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[WikiDbImage rotatext.jpg]

[Tom Krehbiel] shared the following interesting code in the [Tcl chatroom], which may display a large E in various rotation angles (X only, not on all Linuxes...):

tomk: Are you aware that it is possible to rotate single character in a Tk canvas?

kennykb: Rotate single char in Tk canvas? How?

tomk: I have some code that someone (smarter than me) posted. I don't remember when or who. You want me to sent you a copy?

kennykb: Sure, glad to look at it.  This supposed to be Tcl code? Or is someone changing the canvas implementation?

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 proc rotmatrix {size angle} {
    set size [expr {double($size)}]
    set angle [expr {double($angle)*acos(0.0)/90.0}]; # In radians
    set c [expr {$size*cos($angle)}]
    set s [expr {$size*sin($angle)}]
    # Due to Tk's XLFD (X Logical Font Description)
    # parser, we need to round values
    set s [format "\[%.f %.f %.f %.f\]" $c [expr {-$s}] $s $c]
    regsub -all -- "-" $s ~ s
    return $s
 }
 pack [scrollbar .vs -orient vertical -command {.c yview}] -side right -fill y
 pack [scrollbar .hs -orient horizontal -command {.c xview}] -side bottom -fill x
 pack [canvas .c -bg white -xscrollcommand {.hs set} -yscrollcommand {.vs set}]\
        -side left -expand 1 -fill both
 set nb 16
 set size 24
 set size 64
 set text "The Quick Brown Fox jumps over the Lazy Black Dog"
 set text "E"
 .c configure -scrollregion [list -1000 0 1000 [expr {$size*$nb*2}]]
 set x 100
 for {set i 0} {$i < 16} {incr i} {
    set y [expr {10+$i*$size*2}]
    set angle [expr {360.0*$i/$nb}]
    .c create text $x $y -text [format "%.1f½½°    " $angle] -anchor ne -font \
       -adobe-times-medium-r-*-*-$size-*-*-*-*-*-*-*
    .c create text $x $y -text $text -anchor nw -font \
       -adobe-times-medium-r-*-*-[rotmatrix $size $angle]-*-*-*-*-*-*-*
    .c create rectangle [expr {$x-2}] [expr {$y-2}] [expr {$x+2}] [expr {$y+2}]\
       -outline black -fill red
 }
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suchenwi: WOW! YES!

tomk: I added the 64 font size and the text "E". If you remove them you get a string version.

kennykb Guys: Before you get too excited, this is Unix-only and not supported by every X server.

suchenwi: Works here on Solaris via Reflection, but not native on PC - there the E is only scaled smaller. 
But it's definitely only recommendable for a single letter...

bschwarz: doesn't work on linux 

kennykb: The functionality is X, mostly. The comment about Tk's XLFD parser 
has to do with whether Tk will recognize the string as an XLFD or a Tk font name.

trb: works on my linux: 2.2.18.  XFree86 v 3360 tk 8.3

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''[DKF]:'' Note that the above does not work with an IRIX Xserver.
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The [BLT] extension can also [rotate text on a canvas]

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[Category Example] - [Category Graphics]