variable scope inside callback using the "Functions as Layers" feature about jcanvas HOT 4 CLOSED

caleb531 commented on September 25, 2024

variable scope inside callback using the "Functions as Layers" feature

from jcanvas.

Comments (4)

dksmiffs commented on September 25, 2024

Today I've moved away from the "Functions as Layers" approach. I guess I was resisting the 1 shape per layer limitation, because it seemed to break the metaphor, but that's something I can live with. This is no longer a pressing issue for me, so I will close with this comment.

from jcanvas.

caleb531 commented on September 25, 2024

Okay, after examining the source, I know why you are not getting the result
you want.

When I add a new function layer, I actually clone the function so no
function layer is the same across multiple canvases. Unfortunately, this
also means that the new function loses access to the variables it was able
to access through closure.

However, if I don't clone the function, then the layer does not draw when
drawn on successive canvases. That's why I clone the function in the first
place.

Therefore, I'm left in a standstill. I want to clone a function, and
maintain the variables it has access to. Any idea how I do that?

-Caleb

On Thu, Jun 7, 2012 at 8:37 AM, dksmiffs <
[email protected]

wrote:

Caleb,

I'm using the "Functions as Layers" feature - I can live with the
limitations you emailed me yesterday. However, I'm trying to figure out a
way to get external variables into the callback, and the approach shown in
the code below (the only one I've thought of so far) doesn't work. Please
advise.

~ Dave

<!DOCTYPE html>
<html lang="en-US">
 <head>
   <meta charset="utf-8">
   <title>jCanvas outer param access test</title>
 </head>
 <body>
   <div id="graphics">
     <canvas width="500" height="500"></canvas>
   </div>
   <script src="public/resources/jquery/jquery-1.7.2.min.js"></script>
   <script src="public/resources/jcanvas/jcanvas.min.js"></script>
   <script>
     $(document).ready(function() {
       function test(outer) {
         alert(outer);
         $("canvas").addLayer(function(ctx) {
           alert("This alert happens in FF 12.0 and SRWare Iron
18.0.1500.0.");
           // The following alert doesn't happen at all.  Why?
           alert("Why no visibility here on " + outer + "?  Is it because
" +
                 "outer has gone out of scope by the time drawLayers() is
" +
                 "called?");
         });
         $("canvas").drawLayers();
       }
       test("outerValue");
     });
   </script>
 </body>
</html>

Reply to this email directly or view it on GitHub:
#16

from jcanvas.

caleb531 commented on September 25, 2024

Never mind, I solved the issue. Apparently, I just need to create a new
closure. :P

The updated code will be pushed to GitHub (by the time you read this, it
should be online).

-Caleb

On Thu, Jun 7, 2012 at 4:03 PM, Caleb Evans [email protected] wrote:

Okay, after examining the source, I know why you are not getting the
result you want.

When I add a new function layer, I actually clone the function so no
function layer is the same across multiple canvases. Unfortunately, this
also means that the new function loses access to the variables it was able
to access through closure.

However, if I don't clone the function, then the layer does not draw when
drawn on successive canvases. That's why I clone the function in the first
place.

Therefore, I'm left in a standstill. I want to clone a function, and
maintain the variables it has access to. Any idea how I do that?

-Caleb

On Thu, Jun 7, 2012 at 8:37 AM, dksmiffs <
[email protected]
wrote:

Caleb,

I'm using the "Functions as Layers" feature - I can live with the
limitations you emailed me yesterday. However, I'm trying to figure out a
way to get external variables into the callback, and the approach shown in
the code below (the only one I've thought of so far) doesn't work. Please
advise.

~ Dave
<!DOCTYPE html>
<html lang="en-US">
 <head>
   <meta charset="utf-8">
   <title>jCanvas outer param access test</title>
 </head>
 <body>
   <div id="graphics">
     <canvas width="500" height="500"></canvas>
   </div>
   <script src="public/resources/jquery/jquery-1.7.2.min.js"></script>
   <script src="public/resources/jcanvas/jcanvas.min.js"></script>
   <script>
     $(document).ready(function() {
       function test(outer) {
         alert(outer);
         $("canvas").addLayer(function(ctx) {
           alert("This alert happens in FF 12.0 and SRWare Iron
18.0.1500.0.");
           // The following alert doesn't happen at all.  Why?
           alert("Why no visibility here on " + outer + "?  Is it because
" +
                 "outer has gone out of scope by the time drawLayers() is
" +
                 "called?");
         });
         $("canvas").drawLayers();
       }
       test("outerValue");
     });
   </script>
 </body>
</html>
Reply to this email directly or view it on GitHub:
#16

from jcanvas.

dksmiffs commented on September 25, 2024

Fix works for me, thanks much.

from jcanvas.

variable scope inside callback using the "Functions as Layers" feature about jcanvas HOT 4 CLOSED

Comments (4)

Related Issues (20)

Recommend Projects

React

Vue.js

Typescript

TensorFlow

Django

Laravel

D3

Recommend Topics

javascript

web

server

Machine learning

Visualization

Game

Recommend Org

Facebook

Microsoft

Google

Alibaba

D3

Tencent