CUPS Printers Settings Page

The CUPS Printers settings page (located at chrome://settings/cupsPrinters) displays the the currently configured native printers and allows users to set up their own native printers using CUPS.

The Chrome client code which is responsible for handling UI events from this page is located at chrome/browser/ui/webui/settings/ash/cups_printers_handler.cc

The front-end code for this page is located at chrome/browser/resources/settings/printing_page/

Add Printer Dialogs

There are 4 dialogs that are related to adding a printer. The code for these dialogs is located at cups_add_printer_dialog.js

Discovered Printers Dialog

add-printer-discovery-dialog

Displays discovered network and USB printers which are available for setup.

Manual Dialog

add-printer-manually-dialog

Allows users to manually enter the information of a new printer to be added.

Configuring Dialog

add-printer-configuring-dialog

This dialog is used to indicate to a user that their add printer operation is currently in progress.

Manufacturer Model Dialog

add-printer-manufacturer-model-dialog

This dialog allows the user to select the manufacturer and model of the printer that they are attempting to add. Each manufacturer/model combination corresponds to a PPD file, so this dialog is used to select a PPD file for the printer. There is also the option for the user to provide their own PPD file.

This dialog should only be shown in cases where we were unable to match a PPD to the printer that a user attempted to add.

Edit Printer Dialog

settings-cups-edit-printer-dialog

Allows the user to edit an existing configured printer.

The code for this dialog is located at cups_edit_printer_dialog.js

The following fields of the printer may be changed:

Name: The name of the printer displayed in the UI.
Address: The "hostname" of the printer. This can be a valid hostname, IPv4/6 address, and may be followed by an optional port number. This field can only be edited if the existing printer is already a network printer.
Protocol: The protocol used in the printer's URI. If the existing printer is a network printer then this may only be changed to another network protocol. Otherwise the protocol may not be changed at all.
Queue: The "path" which the address points to. For ipp-based URIs this is typically ipp/print.
Manufacturer: The manufacturer of the printer, if this field is changed then the Model field must be changed as well.
Model: The model name of a printer, this name corresponds to a PPD.
User PPD: The user-specified PPD.

If any field other than Name is changed on the existing printer, the revised printer object is reconfigured using the add printer flow.

CUPS Browser Proxy

The CUPS browser proxy is responsible for sending messages from the UI in the settings page to the client code and retrieving results if necessary.

The code for the browser proxy is located at /printing_page/cups_printers_browser_proxy.js

The following table contains message names as they appear in cups_printers_browser_proxy.js and their corresponding functions in cups_printers_handler.cc:

Message Name	Function
`getCupsSavedPrintersList`	`HandleGetCupsSavedPrintersList`
`getCupsEnterprisePrintersList`	`HandleGetCupsEnterprisePrintersList`
`updateCupsPrinter`	`HandleUpdateCupsPrinter`
`removeCupsPrinter`	`HandleRemoveCupsPrinter`
`addCupsPrinter`	`HandleAddCupsPrinter`
`getPrinterInfo`	`HandleGetPrinterInfo`
`getCupsPrinterManufacurersList`	`HandleGetCupsPrinterManufacturers`
`getCupsPrintersModelList`	`HandleGetCupsPrintersModels`
`selectPPDFile`	`HandleSelectPPDFile`
`startDiscoveringPrinters`	`HandleStartDiscovery`
`stopDiscoveringPrinters`	`HandleStopDiscovery`
`getPrinterPpdManufacturerAndModel`	`HandleGetPrinterPpdManufacturerAndModel`
`addDiscoveredPrinter`	`HandleAddDiscoveredPrinter`
`cancelPrinterSetup`	`HandleSetUpCancel`
`getEulaUrl`	`HandleGetEulaUrl`

Javascript Listeners

The following tables contain the different event listeners that exist within the frontend UI code and their corresponding event handler functions.

`cups_add_printer_dialog.js`

Event Name	Event Handler
`on-printer-discovered`	`onPrinterDiscovered_`
`on-printer-discovery-done`	`onPrinterDiscoveryDone_`
`on-add-cups-printer`	`onAddPrinter_`
`on-manually-add-discovered-printer`	`onManuallyAddDiscoveredPrinter_`
`configuring-dialog-closed`	`ConfiguringDialogClosed_`
`open-manually-add-printer`	`openManuallyAddPrinterDialog_`
`open-configuring-printer-dialog`	`openConfiguringPrinterDialog_`
`open-discovery-printers-dialog`	`openDiscoveryPrintersDialog_`
`open-manufacturer-model-dialog`	`openManufacturerModelDialog_`
`no-detected-printer`	`onNoDetectedPrinter_`

`cups_printers.js`

Event Name	Event Handler
`edit-cups-printer-details`	`onShowCupsEditPrinterDialog_`
`on-add-cups-printer`	`onAddPrinter_`
`on-printer-changed`	`printerChanged_`