High speed text box

[Russ Stillman]

Hi,

I am trying to write a program, basically a terminal emulator
(with 24x80 display) that receives data from the serial port,
displays new data on the bottom line and scrolls old data up a
line, and sends keyboard data out the serial port.

VB has problems keeping up with the serial data (depending on
what the other applications are doing) and also cannot keep
up with the display requirements.

I purchased PB/DLL and am trying to come up to speed with it.
I have compiled the "serial.bas" sample program which is very
close to what I need to do. The program puts the received data
in a text box, but the text scrolls up so slow, it doesn't look
like it could keep up with 300 baud, much less 38,400 baud or more.

Can anyone help me with this, or guide me to information on
creating a text window/box that can scroll data (24 x 80 format)
at a very high speed. It doesn't have to have the ability of
scrolling backwards with a scroll bar. The old data can just
be ignored after it has scrolled off the screen. I just need a
simple fixed column width font, just like an old "Adam" terminal.

Thank you very much for your time,

Russ

[E B Knoppert]

Windows has a lot to do when you fill this box.
I recommend storing your incomming data in memory.
Only 'paint' what is becomming visible using the ordinary wm_paint message.

To invoke;
Invalidaterect ByVal 0&, -1 invokes the wmpaint (triggered by incomming data)
There's the place where you decide WHAT to paint on the screen.
For example len of data -80x25



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[Chris Boss]

Russ;

If the text does not need to be edited in any way, then I would use a Static control (like the Label control in VB). In DDT it would be a Label control.

Create a Label control and then set the font to "Terminal" using the %WM_SETFONT message . This will force the text to be fiexed width.

Then use the API to find out the metrics (size) of the Terminal Font used for the control. Lets say the font is 8 x 16 pixels (an example). Use this info to resize your control to hold an 80 x 24 grid.

Update the data in a string variable and then update the entire Label controls text with every new line.

You can use code like this:

SUB UpdateTerminal(byval ND$)
' D$ hold the current text
' N& holds the number of lines
' ND$ holds the new data received (by Line)
STATIC D$
STATIC N&
N&=N&+1
if ND$=chr$(27) then N&=0   ' use esc char for Clear command
Select case N&
   case 1
      D$=ND$
   case 2 to 24
      D$=D$+chr$(13)+chr$(10)+ND$
   case 25
      D$=mid$(D$, instr(D$, chr$(10)+1))
      D$=D$+chr$(13)+chr$(10)+ND$
   case 0
      D$=""   ' clear terminal
   case else
end select

CONTROL SET TEXT hDlg&, Id&, D$

END SUB

The Text (Edit) control has more overhead because it must track the Caret, which a Label control avoids.

A Label control implimented as above will "appear" to scroll as you pass it data.



------------------

[Enoch S Ceshkovsky]

Perhaps it is the way you are updating it. You will do quite a bit of wheel reinventing to write scrollback & copy/paste into a label control. These are 2 critical terminal emulator features. Perhaps if you could paste the function that does all the output to the textbox.
If you really need high high speed output, it might be better to consider pb/cc and do everything with the console.


------------------

[John Hutchins]

I had the same problem.
Forget the edit control and write directly to the window using
TextOut API.
The following is the function I use. Works just like:
locate n,n:color,nrint n$ does in Dos.

'Declare hFont as global & PrintStr as asciiz * 80 & Ink AS LONG
FUNCTION SPRINT(BYVAL hDlg AS LONG,BYVAL Row AS LONG,BYVAL Col AS LONG,BYVAL Ink AS LONG,PrintStr AS ASCIIZ) AS LONG

LOCAL hDC AS LONG
LOCAL Trect AS Rect
LOCAL DiUnit AS DWORD
LOCAL HZDBU AS LONG
LOCAL VTDBU AS LONG
LOCAL ch AS LONG
LOCAL cv AS LONG
LOCAL hBkCol AS LONG
LOCAL STRINGPTR AS ASCIIZ PTR
LOCAL STRINGLEN AS LONG

GetDC hDlG TO hDC
SelectObject hDc,hFont
GetClientRect hDlg,Trect
GetDialogBaseUnits TO DiUnit
HZDBU = LOWRD(DiUnit)
VTDBU = HIWRD(DiUnit)
ch = Col * HZDBU
cv = Row * VTDBU
SetBkMode hDC, %OPAQUE
SetTextColor hDC,Ink
APGREY& = RGB (190,190,190)
SETBKCOLOR hDC,APGREY&
STRINGPTR = VARPTR(PrintStr)
STRINGLEN = LEN(PrintStr)
TextOut hDC,ch,cv,@STRINGPTR,STRINGLEN
ReleaseDC hDlg,hDC
FUNCTION = %TRUE
END FUNCTION
'-----------------
you will need to keep an image of what you write to the screen.
i.e dim buffer(24) as global asciiz * 82
the buffer contents can be used to repaint the screen.
Ink is any predefined color in the winapi.inc

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[Lance Edmonds]

If you don't wish to use what is effectively an owner-drawn control, then it may be easier to tell the edit control or label control not to display new text immediately when you change the content.

Windows provides a method to 'postpone' controls updating themselves - the %WM_SETREDRAW message. Send this message with a false (0) value before sending a 'stream' of new data to the control, and then send a true (non-zero) value to tell the control it can update itself. See WIN32.HLP for more information on this message.

In this way, you could add one character at a time to the edit control, and only let the control update it's appearance when you have a complete line of 'data'.

Food for thought anyway.

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>