PD: Add offset / overall length modes for LinearPattern

This commit adds support for two separate modes of defining distance
between elements in PD's Linear Pattern.

1. Overall Length - which works exactly like it works before,
2. Spacing - which allows user to explicitly define distance (offset) between
   features.

src/Mod/PartDesign/App/FeatureLinearPattern.cpp

@@ -51,25 +51,42 @@ PROPERTY_SOURCE(PartDesign::LinearPattern, PartDesign::Transformed)
 
 const App::PropertyIntegerConstraint::Constraints LinearPattern::intOccurrences = { 1, INT_MAX, 1 };
 
+const char* LinearPattern::ModeEnums[] = { "length", "offset", nullptr };
+
 LinearPattern::LinearPattern()
 {
+    auto initialMode = LinearPatternMode::length;
+
     ADD_PROPERTY_TYPE(Direction,(nullptr),"LinearPattern",(App::PropertyType)(App::Prop_None),"Direction");
     ADD_PROPERTY(Reversed,(0));
+    ADD_PROPERTY(Mode, (long(initialMode)));
     ADD_PROPERTY(Length,(100.0));
+    ADD_PROPERTY(Offset,(10.0));
     ADD_PROPERTY(Occurrences,(3));
     Occurrences.setConstraints(&intOccurrences);
+    Mode.setEnums(ModeEnums);
+    setReadWriteStatusForMode(initialMode);
 }
 
 short LinearPattern::mustExecute() const
 {
     if (Direction.isTouched() ||
         Reversed.isTouched() ||
-        Length.isTouched() ||
+        Mode.isTouched() ||
+        // Length and Offset are mutually exclusive, only one could be updated at once
+        Length.isTouched() || 
+        Offset.isTouched() || 
         Occurrences.isTouched())
         return 1;
     return Transformed::mustExecute();
 }
 
+void LinearPattern::setReadWriteStatusForMode(LinearPatternMode mode)
+{
+    Length.setReadOnly(mode != LinearPatternMode::length);
+    Offset.setReadOnly(mode != LinearPatternMode::offset);
+}
+
 const std::list<gp_Trsf> LinearPattern::getTransformations(const std::vector<App::DocumentObject*>)
 {
     int occurrences = Occurrences.getValue();
@@ -173,7 +190,20 @@ const std::list<gp_Trsf> LinearPattern::getTransformations(const std::vector<App
     dir.Transform(invObjLoc.Transformation());
 
     gp_Vec offset(dir.X(), dir.Y(), dir.Z());
-    offset *= distance / (occurrences - 1);
+
+    switch (static_cast<LinearPatternMode>(Mode.getValue())) {
+        case LinearPatternMode::length:
+            offset *= distance / (occurrences - 1);
+            break;
+
+        case LinearPatternMode::offset:
+            offset *= Offset.getValue();
+            break;
+
+        default:
+            throw Base::ValueError("Invalid mode");
+    }
+
     if (reversed)
         offset.Reverse();
 
@@ -206,4 +236,14 @@ void LinearPattern::handleChangedPropertyType(Base::XMLReader& reader, const cha
     }
 }
 
+void LinearPattern::onChanged(const App::Property* prop)
+{
+    if (prop == &Mode) {
+        auto mode = static_cast<LinearPatternMode>(Mode.getValue());
+        setReadWriteStatusForMode(mode);
+    }
+
+    Transformed::onChanged(prop);
+}
+
 }

src/Mod/PartDesign/App/FeatureLinearPattern.h

@@ -29,6 +29,10 @@
 
 namespace PartDesign
 {
+enum class LinearPatternMode {
+    length,
+    offset
+};
 
 class PartDesignExport LinearPattern : public PartDesign::Transformed
 {
@@ -37,9 +41,11 @@ class PartDesignExport LinearPattern : public PartDesign::Transformed
 public:
     LinearPattern();
 
-    App::PropertyLinkSub Direction;
-    App::PropertyBool    Reversed;
-    App::PropertyLength  Length;
+    App::PropertyLinkSub     Direction;
+    App::PropertyBool        Reversed;
+    App::PropertyEnumeration Mode;
+    App::PropertyLength      Length;
+    App::PropertyLength      Offset;
     App::PropertyIntegerConstraint Occurrences;
 
