[Richard Suchenwirth] 2007-01-23 - Waiting for a lengthy zipping, I hacked up this plaything that simulates credits of a movie, rolling over the [canvas] screen.

[WikiDbImage credits.jpg]

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[Jeff Smith] 2020-11-06 : Below is an online demo using [CloudTk]. This demo runs Rolling credits in an Alpine Linux Docker Container. It is a 27.4MB image which is made up of Alpine Linux + tclkit + Rolling-credits.kit + libx11 + libxft + fontconfig + ttf-linux-libertine. It is run under a user account in the Container. The Container is restrictive with permissions for "Other" removed for "execute" and "read" for certain directories. 

<<inlinehtml>>

<iframe height="300" width="400" src="https://cloudtk.tcl-lang.org/cloudtk/VNC?session=new&Tk=Rolling-credits" allowfullscreen></iframe>

<<inlinehtml>>

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======
 package require Tk
 proc titleshow {w title} {
    set -fill black
    set -font {Helvetica 16}
    set x [expr {[winfo width $w]/2}]
    set y [winfo height $w]
    foreach line [split $title \n] {
        set line [string trim $line]
        if [string match -* $line] {
            eval [linsert $line 0 set]
        } else {
            $w create text $x $y -text $line -fill ${-fill} -font ${-font} \
                -justify center -tag title
            incr y 48
        }
    }
    every 40 "if !\[titleshow'roll $w title -2\] return"
 }
 proc titleshow'roll  {w tag dy} {
    $w move $tag 0 $dy ;# (1)
    foreach i [$w find withtag $tag] {
        set y1 [lindex [$w bbox $i] end]
        if {$y1<0} {$w delete $i}
    }
    llength [$w find withtag $tag]
 }
 proc every {ms body} {eval $body; after $ms [info level 0]}

# That's all the code, here's a testing demo. Lines starting with - set parameters, the others are displayed:

 pack [canvas .c -bg black]
 tkwait visibility .c

 titleshow .c {
    -fill white
    -font {Helvetica 18 italic}
    Richard Suchenwirth presents
    -font {Helvetica 24 bold}
    -fill yellow
    THE IMPORTANCE
    OF BEING UNEARNEST
    -font {Helvetica 18}
    -fill white
    with
    -font {Helvetica 24}
    -fill yellow
    MARILYN MONROE
    GARY COOPER
    PETER SELLERS

    -font {Helvetica 18}
    Camera     Alphonse de Lumiere
    Gaffer     Joe Smith

    -font {Helvetica 10}
    (c) United Hackers, Inc. MMVII
 }
======

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[JM] Richard, this is very nice!

do we have something in the wiki to scroll text in the same line?
like the news at the bottom of the TV screen? - [RS]: You mean, what is sometimes called a [Ticker]?
You could either modify the code above (the line marked (1) in ''titleshow'roll'' has 0 for horizontal movement,
put your desired value there); or, you can do it with a plain [label] like this. First, a proc that "cycles" a string variable, so that "abcd" becomes "bcda":
 proc string'cycle _str {
    upvar 1 $_str str
    set str [string range $str 1 end][string index $str 0]
 }
# Example for test and demo:
 pack [label .l -textvar ticker -anchor w -width 50]
 set ticker "For all those who like to read news while watching a movie, \
 here is a little ticker that displays at the bottom +++ "
 every 100 {string'cycle ::ticker}

[HE] and here is [every]
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[JM] thanks Richard, thanks [HE], but in fact, "every" proc is in this very same page.

btw, homework (based on [RS] hints) is done, and text runs smoother than the label solution.
I will publish tomorrow, giving the credit to Richard, of course (-: - [RS]: For smoother scrolling in the label, use a fixed-pitch font.

[HE] Found it. I tried only the second example. As I missed "every" I looked for the side where it reside. I know [RS] saves everything about tcl anywhere on the wiki :-)
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[nscerqueira]

in order to repeat the text scrolling just change the lines

in the titleshow proc


        every 40 "if !\[titleshow'roll $w title -2\] return"

to         

       every 40 [list titleshow'roll $w $y title -2]n"


and in the the titleshow'roll proc 


                if {$y1<0} {$w delete $i}
to
        
                  if {$y1<0} {$w move $i 0 $y}
        

[schelte] gave most of the help to make this possible.

And don't forget to add the argument to the  titleshow'roll proc , i.e., 

proc titleshow'roll  {w y tag dy} {

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