurvesDrawStyle);
 
     edit->CurveSet = new SoLineSet;
     edit->CurveSet->setName("CurvesLineSet");
@@ -6470,10 +6569,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     MtlBind->value = SoMaterialBinding::PER_FACE;
     crossRoot->addChild(MtlBind);
 
-    drawStyle = new SoDrawStyle;
-    drawStyle->setName("RootCrossDrawStyle");
-    drawStyle->lineWidth = 2;
-    crossRoot->addChild(drawStyle);
+    edit->RootCrossDrawStyle = new SoDrawStyle;
+    edit->RootCrossDrawStyle->setName("RootCrossDrawStyle");
+    edit->RootCrossDrawStyle->lineWidth = std::lround(2 * edit->pixelScalingFactor);
+    crossRoot->addChild(edit->RootCrossDrawStyle);
 
     edit->RootCrossMaterials = new SoMaterial;
     edit->RootCrossMaterials->setName("RootCrossMaterials");
@@ -6500,10 +6599,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     edit->EditCurvesCoordinate->setName("EditCurvesCoordinate");
     editCurvesRoot->addChild(edit->EditCurvesCoordinate);
 
-    drawStyle = new SoDrawStyle;
-    drawStyle->setName("EditCurvesDrawStyle");
-    drawStyle->lineWidth = 3;
-    editCurvesRoot->addChild(drawStyle);
+    edit->EditCurvesDrawStyle = new SoDrawStyle;
+    edit->EditCurvesDrawStyle->setName("EditCurvesDrawStyle");
+    edit->EditCurvesDrawStyle->lineWidth = std::lround(3 * edit->pixelScalingFactor);
+    editCurvesRoot->addChild(edit->EditCurvesDrawStyle);
 
     edit->EditCurveSet = new SoLineSet;
     edit->EditCurveSet->setName("EditCurveLineSet");
@@ -6529,7 +6628,7 @@ void ViewProviderSketch::createEditInventorNodes(void)
     Coordsep->addChild(CoordTextMaterials);
 
     SoFont *font = new SoFont();
-    font->size.setValue(coinFontSize);
+    font->size.setValue(edit->coinFontSize);
 
     Coordsep->addChild(font);
 
@@ -6549,10 +6648,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     edit->EditRoot->addChild(MtlBind);
 
     // use small line width for the Constraints
-    drawStyle = new SoDrawStyle;
-    drawStyle->setName("ConstraintDrawStyle");
-    drawStyle->lineWidth = 1;
-    edit->EditRoot->addChild(drawStyle);
+    edit->ConstraintDrawStyle = new SoDrawStyle;
+    edit->ConstraintDrawStyle->setName("ConstraintDrawStyle");
+    edit->ConstraintDrawStyle->lineWidth = std::lround(1 * edit->pixelScalingFactor);
+    edit->EditRoot->addChild(edit->ConstraintDrawStyle);
 
     // add the group where all the constraints has its SoSeparator
     edit->constrGroup = new SmSwitchboard();
@@ -6566,10 +6665,10 @@ void ViewProviderSketch::createEditInventorNodes(void)
     edit->EditRoot->addChild(MtlBind);
 
     // use small line width for the information visual
-    drawStyle = new SoDrawStyle;
-    drawStyle->setName("InformationDrawStyle");
-    drawStyle->lineWidth = 1;
-    edit->EditRoot->addChild(drawStyle);
+    edit->InformationDrawStyle = new SoDrawStyle;
+    edit->InformationDrawStyle->setName("InformationDrawStyle");
+    edit->InformationDrawStyle->lineWidth = std::lround(1 * edit->pixelScalingFactor);
+    edit->EditRoot->addChild(edit->InformationDrawStyle);
 
     // add the group where all the information entity has its SoSeparator
     edit->infoGroup = new SoGroup();