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Used to determine which event an empty handler is generated for when the component is double-clicked.Ĭopy() should be invoked when the component is copied to the Clipboard. Void EditProperty(TPropertyEditor* PropertyEditor, bool& Continue, bool& FreeEditor) ( TDefaultEditor only) The default behavior is listed in Table 5.10. Index indicates which one.Įdit() is invoked when the component is double-clicked. ĮxecuteVerb() is invoked when one of the custom menu items is selected. It can also be used to hide an item by setting its Visible property to false. This allows the menu item to be customized. PrepareItem() is called for each verb in the context menu, passing the TMenuItem that will be used to represent the verb in the context menu. Void PrepareItem(int Index, const Menus ::TMenuItem* AItem) Use a - to make the menu item a separator bar. The following conventions should be remembered :Īppend. Returns an AnsiString representing the menu item's name as it will appear in the context menu. Returns an int representing the number of menu items (verbs, as in doing words) that are going to be added. TComponentEditor and TDefaultEditor virtual Functions Table 5.11 lists the methods from both classes and details the purpose of each. Īfter the decision has been made as to which component editor class to derive from, the appropriate methods should be overridden. If you do not create a custom component editor for a component, C++Builder uses TDefaultEditor. If you want the component editor to generate an empty event handler for one of three default events or for a particular event, when the component is double-clicked, you should derive it from TDefaultEditor otherwise, derive it from TComponentEditor. Choosing which of the two classes to derive your custom component editor from should be based on the following criteria. Where they differ (as seen in Table 5.10) is in the implementation of the Edit() method. In Figure 5.7 we can see that TComponentEditor and TDefaultEditor are essentially the same in that they offer similar functionality.
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Code to perform the desired action is placed here. If the component has no events, nothing happens.Įdit() is invoked. If none of the previous events exist for the component, a handler is created for the first event that appears. TDefaultEditor: An empty event handler is created for OnChange, OnCreate, or OnClick, whichever appears first in the component's list of event properties. TComponentEditor: If items have been added to the context menu, the first item is executed. The default action depends on the class from which the editor is derived. Code to execute the desired behavior goes here. PrepareItem() is called before the menu item is shown, allowing it to be customized.ĮxecuteVerb() is called only if one of the newly added menu items is clicked. This allows an AnsiString representing each of the menu items to be returned. This is used to return the number of items to be added to the top of the default context menu. The component's context menu is displayed. TComponentEditor and TDefaultEditor Mouse Responses The default behavior of each of the classes is also stated. Table 5.10 lists both mouse events and indicates which of the virtual functions are invoked. Īs was stated initially, creating a custom component editor allows the default behavior that occurs in response to the component being right-clicked or double-clicked in the IDE to be specified.
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This can be referred to when the virtual functions themselves are discussed later in this section, in Table 5.11 and in subsequent sections with the methods ' names. The TComponentEditor inheritance hierarchy.įigure 5.7 shows additional information, namely the virtual functions that should be overridden to customize the component editor's behavior. The relationship between the two is shown in Figure 5.7. Two classes are available for creating component editors: TComponentEditor and TDefaultEditor. Component editors add the possibility of customizing the default behavior associated with editing a component and also allowing additional behavior to be specified.
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This section, like the previous one, presents the background and principles required to create custom component editors.
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Custom component editors also allow the context menu for each component (shown when the component is right-clicked) to be customized, along with specifying the behavior when a component is double-clicked on a form. Component Editors take this further by allowing custom editors for the whole component to be created. The previous section discussed property editors for components as a method of allowing a more intuitive and robust interface at design time.