gonum plot : font error

[Fred]

Hi,

I have 2 computers with Linux Manjaro and  go version 1.16.3.

The same scatter plot works on one computer and produces on the other these already known errors :

# gonum.org/v1/plot/text

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:153:3: cannot use hdlr.Fonts.Lookup(rm, fnt.Size).Face (type *sfnt.Font) as type *truetype.Font in field value

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:154:3: cannot use hdlr.Fonts.Lookup(rm, fnt.Size).Face (type *sfnt.Font) as type *truetype.Font in field value

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:155:3: cannot use hdlr.Fonts.Lookup(it, fnt.Size).Face (type *sfnt.Font) as type *truetype.Font in field value

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:156:3: cannot use hdlr.Fonts.Lookup(bf, fnt.Size).Face (type *sfnt.Font) as type *truetype.Font in field value

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:157:3: cannot use hdlr.Fonts.Lookup(bfit, fnt.Size).Face (type *sfnt.Font) as type *truetype.Font in field value

/home/fred/GO/src/gonum.org/v1/plot/text/latex.go:221:3: cannot use op.Glyph.Font (type *truetype.Font) as type *sfnt.Font in field value

an update does not fix the error.

go get -u gonum.org/v1/plot/...

# cd /home/fred/GO/src/github.com/go-latex/latex; git pull --ff-only

Votre information de configuration indique de fusionner avec la référence 'refs/heads/master'

du serveur distant, mais cette référence n'a pas été récupérée.

package github.com/go-latex/latex/drawtex: exit status 1

the go/src/gonum.org/v1/plot/font directory is the same on both computers. Do I need to install some missing fonts ?

Thanks in advance,

Fred

[Carla Pfaff]

You should really use modules. The module name is "gonum.org/v1/plot", not "github.com/gonum/plot".

$ mkdir scatter-demo

$ cd scatter-demo

$ go mod init scatter-demo

$ edit main.go

# Copy and paste code from https://gist.github.com/sbinet/602522b7399ead414e279e2261d81095 into main.go

# Replace all instances of "github.com/gonum/plot" by "gonum.org/v1/plot" in the imports of main.go:

        "gonum.org/v1/plot"

        "gonum.org/v1/plot/plotter"

        "gonum.org/v1/plot/vg"

$ go mod tidy

$ go build

[Sebastien Binet]

Salut Fred,

On Mon May 17, 2021 at 14:11 CET, Fred wrote:
> Hi,
> I have 2 computers with Linux Manjaro and go version 1.16.3.
> The same scatter plot

> <https://gist.github.com/sbinet/602522b7399ead414e279e2261d81095> works

> on
> one computer and produces on the other these already known errors :

> <https://groups.google.com/g/gonum-dev/c/a8sC1fzV3Mo>

>
> # gonum.org/v1/plot/text
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:153:3: cannot use
> hdlr.Fonts.Lookup(rm, fnt.Size).Face (type *sfnt.Font) as type
> *truetype.Font in field value
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:154:3: cannot use
> hdlr.Fonts.Lookup(rm, fnt.Size).Face (type *sfnt.Font) as type
> *truetype.Font in field value
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:155:3: cannot use
> hdlr.Fonts.Lookup(it, fnt.Size).Face (type *sfnt.Font) as type
> *truetype.Font in field value
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:156:3: cannot use
> hdlr.Fonts.Lookup(bf, fnt.Size).Face (type *sfnt.Font) as type
> *truetype.Font in field value
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:157:3: cannot use
> hdlr.Fonts.Lookup(bfit, fnt.Size).Face (type *sfnt.Font) as type
> *truetype.Font in field value
> /home/fred/GO/src/gonum.org/v1/plot/text/latex.go:221:3: cannot use
> op.Glyph.Font (type *truetype.Font) as type *sfnt.Font in field value

this should indeed be fixed w/ gonum/pl...@v0.9.0.

>
> an update does not fix the error.
>
> go get -u gonum.org/v1/plot/...
> # cd /home/fred/GO/src/github.com/go-latex/latex; git pull --ff-only
> Votre information de configuration indique de fusionner avec la
> référence
> 'refs/heads/master'
> du serveur distant, mais cette référence n'a pas été récupérée.
> package github.com/go-latex/latex/drawtex: exit status 1

this error may come from the fact that go-latex/latex is now using
'main' as its main branch in lieu of 'master'.

hth,
-s

[Fred]

Thanks Carla and Sébastien for your quick answer !

Carla your solution works, when I use modules I do not have font errors. 

What is strange is that I was not using modules in any computer to try this example and it was working in one an not the other :) 

[Roland Müller]

Hello,

applying Carlas's solution I got a failure in line 20 since plot.New() returns a pointer but no pointer, error pair.

Only after changing usage of New() I got the scatter-demo running. May be error message can be enhanced :-)

scatter-demo]$ go build

# scatter-demo
./main.go:20:9: assignment mismatch: 2 variables but plot.New returns 1 values

 20     p := plot.New()
 21     if p == nil {
 22         panic("Plotter cannot be created")
 23     }

BR,
Roland

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[Fred]

@Roland : I saw this change too,  removing the error variable fix the problem :)