Handle paste special case when converting bitmap

Library export to file requires a library container but when pasting, we
paste into an existing library, so we need to skip the library header.

Long term solution would be to allow pasting library with multiple
symbols into existing library

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19688

bitmap2component/bitmap2component.cpp

@@ -34,6 +34,7 @@
 
 #include <build_version.h>
 #include <locale_io.h>
+#include <macros.h>
 #include <potracelib.h>
 #include <reporter.h>
 #include <fmt/format.h>
@@ -127,6 +128,7 @@ int BITMAPCONV_INFO::ConvertBitmap( potrace_bitmap_t* aPotrace_bitmap, OUTPUT_FM
         break;
 
     case SYMBOL_FMT:
+    case SYMBOL_PASTE_FMT:
         m_ScaleX = SCH_IU_PER_MM * 25.4 / aDpi_X;   // the conversion scale from PPI to eeschema iu
         m_ScaleY = -SCH_IU_PER_MM * 25.4 / aDpi_Y;  // Y axis is bottom to Top for components in libs
         createOutputData();
@@ -192,12 +194,15 @@ void BITMAPCONV_INFO::outputDataHeader( const wxString& aBrdLayerName )
         break;
 
     case SYMBOL_FMT:
+        m_Data += fmt::format( "(kicad_symbol_lib (version 20220914) (generator \"bitmap2component\") (generator_version \"{}\")\n",
+                               GetMajorMinorVersion().ToStdString() );
+        KI_FALLTHROUGH;
+
+    case SYMBOL_PASTE_FMT:
         fieldSize = 1.27;             // fields text size in mm (= 50 mils)
         Ypos /= SCH_IU_PER_MM;
         Ypos += fieldSize / 2;
-        m_Data += fmt::format( "(kicad_symbol_lib (version 20220914) (generator \"bitmap2component\") (generator_version \"{}\")\n"
-                               "  (symbol \"{}\" (pin_names (offset 1.016)) (in_bom yes) (on_board yes)\n",
-                               GetMajorMinorVersion().ToStdString(),
+        m_Data += fmt::format( "  (symbol \"{}\" (pin_names (offset 1.016)) (in_bom yes) (on_board yes)\n",
                                m_CmpName.c_str() );
 
         m_Data += fmt::format( "    (property \"Reference\" \"#G\" (at 0 {:g} 0)\n"
@@ -246,6 +251,11 @@ void BITMAPCONV_INFO::outputDataEnd()
         m_Data += "  )\n)\n";
         break;
 
+    case SYMBOL_PASTE_FMT:
+        m_Data += "    )\n";        // end symbol_0_0
+        m_Data += "  )\n";          // end symbol
+        break;
+
     case SYMBOL_FMT:
         m_Data += "    )\n";        // end symbol_0_0
         m_Data += "  )\n";          // end symbol
@@ -336,6 +346,7 @@ void BITMAPCONV_INFO::outputOnePolygon( SHAPE_LINE_CHAIN& aPolygon, const wxStri
         break;
 
     case SYMBOL_FMT:
+    case SYMBOL_PASTE_FMT:
         // The polygon outline thickness is fixed here to 0.01  ( 0.0 is the default thickness)
 #define SCH_LINE_THICKNESS_MM 0.01
         //snprintf( strbuf, sizeof(strbuf), "P %d 0 0 %d", (int) aPolygon.PointCount() + 1, EE_LINE_THICKNESS );