[open] backup a canvas for later reuse

elaci0

Hello again,

how can I code this with Opensesame?

--copy the content of "mySketchpad"  to  myCanvas
--  draw a text over  myCanvas
--  show myCanvas for 2000ms
--  copy  myCanvas to a "temporary"  myBackupCanvas
--  draw other text over  myCanvas
--  show myCanvas for 2000ms
--  copy the   myBackupCanvas  over myCanvas 
--  show   myCanvas for 2000ms

I tried something like this:

from openexp.canvas import canvas

myCanvas=offline_canvas()
myBackupCanvas=offline_canvas()
myCanvas.copy(exp.items["mySketchpad"].canvas)
myCanvas.text("some new text",y=400)
myCanvas.show()
self.time(2000)
myBackupCanvas.copy(myCanvas)   # make a backup copy 
myCanvas.text("other new text",y=800)
myCanvas.show()
self.time(2000)
myCanvas.copy(myBackupCanvas)
myCanvas.show()   # ------------ remark here
self.sleep(2000)

I would expect to see the backupCanvas at the end but instead I see a blank screen, like if the canvas was not copied and it was at its default init (blank)

thanks

elaci0

hmmmm..
changing to psychopy or plegacy backend seems to work, but I'm not willing to switch to those backeds after coding 90% of my LARGE experiment for 'expyriment'

elaci0

I found out that:

mycanvas= canvas(exp)
mycanvas.copy(exp.items["mySketchpad"].canvas)
mycanvas.line(0,0,0,0)    # ---   draw a simple dot
mycanvas.show()

do works, in the meaning that I can see my sketchpad copied.

If I don't draw something I don't see anything into the "mycanvas" while I always thought that the simple copy operation was sufficient to have "something" new into my canvas (which I guess is empty (balnk? null?) when initiatiated.

am I wrong?

thanks!

Josh

Hi,

I haven't used the copy function before, but usually you just simply do something like:

  exp.mycanvas=self.offline_canvas()
  exp.mycanvas.text("this is a text")

  exp.mycopycanvas = exp.mycanvas

And you can also organize your code such that the initial text is drawn onto two canvases. The second text you only draw on the first canvas; and afterwards you display the second canvas again.

Cheers,

Josh

elaci0

hmmm.. that was an option I also though, but after I tried these lines the "mycopycanvas" is empty (if I add another exp.mycopycanvas.show()


at the moment the "copy" works only if I add other object to the copied canvas (now I am adding an 'invisible' line)

eduard

Hi,

As is mentioned here, you have to initialize also the canvas to which you're copying. So, try this code:

mycanvas=self.offline_canvas()
mycanvas.text("this is a text",y=100)

mycopycanvas = self.offline_canvas() # that line is the main difference
mycopycanvas.copy(mycanvas)  
mycopycanvas.text("this is another text",y=500)
mycanvas.show()
self.sleep(1000)
mycopycanvas.show()

self.sleep(1000)

As a side note, as long as you use your canvas only in inline_scripts it is not necessary any more to add the prefix exp. in front of it. Any variables that are defined in inline_scripts are globally available in all inline_scripts (regardless of prep or run phase)

simple copy operation was sufficient to have "something" new into my canvas which I guess is empty (balnk? null?) when initiatiated.

As far as I can see, a copied canvas should be identical with the original canvas. So it shouldn't be necessary to draw something in order to see something on it (of course assuming that the original canvas wasn't empty).

If you want to copy a sketchpad-canvas, you should use the self.copy_sketchpad('my_sketchpad') of the inline_scriptobject. Unfortunately, it doesn't work for me...No clue why.

Hope this cleared things up a bit.

Eduard