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151 Interface Elements CHAPTER 14 Graphical user interfaces, such as Windows, OS/2, and Macintosh, use menus, buttons, windows, and dialog boxes to make applications easier to use. With True BASIC, you can create and control such objects in your own programs. The easiest way to do this is with the True Controls and True Dials libraries of subroutines provided with the language. True Controls is a library of subroutines that let you manage windows, menus, graphical objects, buttons, edit areas, and other interface elements from your True BASIC programs. True Dials is a similar library of routines that let you create dialog boxes as part of your programs. This chapter explains how you can create user-interface elements using the routines from these two libraries. The routines described in this chapter are relatively easy to use, allow control of all user-interface elements, and, in most instances, will meet all of your needs. (Advanced users might want to gain further control of interface elements through direct use of the built-in subroutines OBJECT and TBD. All of the user-interface “objects” are ultimately controlled by these two extremely powerful and complex subroutines. The OBJECT subroutine is used by all the True Controls routines, while True Dials routines call the TBD routine to create and display all dialog boxes and return the user’s response. Advanced programmers who wish to use the OBJECT and TBD routines directly should refer to the reference sections (see Chapters 19 and 21). Examining the source code of TRUEC- TRL.TRU in the TBLIBS folder should help.) The example programs ARCHERY2.TRU, DAYCALC.TRU, PISTON.TRU, and SURVIVE.TRU (in the TBDEMOS directory) provide a good overview of how the convenience routines described in this chapter may be used to enhance programs. The TBDEMOS directory also contains several programs that illustrate the individual objects; those programs have names that begin with DEM. User Interface Objects and Controls The True Controls routines let you create and control the following objects or controls: Window Menu Push button Radio group Check box Group box Static text Edit field List box List button List edit button Graphics Scroll bar Text editor Physical window Pop-down selections for a window’s menu bar Push button with text Several radio buttons, only one of which can be on, with text Text with check box that may be checked on or off Box with or without a title One-line piece of text that cannot be edited One-line text input region that can be edited A (scrollable) selection list of items Button with a pop-down selection list Edit field with a pop-down selection list Several types of graphics objects Horizontal or vertical scroll bar Fully-scrollable text-edit object
152 True BASIC Language System Some of the items, such as the graphics and windows, are objects, while others, such as check boxes, buttons, text editors, and radio groups, are controls. For convenience, we may refer to both types as objects, since there is no distinction in how you use the True Controls routines to handle objects or controls. Dialog boxes are the only control objects not handled by True Controls routines. They are handled by routines in the True Dials library as described later in this chapter. Dialog-box routines are in a separate library because they return information to the program differently than the objects handled by the True Controls routines. Otherwise, dialog boxes are similar to other interface objects. Program Structure with Interface Elements By programming with the interface-element routines you can greatly enhance the appearance and “user-friendliness” of your programs. Along with these enhancements, however, you as the programmer must accept the responsibility for processing all the events that may occur as the user responds to the controls and objects in your program. To do this correctly, you may need to re-think the structure of your programs. The two versions of the Archery program (ARCHERY.TRU and ARCHERY2.TRU in the TBDEMOS directory) illustrate the difference in approach needed for work with interface elements. In programs that don’t use interface routines, input statements may typically be scattered about various program structures. In the original ARCHERY.TRU program, the main loop asks if the player wishes another game and responds appropriately, while the MakeShot subroutine gets the user input for angle and velocity. In both instances, the program pauses until there is a user response. Thus, the program could “spend a lot of time” in the MakeShot subroutine. This works fine for that version of the program, because the user has no opportunity for any other input until a shot is completed and control returns to the main loop. The limited order of events is clearly defined in the main loop, as follows: DO CALL MakeScene CALL PlayGame ! Draws the scene ! Calls MakeShot to get velocity and angle input ! and draw resulting shots until success PRINT “Play another (y or n)?”; GET KEY key PRINT LOOP while key = Ord(“y”) or key = Ord(“Y”) When you program with interface controls and objects, however, you present the user with a greater possibility of responses and your program must be ready to process those responses or “events” as soon as possible. Such programs generally work best with a main “event processor” loop to handle all potential user input. The main event loop may call subroutines to carry out an appropriate action, but those subroutines should not themselves process input. Thus, control can return immediately to the main event loop and prevent events from piling up. In ARCHERY2.TRU, control objects let the user input velocity or angle, fire a shot, call for a new game scene, or quit the game. These objects are always available; the user need not use them in any particular order. To prevent the program from waiting in one subroutine, say for a new velocity and angle, when the user may be indicating a different action, such as firing a shot or getting a new game scene, all event handling is placed in the main loop. The subroutines carry out the same actions as before, but they do so with input obtained in the event loop, as follows: DO ! Main event loop LET x1, x2 = 0 CALL TC_Event (0, event$, window, x1, x2) ! Get next event IF event$ = “KEYPRESS” and x1 = 27 then EXIT DO ! Escape will stop program IF x2 = quit then ! Quit button pressed EXIT DO ELSE IF x2 = fire and event$ = “CONTROL DESELECTED” then CALL MakeShot ! Fire shot with current angle & velocity ELSE IF x2 = newgame and event$ = “CONTROL DESELECTED” then CALL MakeScene ! Draw new scene END IF
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True BASIC Language System Gold Edi
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True BASIC Language System 18. Stat
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ii Save on close The default settin
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iv LOADING LIBRARIES Loading librar
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When you use the UNDO feature the i
