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[cssom-view-1] Clarify the relation of visual viewport and layout viewport with scale transform #13915

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[cssom-view-1] Clarify the relation of visual viewport and layout viewport with scale transform #13915

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ac73a14
Borrow definition of Visual Viewport from CSSOM-View
shubhamg13 May 11, 2026
2efeef1
Clarify the relation of visual viewport and layout viewport with scal…
shubhamg13 May 12, 2026
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10 changes: 9 additions & 1 deletion css-viewport-1/Overview.bs
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Expand Up @@ -106,9 +106,17 @@ difference between the [=initial viewport=] and the [=layout viewport=].
This is the viewport you get after processing the viewport
<code>&lt;meta&gt;</code> tag.
</dd>
<dt><dfn>visual viewport</dfn></dt>
<dd>
The is the portion of the layout viewport that is currently visible.

@emilio emilio May 12, 2026

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nit: "The is" seems mispelled?

But in general, the visual viewport is not only a scale but also a translation right?
This can be smaller than the layout viewport. This is the result of
applying scale transform to its layout viewport. Refer CSSOM-View <a href="https://drafts.csswg.org/cssom-view-1/#visualViewport">visual viewport</a>
</dd>
</dl>

ISSUE: Define visual viewport.
Note: The scale transform of the [=visual viewport=] is often referred to as "pinch-zoom". Conceptually, this transform
changes the size of the CSS <a>reference pixel</a> and changes the size of the layout viewport proportionally so that it
does not cause reflow of the page's contents.

When the [=layout viewport=] cannot fit inside the window or
viewing area, either because the [=layout viewport=] is
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2 changes: 1 addition & 1 deletion cssom-view-1/Overview.bs
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Expand Up @@ -300,7 +300,7 @@ In addition to scrolling, the <a>visual viewport</a> may also apply a scale tran
This transform is applied to the <a>canvas</a> of the <a>layout viewport</a> and does not affect its internal coordinate space.

Note: The scale transform of the visual viewport is often referred to as "pinch-zoom". Conceptually, this transform
changes the size of the CSS <a>reference pixel</a> but changes the size of the layout viewport proportionally so that it
changes the size of the CSS <a>reference pixel</a> and changes the size of the layout viewport (inversally) proportionally so that it
does not cause reflow of the page's contents.

The magnitude of the scale transform is known as the <a>visual viewport</a>'s <dfn>scale factor</dfn>.
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