Clear the undo buffer

Overview

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.

1. 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.

2. 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).

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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 ] }

12. 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.

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