vg/vggio: first import of a Gio-backed canvas

.github/workflows/golangci-lint.yml

@@ -8,6 +8,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - name: cgo-dependencies
+        run: sudo apt install pkg-config libgles2-mesa-dev libxkbcommon-dev libxkbcommon-x11-dev
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v1
         with:

.travis.yml

@@ -1,4 +1,4 @@
-sudo: false
+sudo: true
 
 language: go
 go_import_path: gonum.org/v1/plot
@@ -29,6 +29,9 @@ before_install:
  - go get golang.org/x/tools/cmd/cover
  - go get github.com/mattn/goveralls
 
+before_script:
+ - sudo apt-get install -qq pkg-config libgles2-mesa-dev libxkbcommon-dev libxkbcommon-x11-dev
+
 # Get deps, build, test, and ensure the code is gofmt'ed.
 # If we are building as gonum, then we have access to the coveralls api key, so we can run coverage as well.
 script:

go.mod

@@ -3,13 +3,14 @@ module gonum.org/v1/plot
 go 1.13
 
 require (
+	gioui.org v0.0.0-20200618124658-602d54dc5ef7
 	github.com/ajstarks/svgo v0.0.0-20180226025133-644b8db467af
 	github.com/fogleman/gg v1.3.0
 	github.com/go-latex/latex v0.0.0-20200518072620-0806b477ea35
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/jung-kurt/gofpdf v1.16.2
-	golang.org/x/exp v0.0.0-20190312203227-4b39c73a6495
-	golang.org/x/image v0.0.0-20200430140353-33d19683fad8
+	golang.org/x/exp v0.0.0-20191002040644-a1355ae1e2c3
+	golang.org/x/image v0.0.0-20200618115811-c13761719519
 	gonum.org/v1/gonum v0.7.0
 	rsc.io/pdf v0.1.1
 )

go.sum

@@ -1,3 +1,6 @@
+dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
+gioui.org v0.0.0-20200618124658-602d54dc5ef7 h1:PH02mpvkp5MNZcqi/wWY+YJTG5kvvuyc6kJ/efTGfXE=
+gioui.org v0.0.0-20200618124658-602d54dc5ef7/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/ajstarks/svgo v0.0.0-20180226025133-644b8db467af h1:wVe6/Ea46ZMeNkQjjBW6xcqyQA/j5e0D6GytH95g0gQ=
 github.com/ajstarks/svgo v0.0.0-20180226025133-644b8db467af/go.mod h1:K08gAheRH3/J6wwsYMMT4xOr94bZjxIelGM0+d/wbFw=
@@ -9,6 +12,7 @@ github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
 github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/go-fonts/dejavu v0.1.0 h1:JSajPXURYqpr+Cu8U9bt8K+XcACIHWqWrvWCKyeFmVQ=
 github.com/go-fonts/dejavu v0.1.0/go.mod h1:4Wt4I4OU2Nq9asgDCteaAaWZOV24E+0/Pwo0gppep4g=
+github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-latex/latex v0.0.0-20200518072620-0806b477ea35 h1:uroDDLmuCK5Pz5J/Ef5vCL6F0sJmAtZFTm0/cF027F4=
 github.com/go-latex/latex v0.0.0-20200518072620-0806b477ea35/go.mod h1:PNI+CcWytn/2Z/9f1SGOOYn0eILruVyp0v2/iAs8asQ=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
@@ -24,25 +28,37 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/ruudk/golang-pdf417 v0.0.0-20181029194003-1af4ab5afa58/go.mod h1:6lfFZQK844Gfx8o5WFuvpxWRwnSoipWe/p622j1v06w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190125153040-c74c464bbbf2/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
-golang.org/x/exp v0.0.0-20190312203227-4b39c73a6495 h1:I6A9Ag9FpEKOjcKrRNjQkPHawoXIhKyTGfvvjFAiiAk=
-golang.org/x/exp v0.0.0-20190312203227-4b39c73a6495/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
+golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
+golang.org/x/exp v0.0.0-20191002040644-a1355ae1e2c3 h1:n9HxLrNxWWtEb1cA950nuEEj3QnKbtsCJ6KjcgisNUs=
+golang.org/x/exp v0.0.0-20191002040644-a1355ae1e2c3/go.mod h1:NOZ3BPKG0ec/BKJQgnvsSFpcKLM5xXVWnvZS97DWHgE=
 golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067 h1:KYGJGHOQy8oSi1fDlSpcZF0+juKwk/hEMv5SiwHogR0=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
+golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.0.0-20190910094157-69e4b8554b2a/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.0.0-20200430140353-33d19683fad8 h1:6WW6V3x1P/jokJBpRQYUJnMHRP6isStQwCozxnU7XQw=
 golang.org/x/image v0.0.0-20200430140353-33d19683fad8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
-golang.org/x/mobile v0.0.0-20190312151609-d3739f865fa6/go.mod h1:z+o9i4GpDbdi3rU15maQ/Ox0txvL9dWGYEHz965HBQE=
-golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/image v0.0.0-20200618115811-c13761719519 h1:1e2ufUJNM3lCHEY5jIgac/7UTjd6cgJNdatjPdFWf34=
+golang.org/x/image v0.0.0-20200618115811-c13761719519/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
+golang.org/x/mobile v0.0.0-20190719004257-d2bd2a29d028/go.mod h1:E/iHnbuqvinMTCcRqshq8CkpyQDoeVncDDYHnLhea+o=
+golang.org/x/mod v0.1.0/go.mod h1:0QHyrYULN0/3qlju5TqG8bIK38QM8yzMo5ekMj3DlcY=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9 h1:1/DFK4b7JH8DmkqhUk48onnSfrPzImPoVxuomtbT2nk=
+golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190206041539-40960b6deb8e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20190312151545-0bb0c0a6e846/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/tools v0.0.0-20190927191325-030b2cf1153e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gonum.org/v1/gonum v0.0.0-20180816165407-929014505bf4/go.mod h1:Y+Yx5eoAFn32cQvJDxZx5Dpnq+c3wtXuadVZAcxbbBo=
 gonum.org/v1/gonum v0.7.0 h1:Hdks0L0hgznZLG9nzXb8vZ0rRvqNvAcgAp84y7Mwkgw=
 gonum.org/v1/gonum v0.7.0/go.mod h1:L02bwd0sqlsvRv41G7wGWFCsVNZFv/k1xzGIxeANHGM=

