Define Print Preview default printer selection policy

components/policy/resources/policy_templates.json

 {
 # policy_templates.json - Metafile for policy templates
 #
 # The content of this file is evaluated as a Python expression.
 #
 # This file is used as input to generate the following policy templates:
 # ADM, ADMX+ADML, MCX/plist and html documentation.
 #
 # Policy templates are user interface definitions or documents about the
 # policies that can be used to configure Chrome. Each policy is a name-value
@@ skipping 105 matching lines @@
 #   templates and documentation. The policy definition list that Chrome sees
 #   will include policies marked with 'future'. If a WIP policy isn't meant to
 #   be seen by the policy providers either, the 'supported_on' key should be set
 #   to an empty list.
 #
 # IDs:
 #   Since a Protocol Buffer definition is generated from this file, unique and
 #   persistent IDs for all fields (but not for groups!) are needed. These are
 #   specified by the 'id' keys of each policy. NEVER CHANGE EXISTING IDs,
 #   because doing so would break the deployed wire format!
-#   For your editing convenience: highest ID currently used: 307
+#   For your editing convenience: highest ID currently used: 308
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
 #     $1 -> Google Chrome / Chromium
 #     $2 -> Google Chrome OS / Chromium OS
 #     $3 -> Google Chrome Frame / Chromium Frame
 #     $6 is reserved for doc_writer
 #
 # Device Policy:
 #   An additional flag 'device_only' (optional, defaults to False) indicates
@@ skipping 3966 matching lines @@
       'example_value': False,
       'id': 117,
       'caption': '''Disable Print Preview (deprecated)''',
       'desc': '''Show the system print dialog instead of print preview.
 
       When this setting is enabled, <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> will open the system print dialog instead of the built-in print preview when a user requests a page to be printed.
 
       If this policy is not set or is set to false, print commands trigger the print preview screen.''',
     },
     {
+      'name': 'PrintPreviewDefaultPrinterSelection',

[Thiemo Nagel, 2015/10/09 16:35:48]

Why not just DefaultPrinterSelection?

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

In most other places settings and switches for PrintPreview are prefixed so. I
can drop it here, if you think it's a better practice.

[Thiemo Nagel, 2015/10/12 19:10:09]

I think dropping the PrintPreview is easier for users (in this case admins) to
understand, thus I'd be in favour of that.

[Aleksey Shlyapnikov, 2015/10/13 18:14:57]

Done.

+      'type': 'string',
+      'schema': { 'type': 'string' },
+      'supported_on': ['chrome.*:47-', 'chrome_os:47-'],

[Thiemo Nagel, 2015/10/09 16:35:48]

47 has sailed.  Please change to 48.

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

Done.

+      'features': {
+        'dynamic_refresh': True,
+        'per_profile': True,
+      },
+      'example_value': '{ "kind": "cloud", "namePattern": ".*Color" }',

[Thiemo Nagel, 2015/10/09 16:35:48]

Please include an idPattern in the example, too.

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

I'd imagine that in most cases you either match by a name or id, not both at the
same time, but ok. Done.

[Thiemo Nagel, 2015/10/12 19:10:09]

I see.  What is a printer id, anyways?  I was expecting something like
"lc0zeudhs2wlw4ekqtvbjg" but that doesn't seem to be the case?

[Aleksey Shlyapnikov, 2015/10/13 18:14:57]

It depends. For cloud printers that would be the case, some generated id or
GUID, for local printers it will most likely be the same as printer name, for
Privet printers it is provided by the printer, unless it is registered with the
cloud too.
id is more useful for cloud printers, name is a better choice for other types,
but then, if your cloud printer is re-registered often (that is, its id
changes), name match might work here too. So, as I said, it depends.

[Thiemo Nagel, 2015/10/15 15:31:51]

Thanks a lot for the explanation!

Nit: Thinking about this some more: Since you say it doesn't make a lot of sense
to specify name AND idPattern, would it not be useful to change the logic to
look for name OR idPattern?

[Aleksey Shlyapnikov, 2015/10/15 22:12:40]

There're three fields and kind is always joined by AND with the rest. I think
it's more logical to join them all by AND. I'd wait for a feed back and extend
the policy with more features, should there's a demand for more.

+      'id': 308,
+      'caption': '''Print Preview default printer selection policy''',
+      'desc': '''Overrides <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> Print Preview default printer selection rules.

[Thiemo Nagel, 2015/10/09 16:35:48]

How about:

This policy determines the rules for selecting the default printer in <ph
name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> which happens the first time
the print function is used with a profile.

(I'd suggest to avoid the term "Print Preview" because users may not know what
it means.  Probably to them it is just "printing".  Also the headline of the
print preview page is just "Print".)

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

Done.

+
+      Default printer is selected by Print Preview when no printer was previously selected for the current profile.
+
+      When this policy is set, Print Preview will attempt to find a printer matching the specified attributes, printer type, printer id or name patterns, and select it as the current one.

[Thiemo Nagel, 2015/10/09 16:35:48]

Please be more precise about how the final condition is assembled.  (I'm
guessing "kind && (idPattern || namePattern)" but this is not very clear from
the description.)

To be clearer:
"select it as the current one" --> "select it as default printer"

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

It's "matching the _specified_ attributes", that is kind && idPattern &&
namePattern. There is no || condition. If you skip it, we won't care about it.
That's why I did not want to add isPattern to the example, to make it more
obvious that any part can be omitted.
Done to this part.

+
+      If this policy is not set, Print Preview defaults to built-in PDF printer or no printer selected, when PDF printer is not available.
+
+      The value is parsed as JSON object, conforming to the following schema:
+      {
+        "type": "object",
+        "properties": {
+          "kind": {

[Thiemo Nagel, 2015/10/09 16:35:48]

"kind" seems a bit non-descriptive, I think the term "connectivity" (taken from
the description below) would be clearer.

[Aleksey Shlyapnikov, 2015/10/09 21:02:51]

local includes, for example, printers provided by extensions, which is not as
easy to mentally map to 'connectivity'.

+            "description": "Whether to limit the search of the matching printer to a specific set of printers.",
+            "type": {
+              "enum": [ "local", "cloud" ]
+            }
+          },
+          "idPattern": {
+            "description": "Regular expression to match printer id.",
+            "type": "string"
+          },
+          "namePattern": {
+            "description": "Regular expression to match printer display name.",
+            "type": "string"
+          }
+        }
+      }
+
+      Printers connected to Google Cloud Print are considered "cloud", the rest of the printers are classified as "local".
+      Omitting a field means all values match, for example, not specifying connectivity will cause Print Preview to initiate the discovery of all kinds of printers, local and cloud.
+      Regular expression patterns are case sensistive.''',
+    },
+    {
       'name': 'DisableSSLRecordSplitting',
       'type': 'main',
       'schema': { 'type': 'boolean' },
       'supported_on': ['chrome.*:18-', 'chrome_os:18-'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
       'example_value': True,
       'id': 118,
@@ skipping 3518 matching lines @@
       'desc': '''Text appended in parentheses next to the policies top-level container to indicate that those policies are of the Recommended level''',
       'text': 'Default Settings (users can override)',
     },
     'doc_complex_policies_on_windows': {
       'desc': '''Text pointing the user to a help article for complex policies on Windows''',
       'text': '''encoded as a JSON string, for details see <ph name="COMPLEX_POLICIES_URL">https://www.chromium.org/administrators/complex-policies-on-windows<ex>https://www.chromium.org/administrators/complex-policies-on-windows</ex></ph>''',
     },
   },
   'placeholders': [],
 }