From f523f6c3ad4e8db70f81b67486c8311dfcf8b2eb Mon Sep 17 00:00:00 2001
From: PaddleStroke <pierrelouis.boyer@gmail.com>
Date: Fri, 26 Apr 2024 21:27:32 +0200
Subject: [PATCH] TechDraw: Introduce dimension snapping

---
 src/Mod/TechDraw/Gui/QGIViewDimension.cpp | 88 ++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 3 deletions(-)

diff --git a/src/Mod/TechDraw/Gui/QGIViewDimension.cpp b/src/Mod/TechDraw/Gui/QGIViewDimension.cpp
index c8a967b38e..00b2fa8520 100644
--- a/src/Mod/TechDraw/Gui/QGIViewDimension.cpp
+++ b/src/Mod/TechDraw/Gui/QGIViewDimension.cpp
@@ -53,6 +53,7 @@
 #include "QGIDimLines.h"
 #include "QGIVertex.h"
 #include "QGCustomSvg.h"
+#include "TaskSelectLineAttributes.h"
 #include "ViewProviderDimension.h"
 #include "ZVALUE.h"
 
@@ -155,12 +156,24 @@ void QGIDatumLabel::snapPosition(QPointF& pos)
         return;
     }
 
-    // First we try to snap the label to its center position.
+    // We only have snap for distances constraints
+    std::string type = dim->Type.getValueAsString();
+    if(type != "Distance" && type != "DistanceX" && type != "DistanceY") {
+        return;
+    }
+
+    // 1 - We try to snap the label to its center position.
     pointPair pp = dim->getLinearPoints();
     Base::Vector3d p1_3d = Rez::guiX(pp.first());
     Base::Vector3d p2_3d = Rez::guiX(pp.second());
     Base::Vector2d p1 = Base::Vector2d(p1_3d.x, p1_3d.y);
     Base::Vector2d p2 = Base::Vector2d(p2_3d.x, p2_3d.y);
+    if (type == "DistanceX") {
+        p2 = Base::Vector2d(p2.x, p1.y);
+    }
+    else if (type == "DistanceY") {
+        p2 = Base::Vector2d(p1.x, p2.y);
+    }
     Base::Vector2d mid = (p1 + p2) * 0.5;
     Base::Vector2d dir = p2 - p1;
     Base::Vector2d normal = Base::Vector2d(-dir.y, dir.x);
@@ -171,11 +184,80 @@ void QGIDatumLabel::snapPosition(QPointF& pos)
     projPnt = projPnt + mid;
 
     if ((projPnt - posV).Length() < dir.Length() * snapPercent) {
-        pos.setX(projPnt.x - m_dimText->boundingRect().width() * 0.5);
-        pos.setY(projPnt.y - m_dimText->boundingRect().height() * 0.5);
+        posV = projPnt;
+        pos.setX(posV.x - m_dimText->boundingRect().width() * 0.5);
+        pos.setY(posV.y - m_dimText->boundingRect().height() * 0.5);
 
     }
 
+    // 2 - We check for coord/chain dimensions to offer proper snapping
+    auto* qgiv = dynamic_cast<QGIView*>(qgivd->parentItem());
+    if (qgiv) {
+        auto* dvp = dynamic_cast<TechDraw::DrawViewPart*>(qgiv->getViewObject());
+        if (dvp) {
+            std::vector<TechDraw::DrawViewDimension*> dims = dvp->getDimensions();
+            double dimSpacing = Rez::guiX(activeDimAttributes.getCascadeSpacing());
+            snapPercent = 0.2;
+            for (auto& d : dims) {
+                if (d == dim) { continue; }
+
+                std::string dType = d->Type.getValueAsString();
+                if (dType != type) {
+                    continue;
+                }
+
+                pp = d->getLinearPoints();
+                Base::Vector3d ip1_3d = Rez::guiX(pp.first());
+                Base::Vector3d ip2_3d = Rez::guiX(pp.second());
+
+                Base::Vector2d ip1 = Base::Vector2d(ip1_3d.x, ip1_3d.y);
+                Base::Vector2d ip2 = Base::Vector2d(ip2_3d.x, ip2_3d.y);
+                if (type == "DistanceX") {
+                    ip2 = Base::Vector2d(ip2.x, ip1.y);
+                }
+                else if (type == "DistanceY") {
+                    ip2 = Base::Vector2d(ip1.x, ip2.y);
+                }
+                Base::Vector2d imid = (ip1 + ip2) * 0.5;
+                Base::Vector2d idir = ip2 - ip1;
+                Base::Vector2d inormal = Base::Vector2d(-idir.y, idir.x);
+
+                if (type == "Distance" && fabs(dir.x * idir.y - dir.y * idir.x) > Precision::Confusion()) {
+                    //dimensions not parallel
+                    continue;
+                }
+
+                auto* vp = dynamic_cast<ViewProviderDimension*>(Gui::Application::Instance->getViewProvider(d));
+                if (!vp) { continue; }
+                auto* qgivDi(dynamic_cast<QGIViewDimension*>(vp->getQView()));
+                if (!qgivDi) { continue; }
+                auto labeli = qgivDi->getDatumLabel();
+                if (!labeli) { continue; }
+                QPointF posi = labeli->pos();
+                Base::Vector2d posVi = Base::Vector2d(posi.x() + labeli->m_dimText->boundingRect().width() * 0.5,
+                    posi.y() + labeli->m_dimText->boundingRect().height() * 0.5);
+
+                Base::Vector2d projPnt2;
+                projPnt2.ProjectToLine(posV - posVi, idir);
+                projPnt2 = projPnt2 + posVi;
+
+                if ((projPnt2 - posV).Length() < dimSpacing * snapPercent) {
+                    posV = projPnt2;
+                    pos.setX(posV.x - m_dimText->boundingRect().width() * 0.5);
+                    pos.setY(posV.y - m_dimText->boundingRect().height() * 0.5);
+                    break;
+                }
+                else if (fabs((projPnt2 - posV).Length() - fabs(dimSpacing)) < dimSpacing * snapPercent) {
+                    posV = projPnt2 + (posV - projPnt2).Normalize() * dimSpacing;
+                    pos.setX(posV.x - m_dimText->boundingRect().width() * 0.5);
+                    pos.setY(posV.y - m_dimText->boundingRect().height() * 0.5);
+                    break;
+                }
+            }
+        }
+    }
+
+
     setPos(pos); // no infinite loop because if pos doesn't change then itemChanged is not triggered.
 }