35 lines
2.5 KiB
JavaScript
35 lines
2.5 KiB
JavaScript
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(function()
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{function dist2D(x1,y1,x2,y2)
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{var dx=x2-x1;var dy=y2-y1;return Math.sqrt(dx*dx+dy*dy);}
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CanvasRenderingContext2D.prototype.textOverflow="";CanvasRenderingContext2D.prototype.textJustify=false;CanvasRenderingContext2D.prototype.textStrokeMin=0;var state=[];var save=CanvasRenderingContext2D.prototype.save;CanvasRenderingContext2D.prototype.save=function()
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{state.push({textOverflow:this.textOverflow,textJustify:this.textJustify,textStrokeMin:this.textStrokeMin,});save.call(this);}
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var restore=CanvasRenderingContext2D.prototype.restore;CanvasRenderingContext2D.prototype.restore=function()
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{restore.call(this);var s=state.pop();this.textOverflow=s.textOverflow;this.textJustify=s.textJustify;this.textStrokeMin=s.textStrokeMin;}
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CanvasRenderingContext2D.prototype.textPath=function(text,path)
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{var di,dpos=0;var pos=2;function pointAt(dl)
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{if(!di||dpos+di<dl)
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{for(;pos<path.length;)
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{di=dist2D(path[pos-2],path[pos-1],path[pos],path[pos+1]);if(dpos+di>dl)break;pos+=2;if(pos>=path.length)break;dpos+=di;}}
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var x,y,dt=dl-dpos;if(pos>=path.length)
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{pos=path.length-2;}
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if(!dt)
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{x=path[pos-2];y=path[pos-1];}
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else
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{x=path[pos-2]+(path[pos]-path[pos-2])*dt/di;y=path[pos-1]+(path[pos+1]-path[pos-1])*dt/di;}
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return[x,y,Math.atan2(path[pos+1]-path[pos-1],path[pos]-path[pos-2])];}
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var letterPadding=this.measureText(" ").width*0.25;var d=0;for(var i=2;i<path.length;i+=2)
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{d+=dist2D(path[i-2],path[i-1],path[i],path[i+1])}
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if(d<this.minWidth)return;var nbspace=text.split(" ").length-1;if(this.textOverflow!="visible")
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{if(d<this.measureText(text).width+(text.length-1+nbspace)*letterPadding)
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{var overflow=(this.textOverflow=="ellipsis")?'\u2026':this.textOverflow||"";var dt=overflow.length-1;do
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{if(text[text.length-1]===" ")nbspace--;text=text.slice(0,-1);}while(text&&d<this.measureText(text+overflow).width+(text.length+dt+nbspace)*letterPadding)
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text+=overflow;}}
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var start=0;switch(this.textJustify||this.textAlign)
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{case true:case "center":case "end":case "right":{if(this.textJustify)
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{start=0;letterPadding=(d-this.measureText(text).width)/(text.length-1+nbspace);}
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else
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{start=d-this.measureText(text).width-(text.length+nbspace)*letterPadding;if(this.textAlign=="center")start/=2;}
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break;}
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default:break;}
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for(var t=0;t<text.length;t++)
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{var letter=text[t];var wl=this.measureText(letter).width;var p=pointAt(start+wl/2);this.save();this.textAlign="center";this.translate(p[0],p[1]);this.rotate(p[2]);if(this.lineWidth>0.1)this.strokeText(letter,0,0);this.fillText(letter,0,0);this.restore();start+=wl+letterPadding*(letter==" "?2:1);}};})();
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