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GBIC >> PowerBASIC >> Tutorials >> Controls >> Textbox Control

PowerBASIC Information Center Tutorials
These tutorials were written to help you get a quick, but thorough, understanding of PowerBASIC - the scope of the language as well as it's specific capabilities.

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  • Textbox Control
    The textbox control provides a way to display and edit single or multi-line text.

    • Syntax:
      Control Add TextBox, hDlg, id&, txt$, x, y, xx, yy, _
                                            style&, extsytle& CALL callback

    • Source Code Example:
      This short example creates a complete application with a single textbox. When the content is changed, the textbox responds with a message. This tutorial page discusses most of the statements used, however the DDT, Controls, Messages, and Callback tutorials provide background information that may be helpful in understanding the example.

         #Compile Exe
         Global hDlg As Dword
         Function PBMain() As Long
            Dialog New Pixels, 0, "TextBox Test",300,300,200,200, _
                                            %WS_SysMenu, 0 To hDlg
            Control Add TextBox, hDlg, 100,"Edit Me!", 50,50,100,20
            Dialog Show Modal hDlg Call DlgProc
         End Function
         CallBack Function DlgProc() As Long
            If Cb.Msg = %WM_Command And Cb.Ctl = 100 And _
                              Cb.CtlMsg = %EN_Change Then
               MsgBox "Got Focus!"
            End If
         End Function

      An additional example of a callback function is provided further down this page.

    • Visual Examples:
      And here are a few examples of what you can do with the textbox control in PowerBASIC. Variations on the Control Add Textbox statement were used to create the examples. In some cases, other Control statements were used to modify the results.

      The choices are fairly basic - a window in which to view or edit text, either single or multiline. You can change the font, the color, or the justification of the text. Scrollbar display can be controlled. The control can be made readonly and can be made to display "***" for visual protection of password entry. Input can be limited to upper case, lower case, and digits 0-9.

    The Control Add statement is used to create all new controls. Here are the statement's arguments and any special significance to the textbox control.

    • hDlg
      The dialog handle to which the textbox control is to be added. The value was returned by the DIALOG NEW statement.

    • id&
      The id& argument is a control identifier assigned by the programmer. It must be a value of 1-65535. Values of 100+ are suggested, as PowerBASIC pre-assigns identifiers with special meaning. Numeric equates are suggested over the use of literal values.

    • txt$
      The default text is "". During execution a user types in text.

    • x,y and xx,yy
      The integer x,y and xx,yy dimensions use the same units as the parent dialog. (x,y) is the upper/left coordinates of the control. (xx,yy) is the width/height of the control.

    • style& and extstyle&
      The style& and extstyle& arguments (listed below) are optional. If not supplied, default values are used (see the table below). If values are supplied, they completely replace default values (i.e., the entered values are not in addition to the default values).

    • CALL
      The "CALL callback" section is optional. If not supplied, the callback function of the parent dialog is used. An example callback function for textbox controls is provided further down this page. The #MESSAGE COMMAND compiler directive can be used to prevent sending %WS_NOTIFY messages to the callback function. By default, both %WS_NOTIFY and %WS_COMMAND messages are sent.

    Usage Notes
    By default, text is a single line and scrolls to the right. Use %es_multiline to allow text to wrap. To allow pressing ENTER to create a new line, add %es_wantreturn (it overrides default handling of ENTER, which is to activate the dialog default button).

    Justification (left/center/right) only works with multiline text.

    User input can be constrained to upper/lower/number/password content with %es_upper, %es_lower, %es_number and %es_password. Upper/lower/password constraint is applied to text entered in the Control Add statement, but not so for number constraint.

    Scrollbars only apply to multiline text.

    Selected text gets inverted. By default, when a textbox loses focus the selection is hidden. Use %es_nohidesel to keep selection visible when focus is lost.

    With %es_autohscroll, autowrapping is disabled.

    With %es_autovscroll and %es_wantreturn, ENTER forces textbox to scroll when on last line.

    Textbox Control-Specific PowerBASIC Statements
    Although PowerBASIC provides control-specific statements for some controls (Treeview, Imagelist, ...), there are no TEXTBOX PowerBASIC statements.

    Messages, Notifications, Styles, and ExtSstyles
    There are four types of named constants in the following table. All are pulled from the MSDN web site.

    • Notifications - event notifications a control receives
    • Messages - controls may send these
    • Styles - affect the visual look of a control
    • ExtStyles - additional values that affect the visual look

    The first column contains control-specific named constants and the second column contains generic window named constants (textbox controls are windows).

    Also, if the PowerBASIC Help file has an entry on the value, it is highlighted in yellow. If the value was noted in PowerBASIC Help as a default value, it is also shown in bold text.

    In the values for notifications, descriptions starting with -n and -c refer to events received through the %wm_notify and %wm_command messages. By default, PowerBASIC controls can receive both of these messages.


    And here is a short description of many of the named constants corresponding to notifications, styles, and extstyle - particularly those discussed in the PowerBASIC Help topics.