    /** @name methods override feature */
@@ -54,11 +60,18 @@ public:
 
     /** Create transformations
       * Returns a list of (Occurrences - 1) transformations since the first, untransformed instance
-      * is not counted. Each transformation will move the shape it is applied to by the distance
-      * (Length / (Occurrences - 1)) so that the transformations will cover the total Length.
+      * is not counted. 
+      * 
+      * Depending on Mode selection list will be constructed differently:
+      * 1. For "Overall Length" each transformation will move the shape it is applied to by the distance
+      *    (Length / (Occurrences - 1)) so that the transformations will cover the total Length.
+      * 2. For "Spacing" each transformation will move the shape by the distance explicitly given in 
+      *    the Offset parameter.
+      * 
       * If Direction contains a feature and a face name, then the transformation direction will be
       *   the normal of the given face, which must be planar. If it contains an edge name, then the
       *   transformation direction will be parallel to the given edge, which must be linear
+      * 
       * If Reversed is true, the direction of transformation will be opposite
       */
     const std::list<gp_Trsf> getTransformations(const std::vector<App::DocumentObject*> ) override;
@@ -66,6 +79,12 @@ public:
 protected:
     void handleChangedPropertyType(Base::XMLReader& reader, const char* TypeName, App::Property* prop) override;
     static const App::PropertyIntegerConstraint::Constraints intOccurrences;
+    void onChanged(const App::Property* prop) override;
+
+private:
+    static const char* ModeEnums[];
+
+    void setReadWriteStatusForMode(LinearPatternMode mode);
 };
 
 } //namespace PartDesign

src/Mod/PartDesign/Gui/TaskLinearPatternParameters.cpp

@@ -127,8 +127,12 @@ void TaskLinearPatternParameters::connectSignals()
             this, &TaskLinearPatternParameters::onDirectionChanged);
     connect(ui->checkReverse, &QCheckBox::toggled,
             this, &TaskLinearPatternParameters::onCheckReverse);
+    connect(ui->comboMode, qOverload<int>(&QComboBox::activated),
+            this, &TaskLinearPatternParameters::onModeChanged);
     connect(ui->spinLength, qOverload<double>(&Gui::QuantitySpinBox::valueChanged),
             this, &TaskLinearPatternParameters::onLength);
+    connect(ui->spinOffset, qOverload<double>(&Gui::QuantitySpinBox::valueChanged),
+            this, &TaskLinearPatternParameters::onOffset);
     connect(ui->spinOccurrences, &Gui::UIntSpinBox::unsignedChanged,
             this, &TaskLinearPatternParameters::onOccurrences);
     connect(ui->checkBoxUpdateView, &QCheckBox::toggled,
@@ -153,16 +157,22 @@ void TaskLinearPatternParameters::setupUI()
     // ---------------------
 
     ui->spinLength->bind(pcLinearPattern->Length);
+    ui->spinOffset->bind(pcLinearPattern->Offset);
     ui->spinOccurrences->bind(pcLinearPattern->Occurrences);
     ui->spinOccurrences->setMaximum(pcLinearPattern->Occurrences.getMaximum());
     ui->spinOccurrences->setMinimum(pcLinearPattern->Occurrences.getMinimum());
 
     ui->comboDirection->setEnabled(true);
     ui->checkReverse->setEnabled(true);
+    ui->comboMode->setEnabled(true);
     ui->spinLength->blockSignals(true);
     ui->spinLength->setEnabled(true);
     ui->spinLength->setUnit(Base::Unit::Length);
     ui->spinLength->blockSignals(false);
+    ui->spinOffset->blockSignals(true);
+    ui->spinOffset->setEnabled(true);
+    ui->spinOffset->setUnit(Base::Unit::Length);
+    ui->spinOffset->blockSignals(false);
     ui->spinOccurrences->setEnabled(true);
 
     dirLinks.setCombo(*(ui->comboDirection));
@@ -187,6 +197,7 @@ void TaskLinearPatternParameters::setupUI()
         }
     }
 
+    adaptVisibilityToMode();
     updateUI();
     connectSignals();
 }
@@ -198,9 +209,11 @@ void TaskLinearPatternParameters::updateUI()
     blockUpdate = true;
 