vg/vggio/example_vg_test.go

@@ -0,0 +1,74 @@
+// Copyright ©2020 The Gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package vggio_test
+
+import (
+	"log"
+	"os"
+	"time"
+
+	"gioui.org/app"
+	"gioui.org/io/key"
+	"gioui.org/io/system"
+	"gioui.org/unit"
+
+	"gonum.org/v1/plot"
+	"gonum.org/v1/plot/vg"
+	"gonum.org/v1/plot/vg/draw"
+	"gonum.org/v1/plot/vg/vggio"
+)
+
+func ExampleCanvas() {
+	const (
+		w   = 20 * vg.Centimeter
+		h   = 15 * vg.Centimeter
+		dpi = 96
+	)
+	go func(w, h vg.Length) {
+		win := app.NewWindow(
+			app.Title("Gonum"),
+			app.Size(
+				unit.Px(float32(w.Dots(dpi))),
+				unit.Px(float32(h.Dots(dpi))),
+			),
+		)
+		defer win.Close()
+
+		done := time.NewTimer(2 * time.Second)
+		defer done.Stop()
+
+		for {
+			select {
+			case e := <-win.Events():
+				switch e := e.(type) {
+				case system.FrameEvent:
+					p, err := plot.New()
+					if err != nil {
+						log.Fatalf("could not create plot: %+v", err)
+					}
+					p.Title.Text = "My title"
+					p.X.Label.Text = "X"
+					p.Y.Label.Text = "Y"
+
+					cnv := vggio.New(e, w, h, vggio.UseDPI(dpi))
+					p.Draw(draw.New(cnv))
+					cnv.Paint(e)
+
+				case key.Event:
+					switch e.Name {
+					case "Q", key.NameEscape:
+						os.Exit(0)
+					}
+				}
+			case <-done.C:
+				os.Exit(0)
+			}
+		}
+	}(w, h)
+
+	app.Main()
+
+	// Output:
+}

vg/vggio/vg.go

@@ -0,0 +1,104 @@
+// Copyright ©2020 The Gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package vggio provides a vg.Canvas implementation backed by Gioui.
+package vggio // import "gonum.org/v1/plot/vg/vggio"
+
+import (
+	"image/color"
+
+	"gioui.org/f32"
+	"gioui.org/io/system"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/op/paint"
+
+	"gonum.org/v1/plot/vg"
+	"gonum.org/v1/plot/vg/vgimg"
+)
+
+// Canvas implements the vg.Canvas interface,
+// drawing to an image.Image using vgimg and painting that image
+// into a Gioui context.
+type Canvas struct {
+	*vgimg.Canvas
+	gtx layout.Context
+}
+
+// DefaultDPI is the default dot resolution for image
+// drawing in dots per inch.
+const DefaultDPI = 96
+
+// New returns a new image canvas with the provided dimensions and options.
+// The currently accepted options are UseDPI and UseBackgroundColor.
+// If the resolution or background color are not specified, defaults are used.
+func New(e system.FrameEvent, w, h vg.Length, opts ...option) *Canvas {
+	cfg := &config{
+		dpi: DefaultDPI,
+		bkg: color.White,
+	}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	c := &Canvas{
+		gtx: layout.NewContext(new(op.Ops), e),
+		Canvas: vgimg.NewWith(
+			vgimg.UseDPI(cfg.dpi),
+			vgimg.UseWH(w, h),
+			vgimg.UseBackgroundColor(cfg.bkg),
+		),
+	}
+	return c
+}
+
+type config struct {
+	dpi int
+	bkg color.Color
+}
+
+type option func(*config)
+
+// UseDPI sets the dots per inch of a canvas. It should only be
+// used as an option argument when initializing a new canvas.
+func UseDPI(dpi int) option {
+	if dpi <= 0 {
+		panic("DPI must be > 0.")
+	}
+	return func(c *config) {
+		c.dpi = dpi
+	}
+}
+
+// UseBackgroundColor specifies the image background color.
+// Without UseBackgroundColor, the default color is white.
+func UseBackgroundColor(c color.Color) option {
+	return func(cfg *config) {
+		cfg.bkg = c
+	}
+}
+
+func (c *Canvas) pt32(p vg.Point) f32.Point {
+	_, h := c.Size()
+	dpi := c.DPI()
+	return f32.Point{
+		X: float32(p.X.Dots(dpi)),
+		Y: float32(h.Dots(dpi) - p.Y.Dots(dpi)),
+	}
+}
+
+// Paint paints the canvas' content on the screen.
+func (c *Canvas) Paint(e system.FrameEvent) {
+	w, h := c.Size()
+	box := vg.Rectangle{Max: vg.Point{X: w, Y: h}}
+	img := c.Canvas.Image()
+	ops := c.gtx.Ops
+	min := c.pt32(box.Min)
+	max := c.pt32(box.Max)
+	r32 := f32.Rect(min.X, min.Y, max.X, max.Y)
+
+	paint.NewImageOp(img).Add(ops)
+	paint.PaintOp{Rect: r32}.Add(ops)
+
+	e.Frame(ops)
+}