From Newsgroup: comp.lang.tcl

I'm considering experimenting with canvas or more likely with tkpath.
I
want to create an interactive GUI program so that I can create
shapes and modify their properties.
So I need to be able to save all the items that are created and to
be able to load them back in again.

With the tk text widget saving can be done using the dump command and
loading isn't too difficult to do.

But I can't see an equivalent for canvas or for tkpath.

Do canvas or tkpath have support for loading/saving?

(If they don't I can envisage creating my own file format that
keeps track of each item but I don't want to reinvent if this is
already present.)
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl


Mark Summerfield <m.n.summerfield@gmail.com> posted:

I'm considering experimenting with canvas or more likely with tkpath.
I
want to create an interactive GUI program so that I can create
shapes and modify their properties.
So I need to be able to save all the items that are created and to
be able to load them back in again.

With the tk text widget saving can be done using the dump command and
loading isn't too difficult to do.

But I can't see an equivalent for canvas or for tkpath.

Do canvas or tkpath have support for loading/saving?

(If they don't I can envisage creating my own file format that
keeps track of each item but I don't want to reinvent if this is
already present.)

The canvas (and tkpath as well, I guess) offers introspection so that you can indeed save the contents and load it in again. A source of inspiration might be tkpaint (see the Wiki), though I do not know the current status.

Regards,

Arjen
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

On Wed, 19 Nov 2025 11:57:54 GMT, Arjen wrote:

Mark Summerfield <m.n.summerfield@gmail.com> posted:

I'm considering experimenting with canvas or more likely with tkpath.
I
want to create an interactive GUI program so that I can create
shapes and modify their properties.
So I need to be able to save all the items that are created and to
be able to load them back in again.

With the tk text widget saving can be done using the dump command and
loading isn't too difficult to do.

But I can't see an equivalent for canvas or for tkpath.

Do canvas or tkpath have support for loading/saving?

(If they don't I can envisage creating my own file format that
keeps track of each item but I don't want to reinvent if this is
already present.)

The canvas (and tkpath as well, I guess) offers introspection so that you can indeed save the contents and load it in again. A source of inspiration might be tkpaint (see the Wiki), though I do not know the current status.

Regards,

Arjen

Unfortunately none of the links on that page https://wiki.tcl-lang.org/page/Tkpaint work.

I'll see how far I get on my own.

Thanks.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

* Mark Summerfield <m.n.summerfield@gmail.com>
| On Wed, 19 Nov 2025 11:57:54 GMT, Arjen wrote:
| > The canvas (and tkpath as well, I guess) offers introspection so that you can
| > indeed save the contents and load it in again. A source of inspiration might
| > be tkpaint (see the Wiki), though I do not know the current status. --<snip-snip>--

| Unfortunately none of the links on that page
| https://wiki.tcl-lang.org/page/Tkpaint work.

| I'll see how far I get on my own.

For the canvas:
loop
canvas list all => all currently defined objects in stacking order
canvas type id => oval rect ...
canvas coords id => where is it
canvas itemconfigure id => what does it look like

should get you some way.

Can't say for tkpath, but the procedure would be similar.

HTH
R'
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

Am 20.11.2025 um 10:36 schrieb Ralf Fassel:

* Mark Summerfield <m.n.summerfield@gmail.com>
| On Wed, 19 Nov 2025 11:57:54 GMT, Arjen wrote:
| > The canvas (and tkpath as well, I guess) offers introspection so that you can
| > indeed save the contents and load it in again. A source of inspiration might
| > be tkpaint (see the Wiki), though I do not know the current status. --<snip-snip>--

| Unfortunately none of the links on that page
| https://wiki.tcl-lang.org/page/Tkpaint work.

| I'll see how far I get on my own.

For the canvas:
loop
canvas list all => all currently defined objects in stacking order
canvas type id => oval rect ...
canvas coords id => where is it
canvas itemconfigure id => what does it look like

should get you some way.

Can't say for tkpath, but the procedure would be similar.

HTH
R'

Maybe directly ping René Zaumseil or Manfred Rosenberger.
To my knowledge, tk path emphasis a lot of svg compatibility.It is
possible to save a svg file.
It might also possible to load it.

Take care,
Harald
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

Mark Summerfield wrote:

On Wed, 19 Nov 2025 11:57:54 GMT, Arjen wrote:

Mark Summerfield <m.n.summerfield@gmail.com> posted:

I'm considering experimenting with canvas or more likely with
tkpath. I
want to create an interactive GUI program so that I can create
shapes and modify their properties.
So I need to be able to save all the items that are created and to
be able to load them back in again.

With the tk text widget saving can be done using the dump command
and loading isn't too difficult to do.

But I can't see an equivalent for canvas or for tkpath.

