The following table lists all the events generated by Active Accessibility server applications, in ascending numeric order. The EVENT_MIN and EVENT_MAX values represent the lowest and highest possible event values, respectively.
For more information about events, see WinEvents.
EVENT_SYSTEM_SOUND | A sound is being played. | Notes |
EVENT_SYSTEM_ALERT | An alert was generated. | Notes |
EVENT_SYSTEM_FOREGROUND | The foreground window is changing. | Notes |
EVENT_SYSTEM_MENUSTART | An application is entering a modal menu loop. | Notes |
EVENT_SYSTEM_MENUEND | An application is exiting a modal menu loop. | Notes |
EVENT_SYSTEM_MENUPOPUPSTART | A pop-up menu is being displayed. | Notes |
EVENT_SYSTEM_MENUPOPUPEND | A pop-up menu is being removed. | Notes |
EVENT_SYSTEM_CAPTURESTART | A window received mouse capture. | |
EVENT_SYSTEM_CAPTUREEND | A window lost mouse capture. | |
EVENT_SYSTEM_MOVESIZESTART | A window entered a modal move or size loop. | |
EVENT_SYSTEM_MOVESIZEEND | A window exited a modal move or size loop. | |
EVENT_SYSTEM_CONTEXTHELPSTART | A window entered context-sensitive Help mode. | |
EVENT_SYSTEM_CONTEXTHELPEND | A window exited context-sensitive Help mode. | |
EVENT_SYSTEM_DRAGDROPSTART | An application is about to enter drag-and-drop mode. | Notes |
EVENT_SYSTEM_DRAGDROPEND | An application is about to exit drag-and-drop mode. | Notes |
EVENT_SYSTEM_DIALOGSTART | A dialog box was displayed. | Notes |
EVENT_SYSTEM_DIALOGEND | A dialog box was removed. | Notes |
EVENT_SYSTEM_SCROLLINGSTART | A scroll bar is being tracked. | Notes |
EVENT_SYSTEM_SCROLLINGEND | A scroll bar is no longer being tracked. | Notes |
EVENT_SYSTEM_SWITCHSTART | The user pressed ALT+TAB. | Notes |
EVENT_SYSTEM_SWITCHEND | The user released ALT+TAB. | Notes |
EVENT_SYSTEM_MINIMIZESTART | A window object is about to be minimized or maximized. | |
EVENT_SYSTEM_MINIMIZEEND | A window object was minimized or maximized. | |
EVENT_OBJECT_CREATE | An object was created. | Notes |
EVENT_OBJECT_DESTROY | An object was destroyed. | Notes |
EVENT_OBJECT_SHOW | An object is being shown. | Notes |
EVENT_OBJECT_HIDE | An object is being hidden. | Notes |
EVENT_OBJECT_REORDER | A container object's children are changing their z-order placements. | Notes |
EVENT_OBJECT_FOCUS | An object is receiving keyboard focus. | Notes |
EVENT_OBJECT_SELECTION | An object selection change occurred. | Notes |
EVENT_OBJECT_SELECTIONADD | An object was added to the selection. | Notes |
EVENT_OBJECT_SELECTIONREMOVE | An object was removed from the selection. | Notes |
EVENT_OBJECT_SELECTIONWITHIN | Numerous selection changes occurred within a container. | Notes |
EVENT_OBJECT_STATECHANGE | An object's state changed. | Notes |
EVENT_OBJECT_LOCATIONCHANGE | An object is changing location, shape, or size. | Notes |
EVENT_OBJECT_NAMECHANGE | An object's Name property changed. | |
EVENT_OBJECT_DESCRIPTIONCHANGE | An object's Description property changed. | |
EVENT_OBJECT_VALUECHANGE | An object's Value property changed. | |
EVENT_OBJECT_PARENTCHANGE | An object has a new parent object. | |
EVENT_OBJECT_HELPCHANGE | An object's Help property changed. | |
EVENT_OBJECT_DEFACTIONCHANGE | An object's DefaultAction property changed. | |
EVENT_OBJECT_ACCELERATORCHANGE | An object's KeyboardShortcut property changed. |
The system generates this event when a system sound (for menus, and so on) is played. The system will generate this event even if no sound is audible (for example, lack of a sound file to play, no sound card, and so on).
For this event, the WinEventProc callback function will receive the OBJID_SOUND value as the idObject parameter.
Message boxes generate this event when they are displayed.
The system generates this event even if the foreground window is changing to another window in the same thread.
For this event, the WinEventProc callback function's hwnd parameter is the handle to the window that is now in the foreground, and the idObject parameter is OBJID_WINDOW. The idChild parameter is CHILDID_SELF.
For this event, the WinEventProc callback function's hwnd, idObject, and idChild parameters refer to the control with the menu bar or the control activating the context menu.
The hwnd parameter is the handle to the top-level window related to the event. The idObject parameter will be OBJID_MENU or OBJID_SYSMENU for a menu, or OBJID_WINDOW for a pop-up menu. The idChild parameter will be CHILDID_SELF.
For this event, the WinEventProc callback function's hwnd, idObject, and idChild parameters refer to the control with the menu bar or the control activating the context menu.
The hwnd parameter is the handle to the top-level window related to the event. The idObject parameter will be OBJID_MENU or OBJID_SYSMENU for a menu, or OBJID_WINDOW for a pop-up menu. The idChild parameter will be CHILDID_SELF.
For this event, the WinEventProc callback function's hwnd, idObject, and idChild parameters refer to the new pop-up menu being displayed, not the parent item. You can retrieve the parent or pop-up menu by calling the IAccessible::get_accParent method.
When an application displays a pop-up menu, the client will receive an EVENT_SYSTEM_MENUSTART event followed almost immediately by this event.