     PartDesign::LinearPattern* pcLinearPattern = static_cast<PartDesign::LinearPattern*>(getObject());
+    PartDesign::LinearPatternMode mode = static_cast<PartDesign::LinearPatternMode>(pcLinearPattern->Mode.getValue());
 
     bool reverse = pcLinearPattern->Reversed.getValue();
     double length = pcLinearPattern->Length.getValue();
+    double offset = pcLinearPattern->Offset.getValue();
     unsigned occurrences = pcLinearPattern->Occurrences.getValue();
 
     if (dirLinks.setCurrentLink(pcLinearPattern->Direction) == -1){
@@ -210,15 +223,26 @@ void TaskLinearPatternParameters::updateUI()
         dirLinks.setCurrentLink(pcLinearPattern->Direction);
     }
 
-    // Note: These three lines would trigger onLength(), on Occurrences() and another updateUI() if we
-    // didn't check for blockUpdate
+    // Note: This block of code would trigger change signal handlers (e.g. onOccurrences())
+    // and another updateUI() if we didn't check for blockUpdate
     ui->checkReverse->setChecked(reverse);
+    ui->comboMode->setCurrentIndex((long)mode);
     ui->spinLength->setValue(length);
+    ui->spinOffset->setValue(offset);
     ui->spinOccurrences->setValue(occurrences);
 
     blockUpdate = false;
 }
 
+void TaskLinearPatternParameters::adaptVisibilityToMode()
+{
+    auto pcLinearPattern = static_cast<PartDesign::LinearPattern*>(getObject());
+    auto mode = static_cast<PartDesign::LinearPatternMode>(pcLinearPattern->Mode.getValue());
+
+    ui->lengthWrapper->setVisible(mode == PartDesign::LinearPatternMode::length);
+    ui->offsetWrapper->setVisible(mode == PartDesign::LinearPatternMode::offset);
+}
+
 void TaskLinearPatternParameters::onUpdateViewTimer()
 {
     setupTransaction();
@@ -294,6 +318,18 @@ void TaskLinearPatternParameters::onCheckReverse(const bool on) {
     kickUpdateViewTimer();
 }
 
+void TaskLinearPatternParameters::onModeChanged(const int mode) {
+    if (blockUpdate)
+        return;
+    PartDesign::LinearPattern* pcLinearPattern = static_cast<PartDesign::LinearPattern*>(getObject());
+    pcLinearPattern->Mode.setValue(mode);
+
+    adaptVisibilityToMode();
+
+    exitSelectionMode();
+    kickUpdateViewTimer();
+}
+
 void TaskLinearPatternParameters::onLength(const double l) {
     if (blockUpdate)
         return;
@@ -304,6 +340,16 @@ void TaskLinearPatternParameters::onLength(const double l) {
     kickUpdateViewTimer();
 }
 
+void TaskLinearPatternParameters::onOffset(const double o) {
+    if (blockUpdate)
+        return;
+    PartDesign::LinearPattern* pcLinearPattern = static_cast<PartDesign::LinearPattern*>(getObject());
+    pcLinearPattern->Offset.setValue(o);
+
+    exitSelectionMode();
+    kickUpdateViewTimer();
+}
+
 void TaskLinearPatternParameters::onOccurrences(const uint n) {
     if (blockUpdate)
         return;
@@ -352,6 +398,7 @@ void TaskLinearPatternParameters::onUpdateView(bool on)
         pcLinearPattern->Direction.setValue(obj,directions);
         pcLinearPattern->Reversed.setValue(getReverse());
         pcLinearPattern->Length.setValue(getLength());
+        pcLinearPattern->Offset.setValue(getOffset());
         pcLinearPattern->Occurrences.setValue(getOccurrences());
 
         recomputeFeature();
@@ -386,11 +433,21 @@ bool TaskLinearPatternParameters::getReverse() const
     return ui->checkReverse->isChecked();
 }
 
+int TaskLinearPatternParameters::getMode() const
+{
+    return ui->comboMode->currentIndex();
+}
+
 double TaskLinearPatternParameters::getLength() const
 {
     return ui->spinLength->value().getValue();
 }
 
