hplot/vgop: first import

Fixes #986.

Signed-off-by: Sebastien Binet <binet@cern.ch>

hplot/vgop/canvas.go

@@ -0,0 +1,169 @@
+// Copyright ©2023 The go-hep 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 vgop // import "go-hep.org/x/hep/hplot/vgop"
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+
+	"gonum.org/v1/plot/font"
+	"gonum.org/v1/plot/vg"
+)
+
+const (
+	// DefaultWidth and DefaultHeight are the default canvas
+	// dimensions.
+	DefaultWidth  = 4 * vg.Inch
+	DefaultHeight = 4 * vg.Inch
+)
+
+var (
+	_ vg.Canvas      = (*Canvas)(nil)
+	_ vg.CanvasSizer = (*Canvas)(nil)
+)
+
+// Canvas implements vg.Canvas for serialization.
+type Canvas struct {
+	w, h vg.Length
+
+	ops []op
+	ctx fontCtx
+}
+
+type Option func(c *Canvas)
+
+func WithSize(w, h vg.Length) Option {
+	return func(c *Canvas) {
+		c.w = w
+		c.h = h
+	}
+}
+
+// New returns a new canvas.
+func New(opts ...Option) *Canvas {
+	c := &Canvas{
+		w: DefaultWidth,
+		h: DefaultHeight,
+	}
+
+	for _, opt := range opts {
+		opt(c)
+	}
+
+	return c
+}
+
+func (c *Canvas) Size() (w, h vg.Length) {
+	return c.w, c.h
+}
+
+// Reset resets the canvas to the base state.
+func (c *Canvas) Reset() {
+	c.ops = c.ops[:0]
+
+	// FIXME(sbinet): should we also reset the fonts context ?
+}
+
+// ReplayOn replays the set of vector graphics operations onto the
+// destination canvas.
+func (c *Canvas) ReplayOn(dst vg.Canvas) error {
+	if c.ctx.fonts == nil {
+		c.ctx.fonts = make(map[fontID]font.Face)
+	}
+
+	for _, op := range c.ops {
+		err := op.op(c.ctx, dst)
+		if err != nil {
+			return fmt.Errorf("could not apply op %T: %w", op, err)
+		}
+	}
+
+	return nil
+}
+
+func (c *Canvas) add(face font.Face) {
+	if c.ctx.fonts == nil {
+		c.ctx.fonts = make(map[fontID]font.Face)
+	}
+
+	id := fontID(face.Font)
+	c.ctx.fonts[id] = face
+}
+
+func (c *Canvas) append(o op) {
+	c.ops = append(c.ops, o)
+}
+
+// SetLineWidth implements the SetLineWidth method of the vg.Canvas interface.
+func (c *Canvas) SetLineWidth(w vg.Length) {
+	c.append(opSetLineWidth{Width: w})
+}
+
+// SetLineDash implements the SetLineDash method of the vg.Canvas interface.
+func (c *Canvas) SetLineDash(dashes []vg.Length, offs vg.Length) {
+	c.append(opSetLineDash{
+		Dashes:  append([]vg.Length(nil), dashes...),
+		Offsets: offs,
+	})
+}
+
+// SetColor implements the SetColor method of the vg.Canvas interface.
+func (c *Canvas) SetColor(col color.Color) {
+	c.append(opSetColor{Color: col})
+}
+
+// Rotate implements the Rotate method of the vg.Canvas interface.
+func (c *Canvas) Rotate(a float64) {
+	c.append(opRotate{Angle: a})
+}
+
+// Translate implements the Translate method of the vg.Canvas interface.
+func (c *Canvas) Translate(pt vg.Point) {
+	c.append(opTranslate{Point: pt})
+}
+
+// Scale implements the Scale method of the vg.Canvas interface.
+func (c *Canvas) Scale(x, y float64) {
+	c.append(opScale{X: x, Y: y})
+}
+
+// Push implements the Push method of the vg.Canvas interface.
+func (c *Canvas) Push() {
+	c.append(opPush{})
+}
+
+// Pop implements the Pop method of the vg.Canvas interface.
+func (c *Canvas) Pop() {
+	c.append(opPop{})
+}
+
+// Stroke implements the Stroke method of the vg.Canvas interface.
+func (c *Canvas) Stroke(path vg.Path) {
+	c.append(opStroke{Path: append(vg.Path(nil), path...)})
+}
+
+// Fill implements the Fill method of the vg.Canvas interface.
+func (c *Canvas) Fill(path vg.Path) {
+	c.append(opFill{Path: append(vg.Path(nil), path...)})
+}
+
+// FillString implements the FillString method of the vg.Canvas interface.
+func (c *Canvas) FillString(font font.Face, pt vg.Point, str string) {
+	c.add(font)
+	c.append(opFillString{
+		Font:   font.Font,
+		Point:  pt,
+		String: str,
+	})
+}
+
+// DrawImage implements the DrawImage method of the vg.Canvas interface.
+func (c *Canvas) DrawImage(rect vg.Rectangle, img image.Image) {
+	c.append(opDrawImage{
+		Rect:  rect,
+		Image: img,
+	})
+}

hplot/vgop/fonts.go

@@ -0,0 +1,23 @@
+// Copyright ©2023 The go-hep 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 vgop // import "go-hep.org/x/hep/hplot/vgop"
+
+import (
+	xfnt "golang.org/x/image/font"
+	"gonum.org/v1/plot/font"
+	"gonum.org/v1/plot/vg"
+)
+
+type fontCtx struct {
+	fonts map[fontID]font.Face
+}
+
+type fontID struct {
+	Typeface font.Typeface `json:"typeface,omitempty"`
+	Variant  font.Variant  `json:"variant,omitempty"`
+	Style    xfnt.Style    `json:"style,omitempty"`
+	Weight   xfnt.Weight   `json:"weight,omitempty"`
+	Size     vg.Length     `json:"size,omitempty"`
+}