hs._asm.axuielement

This module allows you to access the accessibility objects of running applications, their windows, menus, and other user interface elements that support the OS X accessibility API.

This is very much a work in progress, so bugs and comments are welcome.

This module works through the use of axuielementObjects, which is the Hammerspoon representation for an accessibility object. An accessibility object represents any object or component of an OS X application which can be manipulated through the OS X Accessibility API -- it can be an application, a window, a button, selected text, etc. As such, it can only support those features and objects within an application that the application developers make available through the Accessibility API.

The basic methods available to determine what attributes and actions are available for a given object are described in this reference documentation. In addition, the module will dynamically add methods for the attributes and actions appropriate to the object, but these will differ between object roles and applications -- again we are limited by what the target application developers provide us.

The dynamically generated methods will follow one of the following templates:

Where action and attribute can be the formal Accessibility version of the attribute or action name (a string usually prefixed with "AX") or without the "AX" prefix. When the prefix is left off, the first letter of the action or attribute can be uppercase or lowercase.

The module also dynamically supports treating the axuielementObject useradata as an array, to access it's children (i.e. #object will return a number, indicating the number of direct children the object has, and object[1] is equivalent to object:children()[1] or, more formally, object:attributeValue("AXChildren")[1]).

You can also treat the axuielementObject userdata as a table of key-value pairs to generate a list of the dynamically generated functions: for k, v in pairs(object) do print(k, v) end (this is essentially what hs._asm.axuielement:dynamicMethods does).

Limited support for parameterized attributes is provided, but is not yet complete. This is expected to see updates in the future.

An object observer is also expected to be added to receive notifications; however as this overlaps with hs.uielement, exactly how this will be done is still being considered.

Examples are (will be soon) provided in a separate document.

Usage

axuielement = require("hs._asm.axuielement")

Contents

Module Constructors
Module Methods
Module Constants

Module Constructors

axuielement.applicationElement(applicationObject) -> axuielementObject

Returns the top-level accessibility object for the application specified by the hs.application object.

Parameters:

  • applicationObject - the hs.application object for the Application.

Returns:

  • an axuielementObject for the application specified

axuielement.applicationElementForPID(pid) -> axuielementObject

Returns the top-level accessibility object for the application with the specified process ID.

Parameters:

  • pid - the process ID of the application.

Returns:

  • an axuielementObject for the application specified, or nil if it cannot be determined

axuielement.systemElementAtPosition(x, y | { x, y }) -> axuielementObject

Returns the accessibility object at the specified position in top-left relative screen coordinates.

Parameters:

  • x, y - the x and y coordinates of the screen location to test, provided as separate parameters
  • { x, y } - the x and y coordinates of the screen location to test, provided as a point-table, like the one returned by hs.mouse.getAbsolutePosition.

Returns:

  • an axuielementObject for the object at the specified coordinates, or nil if no object could be identified.

Notes:

  • See also hs._asm.axuielement:elementAtPosition -- this function is a shortcut for hs._asm.axuielement.systemWideElement():elementAtPosition(...).

  • This function does hit-testing based on window z-order (that is, layering). If one window is on top of another window, the returned accessibility object comes from whichever window is topmost at the specified location.


axuielement.systemWideElement() -> axuielementObject

Returns an accessibility object that provides access to system attributes.

Parameters:

  • None

Returns:

  • the axuielementObject for the system attributes

axuielement.windowElement(windowObject) -> axuielementObject

Returns the accessibility object for the window specified by the hs.window object.

Parameters:

  • windowObject - the hs.window object for the window.

Returns:

  • an axuielementObject for the window specified

Module Methods

axuielement:actionDescription(action) -> string

Returns a localized description of the specified accessibility object's action.

Parameters:

Returns:

  • a string containing a description of the object's action

Notes:

  • The action descriptions are provided by the target application; as such their accuracy and usefulness rely on the target application's developers.

axuielement:actionNames() -> table

Returns a list of all the actions the specified accessibility object can perform.

Parameters:

  • None

Returns:

  • an array of the names of all actions supported by the axuielementObject

Notes:

  • Common action names can be found in the hs._asm.axuielement.actions table; however, this method will list only those names which are supported by this object, and is not limited to just those in the referenced table.

axuielement:asHSApplication() -> hs.application object | nil

If the element referes to an application, return an hs.application object for the element.

Parameters:

  • None

Returns:

  • if the element refers to an application, return an hs.application object for the element ; otherwise return nil

Notes:

  • An element is considered an application by this method if it has an AXRole of AXApplication and has a process identifier (pid).

axuielement:asHSWindow() -> hs.window object | nil

If the element referes to a window, return an hs.window object for the element.

Parameters:

  • None

Returns:

  • if the element refers to a window, return an hs.window object for the element ; otherwise return nil

Notes:

  • An element is considered a window by this method if it has an AXRole of AXWindow.

axuielement:attributeNames() -> table

Returns a list of all the attributes supported by the specified accessibility object.

