Made errors print to stderr so eval wont try to evaluate them

main.cpp

             printf( "Y=0\n" );
             printf( "W=0\n" );
             printf( "H=0\n" );
-            printf( "User right-clicked. Canceled selection.\n" );
+            fprintf( stderr, "User right-clicked. Canceled selection.\n" );
             state = -1;
             running = false;
         }

options.cpp

             if ( i == 0 ) {
                 continue;
             }
-            printf( "Error: Unknown argument %s\n", argv[i] );
-            printf( "Try -h or --help for help.\n" );
+            fprintf( stderr, "Error: Unknown argument %s\n", argv[i] );
+            fprintf( stderr, "Try -h or --help for help.\n" );
             return 1;
         }
     }
     char* x = new char[ arg.size() ];
     int num = sscanf( copy.c_str(), "%s %i", x, returnInt );
     if ( num != 2 ) {
-        printf( "Error parsing command arguments near %s\n", arg.c_str() );
-        printf( "Usage: %s=INT\n", x );
-        printf( "Example: %s=10 or %s=-12\n", x, x );
-        printf( "Try -h or --help for help.\n" );
+        fprintf( stderr, "Error parsing command arguments near %s\n", arg.c_str() );
+        fprintf( stderr, "Usage: %s=INT\n", x );
+        fprintf( stderr, "Example: %s=10 or %s=-12\n", x, x );
+        fprintf( stderr, "Try -h or --help for help.\n" );
         delete[] x;
         return 1;
     }
     char* y = new char[ arg.size() ];
     int num = sscanf( copy.c_str(), "%s %s", x, y );
     if ( num != 2 ) {
-        printf( "Error parsing command arguments near %s\n", arg.c_str() );
-        printf( "Usage: %s=STRING\n", x );
-        printf( "Example: %s=:0 or %s=hostname:0.1\n", x, x );
-        printf( "Try -h or --help for help.\n" );
+        fprintf( stderr, "Error parsing command arguments near %s\n", arg.c_str() );
+        fprintf( stderr, "Usage: %s=STRING\n", x );
+        fprintf( stderr, "Example: %s=:0 or %s=hostname:0.1\n", x, x );
+        fprintf( stderr, "Try -h or --help for help.\n" );
         delete[] x;
         delete[] y;
         return 1;

x.cpp

     // Initialize display
     m_display = XOpenDisplay( display.c_str() );
     if ( !m_display ) {
-        printf( "Failed to open X display %s\n", display.c_str() );
+        fprintf( stderr, "Error: Failed to open X display %s\n", display.c_str() );
         return 1;
     }
     m_screen    = ScreenOfDisplay( m_display, DefaultScreen( m_display ) );
                             PointerMotionMask | ButtonPressMask | ButtonReleaseMask,
                             GrabModeAsync, GrabModeAsync, m_root, xfontcursor, CurrentTime );
     if ( err != GrabSuccess ) {
-        printf( "Failed to grab X cursor.\n" );
+        fprintf( stderr, "Error: Failed to grab X cursor.\n" );
         return 1;
     }