Paged mode DISPLAY ARRAY

Dynamic dialogs using DISPLAY ARRAY can use ON FILL BUFFER events to fill pages of rows.

The ON FILL BUFFER event

The concept of paged mode and ON FILL BUFFER trigger is explained in Paged mode of DISPLAY ARRAY. Read this first.

With dynamic dialogs, the data rows must be provided when the ON FILL BUFFER event occurs. The program code must provide all field values for each row, from a row offset position and for a given number of rows that represent a page.

Field values are set with the ui.Dialog.setFieldValue() dialog method. To select the row to be assigned, you must call the ui.Dialog.setCurrentRow() dialog method before setFieldValue() calls. When used in the context of the ON FILL BUFFER event, setCurrentRow() will only define the current row to set field values. After executing the ON FILL BUFFER code, the runtime system will automatically reset the current row in the list.

When implementing a singular DISPLAY ARRAY dynamic dialog, the event string returned by nextEvent() contains "ON FILL BUFFER". When implementing a multiple-dialog with one or more DISPLAY ARRAY sub-dialogs, the nextEvent() returns "ON FILL BUFFER screen-record-name".

Code example

The following example implements a singular list dynamic dialog using the paged mode.

Form definition file form.per:
LAYOUT
TABLE table1
{
[c11      |c12            ]
[c11      |c12            ]
[c11      |c12            ]
[c11      |c12            ]
}
END
END

ATTRIBUTES
EDIT c11 = FORMONLY.cust_id, TITLE="Num";
EDIT c12 = FORMONLY.cust_name, TITLE="Name";
END

INSTRUCTIONS
SCREEN RECORD sr(FORMONLY.*);
END
Program file main.4gl: This version of the sample provides the total number of rows before the dialog loop starts: 
TYPE t_fields DYNAMIC ARRAY OF RECORD
    name STRING,
    type STRING
END RECORD

MAIN
    DEFINE d ui.Dialog
    DEFINE t STRING
    DEFINE fields t_fields
    DEFINE x, ofb_offset, ofb_length INT

    OPEN FORM f1 FROM "form"
    DISPLAY FORM f1

    LET fields[1].name = "cust_id"
    LET fields[1].type = "INTEGER"
    LET fields[2].name = "cust_name"
    LET fields[2].type = "VARCHAR(50)"
    LET d = ui.Dialog.createDisplayArrayTo(fields,"sr")
    CALL d.addTrigger("ON FILL BUFFER")
    CALL d.addTrigger("ON ACTION accept")
    CALL d.setArrayLength("sr",2000)

    WHILE (t := d.nextEvent()) IS NOT NULL
        CASE t
            WHEN "ON FILL BUFFER"
                LET ofb_offset = fgl_dialog_getbufferstart()
                LET ofb_length = fgl_dialog_getbufferlength()
                DISPLAY SFMT("ON FILL BUFFER offset:%1 length:%2",ofb_offset,ofb_length)
                FOR x = ofb_offset TO ofb_offset + ofb_length -1
                    CALL d.setCurrentRow("sr",x)
                    CALL d.setFieldValue("sr.cust_id",x)
                    CALL d.setFieldValue("sr.cust_name",SFMT("Name %1",x))
                END FOR
            WHEN "ON ACTION accept"
                CALL d.accept()
            WHEN "AFTER DISPLAY"
                EXIT WHILE
        END CASE
    END WHILE
    CALL d.close()

END MAIN
If the total number of rows is not known before the dialog executes, set the array length to -1 and stop providing rows in ON FILL BUFFER when the end of the result set is reached:
TYPE t_fields DYNAMIC ARRAY OF RECORD
    name STRING,
    type STRING
END RECORD

MAIN
    DEFINE d ui.Dialog
    DEFINE t STRING
    DEFINE fields t_fields
    DEFINE x, ofb_offset, ofb_length INT

    OPEN FORM f1 FROM "form"
    DISPLAY FORM f1

    LET fields[1].name = "cust_id"
    LET fields[1].type = "INTEGER"
    LET fields[2].name = "cust_name"
    LET fields[2].type = "VARCHAR(50)"
    LET d = ui.Dialog.createDisplayArrayTo(fields,"sr")
    CALL d.addTrigger("ON FILL BUFFER")
    CALL d.addTrigger("ON ACTION accept")
    CALL d.setArrayLength("sr",-1)

    WHILE (t := d.nextEvent()) IS NOT NULL
        CASE t
            WHEN "ON FILL BUFFER"
                LET ofb_offset = fgl_dialog_getbufferstart()
                LET ofb_length = fgl_dialog_getbufferlength()
                DISPLAY SFMT("ON FILL BUFFER offset:%1 length:%2",ofb_offset,ofb_length)
                FOR x = ofb_offset TO ofb_offset + ofb_length -1
                    IF x>100 THEN -- Simulate end of result set
                        EXIT FOR
                    END IF
                    CALL d.setCurrentRow("sr",x)
                    CALL d.setFieldValue("sr.cust_id",x)
                    CALL d.setFieldValue("sr.cust_name",SFMT("Name %1",x))
                END FOR
            WHEN "ON ACTION accept"
                CALL d.accept()
            WHEN "AFTER DISPLAY"
                EXIT WHILE
        END CASE
    END WHILE
    CALL d.close()

END MAIN