Increase LINE_READER max line length to 16 MB

The previous 1 MB limit caused "Maximum line length exceeded" errors
when loading schematics containing large embedded images or other long
quoted tokens.  The S-expression parser (DSNLEXER) requires entire
quoted strings to fit within a single line buffer, so Prettify cannot
split them across lines.  Raise the limit from 1 MB to 16 MB and add
regression tests.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/23162

include/richio.h

@@ -55,7 +55,7 @@
 KICOMMON_API wxString SafeReadFile( const wxString& aFilePath, const wxString& aReadType );
 
 
-#define LINE_READER_LINE_DEFAULT_MAX        1000000
+#define LINE_READER_LINE_DEFAULT_MAX        16000000
 #define LINE_READER_LINE_INITIAL_SIZE       5000
 
 /**

qa/tests/common/test_richio.cpp

@@ -23,18 +23,94 @@
 
 /**
  * @file
- * Test suite for general string functions
+ * Test suite for RICHIO and related formatting utilities
  */
 
 #include <qa_utils/wx_utils/unit_test_utils.h>
 
-// Code under test
 #include <richio.h>
+#include <io/kicad/kicad_io_utils.h>
+
+#define wxUSE_BASE64 1
+#include <wx/base64.h>
+#include <wx/mstream.h>
+
 
-/**
- * Declare the test suite
- */
 BOOST_AUTO_TEST_SUITE( RichIO )
 
 
-BOOST_AUTO_TEST_SUITE_END()
+/**
+ * Verify that Prettify produces well-formed output for large (data ...) blocks such as
+ * base64-encoded images, and that STRING_LINE_READER can read the result.
+ *
+ * Regression test for https://gitlab.com/kicad/code/kicad/-/issues/23162
+ */
+BOOST_AUTO_TEST_CASE( PrettifyLargeImageData )
+{
+    STRING_FORMATTER fmt;
+
+    fmt.Print( "(kicad_sch (version 20231120) (generator \"eeschema\")" );
+    fmt.Print( "(image (at 0 0)" );
+
+    const size_t imageSize = 2 * 1024 * 1024;
+    std::vector<uint8_t> fakeImage( imageSize, 0x42 );
+
+    wxMemoryOutputStream stream;
+    stream.Write( fakeImage.data(), fakeImage.size() );
+
+    KICAD_FORMAT::FormatStreamData( fmt, *stream.GetOutputStreamBuffer() );
+
+    fmt.Print( ")" );  // close image
+    fmt.Print( ")" );  // close kicad_sch
+
+    std::string buf = fmt.GetString();
+
+    KICAD_FORMAT::Prettify( buf );
+
+    BOOST_CHECK_NO_THROW(
+    {
+        STRING_LINE_READER reader( buf, "test" );
+
+        while( reader.ReadLine() )
+        {
+            // just consume
+        }
+    } );
+}
+
+
+/**
+ * Verify that STRING_LINE_READER can handle prettified output containing a very long
+ * quoted string (e.g. a property value that exceeds the old 1 MB limit).
+ *
+ * Regression test for https://gitlab.com/kicad/code/kicad/-/issues/23162
+ */
+BOOST_AUTO_TEST_CASE( PrettifyLongQuotedString )
+{
+    const size_t longLen = 1100000;
+    std::string longValue( longLen, 'A' );
+
+    STRING_FORMATTER fmt;
+
+    fmt.Print( "(kicad_sch (version 20231120)" );
+    fmt.Print( "(property \"Description\" %s (at 0 0 0))",
+               fmt.Quotes( longValue ).c_str() );
+    fmt.Print( ")" );
+
+    std::string buf = fmt.GetString();
+
+    KICAD_FORMAT::Prettify( buf );
+
+    BOOST_CHECK_NO_THROW(
+    {
+        STRING_LINE_READER reader( buf, "test" );
+
+        while( reader.ReadLine() )
+        {
+            // just consume
+        }
+    } );
+}
+
+
+BOOST_AUTO_TEST_SUITE_END()