extensions/renderer/resources/printer_provider_custom_bindings.js

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 var binding = require('binding').Binding.create('printerProvider');
   6 var printerProviderInternal = require('binding').Binding.create(
   7     'printerProviderInternal').generate();
   8 var eventBindings = require('event_bindings');
   9 var blobNatives = requireNative('blob_natives');
  10
  11 var printerProviderSchema =
  12     requireNative('schema_registry').GetSchema('printerProvider')
  13 var utils = require('utils');
  14 var validate = require('schemaUtils').validate;
  15
  16 // Custom bindings for chrome.printerProvider API.
  17 // The bindings are used to implement callbacks for the API events. Internally
  18 // each event is passed requestId argument used to identify the callback
  19 // associated with the event. This argument is massaged out from the event
  20 // arguments before dispatching the event to consumers. A callback is appended
  21 // to the event arguments. The callback wraps an appropriate
  22 // chrome.printerProviderInternal API function that is used to report the event
  23 // result from the extension. The function is passed requestId and values
  24 // provided by the extension. It validates that the values provided by the
  25 // extension match chrome.printerProvider event callback schemas. It also
  26 // ensures that a callback is run at most once. In case there is an exception
  27 // during event dispatching, the chrome.printerProviderInternal function
  28 // is called with a default error value.
  29 //
  30
  31 // Handles a chrome.printerProvider event as described in the file comment.
  32 // |eventName|: The event name.
  33 // |prepareArgsForDispatch|: Function called before dispatching the event to
  34 //     the extension. It's called with original event |args| list and callback
  35 //     that should be called when the |args| are ready for dispatch. The
  36 //     callbacks should report whether the argument preparation was successful.
  37 //     The function should not change the first argument, which contains the
  38 //     request id.
  39 // |resultreporter|: The function that should be called to report event result.
  40 //     One of chrome.printerProviderInternal API functions.
  41 function handleEvent(eventName, prepareArgsForDispatch, resultReporter) {
  42   eventBindings.registerArgumentMassager(
  43       'printerProvider.' + eventName,
  44       function(args, dispatch) {
  45         var responded = false;
  46
  47         // Validates that the result passed by the extension to the event
  48         // callback matches the callback schema. Throws an exception in case of
  49         // an error.
  50         var validateResult = function(result) {
  51           var eventSchema =
  52               utils.lookup(printerProviderSchema.events, 'name', eventName);
  53           var callbackSchema =
  54               utils.lookup(eventSchema.parameters, 'type', 'function');
  55
  56           validate([result], callbackSchema.parameters);
  57         };
  58
  59         // Function provided to the extension as the event callback argument.
  60         // It makes sure that the event result hasn't previously been returned
  61         // and that the provided result matches the callback schema. In case of
  62         // an error it throws an exception.
  63         var reportResult = function(result) {
  64           if (responded) {
  65             throw new Error(
  66                 'Event callback must not be called more than once.');
  67           }
  68
  69           var finalResult = null;
  70           try {
  71             validateResult(result);  // throws on failure
  72             finalResult = result;
  73           } finally {
  74             responded = true;
  75             resultReporter(args[0] /* requestId */, finalResult);
  76           }
  77         };
  78
  79         prepareArgsForDispatch(args, function(success) {
  80           if (!success) {
  81             // Do not throw an exception since the extension should not yet be
  82             // aware of the event.
  83             resultReporter(args[0] /* requestId */, null);
  84             return;
  85           }
  86           dispatch(args.slice(1).concat(reportResult));
  87         });
  88       });
  89 }
  90
  91 // Sets up printJob.document property for a print request.
  92 function createPrintRequestBlobArguments(args, callback) {
  93   printerProviderInternal.getPrintData(args[0] /* requestId */,
  94                                        function(blobInfo) {
  95     if (chrome.runtime.lastError) {
  96       callback(false);
  97       return;
  98     }
  99
 100     // |args[1]| is printJob.
 101     args[1].document = blobNatives.TakeBrowserProcessBlob(
 102         blobInfo.blobUuid, blobInfo.type, blobInfo.size);
 103     callback(true);
 104   });
 105 }
 106
 107 handleEvent('onGetPrintersRequested',
 108             function(args, callback) { callback(true); },
 109             printerProviderInternal.reportPrinters);
 110
 111 handleEvent('onGetCapabilityRequested',
 112             function(args, callback) { callback(true); },
 113             printerProviderInternal.reportPrinterCapability);
 114
 115 handleEvent('onPrintRequested',
 116             createPrintRequestBlobArguments,
 117             printerProviderInternal.reportPrintResult);
 118
 119 exports.binding = binding.generate();