When a pop-up menu disappears, the client will receive this message followed almost immediately by the EVENT_SYSTEM_MENUEND event.
Applications that support drag-and-drop operations must send this event; the system does not.
Applications that support drag-and-drop operations must send this event; the system does not.
Applications must send this event after the dialog box is completely initialized and visible.
Applications must send this event just before the dialog box is removed from the screen.
This event applies to scroll bars contained in windows and top-level scroll bar controls. Top-level scroll bar controls are identified by the OBJID_HSCROLL and OBJID_VSCROLL object ID values.
This event applies to scroll bars contained in windows and top-level scroll bar controls. Top-level scroll bar controls are identified by the OBJID_HSCROLL and OBJID_VSCROLL object ID values.
For this event notification, the hwnd parameter of the WinEventProc callback function identifies the window that the user is switching to.
If only one application is running when the user presses ALT+TAB, the client application can receive an EVENT_SYSTEM_SWITCHEND event without a corresponding EVENT_SYSTEM_SWITCHSTART event.
For this event notification, the hwnd parameter of the WinEventProc callback function identifies the window that the user switched to.
If only one application is running when the user presses ALT+TAB, the client application can receive this event without a corresponding EVENT_SYSTEM_SWITCHSTART event.
In the case of window objects only, both the parent and the child send this event. The child window sends the event when created, and the parent sends it after creation is complete. Note that the child window is responsible for sending this event before the parent.
If the client is using synchronous callbacks, it should not attempt to retrieve the parent object (by using IAccessible::get_accParent) until after control is yielded to the operating system.
In the case of window objects only, both the parent and the child send this event. The child window sends the event when it is destroyed, and the parent sends it after destruction is complete. Note that the child window is responsible for sending this event before the parent. It is assumed that all the children of an object are destroyed when the parent is destroyed. This event is also sent when an application is shutting down.
Calling IAccessible properties at this point can cause a crashin particular, when the call references a DLL that is unloaded first. Calling the IAccessible::get_accName method is a good example. It eventually calls SysAllocString, a Win32 API call. exported by oleaut32.dll. If oleaut32.dll is unloaded first, it crashes. Therefore, upon receiving the EVENT_OBJECT_DESTROY, call these properties only for visible windows. Only invisible windows are dangerous because some of them are destroyed after a majority of the system has already been destroyed. To get the name of the invisible window, try using GetWindowText, a Win32 API call.
When a parent object is being shown, all child objects are, of course, visible on the screen. Therefore, server applications must not send this event for the child objects.
When a parent object is being hidden, all child objects are, of course, no longer visible on the screen. They still have the same "visible" status, but are not truly visible. Therefore, server applications must not send this event for the child objects.
The object referred to in the hwnd and idObject parameters of the WinEventProc callback function identify the parent container object in which z-ordering is occurring. This is because if one child changes its z-order, all of them must change.
The parameters received in the WinEventProc callback function describe the object that is receiving the keyboard focus.
There is only one focused child item in a parent. The focused child is the object that receives keystrokes at a given moment. Hence, server applications must only send this notification describing where the new focus is going. That is, a new item that gets the focus implies that the old one is losing it.
Do not confuse object focus with object selection. For more information, see Accessible Object Selection and Focus.
Server applications send this notification when the item being selected is within the same container as the last selected object.
The hwnd and idObject parameters of the WinEventProc callback function describe the container, and the idChild parameter identifies the object that is selected. The idChild parameter can be OBJID_WINDOW if the selected child is a window that also contains objects.
Do not confuse object selection with object focus. For more information, see Accessible Object Selection and Focus.
Server applications send this notification when an object or objects have been added to the selection within a container. This is appropriate when the number of newly selected items is very small.
The hwnd and idObject parameters of the WinEventProc callback function describe the container, and the idChild parameter is the child that was added to the selection.
Do not confuse object selection with object focus. For more information, see Accessible Object Selection and Focus.
Server applications send this notification when an object or objects have been removed from the selection within a container. Like the EVENT_OBJECT_SELECTIONADD event, this is appropriate when the number of newly selected items is very small.
The hwnd and idObject parameters of the WinEventProc callback function describe the container, and the idChild parameter identifies the child that was added to the selection.
Do not confuse object selection with object focus. For more information, see Accessible Object Selection and Focus.
A server application sends this notification when the selected items within a control have changed substantially. Effectively, this notification informs the client that many selection changes have occurred (instead of sending several EVENT_OBJECT_SELECTIONADD or EVENT_OBJECT_SELECTIONREMOVE events). The client can query for the selected items by calling the container object's IAccessible::get_accSelection method and enumerating the selected items.
For this event notification, the hwnd and idObject parameters of the WinEventProc callback function describe the container in which the changes occurred.
Do not confuse object selection with object focus. For more information, see Accessible Object Selection and Focus.
A state change can occur when a button object has been pressed or released, when an object is being enabled or disabled, or whatever else is pertinent for a given object. USER sends these events on behalf of standard controls, like push buttons and check boxes.
For this event notification, the idChild parameter of the WinEventProc callback function identifies the child object whose state changed.
This event is generated in response to the topmost level object that has changed, not for any children it might contain. For example, if the user resizes a top-level window, USER generates this notification for the window, but not for the menu bar, title bar, scroll bars, or other objects that are also changing.
USER generates this event for windows that are changing. It does not do this for every nonfloating child window when the parent moves. However, if an application explicitly resizes child windows as a result of being sized, USER will generate multiple events for the resized children. Additionally, USER generates this event for two nonwindow system objects: the system caret and the cursor.
For this event notification, the idChild parameter of the WinEventProc callback function identifies the child object that changed.
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