Revert "Reintroduce constexpr to COLOR4D"

This reverts commit 33da9b2327 and the
following commit dc08c48f33.

C++17 changed the behavior of static class member variables that are
constexpr defined. Previously this definition/declaration split was
valid for constexpr members, but after C++17 the static constexpr member
variables are automatically inlined, so the declaration is no longer
exported in some compilers (GCC 9/10/11 seem to have problems).

An alternate way of constexpr member variables is putting the
initialization in the class definition, but we can't init a COLOR4D
object when defining the COLOR4D class.

For now, revert this change until we can figure out the proper way of
architecting these colors.

common/gal/color4d.cpp

@@ -521,12 +521,11 @@ COLOR4D& COLOR4D::Desaturate()
     return *this;
 }
 
-// These call the 5-argument constructor to get a constexpr COLOR4D object.
-// The 5th argument isn't actually used at all, so its bool value doesn't matter.
-constexpr COLOR4D COLOR4D::UNSPECIFIED( 0, 0, 0, 0, true );
-constexpr COLOR4D COLOR4D::WHITE( 1, 1, 1, 1, true );
-constexpr COLOR4D COLOR4D::BLACK( 0, 0, 0, 1, true );
-constexpr COLOR4D COLOR4D::CLEAR( 1, 0, 1, 0, true );
+
+const COLOR4D COLOR4D::UNSPECIFIED( 0, 0, 0, 0 );
+const COLOR4D COLOR4D::WHITE( 1, 1, 1, 1 );
+const COLOR4D COLOR4D::BLACK( 0, 0, 0, 1 );
+const COLOR4D COLOR4D::CLEAR( 1, 0, 1, 0 );
 
 
 double COLOR4D::Distance( const COLOR4D& other ) const

cvpcb/CMakeLists.txt

@@ -72,7 +72,6 @@ target_link_libraries( cvpcb_kiface
     3d-viewer
     gal
     common
-    gal       # Circular dependency between gal and common now
     kimath
     ${PCBNEW_IO_LIBRARIES}
     Boost::headers

eeschema/CMakeLists.txt

@@ -437,7 +437,6 @@ target_link_libraries( eeschema
     # There's way too much crap coming in from common yet.
     gal
     common
-    gal       # Circular dependency between gal and common now
     argparse::argparse
     ${wxWidgets_LIBRARIES}
     )
@@ -481,7 +480,6 @@ target_link_libraries( eeschema_kiface
     PRIVATE
         common
         eeschema_kiface_objects
-        gal       # Circular dependency between gal and common now
         markdown_lib
         scripting
         sexpr

gerbview/CMakeLists.txt

@@ -112,7 +112,6 @@ target_link_libraries( gerbview
     # There's way too much crap coming in from common yet.
     gal
     common
-    gal       # Circular dependency between gal and common now
     core
     nlohmann_json
     ${wxWidgets_LIBRARIES}
@@ -156,7 +155,6 @@ target_link_libraries( gerbview_kiface
         nlohmann_json
         gal
         common
-        gal       # Circular dependency between gal and common now
         core
         gerbview_kiface_objects
         ${wxWidgets_LIBRARIES}

include/gal/color4d.h

@@ -129,37 +129,6 @@ public:
         wxASSERT( a >= 0.0 && a <= 1.0 );
     }
 
-    /**
-     * A COLOR4D constructor that is constexpr-capable.
-     *
-     * This constructor simply adds a 5th unused argument to differentiate it from
-     * the normal 4-argument constructor, so any COLOR4D instances that should be compile-time
-     * created should call this 5-argument version, while everyother instance should use the
-     * 4-argument version.
-     *
-     * @param aRed     is the red component   [0.0 .. 1.0].
-     * @param aGreen   is the green component [0.0 .. 1.0].
-     * @param aBlue    is the blue component  [0.0 .. 1.0].
-     * @param aAlpha   is the alpha value     [0.0 .. 1.0].
-     * @param aIsConst is just an argument to differentiate this constructor from the 4-argument one,
-     *                 actual value doesn't matter.
-     */
-    constexpr COLOR4D( double aRed, double aGreen, double aBlue, double aAlpha, bool aIsConst ) :
-        r( aRed ),
-        g( aGreen ),
-        b( aBlue ),
-        a( aAlpha )
-    {
-        /*!!!!!!!!!!!!!!!!!!!!!!
-         * DO NOT change these to wxASSERT or collapse this into the other constructor,
-         * it must remain separate to ensure COLOR4D objects can be compile-time constructed
-         */
-        assert( r >= 0.0 && r <= 1.0 );
-        assert( g >= 0.0 && g <= 1.0 );
-        assert( b >= 0.0 && b <= 1.0 );
-        assert( a >= 0.0 && a <= 1.0 );
-    }
-
     /**
      * @param aColor is one of KiCad's palette colors.
      * @see EDA_COLOR_T

pagelayout_editor/CMakeLists.txt

@@ -85,7 +85,6 @@ target_link_libraries( pl_editor
     # There's way too much crap coming in from common yet.
     gal
     common
-    gal       # Circular dependency between gal and common now
     core
     ${wxWidgets_LIBRARIES}
     )
@@ -104,7 +103,6 @@ add_library( pl_editor_kiface MODULE
 target_link_libraries( pl_editor_kiface
     gal
     common
-    gal       # Circular dependency between gal and common now
     core
     ${wxWidgets_LIBRARIES}
     )

pcbnew/CMakeLists.txt

@@ -626,7 +626,6 @@ make_lexer(
 target_link_libraries( pcbnew_kiface_objects
     PRIVATE
         common
-        gal       # Circular dependency between gal and common now
         core
         dxflib_qcad
         nanosvg