Example: Single Data Type Data in a Table Widget

The following procedures build a simple application that allows the user to select data from a table, plotting the data in a draw window and optionally displaying the data values in a text widget. The user can switch the table between standard and disjoint selection modes.

This example is included in the file table_widget_example1.pro in the examples/doc/widgets subdirectory of the IDL distribution. Run this example procedure by entering table_widget_example1 at the IDL command prompt or view the file in an IDL Editor window by entering .EDIT table_widget_example1.pro. See Running the Example Code if IDL does not run the program as expected.

; Event-handler routine

PRO table_widget_example1_event, ev

 

  ; Retrieve the anonymous structure contained in the user value of

  ; the top-level base widget.

  WIDGET_CONTROL, ev.top, GET_UVALUE=stash

 

  ; Retrieve the table's selection mode and selection.

  disjoint = WIDGET_INFO(stash.table, /TABLE_DISJOINT_SELECTION)

  selection = WIDGET_INFO(stash.table, /TABLE_SELECT)

 

  ; Check to see whether a selection exists, setting the

  ; variable 'hasSelection' accordingly.

  IF (selection[0] ne -1) THEN hasSelection = 1 $

    ELSE hasSelection = 0

 

  ; If there is a selection, get the value.

  IF (hasSelection) THEN WIDGET_CONTROL, stash.table, $     GET_VALUE=value, /USE_TABLE_SELECT

 

  ; The following sections define the application's reactions to

  ; various types of events.

 

  ; If the event came from the table, plot the selected data.

  IF ((ev.ID eq stash.table) AND hasSelection) THEN BEGIN

    WSET, stash.draw

    PLOT, value

  ENDIF

 

  ; If the event came from the 'Show Selected Data' button, display

  ; the data in the text widget.

  IF ((ev.ID eq stash.b_value) AND hasSelection) THEN BEGIN

    IF (disjoint eq 0) THEN BEGIN

      WIDGET_CONTROL, stash.text, SET_VALUE=STRING(value, /PRINT)

    ENDIF ELSE BEGIN

      WIDGET_CONTROL, stash.text, SET_VALUE=STRING(value)

    ENDELSE

  ENDIF

 

  ; If the event came from the 'Show Selected Cells' button,

  ; display the selection information in the text widget. Use

  ; different displays for standard and disjoint selections.

  IF ((ev.ID eq stash.b_select) AND hasSelection) THEN BEGIN

    IF (disjoint eq 0) THEN BEGIN

      ; Create a string array containing the column and row

      ; values of the selected rectangle.

      list0 = 'Standard Selection'

      list1 = 'Left: ' + STRING(selection[0])

      list2 = 'Top: ' + STRING(selection[1])

      list3 = 'Right: ' + STRING(selection[2])

      list4 = 'Bottom: ' + STRING(selection[3])

      list = [list0, list1, list2, list3, list4]

    ENDIF ELSE BEGIN

      ; Create a string array containing the column and row

      ; information for the selected cells.

      n = N_ELEMENTS(selection)

      list = STRARR(n/2+1)

      list[0] = 'Disjoint Selection'

      FOR j=0,n-1,2 DO BEGIN

        list[j/2+1] = 'Column: ' + STRING(selection[j]) + $

          ', Row: ' + STRING(selection[j+1])

      ENDFOR

    ENDELSE

    WIDGET_CONTROL, stash.text, SET_VALUE=list

  ENDIF

 

  ; If the event came from the 'Change Selection Mode' button,

  ; change the table selection mode and the title of the button.

  IF (ev.ID eq stash.b_change) THEN BEGIN

    IF (disjoint eq 0) THEN BEGIN

      WIDGET_CONTROL, stash.table, TABLE_DISJOINT_SELECTION=1

      WIDGET_CONTROL, stash.b_change, $

        SET_VALUE='Change to Standard Selection Mode'

    ENDIF ELSE BEGIN

      WIDGET_CONTROL, stash.table, TABLE_DISJOINT_SELECTION=0

      WIDGET_CONTROL, stash.b_change, $

        SET_VALUE='Change to Disjoint Selection Mode'

    ENDELSE

  ENDIF

 

  ; If the event came from the 'Quit' button, close the

  ; application.

  IF (ev.ID eq stash.b_quit) THEN WIDGET_CONTROL, ev.TOP, /DESTROY

 

END

 

; Widget creation routine.

PRO table_widget_example1

 

  ; Create data to be displayed in the table.

  data = DIST(7)

 

  ; Create initial text to be displayed in the text widget.

  help = ['Select data from the table below using the mouse.']

 

  ; Create the widget hierarchy.

  base = WIDGET_BASE(/COLUMN)

  subbase1 = WIDGET_BASE(base, /ROW)

  draw = WIDGET_DRAW(subbase1, XSIZE=250, YSIZE=250)

  subbase2 = WIDGET_BASE(subbase1, /COLUMN)

  text = WIDGET_text(subbase2, XS=50, YS=8, VALUE=help, /SCROLL)

  b_value = WIDGET_BUTTON(subbase2, VALUE='Show Selected Data')

  b_select = WIDGET_BUTTON(subbase2, VALUE='Show Selected Cells')

  b_change = WIDGET_BUTTON(subbase2, $

    VALUE='Change to Disjoint Selection Mode')

  b_quit = WIDGET_BUTTON(subbase2, VALUE='Quit')

  table = WIDGET_TABLE(base, VALUE=data, /ALL_EVENTS)

 

  ; Realize the widgets.

  WIDGET_CONTROL, base, /REALIZE

 

  ; Get the widget ID of the draw widget.

  WIDGET_CONTROL, draw, GET_VALUE=drawID

 

  ; Create an anonymous structure to hold widget IDs. This

  ; structure becomes the user value of the top-level base

  ; widget.

  stash = {draw:drawID, table:table, text:text, b_value:b_value, $

           b_select:b_select, b_change:b_change, b_quit:b_quit}

 

  ; Set the user value of the top-level base and call XMANAGER

  ; to manage everything.

  WIDGET_CONTROL, base, SET_UVALUE=stash

  XMANAGER, 'table_widget_example1', base

 

END

The following things about this example are worth noting:

• It is important to check whether a selection exists before using WIDGET_CONTROL to retrieve the selection.
• Data from disjoint selections is handled differently than data from standard selections.
• For a relatively simple application, passing a group of widget IDs via the top-level base widget’s user value allows using a single event routine rather than separate event routines for each widget.