Containers: Client-Item Notifications
This article discusses the overridable functions that the MFC framework calls when server applications modify items in your client application's document.
COleClientItem defines several overridable functions that are called in response to requests from the component application, which is also called the server application. These overridables usually act as notifications. They inform the container application of various events, such as scrolling, activation, or a change of position, and of changes that the user makes when editing or otherwise manipulating the item.
The framework notifies your container application of changes through a call to COleClientItem::OnChange, an overridable function whose implementation is required. This protected function receives two arguments. The first specifies the reason the server changed the item:
Notification |
Meaning |
|---|---|
OLE_CHANGED |
The OLE item's appearance has changed. |
OLE_SAVED |
The OLE item has been saved. |
OLE_CLOSED |
The OLE item has been closed. |
OLE_RENAMED |
The server document containing the OLE item has been renamed. |
OLE_CHANGED_STATE |
The OLE item has changed from one state to another. |
OLE_CHANGED_ASPECT |
The OLE item's draw aspect has been changed by the framework. |
These values are from the OLE_NOTIFICATION enumeration, which is defined in AFXOLE.H.
The second argument to this function specifies how the item has changed or what state it has entered:
When first argument is |
Second argument |
|---|---|
OLE_SAVED or OLE_CLOSED |
Is not used. |
OLE_CHANGED |
Specifies the aspect of the OLE item that has changed. |
OLE_CHANGED_STATE |
Describes the state being entered (emptyState, loadedState, openState, activeState, or activeUIState). |
For more information about the states a client item can assume, see Containers: Client-Item States.
The framework calls COleClientItem::OnGetItemPosition when an item is being activated for in-place editing. Implementation is required for applications that support in-place editing. The MFC Application Wizard provides a basic implementation, which assigns the item's coordinates to the CRect object that is passed as an argument to OnGetItemPosition.
If an OLE item's position or size changes during in-place editing, the container's information about the item's position and clipping rectangles must be updated and the server must receive information about the changes. The framework calls COleClientItem::OnChangeItemPosition for this purpose. The MFC Application Wizard provides an override that calls the base class's function. You should edit the function that the application wizard writes for your COleClientItem-derived class so that the function updates any information retained by your client-item object.