Parameters:

  • None

Returns:

  • an array of the names of all attributes supported by the axuielementObject

Notes:

  • Common attribute names can be found in the hs._asm.axuielement.attributes tables; however, this method will list only those names which are supported by this object, and is not limited to just those in the referenced table.

axuielement:attributeValue(attribute) -> value

Returns the value of an accessibility object's attribute.

Parameters:

Returns:

  • the current value of the attribute, or nil if the attribute has no value

axuielement:attributeValueCount(attribute) -> integer

Returns the count of the array of an accessibility object's attribute value.

Parameters:

Returns:

  • the number of items in the value for the attribute, if it is an array, or nil if the value is not an array.

axuielement:dynamicMethods([keyValueTable]) -> table

Returns a list of the dynamic methods (short cuts) created by this module for the object

Parameters:

  • keyValueTable - an optional boolean, default false, indicating whether or not the result should be an array or a table of key-value pairs.

Returns:

  • If keyValueTable is true, this method returns a table of key-value pairs with each key being the name of a dynamically generated method, and the value being the corresponding function. Otherwise, this method returns an array of the dynamically generated method names.

Notes:

  • the dynamically generated methods are described more fully in the reference documentation header, but basically provide shortcuts for getting and setting attribute values as well as perform actions supported by the Accessibility object the axuielementObject represents.

axuielement:elementAtPosition(x, y | { x, y }) -> axuielementObject

Returns the accessibility object at the specified position in top-left relative screen coordinates.

Parameters:

  • x, y - the x and y coordinates of the screen location to test, provided as separate parameters
  • { x, y } - the x and y coordinates of the screen location to test, provided as a point-table, like the one returned by hs.mouse.getAbsolutePosition.

Returns:

  • an axuielementObject for the object at the specified coordinates, or nil if no object could be identified.

Notes:

  • This method can only be called on an axuielementObject that represents an application or the system-wide element (see hs._asm.axuielement.systemWideElement).

  • This function does hit-testing based on window z-order (that is, layering). If one window is on top of another window, the returned accessibility object comes from whichever window is topmost at the specified location.

  • If this method is called on an axuielementObject representing an application, the search is restricted to the application.
  • If this method is called on an axuielementObject representing the system-wide element, the search is not restricted to any particular application. See hs._asm.axuielement.systemElementAtPosition.

axuielement:elementSearch(matchCriteria, [isPattern], [includeParents]) -> table

Returns a table of axuielementObjects that match the specified criteria. If this method is called for an axuielementObject, it will include all children of the element in its search. If this method is called for a table of axuielementObjects, it will return the subset of the table that match the criteria.

Parameters:

  • matchCriteria - the criteria to compare against the accessibility objects
  • isPattern - an optional boolean, default false, specifying whether or not the strings in the search criteria should be considered as Lua patterns (true) or as absolute string matches (false).
  • includeParents - an optional boolean, default false, indicating that the parent of objects should be queried as well. If you wish to specify this parameter, you must also specify the isPattern parameter. This parameter is ignored if the method is called on a result set from a previous invocation of this method or hs._asm.axuielement:getAllChildElements.

Returns:

  • a table of axuielementObjects which match the specified criteria. The table returned will include a metatable which allows calling this method on the result table for further narrowing the search.

Notes:

  • this method makes heavy use of the hs._asm.axuielement:matches method and pre-creates the necessary dynamic functions to optimize its search.

  • You can use this method to retrieve all of the current axuielementObjects for an application as follows:

    ax = require"hs._asm.axuielement"
    elements = ax.applicationElement(hs.application("Safari")):elementSearch({})
    
  • Note that if you started from the window of an application, only the children of that window would be returned; you could force it to gather all of the objects for the application by using :elementSearch({}, false, true).
  • However, this method of querying for all elements can be slow -- it is highly recommended that you use hs._asm.axuielement:getAllChildElements instead, and ideally with a callback function.
    ax = require"hs._asm.axuielement"
    ax.applicationElement(hs.application("Safari")):getAllChildElements(function(t)
     elements = t
     print("done with query")
    end)
    
  • Whatever option you choose, you can use this method to narrow down the result set. This example will print the frame for each button that was present in Safari when the search occurred which has a description which starts with "min" (e.g. "minimize button") or "full" (e.g. "full screen button"):
    for i, v in ipairs(elements:elementSearch({
                                     role="AXButton",
                                     roleDescription = { "^min", "^full"}
                                 }, true)) do
     print(hs.inspect(v:frame()))
    end
    

axuielement:getAllChildElements([parent], [callback]) -> table | axuielementObject

Query the accessibility object for all child objects (and their children...) and return them in a table.

Paramters:

  • parent - an optional boolean, default false, indicating that the parent of objects should be queried as well.
  • callback - an optional function callback which will receive the results of the query. If a function is provided, the query will be performed in a background thread, and this method will return immediately.

Returns:

  • If no function callback is provided, this method will return a table containing this element, and all of the children (and optionally parents) of this element. If a function callback is provided, this method returns the axuielementObject.

Notes:

  • The table generated, either as the return value, or as the argument to the callback function, has the hs._asm.axuielement.elementSearchTable metatable assigned to it. See hs._asm.axuielement:elementSearch for details on what this provides.

