[css-position]: Sticky Positioning: Siblings should overlap

>From my observation, sticky positioning will mainly be used as bread crumbs 
for displaying header sections in HTML documents.

I couldn't find the corresponding behaviour described in the specification 
(https://drafts.csswg.org/css-position/#sticky-pos) that's why I'd like to 
suggest the following behaviour to be considered for the specification:

Sibling sticky positioned elements should overlap.

See here for a mock-up visualization:
https://www.dropbox.com/s/x6pov8az7mz6cpg/Sticky%20Positioning%20Suggestion.mov


Here's the pseudo HTML/CSS code for document displayed in the above movie 
clip:

<html>
  <head>
    <title>CSS Sticky Positioning Suggestion</title>
    <style type="text/css">
      h1, h2, h3  { position: sticky; }
    </style>
  </head>
  <body>
    <div class="Title">
      <h1>An Historical Sketch Of The Progress ...</h1>
      <div>I will here give ...</div>

      <div class="Section">
        <h2>I - Variation Under Domestication</h2>

        <div class="Chapter">
          <h3>a) Causes of Variability</h3>
          <div>When we compare ...</div>
          <h3>b)  Effects Of Habit And Of The ...</h3>
          <div>Changed habits produce ...</div>
        </div>
      </div>

      <div class="Section">
        <h2>II - Variation Under Nature</h2>
        <div>Applying the principles ...</div>

        <div class="Chapter">
          <h3>a)  Individual Differences</h3>
          <div>The many slight differences ...</div>
          <h3>b)  Doubtful Species</h3>
          <div>The forms which possess ...</div>
        </div>
      </div>
    </div>
  </body>
</html>


Axel Dahmen

Received on Wednesday, 30 December 2015 18:30:39 UTC