WinEdDeclareUndo (Function)

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WinEdDeclareUndo (Function)

In french: FenEdDéclareUndo

Declares how to cancel an action that was added by WinEdDo. This function is linked to the "Modification of the interface by the end user" feature.

This function is mainly used when creating an editor by programming (see "Remarks").

Example

WinEdDo(WIN_MyEditor, ProcCreateCap, "New")
INTERNAL PROCÉDURE ProcCreateCap(sCap)
pNew is Control
pNew <- ControlCreate("STC_" + GetIdentifier(), typText, 150, 150, 80, 20)
pNew..Caption = sCap
WinEdDeclareUndo(ProcCancel)
INTERNAL PROCÉDURE ProcCancel()
ControlDelete(pNew)
END
END

WinEdDeclareUndo(UndoOperation, CUSTOMER.CustomerID)

// Management of Undo
INTERNAL PROCÉDURE UndoOperation(nCustomerID)

IF HReadSeekFirst(CUSTOMER, CustomerID, nCustomerID) THEN
SourceToScreen()
END

Syntax

WinEdDeclareUndo(<WLanguage procedure> [, <Parameter 1> [... [, <Parameter N>]]])

<WLanguage procedure>: Procedure name

Name of WLanguage procedure to run. The code of this procedure must allow to cancel the action created by WinEdDo.
Using an internal procedure provides a direct access to the local variables.

<Parameter 1>: Any optional type

First optional parameter that will be passed to the procedure.
In most cases, these parameter are values used to restore the previous status.

<Parameter N>: Any optional type

Nth optional parameter that will be passed to the procedure.
In most cases, these parameter are values used to restore the previous status.

Remarks

Use example

WinEdDo is used to create custom actions (control creation for example) that support the undo/redo.

Let's take a simple example: creating an editor of graphic objects.

A button is used to create a shape. The user must have the ability to cancel the shape creation. The following operations are performed:

Switching the window to modification mode (WinEdActive).
Call to WinEdDo. The procedure called by this function is used to create the shape. This procedure also contains the call to WinEdDeclareUndo. WinEdDeclareUndo is used to define the behavior in case of cancellation by the user.
Switching the window to normal mode (WinEdActive).

The end user can cancel this action (Ctrl + Z or WinEdUndo): then, the <WLanguage procedure> will be called.

Error

A WLanguage error occurs if WinEdDeclareUndo is called outside a procedure added by WinEdDo.

Related Examples:

Training (WINDEV): WD Graphic Objects

[ + ] This example illustrates the power of WLanguage in object oriented programming.
This example is a graphic object editor.

It is possible to:
- move, resize objects
- make selections with a lasso or a mouse
- cut/copy/paste objects
- delete/duplicate objects
- save the created documents and print them.

The main technical features presented and documented are:
- management of an object clipboard
- UNDO/REDO management
- serialization and deserialization of objects
- algorithms for managing graphic objects (proportional resizing, management of move rules, etc...)

Component : wd250obj.dll