How to manipulate Canvas elements

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Revision as of 18:42, 5 December 2017 by Rodolfo (talk | contribs) (→‎polyline)
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The purpose of this document is to introduce the plot2D tool and provide basic information about its use.
Plot2D is nothing more than a collection of helpers that aims to facilitate the task of coding. It makes intensive use of the Canvas API, a mandatory reference for those who intend to refine the result beyond what is offered by plot2D.
It is assumed here that you already have a minimal knowledge about Canvas.
For now Plot2D resides in the SpokenGCA addon (and you may download it from here) , but the idea is that in the future it could be included in the $FG-ROOT/Nasal/canvas directory.

"Create" helpers

line

Parameters: (group, from, to, color)

Plots a line as <group>'s child.

  • from as [x,y] in pixels.
  • to as [x,y] in pixels.
  • color optional as [r,g,b] or "#rrggbb", Black by default.
example Screenshot
var window = canvas.Window.new([200,200],"dialog")
    .set("title","Plot2D demo"  );
var myCanvas = window.createCanvas()
    .set("background", "#eeeeee");
var root = myCanvas.createGroup();
var myGroup = root.createChild("group");
canvas.plot2D.line(myGroup,[20,20],[50,100]);
canvas.plot2D.line(myGroup,[20,180],[180,20],'#ee0000')
    .setStrokeLineWidth(2);
Plot2D.line.png

hzLine

Parameters: (group, from, length, color)

Plots an horizontal line as <group>'s child.

  • from as [x,y] in pixels.
  • length in pixels.
  • color optional as [r,g,b] or "#rrggbb". Black by default.

vtLine

Parameters: (group, from, length, color)

Plots a vertical line as <group>'s child.

  • from as [x,y] in pixels.
  • length in pixels.
  • color optional as [r,g,b] or "#rrggbb". Black by default.

dashedLine

Parameters: (group, from, length, color)

Plots a vertical line as <group>'s child.

  • from as [x,y] in pixels.
  • to as [x,y] in pixels.
  • dash optional dash&space lengths in pixels, 8 pixels by default.
  • color optional as [r,g,b] or "#rrggbb". Black by default.
example Screenshot
var window = canvas.Window.new([200,200],"dialog").set("title","Plot2D demo"  );
var myCanvas = window.createCanvas().set("background", "#eeeeee");
var root = myCanvas.createGroup();
var myGroup = root.createChild("group");
canvas.plot2D.dashedLine(myGroup,[20,20],[150,120]).setStrokeLineWidth(2);
var (red,blue) = ['#ee0000', [0,0,1] ];
canvas.plot2D.hzLine(myGroup,[30,40],120,red);
canvas.plot2D.vtLine(myGroup,[120,180],-110,blue);
Plot2D.dashedLine example.png

rectangle

Parameters: (group, size ,origin=nil, color="#0", fill=nil, rounded=nil)

Plots a rectangle as <group>'s child.

  • size as [width,height] in pixels.
  • origin optional as [x,y] in pixels, [0,0] by default.
  • color optional border color as [r,g,b] or "#rrggbb" or nil (for no border). Black by default.
  • fill optional fill color as [r,g,b] or "#rrggbb", No filled by default.
  • rounded optional corner radius in pixels, Not rounded by default.

grid

Parameters: (group, size, dx, dy, origin=nil, color="#0", border=1)

Plots a grid as <group>'s child.

  • size as [width,height] in pixels.
  • dx tiles width in pixels.
  • dy tiles height in pixels.
  • color optional grid color as [r,g,b] or "#rrggbb". Black by default.
  • origin optional as [x,y] in pixels, [0,0] by default.
  • border optional as boolean, True by default.
example Screenshot
var window = canvas.Window.new([200,200],"dialog").set("title","Plot2D demo"  );
var myCanvas = window.createCanvas().set("background", "#eeeeee");
var root = myCanvas.createGroup();
var myGroup = root.createChild("group");
var (red,blue,grey) = ['#ee0000', [0,0,1], [.8,.8,.8] ];
  ## Note: to eventually handle an element, you must assign a variable:
var myRect = canvas.plot2D.rectangle(myGroup,[40,160],[15,20],red,grey,10);
myRect.setStrokeLineWidth(3);
canvas.plot2D.grid(myGroup,[120,100],20,25,[70,30],blue).setRotation(30*D2R);
Plot2D.rectangle and grid.png

text

parameters: (group, text, origin=nil, size=nil, color="#0", align="left-baseline")

Plots a text as <group>'s child.

  • text the text itself as string.
  • origin optional as [x,y] in pixels, [0,0] by default.
  • size optional font size and aspect as [<size-px>,<height/width>]. [11,1] by default.
  • color optional font color as [r,g,b] or "#rrggbb". Black by default.
  • align optional origin reference. "left-baseline" by default.

polyline

parameters: (group, xSet, ySet, color="#0", symmetrical=' ')

Plots a polyLine as <group>'s child.

  • xSet as [x0,...,xn] in pixels.
  • ySet as [y0,...,yn] in pixels.
  • color optional grid color as [r,g,b] or "#rrggbb". Black by default.
  • symmetrical optional string, may be 'x', 'y', 'xy' or 'yx'. Non symmetrical by default.
example Screenshot
var window = canvas.Window.new([200,200],"dialog").set("title","Plot2D demo"  );
var myCanvas = window.createCanvas().set("background", "#eeeeee");
var root = myCanvas.createGroup();
var myGroup = root.createChild("group");
var (red,blue,green,orange) = ['#ee0000', [0,0,1], [0,0.8,0], '#ea9a32' ];
canvas.plot2D.polyline(myGroup,[150,181,194,157,199],[52,20,64,28,36]);
   ## 3 vertices with default values:
canvas.plot2D.polyline(myGroup,[20,30,70],[15,55,65]);
canvas.plot2D.text(myGroup,'defaults',[75,25]);
   ## 3 vertices with symmetrical = 'x':
canvas.plot2D.polyline(myGroup,[20,30,70],[130,170,180],blue,"x");
canvas.plot2D.text(myGroup,'Symmetrical="x"',[20,195],,blue);
   ## 3 vertices with symmetrical = 'y':
canvas.plot2D.polyline(myGroup,[150,160,200],[90,130,140],red,"y");
canvas.plot2D.text(myGroup,'Symmetrical="y"',[198,180],,red,'right-baseline');
   ## 3 vertices with symmetrical = 'xy':
canvas.plot2D.polyline(myGroup,[50,60,100],[100,140,150],green,"xy");
canvas.plot2D.text(myGroup,'Symmetrical="xy"',[55,75],,green);
   ## 3 vertices with symmetrical = 'yx':
canvas.plot2D.polyline(myGroup,[100,110,150],[50,90,100],orange,"yx");
canvas.plot2D.text(myGroup,'Symmetrical="yx"',[12,125],,orange);
plot2D.polyline example