+double TaskLinearPatternParameters::getOffset() const
+{
+    return ui->spinOffset->value().getValue();
+}
+
 unsigned TaskLinearPatternParameters::getOccurrences() const
 {
     return ui->spinOccurrences->value();
@@ -436,6 +493,7 @@ void TaskLinearPatternParameters::apply()
     FCMD_OBJ_CMD(tobj,"Reversed = " << getReverse());
 
     ui->spinLength->apply();
+    ui->spinOffset->apply();
     ui->spinOccurrences->apply();
 }
 

src/Mod/PartDesign/Gui/TaskLinearPatternParameters.h

@@ -59,7 +59,9 @@ private Q_SLOTS:
     void onUpdateViewTimer();
     void onDirectionChanged(int num);
     void onCheckReverse(const bool on);
+    void onModeChanged(const int mode);
     void onLength(const double l);
+    void onOffset(const double o);
     void onOccurrences(const uint n);
     void onUpdateView(bool) override;
     void onFeatureDeleted() override;
@@ -72,13 +74,16 @@ protected:
     void clearButtons() override;
     void getDirection(App::DocumentObject*& obj, std::vector<std::string>& sub) const;
     bool getReverse() const;
+    int getMode() const;
     double getLength() const;
+    double getOffset() const;
     unsigned getOccurrences() const;
 
 private:
     void connectSignals();
     void setupUI();
     void updateUI();
+    void adaptVisibilityToMode();
     void kickUpdateViewTimer() const;
 
 private:

src/Mod/PartDesign/Gui/TaskLinearPatternParameters.ui

@@ -70,29 +70,106 @@
     </widget>
    </item>
    <item>
-    <layout class="QHBoxLayout" name="horizontalLayout_2">
+    <layout class="QHBoxLayout">
      <item>
-      <widget class="QLabel" name="label_2">
+      <widget class="QLabel" name="labelMode">
        <property name="text">
-        <string>Length</string>
+        <string>Mode</string>
        </property>
       </widget>
      </item>
      <item>
-      <widget class="Gui::QuantitySpinBox" name="spinLength">
-       <property name="keyboardTracking">
-        <bool>false</bool>
-       </property>
-       <property name="unit" stdset="0">
-        <string notr="true">mm</string>
-       </property>
-       <property name="value">
-        <double>100.000000000000000</double>
-       </property>
+      <widget class="QComboBox" name="comboMode">
+       <item>
+        <property name="text">
+         <string>Overall Length</string>
+        </property>
+       </item>
+       <item>
+        <property name="text">
+         <string>Offset</string>
+        </property>
+       </item>
       </widget>
      </item>
     </layout>
    </item>
+   <item>
+    <widget class="QWidget" name="lengthWrapper" native="true">
+     <layout class="QHBoxLayout" name="_3">
+      <property name="leftMargin">
+       <number>0</number>
+      </property>
+      <property name="topMargin">
+       <number>0</number>
+      </property>
+      <property name="rightMargin">
+       <number>0</number>
+      </property>
+      <property name="bottomMargin">
+       <number>0</number>
+      </property>
+      <item>
+       <widget class="QLabel" name="labelLength">
+        <property name="text">
+         <string>Length</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="Gui::QuantitySpinBox" name="spinLength" native="true">
+        <property name="keyboardTracking" stdset="0">
+         <bool>false</bool>
+        </property>
+        <property name="unit" stdset="0">
+         <string notr="true">mm</string>
+        </property>
+        <property name="value" stdset="0">
+         <double>100.000000000000000</double>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
+   <item>
+    <widget class="QWidget" name="offsetWrapper" native="true">
+     <layout class="QHBoxLayout" name="_2">
+      <property name="leftMargin">
+       <number>0</number>
+      </property>
+      <property name="topMargin">
+       <number>0</number>
+      </property>
+      <property name="rightMargin">
+       <number>0</number>
+      </property>
+      <property name="bottomMargin">
+       <number>0</number>
+      </property>
+      <item>
+       <widget class="QLabel" name="labelOffset">
+        <property name="text">
+         <string>Offset</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="Gui::QuantitySpinBox" name="spinOffset" native="true">
+        <property name="keyboardTracking" stdset="0">
+         <bool>false</bool>
+        </property>
+        <property name="unit" stdset="0">
+         <string notr="true">mm</string>
+        </property>
+        <property name="value" stdset="0">
+         <double>10.000000000000000</double>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
      <item>