Gerbview: fix a maximum number (50) of Error messages in report list.

Having a lot of errors can happen when trying to open a non gerber files
(this is easy when loading a zip archive).
With a *lot* of errors (if a large .step file is found) Gerbview can hang.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20799

(cherry picked from commit d5cf54197468a825ba8cf09b46d228d9f425f7d1)

gerbview/gerber_file_image.cpp

@@ -112,6 +112,20 @@ GERBER_FILE_IMAGE::~GERBER_FILE_IMAGE()
 }
 
 
+void GERBER_FILE_IMAGE::AddMessageToList( const wxString& aMessage )
+{
+    /* Add a message to the message list, but only if there are less than max_messages
+     * to avoid very long list (can happens if trying to read a non gerber file)
+     */
+    const int max_messages = 50;    // Arbitrary but reasonable value.
+
+    if( m_messagesList.size() < max_messages )
+        m_messagesList.Add( aMessage );
+    else if( m_messagesList.size() == max_messages )
+        m_messagesList.Add( _( "Too many messages, some are skipped" ) );
+}
+
+
 void GERBER_FILE_IMAGE::SetDrawOffetAndRotation( VECTOR2D aOffsetMM, EDA_ANGLE aRotation )
 {
     m_DisplayOffset.x = KiROUND( aOffsetMM.x * gerbIUScale.IU_PER_MM );

gerbview/gerber_file_image.h

@@ -212,10 +212,7 @@ public:
     /**
      * Add a message to the message list
      */
-    void AddMessageToList( const wxString& aMessage )
+    void AddMessageToList( const wxString& aMessage );
-    {
-        m_messagesList.Add( aMessage );
-    }
 
     /**
      * Return the current coordinate type pointed to by XnnYnn Text (XnnnnYmmmm).

gerbview/readgerb.cpp

@@ -323,7 +323,7 @@ bool GERBER_FILE_IMAGE::LoadGerberFile( const wxString& aFullFileName )
                 break;
 
             default:
-                msg.Printf( wxT( "Unexpected char 0x%2.2X" ), *text );
+                msg.Printf( wxT( "Unexpected char 0x%2.2X (%c)" ), *text, *text );
                 AddMessageToList( msg );
                 text++;
                 break;