        %en_change             -c text has changed (after screen updated)
        %en_errspace           -c insufficient space
        %en_hscroll            -c horizontal scroll bar clicked (before update)
        %en_killfocus          -c textbox loses keyboard focus
        %en_maxtext            -c maximum character length exceeded. truncates text.
        %en_setfocus           -c textbox receives keyboard focus
        %en_update             -c text change, before screen update
        %en_vscroll            -c vertical scrollbar clicked (before update)
        %es_autohscroll        - auto horizontal scroll (10 chars)
        %es_autovscroll        - auto vertical scroll, use WANTRETURN, MULTILINE
        %es_center             - center text
        %es_left               - left align text
        %es_lowercase          - convert to lowercase (during entry)
        %es_multiline          - allow multi-line of text. use ES_WANTRETURN
        %es_nohidesel          - invert selection, regardless of focus
        %es_number             - allow only digits (- + not allowed)
        %es_oemconvert         - convert to OEM character set
        %es_password           - display all * regardless of character entered
        %es_readonly           - prevent text entry. allows select/copy
        %es_right              - right align text
        %es_uppercase          - convert to uppercase (during entry)
        %es_wantreturn         - ENTER inserts CRLF. n/a on single line textbox
        %wm_ctlcoloredit       -  before read-only/disabled control redrawn
        %ws_border             - use thin line border
        %ws_ex_clientedge      - apply sunken edge border
        %ws_ex_left            - generic left-aligned properties
        %ws_ex_right           - generic right-aligned properties
        %ws_ex_staticedge      - apply 3D border
        %ws_ex_transparent     - draw controls/windows beneath control first
        %ws_ex_windowedge      - apply raised edge border
        %ws_group              - starts/ends group. use %ws_tabstop style.
        %ws_hscroll            - autodisplay horizontal scroll
        %ws_tabstop            - allows receipt of keyboard focus
        %ws_vscroll            - autodisplay vertical scroll

    Callback Function
    A control can have its own callback function, or use the parent dialog callback function.

    A control callback function should return TRUE to indicate it has processed the message. This prevents unnecessarily calling the dialog callback function, which will process the message if no control callback function is available, or if the control callback function returns FALSE.

    By default, both %WM_COMMAND and %WM_NOTIFY messages are received. However, if the #MESSAGE COMMAND compiler directive is invoked, the %WM_NOTIFY messages will not be available.

    Here's a sample textbox control callback function.

       CallBack Function cbTextBox()
          Select Case CB.MSG
             Case %WM_COMMAND
                Select Case CB.CTLMSG
                   Case %en_change
                   Case %en_errspace
                   Case %en_hscroll
                   Case %en_killfocus
                   Case %en_maxtext
                   Case %en_setfocus
                   Case %en_update
                   Case %en_vscroll
                End Selection
          End Select
       End Function

    In each Case section, add the statements the application needs to respond to the event. Also, be sure to add "Function=1" as appropriate to indicate that the event was handled by the callback function.

    CONTROL Statement Syntax
    The following table lists the various Control statements (except the ADD statements). Most, but not all, can be used with the textbox control. A one-line description of the statement and then its syntax are presented.

      CONTROL DISABLEdisable
      hDlg, id&
      CONTROL ENABLEenable hDlg, id&
      CONTROL GET CHECKcheck state hDlg, id& TO iResult1&
      CONTROL GET CLIENTtop/left location hDlg, id& TO wide&, high&
      CONTROL GET LOCtop/left location hDlg, id& TO x&, y&
      CONTROL GET SIZEwidth/height hDlg, id& TO width&, height&
      CONTROL GET TEXTtext hDlg, id& TO txt$
      CONTROL GET USERget user data hDlg, id&, index& TO retvar&
      CONTROL HANDLE window handle for control id hDlg, id& TO hCtl&
      CONTROL KILLremove control hDlg, id&
      CONTROL POSTput message in queue (non-blocking) hDlg, id&, Msg&, wParam&, lParam&
      CONTROL REDRAWschedule redraw of control hDlg, id&
      CONTROL SENDsend message to control, wait for processing hDlg, id&, Msg&, wParam&, lParam& TO iResult2&
      CONTROL SET CHECKset check for 3state or checkbox hDlg, id&, checkstate&
      CONTROL SET CLIENTchange size to specific client area size hDlg, id&, wide&, high&
      CONTROL SET COLORset fg/bg color hDlg, id&, fgcolor&, bgcolor&
      CONTROL SET FOCUSset focus hDlg, id&
      CONTROL SET FONTselect font for a control hDlg, id&, fonthandle&
      CONTROL SET LOCrelocate control within dialog hDlg, id&, x&, y&
      CONTROL SET OPTIONset check state of option control hDlg, id&, minid&, maxid&
      CONTROL SET SIZEchange control size hDlg, id&, width&, height&
      CONTROL SET TEXTchange control text hDlg, id&, text$
      CONTROL SET USERset user data hDlg, id&, index&, uservalue&
      CONTROL SHOW STATE     toggle visibility hDlg, id&, showstate& TO iResult3&

    If you have any suggestions or corrections, please let me know.