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directly to the computer. If you cl
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You are free to use upper or lower
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PREFERENCES Under the SETTINGS menu
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xii The reset button restores the t
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LINE NUMBERS Legacy code often uses
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xiv The True BASIC Editor menus Nor
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• CUT - will copy any highlighted
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xviii Remember that the default dir
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xx • COLORTEXT - this feature use
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angle brackets, e.g. and this will
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1 A Word on Style CHAPTER 1 Before
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A Word on Style 3 —————
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A Word on Style 5 ment. You may als
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7 CHAPTER 2 Constants, Variables, a
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Constants, Variables, and Expressio
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Constants, Variables, and Expressio
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13 Output Statements CHAPTER 3 Gene
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Output Statements 15 Printing Blank
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Output Statements 17 3 9 27 4 16 64
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Output Statements 19 This section i
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Output Statements 21 Examples of Fl
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Output Statements 23 Here are some
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Output Statements 25 Printing to a
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27 Input Statements CHAPTER 4 Most
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Input Statements 29 INPUT PROMPT
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Input Statements 31 Special keys su
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Input Statements 33 Turning the Tex
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35 Decision Structures CHAPTER 5 Tr
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Decision Structures 37 not(x-2 = z)
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Decision Structures 39 Nested IF St
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Loop Structures 41 Loop Structures
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Loop Structures 43 Although infinit
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Loop Structures 45 change the limit
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47 Data as Part of the Program CHAP
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Data as Part of the Program 49 Beca
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51 Built-in Functions CHAPTER 8 Tru
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Built-in Functions 53 Mathematical
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Built-in Functions 55 SEC(x) Secant
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Built-in Functions 57 LOOP END As i
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Built-in Functions 59 spaces are no
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Built-in Functions 61 Arrays and Ma
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Arrays and Matrices 63 LOOP END The
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Arrays and Matrices 65 will print t
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Arrays and Matrices 67 DIM name$(1)
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Arrays and Matrices 69 MAT INPUT so
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Arrays and Matrices 71 in each dime
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Arrays and Matrices 73 Scalar Multi
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Arrays and Matrices 75 MAT READ a D
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Arrays and Matrices 77 The SortS su
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Arrays and Matrices 79 ————
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Arrays and Matrices 81 CPSortN(a(),
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Arrays and Matrices 83 The first tw
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85 User-defined Functions and Subro
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User-defined Functions and Subrouti
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99 Libraries and Modules CHAPTER 11
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Page 188 and 189: Interface Elements 157 ————
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Error Handling 201 Passing Errors Y
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Error Handling 203 The first proced
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205 Constants, Variables, Expressio
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217 CHAPTER 18 Statements, Built-in
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307 Object Subroutine CHAPTER 19 Th
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Object Subroutine 309 OBJM_PAGESETU
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Object Subroutine 313 nates of the
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Object Subroutine 315 CALL Object (
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Object Subroutine 317 The TXE VScro
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Object Subroutine ICONIZABLE FOCUS
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Object Subroutine 321 PLOT TEXT OPA
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Object Subroutine PAGE VERTICAL SIN
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Object Subroutine LEFT RELATIVE RIG
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Object Subroutine 327 LET values(2)
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Object Subroutine RIGHT RELATIVE BO
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Object Subroutine 331 Scroll Bar Au
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Object Subroutine WRAP MARGIN READO
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Object Subroutine TRAP CHAR KEY EVE
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337 Sys_Event Subroutine CHAPTER 20
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Sys_Event Subroutine 339 REFRESH SE
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Sys_Event Subroutine 341 Events for
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Sys_Event Subroutine 343 The follow
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345 TBD or TBDX Subroutines CHAPTER
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TBD or TBDX Subroutine 347 The valu
