Using Server Annotation
This topic provides information about using server annotation to specify a callback object.
To override a property that specifies a callback object
- Obtain an IAccessible interface pointer to the accessible element that is to be annotated.
- Call QueryInterface on the accessible element to get an IAccIdentity interface pointer.
- Call IAccIdentity::GetIdentityString() on the IAccIdentity interface pointer to obtain a string that uniquely identifies the accessible element that is to be annotated.
- Use CoCreateInstance or CoCreateInstanceEx to create the IAccPropServices object.
- Create a Component Object Model (COM) object that implements IAccPropServer.
- Call IAccPropServices::SetPropServer, passing the identity string, a GUID indicating the property to be overridden, and a pointer to the IAccPropServer callback object.
- Release interface pointers and free memory.
When a client requests the property of the accessible element, the callback object will be called and will return the value to the client.
As when specifying a value, server developers can alternatively use the IAccPropServices::ComposeHwndIdentityString method to obtain an identity string; or they can use the IAccPropServices::SetHwndPropServer method and specify the hwnd, idObject, or idChild parameters instead of an identity string.
When using either SetPropServer or SetHwndPropServer on a container object, server developers can optionally specify that the overriding information should also apply to all element children of that container.
Servers can explicitly clear the annotation at any time by using IAccPropServices::ClearProps. This is usually not required, as the annotation service will automatically clean up and release annotation information when the accessible element being annotated disappears.
Below is a list of properties that can be annotated using this procedure.
Properties Supported When Specifying a Callback
When specifying a callback, the following properties can be annotated. Currently these properties cannot be annotated directly by specifying a value.
| Property | Type |
|---|---|
| PROPID_ACC_NAME | VT_BSTR |
| PROPID_ACC_DESCRIPTION | VT_BSTR |
| PROPID_ACC_ROLE | VT_I4 |
| PROPID_ACC_STATE | VT_I4 |
| PROPID_ACC_HELP | VT_BSTR |
| PROPID_ACC_KEYBOARDSHORTCUT | VT_BSTR |
| PROPID_ACC_DEFAULTACTION | VT_BSTR |
| PROPID_ACC_VALUEMAP | VT_BSTR |
| PROPID_ACC_ROLEMAP | VT_BSTR |
| PROPID_ACC_STATEMAP | VT_BSTR |
| PROPID_ACC_FOCUS | VT_DISPATCH VT_I4 |
| PROPID_ACC_SELECTION | VT_DISPATCH VT_I4 VT_UNKNOWN |
| PROPID_ACC_PARENT | VT_DISPATCH |
| PROPID_ACC_NAV_UP | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_DOWN | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_LEFT | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_RIGHT | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_PREV | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_NEXT | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_FIRSTCHILD | VT_DISPATCH VT_I4 |
| PROPID_ACC_NAV_LASTCHILD | VT_DISPATCH VT_I4 |