Object-oriented Software in Ada 95

330 TUI the implementation
23.2.1 Constants used in the TUI
The TUI uses several constants to define the state of the TUI and its environment. The size of the screen and the
maximum size of windows created on the screen are defined by:
package Pack_Constants is
Vdt_Max_X : constant := 79; --Columns on VDT
Vdt_Max_Y : constant := 25; --Lines on VDT
Window_Max_X : constant := 79; --MAX columns window
Window_Max_Y : constant := 25; --MAX lines window
Various special characters that can be sent to or are used by the TUI, have the following values:
C_Cursor
C_Blank
C_Win_A
C_Win_Pas
C_Exit
C_Where
C_Action
C_Switch
C_Menu
C_Del
: constant Character := '*';
: constant Character := ' ';
: constant Character := '#';
: constant Character := '+';
: constant Character := Character'Val(05); --^E
: constant Character := Character'Val(255);
: constant Character := Character'Val(13); --cr
: constant Character := Character'Val(09); --ht
: constant Character := Character'Val(27); --esc
: constant Character := Character'Val(08); --^B
Various internal states and representations of actions are defined in the list below. In this list, the arrow keys
that a user presses to interact with the TUI are internally defined as a single character. This is to simplify the
internal code that processes the key's representations.
C_No_Char
: constant Character := Character'Val(00);
C_Left : constant Character := Character'Val(12); --^L
C_Right : constant Character := Character'Val(18); --^R
C_Up : constant Character := Character'Val(21); --^U
C_Down : constant Character := Character'Val(04); --^D
end Pack_Constants;
23.2.2 Raw input and output
The TUI works on the assumption that a character is sent immediately to the screen without any internal
processing or buffering. Likewise, the TUI receives each character as it is typed without any internal buffering or
processing.
An Ada package specification and possible implementation are shown below. In this implementation, a library
procedure C_No_Echo written in the language C is used to turn off the echoing of the character that is read
immediately from the keyboard.
© M A Smith - May not be reproduced without permission