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TBD or TBDX Subroutine 349 Parm1$ i
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351 Interface Library Routines CHAP
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Interface Library Routines 353 Wind
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Interface Library Routines 355 abso
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Interface Library Routines 357 TC_S
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Interface Library Routines 359 Exce
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Interface Library Routines 363 The
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Interface Library Routines 365 TC_W
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Interface Library Routines 369 Chec
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Interface Library Routines 373 TC_G
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Interface Library Routines 375 TC_G
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Interface Library Routines 377 Grou
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Interface Library Routines 379 List
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Interface Library Routines 381 TC_R
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Interface Library Routines 383 Stat
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Interface Library Routines 385 TC_T
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Interface Library Routines 387 the
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Interface Library Routines 389 LET
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Interface Library Routines 391 CALL
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Interface Library Routines 393 The
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Interface Library Routines 395 do l
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Interface Library Routines 397 Summ
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Interface Library Routines 399 SXOF
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Interface Library Routines 401 Com_
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A Note About Speed The communicatio
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Additional Library Routines 405 ERR
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407 Additional Library Procedures C
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Math Libraries 409 ACOT Function Li
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Math Libraries 411 AND Function Lib
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Math Libraries 413 Note: The ASINH
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Math Libraries 415 produces the fol
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Math Libraries 417 Exceptions: See
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Math Libraries Example: in the valu
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String Handling Libraries 421 Detai
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String Handling Libraries 423 CHARI
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String Handling Libraries 427 Excep
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String Handling Libraries 431 produ
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String Handling Libraries 437 DO WH
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String Handling Libraries 441 NEXTW
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String Handling Libraries 445 Detai
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String Handling Libraries 455 Usage
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Sorting and Searching Libraries 457
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Graphics Libraries 471 Example: The
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Graphics Libraries 473 DATA 17543,9
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Graphics Libraries 477 ASKBARTYPE S
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Graphics Libraries 479 Example: Exc
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Graphics Libraries 481 See also: SE
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Graphics Libraries 485 See also: 11
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Graphics Libraries 489 Example: By
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Graphics Libraries 495 MULTIBAR Sub
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Graphics Libraries 497 Summary: Det
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Graphics Libraries 499 Example: A p
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Graphics Libraries 501 If the value
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Graphics Libraries 503 Available Gr
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Graphics Libraries 505 Example: Exc
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Graphics Libraries 507 Details: Exa
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24-1 CHAPTER 24 Calling C Routines
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Calling C Routines in True BASIC 24
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25-1 CHAPTER 25 Using SOCKET Routin
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Using SOCKET Routines in True BASIC
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Using SOCKET Routines in True BASIC
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True BASIC - Updated CHAIN Document
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549 APPENDIX Line Numbers H There a
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555 APPENDIX Index of True BASIC St
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Appendix I: Index of True BASIC Sta
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Appendix I: Control Object Attribut
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Appendix I: Graphic Object Attribut
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Appendix I: Graphic Object Attribut
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Appendix I: Window Object Attribute
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Appendix I: Window Object Attribute
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Appendix I: Events Attributes 597 K
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599 APPENDIX J Debugging and Correc
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Appendix J: Debugging and Correctin
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Appendix J: Debugging and Correctin
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606 True BASIC Language System You
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608 True BASIC Language System Most
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612 True BASIC Language System W In
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614 True BASIC Language System WBDI
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638 True BASIC Language System RECS
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