Add configuration and functional option to scroll a stack without skipping images

[jdnarvaez]

I wanted a way to consume scroll events and prevent the stack state from progressing to the next index until the currently request index had been drawn. I think this covers that.

[coveralls]

Coverage decreased (-0.03%) to 3.98% when pulling 735e0ca on jdnarvaez:jdnarvaez/scrollWithoutSkipping into 2918218 on cornerstonejs:master.

[swederik]

Thanks for the contribution! I'll try to get to this ASAP, but it will likely be after the holidays.

[dannyrb]

You should be able to merge this check and default with the above check. For example:

Previous:

if (config && config.loop) {
  loop = config.loop;
}

Becomes:

if (config) {
  loop = config.loop !== undefined ? config.loop : false;
  allowSkipping = config.allowSkipping !== undefined ? config.allowSkipping : true;
}

[jdnarvaez]

Can do.

[dannyrb]

Maybe I'm missing it. Is this the right event?

[jdnarvaez]

I believe it is, as this seems to be the event that is triggered when the index actually changes.

[dannyrb]

Trying to make sure I understand. In your new implementation, you bypass the scrollToIndex and instead:

1. Record the "pending" image change
2. Call scrollWithoutSkipping

Where we:

1. Verify the "pending" final scroll image is not already being displayed
2. Register a cornerstonenewimage event listener that
   • When the next image rendered matches the next "pending image"
     • We pop of the pending image event (it's no longer pending :P)
     • Remove the listener
     • Call scrollWithoutSkipping if we have more pending items
3. ^ Now that something is listening, we call scrollToIndex

I think this would force stackScroll requests to process in order, So if the stack scroll calls are:

• display image 1
• display image 2
• display image 3
• etc.

Then they should all display in order without skipping.

Note: I've also added some comments to your code with additional questions.

Follow-up question for @swederik, does scrollToIndex uhh.. Scroll? It looks like it queues up and loads whatever newImageId you give it?

[jdnarvaez]

Correct. As far as I can tell scrollToIndex just queues the image call, which may or may not execute in order depending on how long the loadImage request takes.

[swederik]

Looks good to me! Indeed scrollToIndex just queues it up.

[adreyfus]

ERROR in ./src/stackTools/stackScroll.js
/home/travis/build/cornerstonejs/cornerstoneTools/src/stackTools/stackScroll.js
  52:58  error  Parsing error: Unexpected token ||

[swederik]

Thanks @adreyfus I don't know why it wasn't clear that the build was failing before I merged that...

[jdnarvaez]

Sorry about that, I didn't see that either when building.