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Base class for undoable commands records. More...
#include <FXUndoList.h>
Public Member Functions | |
| FXival | nrefs () const |
| void | ref () |
| void | unref () |
| virtual void | undo ()=0 |
| Undo this command. | |
| virtual void | redo ()=0 |
| Redo this command. | |
| virtual FXuval | size () const |
| Return the size of the information in the undo record. More... | |
| virtual FXString | undoName () const |
| Name of the undo command to be shown on a button; for example, "Undo Delete". | |
| virtual FXString | redoName () const |
| Name of the redo command to be shown on a button; for example, "Redo Delete". | |
| virtual FXbool | canMerge () const |
| Return true if this command could possibly be merged with a previous undo command. More... | |
| virtual FXuint | mergeWith (FXCommand *command) |
| Called by the undo system to try and merge the new incoming command with this command. More... | |
 Public Member Functions inherited from FX::FXObject | |
| const FXchar * | getClassName () const |
| Get class name of some object. | |
| FXbool | isMemberOf (const FXMetaClass *metaclass) const |
| Check if object is member of metaclass. | |
| virtual long | tryHandle (FXObject *sender, FXSelector sel, void *ptr) |
| Try handle message safely, catching certain exceptions. | |
| virtual long | onDefault (FXObject *, FXSelector, void *) |
| Called for unhandled messages. | |
| virtual void | save (FXStream &store) const |
| Save object to stream. | |
| virtual void | load (FXStream &store) |
| Load object from stream. | |
| virtual | ~FXObject () |
| Virtual destructor. | |
Base class for undoable commands records.
Each undo records all the information necessary to undo, as well as redo, a given operation. Since commands are derived from FXObject, subclassed commands may be able to implement their behaviour by sending messages (like ID_SETINTVALUE, etc) as well as simple API calls to objects to be modified. Small, incremental undo commands may sometimes be consolidated into larger ones, by merging consecutive commands. A merge is effected by calling the mergeWith() API after first establishing that merging is possible with canMerge(). When commands are merged, the incoming (new) command is deleted and not added to the undo list. In some cases, the incoming command may completely cancel the existing commands, causing both to be deleted. In that case the prior command will be removed from the undo list. To allow UndoList to manage memory, your subclassed Command should re-implement size() and return the amount of memory used by your undo command. This way, bookkeeping periodically pare down undo commands to keep memory usage in check.
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Return true if this command could possibly be merged with a previous undo command.
This is useful to combine e.g. multiple consecutive single-character text changes into a single block change. The default implementation returns false.
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Called by the undo system to try and merge the new incoming command with this command.
When overriding this API, return:
0 if incoming command could not be merged into this command, 1 if incoming command could be merged into this command, 2 if incoming command completely cancels effect of this command.
The default implementation returns 0.
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virtual |
Return the size of the information in the undo record.
The undo list may be periodically trimmed to limit memory usage to a certain limit. For proper accounting, value returned should include the size of the command record itself as well as any data linked from it.
Reimplemented in FX::FXUndoList, and FX::FXCommandGroup.
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Copyright © 1997-2022 Jeroen van der Zijp
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