Create document flow in canvas

#javascript #frontend #canvas #css

Introduction

Use the render function to create a document flow in the canvas and quickly implement the layout.

Respontory

If there is a problem in use, check the code in the example, click to view DEMO

Try it in CodePen

vue component vue-easy-canvas
Support document flow, refer to web, no need to set x, y, width and height
Compatible with small programs and web, no third-party dependencies
Support componentization, global components and local components
Support events
High performance, scroll-view supports dirty rectangles and only draws the visible part
Support operation element, similar to operation dom to modify document flow

Supporting elements

[x] view basic element, similar to div
[x] text text supports automatic line wrapping and over omitted functions, currently text is implemented as inline-block
[x] ʻimageimagesrcmodesupports aspectFit and aspectFill, other css features are the same as web supportload` event to monitor image loading and drawing completion
[x] scroll-view scroll container, you need to set direction in the style to support x, y, xy, and set the specific size. Set renderOnDemand to draw only the visible part

Styles

Use numbers where the attribute uses pixels

[x] display block | inline-block | flex, text is inline by default
[x] width auto 100% Number This box model uses border-box and cannot be modified
[x] height
[x] flex flex does not support auto, use width directly for fixed width
[x] minWidth maxWidth minHeight maxHeight If the specific width is set, the height will not take effect
[x] margin marginLeft,marginRight,marginTop,marginBottom margin supports array abbreviations such as [10,20] [10,20,10,20]
[x] paddingLeft,paddingRight,paddingTop,paddingBottom Same as above
[x] backgroundColor
[x] borderRadius
[x] borderWidth borderTopWidth ... Set the thin border directly to 0.5
[x] borderColor
[x] lineHeight font related only valid in text
[x] color
[x] fontSize
[x] textAlign left right center
[x] textIndent Number
[x] verticalAlign top middle bottom
[x] justifyContent flex-start center flex-end flex layout align horizontally
[x] ʻalignItems` flex-start center flex-end flex layout align it vertically
[x] maxLine maximum number of lines, exceeding the automatic ellipsis, only supports use in text
[x] whiteSpace normal nowrap controls line breaks, not fonts
[x] ʻoverflow` hidden If rounded corners are added, hidden will be added automatically
[] flexDirection
[x] borderStyle dash Array See ctx.setLineDash() for details
[x] shadowBlur set the shadow will automatically add overflow:hidden;
[x] shadowColor
[x] shadowOffsetX
[x] shadowOffsetY
[x] position static ʻabsolute`
[x] ʻopacityNumber`

Installation

bash npm install easy-canvas-layout --save

Usage

Basic

` javascript
import easyCanvas from'easy-canvas-layout'

// create a layer bind with ctx
const layer = easyCanvas.createLayer(ctx, {
  dpr: 2,
  width: 300,
  height: 600,
})

// create a node tree
// c(tag,options,children)
const node = easyCanvas.createElement((c) => {
  return c('view', {
    styles: {backgroundColor:'#000' }, // style
    attrs:(), // attributes such as src
    on:{} // events such as click load
  },
  [
    c('text',{color:'#fff'},'Hello World')
  ])
})

// mount
node.mount(layer)

Register Component

` javascript
...

function button(c,text){
  return c(
    'view',
    {
      styles: {
        backgroundColor:'#ff6c79',
        borderRadius: 10,
        borderColor:'#fff',
        display:'inline-block',
        margin: 2,
        padding:[0,10]
      },
    },
    [
      c(
        'text',
        {
          styles: {
            lineHeight: 20,
            color:'#fff',
            textAlign:'center',
            fontSize: 11,
          },
        },
        text
      ),
    ]
  )
}

easyCanvas.component('button',(opt,children,c) => button(c,children))

const node = easyCanvas.createElement((c) => {
  return c('view',{},[
    c('button',(),'This is a global component')
  ])
})

...

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