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Using Extended Tables

Flow of Control in Extended Tables

When an SCL program for an extended table runs, this process takes place:

1. The INIT section runs.

2. The GETROW section runs. Each row in the table is displayed.

3. The program waits for user input.

4. If a user modifies a row in the table, the PUTROW section runs for that row, the MAIN section runs, and the GETROW section runs again to display the table with the modified value. Then the program waits for more user input.

In the process, the GETROW section runs for all visible rows each time the PUTROW section runs, no matter how many rows the PUTROW section processes.

In addition, the GETROW section runs when an extended table receives a _refresh method. An extended table receives a _refresh method in these cases:

• the frame is displayed initially

• users scroll (both vertically and horizontally)

• users enter the END command, if one of the rows contains a widget that is in error and the widget is not displayed (the widget is forced into view by setting its row to the top)

• these extended table methods are executed:
  • _erroron or _erroroff_ (if a row or widget name is passed in)

  • _needRefresh

  • _needRowRefresh

  • _selectRow or _unselectRow

  • _setMaxcol

  • _setMaxrow

  • _setMaxsel

  • _setToprow

  • _setViscol

  • _setVisrow

  • _unselectAll

  For some of these methods, GETROW runs only if the method affects the display. See the individual methods for more information.

  Because you can create a frame with multiple extended tables, the GETROW section does not always execute after the MAIN section runs. If GETROW were to run every time the MAIN section ran, modifying a widget outside of the extended tables would cause all GETROW sections in the table to run, whether they relied on the modified object or not. Potentially, this could slow down an application, especially if the GETROW section performed extensive work.

  You can override this behavior using the _needRefresh method defined in the Widget class. The _needRefresh method allows the table to receive a _refresh method. You can also use the Extended Table method, _needRowRefresh.

Automatic Instance Variables

Two special instance variables, _currow and _curcol, are added to the extended table object and all objects within the extended table. These two instance variables are marked as "automatic" so that when the extended table's _getrowLabel or _putrowLabel method, or an object's _objectLabel or _select method run, these variables are automatically initialized to the correct values.

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