Adjusting line space based on the text layer scale

Thank you for the help! And here is more detail of what I am trying to achieve:

I have applied the following expression to the scale of a regular Point Text layer, so when the content you type in is larger then 500 pixels, it will scaling down the layer so it won’t exceed 500 pixels

s=thisLayer;

scl=500;

x=s.sourceRectAtTime(time,false).width;

if (x>scl)

{[scl/x*value[0],scl/x*value[1]]}

else

{value}

It’s working pretty nice.

But when I input line return to the text: since the expression scales the whole layer, including the vertical scale, it’s not visually what I want:

I hope to keep the line spacing between lines visually the same even after the scale expression scales down the whole layer:

So I developed the following expression, and put on the line space

TextHeight=sourceRectAtTime(time,false).height;

BeforeHeight=TextHeight;

AfterHeight=TextHeight*scale[1]/100;

LineSpace=(BeforeHeight-AfterHeight)/4*100/scale[1];

[value[0],LineSpace]

This expression kind of works when I change the preview resolution to force the preview refresh, or use Edit>Purge>Image Cache Memory, but sometimes both ways won’t work

I assume the reason is because the line space expression makes it react to the layer height, but when the line spacing increases, the layer height will also increase, then the expression will make the line space to react to that… which creates a “loop” and confuses the AE.

If that’s the case, I am wondering if that’s other way to achieve the line spacing purpose without creating that “loop”, or maybe an better/ easier way to force refresh the preview so it can work every time? Greatly apprecaite for the help!

Attached with the AE file to better illustrate the situation:

https://www.dropbox.com/s/k8fbfsnxmgfuyrp/LineSpaceReactToScaling_Sample.aep?dl=0

The comp resolution is the last thing you should be using to drive leading (line spacing). Your screenshot animation is interesting but it doesn't show us how you set this up. There is no Text Animator for Point (font) size, but there is for Line Spacing and for scale but if you change scale you need to also change tracking, but that makes the text box change size.

 If these are individual lines of text followed by a return rather than a text box with flowing text you are still going to have problems. 

I think you want to set an area for a text box then automatically resize the font and the line spacing so that the text box always stays the same size. Please let us know if that is what you want to do. A screenshot showing the modified properties of the text layer will also help. UU + Print Screen + Paste is the only way I can figure out what you are doing and figure out why it isn't working.