[css-grid] Put some notes about flexing in a comment.

--HG--
extra : rebase_source : e0f8729cb7133d53d45a4aa9689dccaf0f8997a7

Author: tabatkins

css-grid/Overview.bs

@@ -2868,6 +2868,43 @@ Process Flexible Tracks</h3>
 	is greater than the track's <a>base size</a>,
 	set its <a>base size</a> to that product.
 
+<!--
+shrinkwrapping FRs
+  < min-content case
+    * never happens: tracks don't shrink below their base size
+  min-content case
+    * each flex track at its min-content size, might be uneven
+  in-between case
+    * each flex track >= min-content size, approaching all FRs equal
+ midpoint case
+    * each flex track is at least its min-content size, all FRs are equal
+  max-content case
+    * largest max-content track is at max-content, all FRs are equal
+  > max-content case
+    * each flex track is at least its max-content size, all FRs are equal
+
+Conclusion: 1FR's base size is by default equivalent to min-content,
+we'll say it is equivalent to "use min-size property".
+
+Difference in behavior of having min-content size (by accident) vs. sizing under min-content constraint!!!
+Question to author: do you want even FRs, or do you want to minimize overflow? Probably depends on 'overflow', just like in Flexbox! Nope, always minimize overflow. Even FRs will result in tracks beign *larger* than in an equivalent fixed-size container case, which doesn't make sense.
+
+I think we can copy the "treat available space as 0/infinite in min/max constraint situations" paragraph down to the flexing paragraph. That'll produce the "minimum size" behavior for flexible things.
+
+If you're sizing by intrinsic size, you use max(grid items' content size, grid item's min-size property).
+For flexible lengths, we could do the same thing OR we could just use the grid item's min-size property, treating auto as min-content.
+
+Interesting question: should 'auto' mean minmax(min-content, max-content) or minmax('min-size property', max-content)?
+
+What effect does min-size: auto vs. 0 have?
+
+Consider: minmax(auto, ?) to mean minmax('min-size property', ?)
+Consider: auto to mean minmax(auto, max-content) instead of minmax(min-content, max-content) --
+  otherwise if you set a grid item's min-width to 50px, it will still use the min-content size as a minimum;
+  this way it honors min-width: 50px, which probably is what you want.
+  (Definitely want the default to be min-content, but min-width: auto gives us that.)
+-->
+
 
 <h4 id="algo-find-fr-size">
 Find the Size of an ''fr''</h4>

css-grid/Overview.html

@@ -2920,6 +2920,8 @@ <h3 class="heading settled heading" data-level=10.6 id=algo-flex-tracks><span cl
 	is greater than the track’s <a data-link-type=dfn href=#base-size title="base size">base size</a>,
 	set its <a data-link-type=dfn href=#base-size title="base size">base size</a> to that product.</p>
 
+<p></p>
+
 
 <h4 class="heading settled heading" data-level=10.6.1 id=algo-find-fr-size><span class=secno>10.6.1 </span><span class=content>
 Find the Size of an <span class=css data-link-type=maybe title=fr>fr</span></span><a class=self-link href=#algo-find-fr-size></a></h4>