Libris Britannia 4/science library(b).zip/science library(b)/INFO/QHELP135.ZIP/QHELP135.DOC

Text File | 1987-03-26 | 7KB | 107 lines

                        QHELP135.COM by Bob Montgomery 3/26/87

     This program is an example of HELP.ASM by Bob Montgomery, which was a
     rewrite of QHELP.ASM by Kurt Schelin, and is a template for creating
     your own popup help screens. It contains all of the assembly code
     required to make your message pop up using your choice of a shift key
     combination for the hot keys; the shift keys are Cntrl, Alt, Left
     Shift, Right Shift, Caps Lock, Number Lock, and Scroll Lock. The code
     is written in A86 assembler formats; I prefer A86 because it doesn't
     need the org, segment, assume, ends, etc assembler directives and is
     a little smarter. Border characters can be used to partition the help
     display, and to make it look more professional. The program
     automatically centers the help screen on the display, in the colors
     you selected with the Colattr equate.

     The help message can be any message you desire with the following
     restrictions:
          1. The message must not exceed 80 characters/line-dictated by
             screen width.
          2. The message cannot exceed 25 lines-dictated by the screen
             length.
          3. Each line must be the same length-blank filled to make so.

     To make your own help screen, pick a combination of shift keys to be
     your hot keys and change the equate called Hotkey to the sum of these
     keys. In the template, the hot keys are Cntrl-Left Shift. Then,
     change the Colattr equate for the colors you want the help window to
     be; the first nibble is the background color (0-7), and the second
     nibble is the foreground color (0-15). If you want the help window to
     blink, add 8 to the background color. Then change the db statements
     at Hlpst and the following lines to your message; remember that each
     line must have the same number of characters. In the template, each
     line is a different upper case alphabetic letter. You may have from 1
     to 80 characters/line, and you may have from 1 to 25 lines for your
     help screen. The program will automatically center the help screen on
     the display; that's what the equates following the help message do.
     Then, assemble the source to the filename of your choice, and you
     have a help screen COM program. The help screen for QEdit135 is used
     in this example.

     The program works with all displays (Monochrome, CGA, and EGA) in all
     80 column text modes (will not work in graphics mode). It is a
     'terminate and stay resident' program, and can be used with MARK &
     RELEASE to free up memory when it is no longer required. For
     instance, with QEdit, I do MARK, QHELP, QEDIT (filename), RELEASE in
     a batch file or as CED synonyms.

     The source is liberally commented so you can understand how it works.
     The first thing that happens when you call it is a jump to the
     initialize routine, which gets and saves the old keyboard interrupt
     (Int 9) and the vectors the keyboard interrupt to this program. Then,
     it terminates but stays resident, and the Start portion of the
     program handles all keyboard interrupts from this point on.

     A keyboard interrupt is generated each time a key is pressed or
     released, and the neccessary steps required to get the key are known
     only to the BIOS Int 9 routine. Therefore, we must call the BIOS Int
     9 routine from this program to handle the key action. The only
     problem with this is that the BIOS Int 9 program is an interrupt
     handler and not a subroutine, which means it pops the return address
     (like a subroutine) and the flag register at completion. To fake it
     out and keep the stack pointer where it should be, we push the flags
     before calling the BIOS Int 9 routine (as a subroutine), and it pops
     the flags when it is done. The only thing the program looks for is
     the hot key combination on each keyboard interrupt, and it uses a
     BIOS service (Int 16-get shift status) to do this. Any other keys are
     ignored, but the action required to record the key press or release
     has been done by the call to the BIOS Int 9 routine in the new Int 9
     program.  If the hot keys have been pressed, the program checks a
     flag to see if the help screen is already up; if so, the hot keys are
     ignored. This is done in the Start portion of the program.

     If the hot keys are pressed and the help screen is not up, the
     program then determines the current video mode and page, and saves
     it. From this, the current video display area of memory is
     determined. Then, the cursor is disabled and the help window area of
     the display is copied to a buffer in the program, so it can be
     restored when the help window is removed. The help window data is
     then copied to display memory with whatever attribute (color) you
     selected, and the display is then unblanked. A flag is set to
     indicate that the help window is up. Your help data is now visible on
     the display, and is centered horizontally and vertically, and in the
     color you selected with the Colattr equate (if you have a color
     display). To avoid 'snow' on CGA monitors while video memory is being
     accessed, the display is blanked during video read/write times, and
     blanking and unblanking occur at vertical retrace time; this is not
     done for the monochrome monitor, since it doesn't have the 'snow'
     problem.

     Now the program waits for the Escape key, and ignores all others.
     When the Escape key is finally pressed, video is disabled and the old
     screen data is put back on the display. Then the cursor is enabled
     and the display is unblanked, and you have your original screen back.
     The flag which indicates the help screen is up is cleared, and the
     program resumes looking for the hot keys.

     I hope this program is of some use to you, and you are free to copy
     and distribute it, but please distribute it in its original form so
     it can be used by others. I also hope you follow the source listing,
     and maybe learn something in the process. This is my contribution to
     the shareware community. Enjoy the program.

     If you have any comments or suggestions, I can be contacted at the
     Black Hole BBS in Orlando, Fl., 1200/2400 Baud [phone].

     Bob Montgomey