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Example: Single Data Type Data in a Table Widget

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.
  ; 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
  ; 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)
      WIDGET_CONTROL, stash.text, SET_VALUE=STRING(value)
  ; 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]
      ; 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])
    WIDGET_CONTROL, stash.text, SET_VALUE=list
  ; 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.b_change, $
        SET_VALUE='Change to Standard Selection Mode'
      WIDGET_CONTROL, stash.b_change, $
        SET_VALUE='Change to Disjoint Selection Mode'
  ; If the event came from the 'Quit' button, close the
  ; application.
  IF (ev.ID eq stash.b_quit) THEN WIDGET_CONTROL, ev.TOP, /DESTROY
; 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.
  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.
  ; Get the widget ID of the draw widget.
  ; 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.
  XMANAGER, 'table_widget_example1', base

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 the use of a single event routine rather than separate event routines for each widget.

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