Clear the undo/redo buffer by using the ClearUndoBuffer method.
Example
- Create a transient object that lists the number of possible undos and redos.
- Check the number of possible undos and redos.
- Create a sheet and add two children (list objects) to that sheet.
- Check the number of possible undos and redos.
- Undo the creation of the last list object.
- Check the number of possible undos and redos.
- Redo the creation of the list object.
- Check the number of possible undos and redos.
- Clear the undo buffer.
- Check the number of possible undos and redos.
-
Create a transient object that lists the number of possible undos and redos. qUndoInfoDef: {} is added in the object definition to enable retrieving the number of undos and redos. The list is named UndoList01 ( "qId": "UndoList01").
The client sends:
{ "jsonrpc": "2.0", "id": 1, "method": "CreateSessionObject", "handle": 1, "params": [ { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qUndoInfoDef": {} } ] }The engine returns:
{ "jsonrpc": "2.0", "id": 1, "result": { "qReturn": { "qType": "GenericObject", "qHandle": 2 } }, "change": [ 2 ] }The undo list is created and has 2 as a handle.
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Get the layout of the undo list. The handle of the request is 2 because the list has 2 as a handle.
The client sends:
{ "jsonrpc": "2.0", "id": 2, "method": "GetLayout", "handle": 2, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 2, "result": { "qLayout": { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qMeta": {}, "qSelectionInfo": {}, "qUndoInfo": { "qUndoCount": 0, "qRedoCount": 0 } } } }Since no action (create/delete, update) has been performed, the undo and redo counters are set to 0 (qUndoCount and qRedoCount are set to 0).
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Create a sheet Sheet01. The handle of the request is 1 because the CreateObject method applies at app level and the handle of the app is 1.
The client sends:
{ "jsonrpc": "2.0", "id": 3, "method": "CreateObject", "handle": 1, "params": [ { "title": "Sheet 1", "description": "Description of sheet 1", "qInfo": { "qId": "Sheet01", "qType": "sheet" }, "qChildListDef": { "qData": { "title": "/title", "description": "/description", "meta": "/meta", "order": "/order", "id": "/qInfo/qId", "type": "/qInfo/qType", "lb": "/qListObjectDef", "hc": "/qHyperCubeDef" } } } ] }The engine returns:
{ "jsonrpc": "2.0", "id": 3, "result": { "qReturn": { "qType": "GenericObject", "qHandle": 3 }, "qInfo": { "qId": "Sheet01", "qType": "sheet" } }, "change": [ 2, 3 ] }The sheet Sheet01 is created and has 3 as a handle.
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Create a list object LI01 in the sheet (qId set to LI01).The handle of the request is 3 which is the handle of the sheet. The list object LI01 is a child of the sheet.
The client sends:
{ "jsonrpc": "2.0", "id": 4, "method": "CreateChild", "handle": 3, "params": [ { "qInfo": { "qId": "LI01", "qType": "ListObject" }, "qListObjectDef": { "qStateName": "$", "qLibraryId": "", "qDef": { "qFieldDefs": [ "Country" ], "qFieldLabels": [ "Country Label" ], "qSortCriterias": [ { "qSortByLoadOrder": 1 } ] }, "qInitialDataFetch": [ { "qTop": 0, "qHeight": 1, "qLeft": 0, "qWidth": 1 } ] } } ] }The engine returns:
{ "jsonrpc": "2.0", "id": 4, "result": { "qReturn": { "qType": "GenericObject", "qHandle": 4 }, "qInfo": { "qId": "LI01", "qType": "ListObject" } }, "change": [ 4 ] }The list object LI01 is created . Its handle is 4.
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Create a list object LI02 in the sheet (qId set to LI02).The handle of the request is 3, which is the handle of the sheet. The list object LI02 is a child of the sheet.