Do canvas or tkpath have support for loading/saving?

(If they don't I can envisage creating my own file format that
keeps track of each item but I don't want to reinvent if this is
already present.)

The canvas (and tkpath as well, I guess) offers introspection so that
you can indeed save the contents and load it in again. A source of
inspiration might be tkpaint (see the Wiki), though I do not know the
current status.

Regards,

Arjen

Unfortunately none of the links on that page https://wiki.tcl-lang.org/page/Tkpaint work.

I'll see how far I get on my own.

Thanks.

In my experience it's not a good idea to use canvas or text widgets as
memory. It's simpler to have some data structure in real memory to
contain all the information, and use the text or canvas simply as a
display device, driven by a routine that accesses the real memory.
--
*********** To reply by e-mail, make w single in address **************
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

On Thu, 20 Nov 2025 10:36:27 +0100
Ralf Fassel <ralfixx@gmx.de> wrote:

[...]

For the canvas:
loop
canvas list all => all currently defined objects in stacking order
canvas type id => oval rect ...
canvas coords id => where is it
canvas itemconfigure id => what does it look like

should get you some way.

Except for window items, where it would take a bit more work, this code
works well serializing/deserializing canvas items:

# start
proc canvas_dump {c} {
lmap item [$c find all] {
set type [$c type $item]
# skip if item type is window
if {$type eq "window"} continue
set res [list $type [$c coords $item]]
foreach opt [$c itemconfigure $item] {
lappend res [lindex $opt 0] [lindex $opt end]
}
set res
}
}

proc canvas_restore {c dump} {
foreach item $dump {
$c create {*}$item
}
}
# end

This will copy items *appearance* from a canvas to another, but will
not copy behaviour. You have to instrospect bindings, at both canvas
and items level (tags and id's), to get a better copy.

Regards.
--
Emiliano <emiliano@example.invalid>
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

* Emiliano <emiliano@example.invalid>
--<snip-snip>--
| Except for window items, where it would take a bit more work, this code
| works well serializing/deserializing canvas items:
--<snip-snip>--
| This will copy items *appearance* from a canvas to another, but will
| not copy behaviour. You have to instrospect bindings, at both canvas
| and items level (tags and id's), to get a better copy.

Ah, right, window items, bindings etc. There always is more to it than
it seems at the first glance :-)

R'
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl


Mark Summerfield <m.n.summerfield@gmail.com> posted:

Do canvas or tkpath have support for loading/saving?

(If they don't I can envisage creating my own file format that
keeps track of each item but I don't want to reinvent if this is
already present.)

Ulis had made such work before : https://wiki.tcl-lang.org/page/Serializing+a+canvas+widget
(and should work for windows)
TkPaint is much more complex because it manages options : colors, zoom, grid, .... and has specific
specific tools : deform, rectangle with round corners ...
Some parts were inspired by Impress : https://www.ntlug.org/~ccox/impress/ which was sophisticated at the time.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.tcl

On Thu, 20 Nov 2025 20:23:56 -0300, Emiliano wrote:

On Thu, 20 Nov 2025 10:36:27 +0100
Ralf Fassel <ralfixx@gmx.de> wrote:

[...]

For the canvas:
loop
canvas list all => all currently defined objects in stacking order
canvas type id => oval rect ...
canvas coords id => where is it
canvas itemconfigure id => what does it look like

should get you some way.

Except for window items, where it would take a bit more work, this code
works well serializing/deserializing canvas items:

# start
proc canvas_dump {c} {
lmap item [$c find all] {
set type [$c type $item]
# skip if item type is window
if {$type eq "window"} continue
set res [list $type [$c coords $item]]
foreach opt [$c itemconfigure $item] {
lappend res [lindex $opt 0] [lindex $opt end]
}
set res
}
}

proc canvas_restore {c dump} {
foreach item $dump {
$c create {*}$item
}
}
# end

This will copy items *appearance* from a canvas to another, but will
not copy behaviour. You have to instrospect bindings, at both canvas
and items level (tags and id's), to get a better copy.

Regards.

Thank you and the others who have replied.

In the end I came to the same conclusion about canvas as Ian and have
created a SQLite database to store my canvas items data, especially
since I want to support undo/redo. (I don't agree about tk's text
widget though; I can dump & load that just fine.)

I've also decided to start out with canvas rather than tkpath.

However, one problem I've hit straight away is that I can't work out
how to get and set a canvas item's z-order -- or stacking order in
canvas terminology. (I am only interested in shapes, not nested
widgets or windows.) I know I can raise and lower and can use
`canvas find all` to get an ordering, so I guess I'll have to
do it that way.
--- Synchronet 3.21a-Linux NewsLink 1.2