TheGameCreators - CodeBase - Scrolling Text Example

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Category: Text

Version: 1.0

Information

Uploaded: 24th Feb 2006 14:41

Modified: 1st Jan 1970 01:00

Author: Anonymous Coder

Summary

Simple upward scrolling of lines as new lines are added.

Full Description

This is a nifty little example of how to shift lines of text upward every time a new line is added to the bottom. It's really just an illusion, though. What is really happening is that the text box erases and the old lines + new line are reprinted with the exception of the topmost line which appears to "scroll" off into nowhere. If anyone knows of a better way to do this (or mimic windows scroll bars), I'd love to know. - Jeff Scanga (Scanga@AOL.COM)

DarkBASIC Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

` Scrolling Text Example

` By Jeff Scanga   2-24-2006

` Scanga@AOL.com

` This defines the message variable that will contain different lines of text.

DIM Msg$(20)

CLS

`Draws a little text box that looks sort of like the National Geographic Logo

INK RGB(255,255,159),0

BOX 150,100,300,110

BOX 150,290,300,300

BOX 150,100,160,300

BOX 290,100,300,300

INK RGB(252,82,146),0

` This is just my lazy way of creating 20 different sample lines of text.

FOR X = 1 TO 20

Msg$(X) = "Line " + STR$(X)

NEXT X

TEXT 175,305,"<Click the Mouse Button to Proceed>"

SYNC ON

` This first loop sets up the logic to print 20 lines of text within that box, and scrolls them when necessary.

FOR Y = 1 TO 20

` The first 12 lines don't need scrolling.  Can you Guess why?

` You guessed it!  The box is big enough to contain the first 12 lines.

IF Y < 13 THEN TEXT 161,96+(Y*15),Msg$(Y)

` Now, we've reached line 12 so now we have to scroll up.  This next Loop is for doing that.

IF Y > 12

` Here's the dirty trick:  I don't really know how to scroll, so I'm faking it.

` I first erase the entire box...

GOSUB ERASE

` ...Then I set up another loop to re-print the 12 lines except that this time

` I only print from Line 2 to Line 13.

FOR Z = 1 TO 12

TEXT 161,96+(Z*15),Msg$((Y-12)+Z)

NEXT Z

` As the program goes back to the beginning of the loop, it will come to this nested loop

` again, erase the box again, and then reprint from Line 3 to Line 14 and so on until it

` finishes at Line 20.

ENDIF

SUSPEND FOR MOUSE

NEXT Y

SYNC OFF

`Disable the "SYNC ON" and "SYNC OFF" commands to see what's REALLY happening.

`It will be obvious that I'm cheating and not really scrolling, but erasing and reprinting.

` This is just a simple sub-routine to erase our box.

Erase:

INK 0,0

BOX 161,111,289,289

INK RGB(252,82,146),0

RETURN

REMSTART

Now - what I would like to know is if there is a better way to do scrolling.

This seems to be some rather tedious code, so I'm curious if someone has a better technique.

Please write me at Scanga@aol.com if you have.

I would also like to know how I might accomplish smooth scrolling with text.

True smooth scrolling would advance the lines of text a couple of pixels at a time.

This would mean that as a line advances it would get cut off by the top of the frame and only

a portion of that line would be visible.  Perhaps I have to convert the text to an image.

Somehow, that doesn't seem to be the way to go.

Anyway,

Thanks for trying out my code!

- Jeff Scanga

REMEND

` Nothing to see here.  Please disperse.

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Author Name:	Anonymous Coder
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CodeBase - Scrolling Text Example