Object-oriented Software in Ada 95

332 TUI the implementation
The implementation code for Get_Immediate is shown mapping the three-character ANSI sequence for the
arrow keys into an internal single character to representation. The actual character (s) generated will depend on
the operating environment. The arrow key presses are mapped upon input into the character constants C_LEFT,
C_RIGHT, C_UP and C_DOWN so that they can be processed in the program in a machine-independent way.
with Raw_Io, Pack_Constants;
use Raw_Io, Pack_Constants;
package body Pack_Md_Io is
procedure Put( Ch:in Character ) is
begin
Raw_Io.Put( Ch );
end Put;
procedure Put( Str:in String ) is
begin
Raw_Io.Put( Str );
end Put;
procedure Get_Immediate( Ch:out Character) is
Esc: constant Character := Character'Val(27);
begin
Raw_Io.Get_Immediate( Ch );
if Ch = Esc then
--ESC
Raw_Io.Get_Immediate( Ch ); --[
if Ch = '[' then
Raw_Io.Get_Immediate( Ch );
case Ch is
when 'A' => Ch := C_Up; --A - Up arrow
when 'B' => Ch := C_Down; --B - Down arrow
when 'C' => Ch := C_Right; --C - Right arrow
when 'D' => Ch := C_Left; --D - Left arrow
when others => Ch := '?';
end case;
end if;
end if;
end Get_Immediate;
end Pack_Md_Io;
--? - Unknown
Note:
In the implementation of get_immediate the arrow keys are converted into an internal single
character. The implementation for Raw_Io that I used returns three characters when an arrow key is
pressed.
One way of simplifying this procedure is to make the user of the TUI use the following control keys for
arrow movements.
Character
^L
^R
^U ^D
Meaning
Same as left arrow key
Same as right arrow key
Same as up arrow / down arrow key
These definitions can, of course, be changed by modifying the definitions of C_Up etc. in the package
Pack_Constants.
© M A Smith - May not be reproduced without permission