proc zoominit {c {zfact {1.1}}} {
# save zoom state in a global variable with the same name as the canvas handle
upvar #0 $c data
set data(zdepth) 1.0
set data(idle) {}
# add mousewheel bindings to canvas
bind $c <Button-4> "zoom $c $zfact"
bind $c <Button-5> "zoom $c [expr {1.0/$zfact}]"
bind $c <MouseWheel> "if {%D > 0} {zoom $c $zfact} else {zoom $c [expr {1.0/$zfact}]}"
}
proc zoom {c fact} {
upvar #0 $c data
# zoom at the current mouse position
set x [$c canvasx [expr {[winfo pointerx $c] - [winfo rootx $c]}]]
set y [$c canvasy [expr {[winfo pointery $c] - [winfo rooty $c]}]]
$c scale all $x $y $fact $fact
# save new zoom depth
set data(zdepth) [expr {$data(zdepth) * $fact}]
# update fonts only after main zoom activity has ceased
after cancel $data(idle)
set data(idle) [after idle "zoomtext $c"]
}
proc zoomtext {c} {
upvar #0 $c data
# adjust fonts
foreach {i} [$c find all] {
if { ! [string equal [$c type $i] text]} {continue}
set fontsize 0
# get original fontsize and text from tags
# if they were previously recorded
foreach {tag} [$c gettags $i] {
scan $tag {_f%d} fontsize
scan $tag "_t%\[^\0\]" text
}
# if not, then record current fontsize and text
# and use them
set font [$c itemcget $i -font]
if {!$fontsize} {
set text [$c itemcget $i -text]
if {[llength $font] < 2} {
#new font API
set fontsize [font actual $font -size]
} {
#old font API
set fontsize [lindex $font 1]
}
$c addtag _f$fontsize withtag $i
$c addtag _t$text withtag $i
}
# scale font
set newsize [expr {int($fontsize * $data(zdepth))}]
if {abs($newsize) >= 4} {
if {[llength $font] < 2} {
#new font api
font configure $font -size $newsize
} {
#old font api
set font [lreplace $font 1 1 $newsize] ; # Save modified font! [ljl]
}
$c itemconfigure $i -font $font -text $text
} {
# suppress text if too small
$c itemconfigure $i -text {}
}
}
# update canvas scrollregion
set bbox [$c bbox all]
if {[llength $bbox]} {
$c configure -scrollregion $bbox
} {
$c configure -scrollregion [list -4 -4 \
[expr {[winfo width $c]-4}] \
[expr {[winfo height $c]-4}]]
}
}
# test code
set f [font create -family sans] ; # use private font instance to avoid modifying font outside of this canvas [JCE]
pack [canvas .c] -expand true -fill both
zoominit .c
.c create text 50 50 -text "Hello, World!" -font $f ; # use private font instance [JCE]
.c create rect [.c bbox all]Schnexel This is useless if you want to keep (halfways) control over them coordinates. With
JCE - 2009-10-14 11:35:50I don't understand Schnexel's comment.I have tested my code and (after fixing for changes to the font API that happened sometime in the last 10 years) it still works for me.None of the x,y coordinates in the canvas are changed by the zooming operation, so there is no accumulation of errors.
[ljl] Fixed minor issue with saving font for old API
JCE - 2010-10-21 11:31:00Modified to use a private font instance in the test case. This avoids changing the fontsize outside of this canvas when used as part of a larger GUI.
$c scale all $x $y $fact $factyou manipulate them in a non-reversible manner, when $x $y are varying.Tcl/Tk can change floating point numbers even if you just copy them around the canvas (e.g. splitting 1 line in 2), even with ::tcl_precision 17... (eek! forget nontrivial graphical numerics with Tcl/Tk...). Nevertheless, here´s how I keep the coordinates "constant" modulo zoom factor:
# zoom at the current mouse position
set xx [expr {[winfo pointerx $c] - [winfo rootx $c]}] ;# $xx is bind´s %x
set yy [expr {[winfo pointery $c] - [winfo rooty $c]}]
set canvX [expr {[$c canvasx $xx]*$fact}]
set canvY [expr {[$c canvasy $yy]*$fact}]
$c scale all 0 0 $fact $fact
set bbox [$c bbox all]
$c configure -scrollregion $bbox
set mx [expr ($canvX-$xx-[lindex $bbox 0]+1.0)/([lindex $bbox 2]-[lindex $bbox 0])]
set my [expr ($canvY-$yy-[lindex $bbox 1]+1.0)/([lindex $bbox 3]-[lindex $bbox 1])]
if { $mx<0.0 } { set mx 0.0 } elseif { $mx>1.0 } { set mx 1.0 }
if { $my<0.0 } { set my 0.0 } elseif { $my>1.0 } { set my 1.0 }
$c xview moveto $mx
$c yview moveto $myIt's an adaption from my code, I have not tested it with the above (no time & no mousewheel). Note the +1.0, it's to avoid zoom-drifting.JCE - 2009-10-14 11:35:50I don't understand Schnexel's comment.I have tested my code and (after fixing for changes to the font API that happened sometime in the last 10 years) it still works for me.None of the x,y coordinates in the canvas are changed by the zooming operation, so there is no accumulation of errors.
[ljl] Fixed minor issue with saving font for old API
JCE - 2010-10-21 11:31:00Modified to use a private font instance in the test case. This avoids changing the fontsize outside of this canvas when used as part of a larger GUI.
