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Undo events?

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T O P I C R E V I E W
PeterPanino	Posted - Sep 14 2017 : 04:19:18 When the user has returned to the beginning of the Undo chain by doing repeated Undo (so there are not any more changes left to Undo), how can I get notified? There are no Undo events in TImageEnView to notify me about the current position in the Undo chain when the user undoes a change. Generally, I prefer being notified instead of having to ask.
7 L A T E S T R E P L I E S (Newest First)
xequte	Posted - Sep 18 2017 : 16:50:13 Hi Ctrl-Z? So, are you using a TImageEnViewUndo action? What type of method is being undone? Nigel Xequte Software www.xequte.com nigel@xequte.com
PeterPanino	Posted - Sep 18 2017 : 09:01:36 I work with CodeSite which gives me an exact feedback from what happens at run-time. 1. Place a CodeSite.Send in the OnImageChange event-handler: procedure TFormMain.imgImportEditorImageChange(Sender: TObject); begin CodeSite.Send('TFormMain.imgImportEditorImageChange: test'); end; 2. Then I press Ctrl-Z (on my German keyboard) ONCE to Undo a previous Edit action. 3. In the CodeSite Live Viewer you can see that the OnImageChange event-handler has been called twice (in a time-distance of 3 milliseconds):
xequte	Posted - Sep 17 2017 : 20:13:53 Hi Peter I cannot reproduce the duplicate OnImageChange call. Can you give me more info. You can email us for a pre-release which includes OnUndoRedo. Nigel Xequte Software www.xequte.com nigel@xequte.com
PeterPanino	Posted - Sep 16 2017 : 16:05:02 Hi Nigel, 1. any Undo de facto calls the OnImageChange event-handler TWICE which is inefficient and could lead to logical contradictions (if you do other things in this event-handler). 2. Also the fact that both image-processings and Undo call the OnImageChange event-handler could lead to logical contradictions and thus unwanted effects. Considering this I think an OnUndoRedo event would make sense because it would allow reacting only to changes in the Undo chain and thus handling these changes more consistently.
xequte	Posted - Sep 14 2017 : 22:26:29 Hi I'll add an OnUndoRedo event in the next update, but you can just use the OnImageChange event: procedure TForm1.ImageEnView1ImageChange(Sender: TObject); begin // Update status of buttons btnSave.Enabled := ImageEnView1.IEBitmap.Modified; btnUndo.Enabled := ImageEnView1.Proc.CanUndo; btnRedo.Enabled := ImageEnView1.Proc.CanRedo; end; Nigel Xequte Software www.xequte.com nigel@xequte.com
PeterPanino	Posted - Sep 14 2017 : 12:35:08 Bill, thank you for the answer. I strongly suggest implementing an EVENT OnUndoRedo which contains as parameters: • UndoAction: Boolean (if True, the user has made an Undo, if False, the user has made a Redo) • var UndoPos: Integer (current position in the Undo chain; if 0, there is nothing to Undo) This is much better and more efficient and more logical and more useful than having explicitly to ask for this information! PLEASE!
w2m	Posted - Sep 14 2017 : 10:09:09 procedure TForm1.UndoClick(Sender: TObject); begin If ImageEnView1.Proc.CanUndo then begin ImageEnView1.Proc.Undo; ImageEnView1.Proc.ClearUndo; else ShowMessage('Nothing to Undo!'); end; Bill Miller Adirondack Software & Graphics Email: w2m@hughes.net EBook: http://www.imageen.com/ebook/ Custom Commercial ImageEn Development