Restrict progressbar to fixed width.

As more and more examples will be processed with this script, the
progresbar would grow way too long. This commit makes the width of
the bar fixed. Every character in the bar now equals 5% progress,
regardless of the number of examples.

bin/example-screenshot.js

@@ -85,31 +85,44 @@
       return util.appendSlash(baseurl) + name + '?mode=' + mode;
     },
     /**
-     * Simple progressbar logger that uses our globals.
+     * Simple progressbar logger that uses our globals pageindex & lenHtmlFiles.
      */
     logProgress: function() {
       var doneSymbol = '-',
           todoSymbol = ' ',
-          str = '[',
-          percent = (lenHtmlFiles === 0) ? 0 : (pageindex / lenHtmlFiles * 100),
+          currentSymbol = '>',
+          barStrLeft = '[',
+          barStrRight = ']',
+          progresStep = 5, // one doneSymbol equals this percentage
+          totalSteps = Math.round(100 / progresStep),
+          ratio = (lenHtmlFiles === 0) ? 0 : (pageindex / lenHtmlFiles),
+          percent = (ratio === 0) ? 0 : ratio * 100,
+          normalizedNumDone = Math.floor(ratio * totalSteps),
+          normalizedNumTodo = totalSteps - normalizedNumDone,
+          progressLine = '',
           i = 0;
-      for (; i < pageindex; i++) {
-        str += doneSymbol;
+      // the progress bar
+      progressLine += barStrLeft;
+      for (; i < normalizedNumDone; i++) {
+        progressLine += doneSymbol;
       }
-      for (i = 0; i < lenHtmlFiles - pageindex; i++) {
-        str += (i === 0) ? '>' : todoSymbol;
+      for (i = 0; i < normalizedNumTodo; i++) {
+        progressLine += (i === 0) ? currentSymbol : todoSymbol;
       }
-      str += ']';
+      progressLine += barStrRight;
+      // the percentage information
+      // pad if necessary
       if (percent < 10) {
-        str += '  ';
+        progressLine += '  ';
       } else if (percent < 100) {
-        str += ' ';
+        progressLine += ' ';
       }
-      str += ' ' + percent.toFixed(1) + ' % done';
+      progressLine += ' ' + percent.toFixed(1) + ' % done';
+      // additional information
       if (fileName !== '') {
-        str += ', ' + util.baseName(fileName) + '';
+        progressLine += ', ' + util.baseName(fileName) + '';
       }
-      console.log(str);
+      console.log(progressLine);
     }
   };