How to debug scripted ePub3 in iBooks?

Question

I have an ePub3 book involving scripting which works fine with Readium, but only partially in iBooks. My guess is that the JavaScript is erroring out at some point (although as a standard web app the exact same code works fine in Safari). Any thoughts on how to go about debugging this?

Quadrennial

Update: this problem turned out not to be a scripting problem, but rather missing content due to some apparent differences in how iBooks handles overflow in the CSS sense--it seems to hide overflow in some cases even when the CSS would indicate it should not. – Quadrennial

Good question nevertheless. IBooks does allow for WebSockets so perhaps a solution could be built on top of it to provide debugging.. – Nel

Good idea. My initial solution was a real simple "console" which allows you to type in and evaluate JS expressions. – Quadrennial

AlexanderN : Did you manage to establish an external connection from iBooks with WebSockets ? I cannot do that – Fancyfree

@AlexanderN I did not try, but if someone else manages to make this work, I'd love to hear the details. – Quadrennial

iBooks will not allow JS to make external network connections of any kind, so WebSockets simply won't work. – Admissible

Answer 1

Azardi Online can be used to read the file using the browser. The built-in or add-in console can be used from there to debug. Or a console shim can be created:

if(!console) {
  console = {
    "_log" : [],
    "log" : function() {
      var arr = [];
      for ( var i = 0; i < arguments.length; i++ ) {
        arr.push( arguments[ i ] );
      }
      this._log.push( arr.join( ", ") );
    },
    "trace" : function() {
      var stack;
      try {
        throw new Error();
      } catch( ex ) {
        stack = ex.stack;
      }
      console.log( "console.trace()\n" + stack.split( "\n" ).slice( 2 ).join( "  \n" ) );
    },
    "dir" : function( obj ) {
      console.log( "Content of " + obj );
      for ( var key in obj ) {
        var value = typeof obj[ key ] === "function" ? "function" : obj[ key ];
        console.log( " -\"" + key + "\" -> \"" + value + "\"" );
      }
    },
    "show" : function() {
      alert( this._log.join( "\n" ) );
      this._log = [];
    }
  };

  window.onerror = function( msg, url, line ) {
    console.log("ERROR: \"" + msg + "\" at \"" + "\", line " + line);
  }

  window.addEventListener( "touchstart", function( e ) {
    if( e.touches.length === 3 ) {
      console.show();
    }
  } );
}

References

• Azardi Online

• Event Handler Attributes

• Debugging JavaScript on Android and iOS

Tetrarch

Yes, or I could run it in Readium, but Readium is not iBooks and neithe is Azardi, unfortunately, as fine a product as that is. But running it in the browser on iPad with its minimalistic console support is a useful idea, thanks, accepting this answer. – Quadrennial

Answer 2

You can enable the Webkit Web Inspector in iBooks with this line in your terminal app to change its settings:

defaults write com.apple.iBooksX WebKitDeveloperExtras -bool YES

You'll find the inspector after re-starting iBooks in the context menu (More > Show Inspector). All the inspector tools are available including console etc.

Attrition

Doesn't seem to work anymore – Oligarchy