From 66de7f3968fc479267b5233f10ed5fc7f427a28d Mon Sep 17 00:00:00 2001
From: PaddleStroke <pierrelouis.boyer@gmail.com>
Date: Thu, 1 Feb 2024 13:58:13 +0100
Subject: [PATCH] SoDatumLabel: Add arrowheads to angles. And improve arrowhead
 rendering.

---
 src/Gui/SoDatumLabel.cpp | 57 +++++++++++++++++++++++++++++++---------
 1 file changed, 45 insertions(+), 12 deletions(-)

diff --git a/src/Gui/SoDatumLabel.cpp b/src/Gui/SoDatumLabel.cpp
index 52f1823317..f5fad40ee5 100644
--- a/src/Gui/SoDatumLabel.cpp
+++ b/src/Gui/SoDatumLabel.cpp
@@ -924,7 +924,7 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
         // Set GL Properties
         glLineWidth(this->lineWidth.getValue());
         glColor3f(t[0], t[1], t[2]);
-        float margin = this->imgHeight / 4.0;
+        float margin = this->imgHeight / 3.0;
 
 
         SbVec3f perp1 = p1_ + normal * (length + offset1 * scale);
@@ -974,15 +974,17 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
             glVertex2f(par4[0], par4[1]);
         glEnd();
 
+        float arrowWidth = margin * 0.5;
+
         SbVec3f ar1 = par1 + ((flipTriang) ? -1 : 1) * dir * 0.866f * 2 * margin;
-        SbVec3f ar2 = ar1 + normal * margin;
-                ar1 -= normal * margin;
+        SbVec3f ar2 = ar1 + normal * arrowWidth;
+        ar1 -= normal * arrowWidth;
 
         SbVec3f ar3 = par4 - ((flipTriang) ? -1 : 1) * dir * 0.866f * 2 * margin;
-        SbVec3f ar4 = ar3 + normal * margin ;
-                ar3 -= normal * margin;
+        SbVec3f ar4 = ar3 + normal * arrowWidth;
+        ar3 -= normal * arrowWidth;
 
-        //Draw a pretty arrowhead (Equilateral) (Eventually could be improved to other shapes?)
+        // Draw the arrowheads
         glBegin(GL_TRIANGLES);
             glVertex2f(par1[0], par1[1]);
             glVertex2f(ar1[0], ar1[1]);
@@ -1059,13 +1061,14 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
 
         textOffset = pos;
 
-        float margin = this->imgHeight / 4.0;
+        float margin = this->imgHeight / 3.0;
 
         // Create the arrowhead
+        float arrowWidth = margin * 0.5;
         SbVec3f ar0  = p2;
         SbVec3f ar1  = p2 - dir * 0.866f * 2 * margin;
-        SbVec3f ar2  = ar1 + normal * margin;
-        ar1 -= normal * margin;
+        SbVec3f ar2  = ar1 + normal * arrowWidth;
+        ar1 -= normal * arrowWidth;
 
         SbVec3f p3 = pos +  dir * (this->imgWidth / 2 + margin);
         if ((p3-p1).length() > (p2-p1).length())
@@ -1094,8 +1097,8 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
             // create second arrowhead
             SbVec3f ar0_1  = p1;
             SbVec3f ar1_1  = p1 + dir * 0.866f * 2 * margin;
-            SbVec3f ar2_1  = ar1_1 + normal * margin;
-            ar1_1 -= normal * margin;
+            SbVec3f ar2_1  = ar1_1 + normal * arrowWidth;
+            ar1_1 -= normal * arrowWidth;
 
             glBegin(GL_TRIANGLES);
                 glVertex2f(ar0_1[0], ar0_1[1]);
@@ -1125,7 +1128,7 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
         // Only the angle intersection point is needed
         SbVec3f p0 = points[0];
 
-        float margin = this->imgHeight / 4.0;
+        float margin = this->imgHeight / 3.0;
 
         // Load the Parameters
         float length     = this->param1.getValue();
@@ -1195,6 +1198,36 @@ void SoDatumLabel::GLRender(SoGLRenderAction * action)
             glVertex2f(pnt4[0],pnt4[1]);
         glEnd();
 
+        // Create the arrowheads
+        float arrowLength = margin * 2;
+        float arrowWidth = margin * 0.5;
+
+        // Normals for the arrowheads
+        SbVec3f dirStart(v1[1], -v1[0], 0);
+        SbVec3f dirEnd(-v2[1], v2[0], 0);
+
+        // Calculate arrowhead points for start angle
+        SbVec3f startArrowBase = p0 + r * v1;
+        SbVec3f startArrowLeft = startArrowBase - arrowLength * dirStart + arrowWidth * v1;
+        SbVec3f startArrowRight = startArrowBase - arrowLength * dirStart - arrowWidth * v1;
+
+        // Calculate arrowhead points for end angle
+        SbVec3f endArrowBase = p0 + r * v2;
+        SbVec3f endArrowLeft = endArrowBase - arrowLength * dirEnd + arrowWidth * v2;
+        SbVec3f endArrowRight = endArrowBase - arrowLength * dirEnd - arrowWidth * v2;
+
+        // Draw arrowheads
+        glBegin(GL_TRIANGLES);
+        // Start angle arrowhead
+        glVertex2f(startArrowBase[0], startArrowBase[1]);
+        glVertex2f(startArrowLeft[0], startArrowLeft[1]);
+        glVertex2f(startArrowRight[0], startArrowRight[1]);
+
+        // End angle arrowhead
+        glVertex2f(endArrowBase[0], endArrowBase[1]);
+        glVertex2f(endArrowLeft[0], endArrowLeft[1]);
+        glVertex2f(endArrowRight[0], endArrowRight[1]);
+        glEnd();
     }
     else if (this->datumtype.getValue() == SYMMETRIC) {