[TD]Fix section snapping (fix #15961) (#15450)

* [TD]Add view snapping preferences

* [TD]fix section snapping algo

- snap sections to section normal line.
- snap views to other views in X&Y

* [TD]fix snapping to ProjectionGroups

src/Mod/TechDraw/App/DrawUtil.cpp

@@ -271,6 +271,37 @@ double DrawUtil::incidenceAngleAtVertex(TopoDS_Edge e, TopoDS_Vertex v, double t
     return incidenceAngle;
 }
 
+
+//! true if actualAngle(degrees) is within allowableError [0,360] of
+//! targetAngle (degrees)
+bool DrawUtil::isWithinRange(double actualAngleIn, double targetAngleIn, double allowableError)
+{
+    constexpr double DegreesPerRevolution{360};
+    constexpr double DegreesPerHalfRevolution{180};
+    // map both angles from [0, 360] to [-180, 180].  This solves the problem of
+    // comparing angles near 0, such as 5deg & 355deg where the desired answer is
+    // 10, not 350;
+    double actualAngleDeg = actualAngleIn;
+    if (actualAngleDeg < DegreesPerRevolution &&
+        actualAngleDeg > DegreesPerHalfRevolution) {
+        actualAngleDeg = actualAngleDeg - DegreesPerRevolution;
+    }
+
+    double targetAngleDeg = targetAngleIn;
+    if (targetAngleDeg < DegreesPerRevolution &&
+        targetAngleDeg > DegreesPerHalfRevolution) {
+        targetAngleDeg = targetAngleDeg - DegreesPerRevolution;
+    }
+
+    double actualError = fabs(targetAngleDeg - actualAngleDeg);
+    if (actualError <= allowableError) {
+        return true;
+    }
+
+    return false;
+}
+
+
 bool DrawUtil::isFirstVert(TopoDS_Edge e, TopoDS_Vertex v, double tolerance)
 {
     TopoDS_Vertex first = TopExp::FirstVertex(e);

src/Mod/TechDraw/App/DrawUtil.h

@@ -275,6 +275,9 @@ public:
     static Base::Vector3d  toAppSpace(const DrawViewPart& dvp, const Base::Vector3d& inPoint);
     static Base::Vector3d  toAppSpace(const DrawViewPart& dvp, const QPointF& inPoint);
 
+    static bool isWithinRange(double actualAngleIn, double targetAngleIn, double allowableError);
+
+
     //debugging routines
     static void dumpVertexes(const char* text, const TopoDS_Shape& s);
     static void dumpEdge(const char* label, int i, TopoDS_Edge e);

src/Mod/TechDraw/App/DrawView.cpp

@@ -42,9 +42,10 @@
 #include "DrawUtil.h"
 #include "DrawViewClip.h"
 #include "DrawViewCollection.h"
+#include "DrawProjGroup.h"
+#include "DrawProjGroupItem.h"
 #include "Preferences.h"
 
-
 using namespace TechDraw;
 using DU = DrawUtil;
 
@@ -652,6 +653,22 @@ void DrawView::setScaleAttribute()
     }
 }
 
+//! due to changes made for the "intelligent" view creation tool, testing for a view being an
+//! instance of DrawProjGroupItem is no longer reliable, as views not in a group are sometimes
+//! created as DrawProjGroupItem without belonging to a group.  We now need to test for the existance
+//! of the parent DrawProjGroup
+bool DrawView::isProjGroupItem(DrawViewPart* item)
+{
+    auto dpgi = dynamic_cast<DrawProjGroupItem*>(item);
+    if (!dpgi) {
+        return false;
+    }
+    auto group = dpgi->getPGroup();
+    if (!group) {
+        return false;
+    }
+    return true;
+}
 int DrawView::prefScaleType()
 {
     return Preferences::getPreferenceGroup("General")->GetInt("DefaultScaleType", 0);

src/Mod/TechDraw/App/DrawView.h

@@ -40,7 +40,7 @@ class DrawPage;
 class DrawViewCollection;
 class DrawViewClip;
 class DrawLeaderLine;
-/*class CosmeticVertex;*/
+class DrawViewPart;
 
