From 5cd88dbd203a442f0640207e4655b33439349071 Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sun, 3 Sep 2023 20:43:20 +0100
Subject: [PATCH] Bug fixes for paste margins on custom-shaped pads.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/15125

(cherry picked from commit 60419f542a7e9719a0d6164fac1fdf165b9ae319)
---
 pcbnew/dialogs/dialog_pad_properties.cpp |  2 +-
 pcbnew/pad.cpp                           | 26 +++++++++++++++++++-----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/pcbnew/dialogs/dialog_pad_properties.cpp b/pcbnew/dialogs/dialog_pad_properties.cpp
index e231bbdad2..3b8ad6e2e8 100644
--- a/pcbnew/dialogs/dialog_pad_properties.cpp
+++ b/pcbnew/dialogs/dialog_pad_properties.cpp
@@ -1250,7 +1250,7 @@ bool DIALOG_PAD_PROPERTIES::padValuesOK()
 
     if( m_dummyPad->GetShape() == PAD_SHAPE::CUSTOM )
     {
-        // allow 0-sized anchor pads
+        pad_size = m_dummyPad->GetBoundingBox().GetSize();
     }
     else if( m_dummyPad->GetShape() == PAD_SHAPE::CIRCLE )
     {
diff --git a/pcbnew/pad.cpp b/pcbnew/pad.cpp
index 6f62fcc8a0..1e8dc15bcb 100644
--- a/pcbnew/pad.cpp
+++ b/pcbnew/pad.cpp
@@ -942,11 +942,14 @@ VECTOR2I PAD::GetSolderPasteMargin() const
     pad_margin.y = margin + KiROUND( m_size.y * mratio );
 
     // ensure mask have a size always >= 0
-    if( pad_margin.x < -m_size.x / 2 )
-        pad_margin.x = -m_size.x / 2;
+    if( m_padShape != PAD_SHAPE::CUSTOM )
+    {
+        if( pad_margin.x < -m_size.x / 2 )
+            pad_margin.x = -m_size.x / 2;
 
-    if( pad_margin.y < -m_size.y / 2 )
-        pad_margin.y = -m_size.y / 2;
+        if( pad_margin.y < -m_size.y / 2 )
+            pad_margin.y = -m_size.y / 2;
+    }
 
     return pad_margin;
 }
@@ -1683,7 +1686,7 @@ void PAD::TransformShapeToPolygon( SHAPE_POLY_SET& aBuffer, PCB_LAYER_ID aLayer,
         outline.Rotate( m_orient );
         outline.Move( VECTOR2I( padShapePos ) );
 
-        if( aClearance )
+        if( aClearance > 0 )
         {
             int numSegs = std::max( GetArcToSegmentCount( aClearance, aError, FULL_CIRCLE ),
                                                           pad_min_seg_per_circle_count );
@@ -1699,6 +1702,19 @@ void PAD::TransformShapeToPolygon( SHAPE_POLY_SET& aBuffer, PCB_LAYER_ID aLayer,
             outline.Simplify( SHAPE_POLY_SET::PM_FAST );
             outline.Fracture( SHAPE_POLY_SET::PM_FAST );
         }
+        else if( aClearance < 0 )
+        {
+            // Negative clearances are primarily for drawing solder paste layer, so we don't
+            // worry ourselves overly about which side the error is on.
+
+            int numSegs = std::max( GetArcToSegmentCount( aClearance, aError, FULL_CIRCLE ),
+                                                          pad_min_seg_per_circle_count );
+
+            // aClearance is negative so this is actually a deflate
+            outline.Inflate( aClearance, numSegs );
+            outline.Simplify( SHAPE_POLY_SET::PM_FAST );
+            outline.Fracture( SHAPE_POLY_SET::PM_FAST );
+        }
 
         aBuffer.Append( outline );
         break;