The client sends:
{ "jsonrpc": "2.0", "id": 5, "method": "CreateChild", "handle": 3, "params": [ { "qInfo": { "qId": "LI02", "qType": "ListObject" }, "qListObjectDef": { "qStateName": "$", "qLibraryId": "", "qDef": { "qFieldDefs": [ "Country" ], "qFieldLabels": [ "Country Label" ], "qSortCriterias": [ { "qSortByLoadOrder": 1 } ] }, "qInitialDataFetch": [ { "qTop": 0, "qHeight": 1, "qLeft": 0, "qWidth": 1 } ] } } ] }The engine returns:
{ "jsonrpc": "2.0", "id": 5, "result": { "qReturn": { "qType": "GenericObject", "qHandle": 5 }, "qInfo": { "qId": "LI02", "qType": "ListObject" } }, "change": [ 5 ] }The list object LB01 is created . Its handle is 5.
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Get the layout of the undo list. The handle of the request is 2 because the list has 2 as a handle.
The client sends:
{ "jsonrpc": "2.0", "id": 6, "method": "GetLayout", "handle": 2, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 6, "result": { "qLayout": { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qMeta": {}, "qSelectionInfo": {}, "qUndoInfo": { "qUndoCount": 3, "qRedoCount": 0 } } } }The number of possible undos (qUndoCount) is 3 and the number of possible redos (qRedoCount) is 0.
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Undo the last list object creation. The handle of the request is 1 because the Undo method applies at the app level and the handle of the app is 1.
The client sends:
{ "jsonrpc": "2.0", "id": 7, "method": "Undo", "handle": 1, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 7, "result": { "qSuccess": true }, "change": [ 2 ], "close": [ 5 ] }The undo is successful (qSuccess is set to true). The list object LI02 is removed.
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Get the layout of the undo list. The handle of the request is 2 because the list uses 2 as a handle.
The client sends:
{ "jsonrpc": "2.0", "id": 8, "method": "GetLayout", "handle": 2, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 8, "result": { "qLayout": { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qMeta": {}, "qSelectionInfo": {}, "qUndoInfo": { "qUndoCount": 2, "qRedoCount": 1 } } } }The number of possible undos (qUndoCount) is 2 and the number of possible redos (qRedoCount) is 1.
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Redo the list object creation. The handle of the request is 1 because the Redo method applies at the app level and the handle of the app is 1.
The client sends:
{ "jsonrpc": "2.0", "id": 9, "method": "Redo", "handle": 1, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 9, "result": { "qSuccess": true }, "change": [ 2 ] }The redo is successful (qSuccess is set to true). The list object LI02 is created.
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Get the layout of the undo list. The handle of the request is 2 because the list uses 2 as a handle.
The client sends:
{ "jsonrpc": "2.0", "id": 10, "method": "GetLayout", "handle": 2, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 10, "result": { "qLayout": { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qMeta": {}, "qSelectionInfo": {}, "qUndoInfo": { "qUndoCount": 3, "qRedoCount": 0 } } } }The number of possible undos (qUndoCount) is 3 and the number of possible redos (qRedoCount) is 0.
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Clear the undo buffer. The handle of the request is 1 because the ClearUndoBuffer method applies at the app level and the handle of the app is 1.
The client sends:
{ "jsonrpc": "2.0", "id": 11, "method": "ClearUndoBuffer", "handle": 1, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 11, "result": {}, "change": [ 2 ] } -
Get the layout of the undo list. The handle of the request is 2 because the list uses 2 as a handle.
The client sends:
{ "jsonrpc": "2.0", "id": 12, "method": "GetLayout", "handle": 2, "params": [] }The engine returns:
{ "jsonrpc": "2.0", "id": 12, "result": { "qLayout": { "qInfo": { "qId": "UndoList01", "qType": "Undo" }, "qMeta": {}, "qSelectionInfo": {}, "qUndoInfo": { "qUndoCount": 0, "qRedoCount": 0 } } } }The undo buffer is cleared. The number of possible undos (qUndoCount) is 0 and the number of possible redos (qRedoCount) is 0.