 /** Base class of all View Features in the drawing module
  */
@@ -123,6 +123,8 @@ public:
 
     virtual App::PropertyLink *getOwnerProperty() { return nullptr; }
 
+    static bool isProjGroupItem(DrawViewPart* item);
+
 protected:
     void onBeforeChange(const App::Property *prop) override;
     void onChanged(const App::Property* prop) override;

src/Mod/TechDraw/App/DrawViewSection.cpp

@@ -80,6 +80,7 @@
 #include <Base/Console.h>
 #include <Base/FileInfo.h>
 #include <Base/Parameter.h>
+#include <Base/Tools.h>
 
 #include <Mod/Part/App/PartFeature.h>
 
@@ -1152,21 +1153,15 @@ gp_Ax2 DrawViewSection::getSectionCS() const
     return sectionCS;
 }
 
-gp_Ax2 DrawViewSection::getProjectionCS(const Base::Vector3d pt) const
+
+//! return the center of the shape resulting from the cut operation
+Base::Vector3d DrawViewSection::getCutCentroid() const
 {
-    Base::Vector3d vNormal = SectionNormal.getValue();
-    gp_Dir gNormal(vNormal.x, vNormal.y, vNormal.z);
-    Base::Vector3d vXDir = getXDirection();
-    gp_Dir gXDir(vXDir.x, vXDir.y, vXDir.z);
-    if (DrawUtil::fpCompare(fabs(gNormal.Dot(gXDir)), 1.0)) {
-        // can not build a gp_Ax2 from these values
-        throw Base::RuntimeError(
-            "DVS::getProjectionCS - SectionNormal and XDirection are parallel");
-    }
-    gp_Pnt gOrigin(pt.x, pt.y, pt.z);
-    return {gOrigin, gNormal, gXDir};
+    gp_Pnt inputCenter = ShapeUtils::findCentroid(m_cutPieces, getProjectionCS());
+    return Base::Vector3d(inputCenter.X(), inputCenter.Y(), inputCenter.Z());
 }
 
+
 std::vector<LineSet> DrawViewSection::getDrawableLines(int i)
 {
     // Base::Console().Message("DVS::getDrawableLines(%d) - lineSets: %d\n", i, m_lineSets.size());

src/Mod/TechDraw/App/DrawViewSection.h

@@ -134,7 +134,6 @@ public:
     virtual TopoDS_Shape getShapeToPrepare() const { return m_cutPieces; }
 
     //CS related methods
-    gp_Ax2 getProjectionCS(Base::Vector3d pt = Base::Vector3d(0.0, 0.0, 0.0)) const override;
     void setCSFromBase(const std::string sectionName);
     void setCSFromBase(Base::Vector3d localUnit);
     void setCSFromLocalUnit(const Base::Vector3d localUnit);
@@ -172,6 +171,8 @@ public:
 
     TopoDS_Shape makeFaceFromWires(std::vector<TopoDS_Wire> &inWires);
 
+    Base::Vector3d getCutCentroid() const;
+
 public Q_SLOTS:
     virtual void onSectionCutFinished(void);
 

src/Mod/TechDraw/App/Preferences.cpp

@@ -599,3 +599,16 @@ bool Preferences::alwaysShowLabel()
 {
     return getPreferenceGroup("General")->GetBool("AlwaysShowLabel", false);
 }
+
+bool Preferences::SnapViews()
+{
+    return getPreferenceGroup("General")->GetBool("SnapViews", true);
+}
+
+//! percentage of view size to use in deciding to snap view or not
+double Preferences::SnapLimitFactor()
+{
+    return getPreferenceGroup("General")->GetFloat("SnapLimitFactor", 0.05);
+}
+
+

src/Mod/TechDraw/App/Preferences.h

@@ -138,6 +138,9 @@ public:
 
     static bool useCameraDirection();
     static bool alwaysShowLabel();
+
+    static bool SnapViews();
+    static double SnapLimitFactor();
 };