  • If parent is true, this method in effect provides all available accessibility objects for the application the object belongs to (or the focused application, if using the system-wide object).

  • If you do not provide a callback function, this method blocks Hammerspoon while it performs the query; such use is not recommended, especially if you set parent to true, as it can block for some time.


axuielement:isAttributeSettable(attribute) -> boolean

Returns whether the specified accessibility object's attribute can be modified.

Parameters:

Returns:

  • a boolean value indicating whether or not the value of the parameter can be modified.

axuielement:matches(matchCriteria, [isPattern]) -> boolean

Returns true if the axuielementObject matches the specified criteria or false if it does not.

Paramters:

  • matchCriteria - the criteria to compare against the accessibility object
  • isPattern - an optional boolean, default false, specifying whether or not the strings in the search criteria should be considered as Lua patterns (true) or as absolute string matches (false).

Returns:

  • true if the axuielementObject matches the criteria, false if it does not.

Notes:

  • if isPattern is specified and is true, all string comparisons are done with string.match. See the Lua manual, section 6.4.1 (help.lua._man._6_4_1 in the Hammerspoon console).
  • the matchCriteria must be one of the following:

    • a single string, specifying the AXRole value the axuielementObject's AXRole attribute must equal for the match to return true
    • an array of strings, specifying a list of AXRoles for which the match should return true
    • a table of key-value pairs specifying a more complex match criteria. This table will be evaluated as follows:
      • each key-value pair is treated as a separate test and the object must match as true for all tests
      • each key is a string specifying an attribute to evaluate. This attribute may be specified with its formal name (e.g. "AXRole") or the informal version (e.g. "role" or "Role").
      • each value may be a string, a number, a boolean, or an axuielementObject userdata object, or an array (table) of such. If the value is an array, then the test will match as true if the object matches any of the supplied values for the attribute specified by the key.
        • Put another way: key-value pairs are "and'ed" together while the values for a specific key-value pair are "or'ed" together.
  • This method is used by hs._asm.axuielement:elementSearch to determine if the given object should be included it's result set. As an optimization for the elementSearch method, the keys in the matchCriteria table may be provided as a function which takes one argument (the axuielementObject to query). The return value of this function will be compared against the value(s) of the key-value pair as described above. This is done to prevent dynamically re-creating the query for each comparison when the search set is large.


axuielement:parameterizedAttributeNames() -> table

Returns a list of all the parameterized attributes supported by the specified accessibility object.

Parameters:

  • None

Returns:

  • an array of the names of all parameterized attributes supported by the axuielementObject

axuielement:parameterizedAttributeValue(attribute, parameter) -> value

Returns the value of an accessibility object's parameterized attribute.

Parameters:

Returns:

  • the current value of the parameterized attribute, or nil if it has no value

Notes:

  • Parameterized attribute support is still considered experimental and not fully supported yet. Use with caution.

axuielement:performAction(action) -> axuielement | false | nil

Requests that the specified accessibility object perform the specified action.

Parameters:

Returns:

  • if the requested action was accepted by the target, returns the axuielementObject; if the requested action was rejected, returns false, otherwise returns nil on error.

Notes:

  • The return value only suggests success or failure, but is not a guarantee. The receiving application may have internal logic which prevents the action from occurring at this time for some reason, even though this method returns success (the axuielementObject). Contrawise, the requested action may trigger a requirement for a response from the user and thus appear to time out, causing this method to return false or nil.

axuielement:pid() -> integer

Returns the process ID associated with the specified accessibility object.

Parameters:

  • None

Returns:

  • the process ID for the application to which the accessibility object ultimately belongs.

axuielement:setAttributeValue(attribute, value) -> axuielementObject | nil

Sets the accessibility object's attribute to the specified value.

Parameters:

Returns:

  • the axuielementObject on success; nil if the attribute could not be set.

Notes:

  • This is still somewhat experimental and needs more testing; use with caution.

Module Constants

axuielement.actions[]

A table of common accessibility object action names, provided for reference.

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.

axuielement.attributes[]

A table of common accessibility object attribute names, provided for reference. The names are grouped into the following subcategories (keys):

  • application
  • dock
  • general
  • matte
  • menu
  • misc
  • system
  • table
  • text
  • window

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.
  • the category name indicates the type of accessibility object likely to contain the member elements.

axuielement.directions[]

A table of common directions which may be specified as the value of an accessibility object property, provided for reference.

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.

axuielement.notifications[]

A table of accessibility object notification names, provided for reference.

Notes:

  • Notification support is currently not provided by this module, so this table is in anticipation of future additions.

axuielement.parameterizedAttributes[]

A table of common accessibility object parameterized attribute names, provided for reference.

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.

axuielement.roles[]

A table of common accessibility object roles, provided for reference.

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.

axuielement.subroles[]

A table of common accessibility object subroles, provided for reference.

Notes:

  • this table is provided for reference only and is not intended to be comprehensive.

License

The MIT License (MIT)

Copyright (c) 2016 Aaron Magill

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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