Resolve viewport dimension features and preserve valid measurements on refresh

tests/fixtures/dim_assoc/README.md

@@ -0,0 +1,16 @@
+# Viewport association fixture
+
+`viewport_associations.dxf` is a synthetic paper-space fixture for line, circle,
+arc, polyline, spline, block-instance, and intersection references through one
+1:2 viewport. `src/app/viewport_dimension_tests.rs` loads it and exercises actual
+association refresh and an edit to the second intersection source.
+
+Each dimension carries `DIMLFAC=-2` and `ACAD_DIMASSOC_CALC_DIMLFAC=-2`. These are
+necessary for its paper definition points and saved model measurements to agree;
+the original fixture omitted both factors. The spline tangent also uses the
+actual touch point `(90, 283.125)` at parameter `0.75`, measured from `(0, 300)`.
+The original endpoint `(120, 300)` was not tangent. Tests verify the cross product
+with the spline derivative and preservation after an unsupported reference edit.
+
+The larger original `115448.dxf` is private and is not included. An opt-in test
+uses `OPENCAD_VIEWPORT_REGRESSION_DXF` to read a local copy without modifying it.

tests/fixtures/dim_assoc/viewport_associations.dxf

@@ -788,6 +788,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -844,6 +860,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -900,6 +932,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -956,6 +1004,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -991,7 +1055,7 @@ AcDbDimension
 71
 5
 42
-120.0
+91.56836585306085
 1
 
 3
@@ -1005,13 +1069,29 @@ AcDbAlignedDimension
 33
 0.0
 14
-135.0
+120.0
 24
-175.0
+166.5625
 34
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -1068,6 +1148,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 DIMENSION
 5
@@ -1124,6 +1220,22 @@ AcDbAlignedDimension
 0.0
 50
 0.0
+1001
+ACAD_DIMASSOC_CALC_DIMLFAC
+1040
+-2.0
+1001
+ACAD
+1000
+DSTYLE
+1002
+{
+1070
+144
+1040
+-2.0
+1002
+}
 0
 ENDSEC
 0
@@ -1475,11 +1587,11 @@ AcDbOsnapPointRef
 91
 -2
 40
-1.0
+0.75
 10
-120.0
+90.0
 20
-300.0
+283.125
 30
 0.0
 75