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The Terminal Emulation control provides a virtual terminal interface
for emulating an ANSI or DEC VT-220 compatible character-based
terminal. It can be used in conjunction with the Telnet interface or
the Remote Command interface to display the output of commands executed
on a server. It can also be used independently of any other
networking control, such as providing emulation services for a serial
connection.
Display Management
The control provides a number of properties and methods to manage
and update the virtual display. The most commonly used methods are:
BackColor
This property can be used to change the background color displayed by
the virtual terminal.
ColorMap
This property array can be used to change the default colors which
are used when escape sequences are used to change the foreground or
background color of a character cell. In most cases the default color
map will be appropriate, but applications can change the RGB values
associated with an entry in the color map if needed. For example, the
default value for the color gray is at position 8 in the color map
index with an RGB value of 192,192,192. If you wanted to use a darker
color, you could change the RGB value to 128,128,128
Emulation
This property specifies the type of emulation that will be performed
by the control. The control is capable of emulating an ANSI console,
a DEC VT-100 and DEC VT-220/320 terminal.
FontName
This property sets the name of the font which is used by the control
to draw text on the display window. Note that there is also a Font
property which returns a Font object for more control over the font
used by the emulator. It is recommended that you only used
fixed-width fonts such as Terminal or Courier New.
FontSize
This property sets the size of the font which is used by the control
to draw text on the display window. Note that there is also a Font
property which returns a Font object for more control over the font
used by the emulator.
ForeColor
This property can be used to change the foreground color displayed by
the virtual terminal.
Write
This is the most commonly used method of writing to the display. This
method will automatically parse the data being written for escape
sequences and update the display appropriately.
Refresh
Refresh the virtual display, updating the current cursor position and
caret. The control will periodically refresh the display
automatically based on its own internal state, but the application
can call this if it wishes to force the display to refresh at that
time.
Reset
This method can be used to reset the display window, the font being
used and the size of the display. Note that resetting the display
causes the contents of the display to be cleared.
Cursor Control
There are a number of properties and methods which enable an
application to have direct control over cursor positioning, clearing
the display and so on. In most cases these methods are called
automatically by the control as the result of processing the escape
sequences found in the data being written to the display. However, an
application can choose to manage the display itself. One important
thing to keep in mind is that the X,Y positions used by these
properties and methods refer to the cursor position in the virtual
display and correspond to columns and rows, not pixels.
There is also a slight difference in terminology that you should be
aware of when reading the technical reference documentation. In
Windows, the term "cursor" is typically used to refer to the
mouse pointer, while "caret" is used to refer to the blinking
marker that is displayed at the current position in the display. In the
documentation for the emulator, the term "cursor" is used in
the same way that it is used for character based terminals, as the
marker for the current position in the display. Therefore, in terms of
the control, you can think of the cursor and the caret as being
synonymous.
CursorX
This property returns the current position of the cursor in the
display, or can be used to change the current position. The current
position is given in columns and indicates where the next text
character will be displayed.
CursorY
This property returns the current position of the cursor in the
display, or can be used to change the current position. The current
position is given in rows and indicates where the next text character
will be displayed.
Clear
This method clears the contents of the display. You can clear from
the start of the display to the current cursor position, from the
current position to the end of the display or the entire display.
DelLine
This method deletes the line at the current cursor position, shifting
the remaining lines in the display up.
InsLine
This method inserts a blank line at the current cursor position,
shifting the following lines down.
ScrollDown
This method scrolls the display down by one line.
ScrollUp
This method scrolls the display up by one line.
Function Key Mapping
Another aspect of terminal emulation is how function keys and other
special keys are handled by the application. The emulation control can
be used to convert Windows virtual key codes into the escape sequences
that are generated by character based terminals.
KeyMap
This property array allows the application to define character
sequences that should be mapped to special keys. When a special key
is pressed in the emulation window and there is an entry for it in
the key map, the KeyMapped event is fired. For example, if the user
presses the F1 key on the keyboard, the control will translate that
key code into the three characters escape sequence ESC O P (the ASCII
codes 27, 79, 80). That sequence of characters should be sent to the
server, which will recognize it as the F1 function key being
pressed. It is important to note that the different emulation types
have different key mappings. Therefore, the server must be set
to recognize the same type of terminal that you are emulating. If you
have the emulation set as VT-220 but the server thinks that you are
emulating a VT-100, it will not recognize some of the escape
sequences correctly.
KeyMapped
This event is generated when the user presses a special key while the
emulation window has focus, and that key is mapped to a string using
the KeyMap property array. Typically an application will use this
event to send the mapped key escape sequence to a server, such
as a Telnet server.
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