Documentation
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Overview ¶
Package atspi is the Linux accessibility bridge: it publishes the widget tree on the AT-SPI bus, where Orca and every other Linux screen reader read it.
A go-widgets window presents ONE surface holding a rasterised widget tree. To AT-SPI that is an opaque rectangle with no structure at all, so without this the application is unreadable and unnavigable. macOS subclasses a view and Windows answers WM_GETOBJECT with a COM object; here an application EXPORTS D-Bus objects and registers them with a registry daemon.
The package is shared by the X11 and Wayland backends because AT-SPI is a D-Bus protocol and knows nothing about either display server.
This file is the OS-independent half — role numbers, filtering, coordinates — so the whole decision layer is exercised by ordinary tests on any host, the split the x11, wayland, cocoa and win32 packages all use.
Index ¶
- Constants
- func Nodes(root toolkit.Widget) []toolkit.A11yNode
- func ParsePressPoint(s string) (x, y int, ok bool)
- func PressPoint(n toolkit.A11yNode) string
- func Publish(root toolkit.Widget, title string, originX, originY int)
- func Role(r toolkit.Role) uint32
- func RoleName(r uint32) string
- func ScreenRect(n toolkit.A11yNode, originX, originY int) (x, y, w, h int32)
- func Skip(n toolkit.A11yNode) bool
- func TakePending() []struct{ ... }
- type Bridge
- type Ref
Constants ¶
const ( RoleInvalid uint32 = 0 RoleAlert uint32 = 2 RoleCheckBox uint32 = 7 RoleComboBox uint32 = 11 RoleFiller uint32 = 20 RoleImage uint32 = 27 RoleLabel uint32 = 29 RoleList uint32 = 31 RoleListItem uint32 = 32 RoleMenu uint32 = 33 RoleMenuBar uint32 = 34 RolePageTab uint32 = 37 RolePanel uint32 = 39 RoleProgressBar uint32 = 41 RolePushButton uint32 = 43 RoleRadioButton uint32 = 44 RoleScrollBar uint32 = 47 RoleSlider uint32 = 51 RoleSpinButton uint32 = 52 RoleStatusBar uint32 = 54 RoleTable uint32 = 55 RoleText uint32 = 61 RoleToggleButton uint32 = 62 RoleToolBar uint32 = 63 RoleTree uint32 = 66 RoleWindow uint32 = 69 RoleApplication uint32 = 75 RoleEntry uint32 = 79 RoleDocFrame uint32 = 82 )
AT-SPI role numbers, read out of pyatspi on a live system rather than guessed: a client ANNOUNCES the role, so a wrong number renames every element for the user.
const ( StateEnabled uint32 = 8 StateFocusable uint32 = 11 StateSensitive uint32 = 24 StateShowing uint32 = 25 StateVisible uint32 = 30 )
AT-SPI state numbers (same provenance as the roles).
Variables ¶
This section is empty.
Functions ¶
func Nodes ¶
Nodes is the tree to publish for a widget root: every meaningful element, in visual order, with the ones no reader could use already removed.
func ParsePressPoint ¶
ParsePressPoint reads back what PressPoint wrote. A malformed value REFUSES rather than defaulting to (0,0), which is a real and usually clickable place.
func PressPoint ¶
PressPoint encodes an element's centre, in the coordinates the input path speaks, so an activation can be replayed as an ordinary click.
Carrying the point ON the element beats a table keyed by index: the tree is rebuilt whenever the frame changes, and an index goes stale the moment content scrolls under a screen-reader user's cursor.
func Publish ¶
Publish republishes the tree for the frame just drawn. The back-end calls it from the same place that presents pixels, so the description never lags them.
activate is how an AT-SPI action reaches the widget tree; it is stored on every call because the back-end owns it and this package must not import a back-end.
func Role ¶
Role maps a toolkit role to its AT-SPI number. Anything unrecognised becomes a panel — AT-SPI's "a thing containing things", the honest answer for a role this table does not know, and never a wrong announcement.
func RoleName ¶
RoleName is the human-readable role a client may read instead of the number. The strings are AT-SPI's own spelling, not ours.
func ScreenRect ¶
ScreenRect converts a node's window-relative rectangle to screen coordinates. AT-SPI asks for extents in BOTH spaces on the same interface, and only the back-end knows where the window sits, so the origin arrives from the caller.
A Wayland client cannot know its own position on screen — the protocol does not tell it — so that back-end passes a zero origin and the two spaces coincide. Reporting a made-up screen position would be worse: a screen reader would point somewhere real and wrong.
func Skip ¶
Skip reports whether a node should be left out of the published tree. An element with no name says nothing a reader could announce and one with no area cannot be pointed at; either is a stop the user has to skip past.
func TakePending ¶
func TakePending() []struct{ X, Y int }
TakePending hands the back-end the activations a client asked for since the last call, to be applied on the thread that owns the widget tree.
KNOWN LIMITATION: the back-end drains this while painting, and the X11 loop blocks on the display socket, so an action taken while the application is otherwise idle is applied on the NEXT event rather than immediately. The click itself lands correctly — measured, clicks: 0 to clicks: 1 — the tree simply republishes a beat later. Closing that needs the loop woken from outside, e.g. a self-addressed X ClientMessage.
It returns nothing when the bridge never came up, which is the normal case on a machine with no accessibility stack running.
Types ¶
type Bridge ¶
type Bridge struct {
// contains filtered or unexported fields
}
Bridge is the live connection and the snapshot being described.
type Ref ¶
type Ref struct {
Name string
Path dbus.ObjectPath
}
Ref is AT-SPI's object reference: the bus name that owns it and its path — the "(so)" every AT-SPI method passes around.
Name is a plain string. In godbus, against which this bridge was first written, dbus.Sender is an ANNOTATION type meaning "inject the caller's name" rather than "a string on the wire", and using it there silently changed this struct's signature so the registry never listed the application. The owned D-Bus has no such type, and the signature is checked rather than assumed: SignatureOfType reports (so) for this and a((so)(so)(so)iiassusau) for the cache item.
Source Files