gopherjs - progress/progress.go

     1  // Package progress creates a simple progress bar in javascript
     2  package progress // import "vimagination.zapto.org/gopherjs/progress"
     3  
     4  import (
     5  	"image/color"
     6  	"io"
     7  	"strconv"
     8  
     9  	"vimagination.zapto.org/gopherjs/xdom"
    10  
    11  	"honnef.co/go/js/dom"
    12  )
    13  
    14  // Bar is a wrapper around a Canvas element to draw a simple progress
    15  // bar.
    16  //
    17  // It also implements dom.Node, so it can be Appended to any other node.
    18  type Bar struct {
    19  	*dom.HTMLCanvasElement
    20  	percent                int
    21  	ctx                    *dom.CanvasRenderingContext2D
    22  	width, height          int
    23  	foreground, background string
    24  }
    25  
    26  // Percent sets the current percentage shown
    27  func (b *Bar) Percent(i int) {
    28  	if i != b.percent {
    29  		b.percent = i
    30  		b.draw()
    31  	}
    32  }
    33  
    34  func (b *Bar) draw() {
    35  	b.ctx.FillStyle = b.background
    36  	b.ctx.FillRect(0, 0, b.width, b.height)
    37  	b.ctx.FillStyle = b.foreground
    38  	b.ctx.FillRect(0, 0, b.width*b.percent/100, b.height)
    39  }
    40  
    41  // New returns a new Bar
    42  func New(fore, back color.Color, width, height int) *Bar {
    43  	c := xdom.Canvas()
    44  	c.Width = width
    45  	c.Height = height
    46  	r, g, b, _ := fore.RGBA()
    47  	foreground := "rgb(" + strconv.Itoa(int(r>>8)) + ", " + strconv.Itoa(int(g>>8)) + ", " + strconv.Itoa(int(b>>8)) + ")"
    48  	r, g, b, _ = back.RGBA()
    49  	background := "rgb(" + strconv.Itoa(int(r>>8)) + ", " + strconv.Itoa(int(g>>8)) + ", " + strconv.Itoa(int(b>>8)) + ")"
    50  	bar := &Bar{
    51  		HTMLCanvasElement: c,
    52  		ctx:               c.GetContext2d(),
    53  		width:             width,
    54  		height:            height,
    55  		foreground:        foreground,
    56  		background:        background,
    57  	}
    58  	bar.draw()
    59  	return bar
    60  }
    61  
    62  // Reader wraps a ProgressBar to automatically update when an io.Reader
    63  // is read
    64  type Reader struct {
    65  	*Bar
    66  	io.Reader
    67  	offset, size int
    68  }
    69  
    70  // Reader returns a Reader type
    71  func (b *Bar) Reader(r io.Reader, size int) *Reader {
    72  	return &Reader{b, r, 0, size}
    73  }
    74  
    75  // Read implements io.Reader
    76  func (r *Reader) Read(p []byte) (int, error) {
    77  	n, err := r.Reader.Read(p)
    78  	r.offset += n
    79  	r.Percent(100 * r.offset / r.size)
    80  	return n, err
    81  }
    82  
    83  // Len returns the total length of the data
    84  func (r *Reader) Len() int {
    85  	return int(r.size)
    86  }