This is a spin-off of https://webcompat.com/issues/14888 STR: 1. Go to https://www.looopings.nl/ Actual: Enjoy a very very wide website Expected: The site fits the screen like in Chrome. Why this is happening: The site contains the line <meta name="viewport" content="width = device-width, initial-scale = 1, minimum-scale = 1, maximum-scale = 0"> maximum-scale = 0 is putting the layout completely off.

I think this bug will be solved by implementing "Resolve min-zoom and max-zoom values" [1] in the spec. [1] https://drafts.csswg.org/css-device-adapt/#constraining-min-max-zoom

Interesting just happens to have a new issue with this.

(In reply to Karl Dubost :karlcow from comment #2) > Interesting just happens to have a new issue with this. So something interesting also with this issue https://webcompat.com/issues/19179 On responsive design mode (RDM) with Firefox Android UA and 360x640 window, we get a wide layout too, even if **meta viewport** is not supposed to be interpreted by RDM. but if we just go out of the RDM, and not reloading (so the mobile layout), we get a layout working even when resizing the window.

(In reply to Karl Dubost :karlcow from comment #3) > On responsive design mode (RDM) with Firefox Android UA and 360x640 window, > we get a wide layout too, even if **meta viewport** is not supposed to be > interpreted by RDM. but if we just go out of the RDM, and not reloading (so > the mobile layout), we get a layout working even when resizing the window. Note that as of a few days ago (bug 1290420), RDM noew respects meta viewport.

Here are two screenshots of the site with adding below meta tag in comment 0 (because the site has already dropped the meta tag). <meta name="viewport" content="width = device-width, initial-scale = 1, minimum-scale = 1, maximum-scale = 0"> Left side is the result of current m-c, right one is the result of the binary in the try. The too wide content is actually being mitigated by the "Resolve min-zoom and max-zoom values" to some extent, but sill wider than Chrome. I think it is because of bug 1423709 and other bugs. Anyway I am going to fix one by one.

nsContentUtils::GetViewportInfo was removed and the comment for the function was moved to nsIDocument::GetViewportInfo in https://hg.mozilla.org/mozilla-central/rev/37d64688bf9d Depends on D8316

Depends on D8317

Depends on D8318

Depends on D8319

https://drafts.csswg.org/css-device-adapt/#constraining-min-max-zoom The test case in this commit fails without this change, width will be 8000 and height will be 4800 respectively when it fails. Depends on D8320

For the reference (and requested by Botond in review), I should have noted what happened when 'maximum-scale=0' is specified along with initial-scale=1. 1. https://hg.mozilla.org/mozilla-central/file/87b544fc71d5/dom/base/nsDocument.cpp#l7327 mScaleMaxFloat = mozilla::clamped( mScaleMaxFloat, kViewportMinScale, kViewportMaxScale); Here, the maximum-scale=0 is clamped to kViewportMinScale which is 0.1. 2. https://hg.mozilla.org/mozilla-central/file/87b544fc71d5/dom/base/nsDocument.cpp#l7452 if (mValidScaleFloat && scaleFloat >= scaleMinFloat && scaleFloat <= scaleMaxFloat) { CSSSize displaySize = ScreenSize(aDisplaySize) / scaleFloat; size.width = std::max(size.width, displaySize.width); size.height = std::max(size.height, displaySize.height); } else if (effectiveValidMaxScale) { CSSSize displaySize = ScreenSize(aDisplaySize) / scaleMaxFloat; size.width = std::max(size.width, displaySize.width); size.height = std::max(size.height, displaySize.height); } Here, |scaleMaxFloat| is 0.1, thus we fails the first if check then effectiveValidMaxScale is true since we have a valid maximum-scale even if it's clamed, so we divide the screen size by |scaleMaxFloat|, which means the viewport size is 10 times bigger than the screen size. And of course, unfortunately there is 'initial-scale=1'.

Pushed by hikezoe@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/ecc77355ba3e Align boolean member in nsViewportInfo. r=botond https://hg.mozilla.org/integration/autoland/rev/930561bbe55d Fix the comment for nsIDOMWindowUtils.getViewportInfo. r=botond https://hg.mozilla.org/integration/autoland/rev/4a79571c40a0 Move getViewportInfo function into viewport_helpers.js. r=botond https://hg.mozilla.org/integration/autoland/rev/d455d8d93e2c Rewrite test_meta_viewportX.html with add_task. r=botond https://hg.mozilla.org/integration/autoland/rev/02de107cdac4 Run meta viewport tests on Desktop. r=botond https://hg.mozilla.org/integration/autoland/rev/2e7851b166ce Implement "Resolve min-zoom and max-zoom values" in the spec. r=botond

https://hg.mozilla.org/mozilla-central/rev/ecc77355ba3e https://hg.mozilla.org/mozilla-central/rev/930561bbe55d https://hg.mozilla.org/mozilla-central/rev/4a79571c40a0 https://hg.mozilla.org/mozilla-central/rev/d455d8d93e2c https://hg.mozilla.org/mozilla-central/rev/02de107cdac4 https://hg.mozilla.org/mozilla-central/rev/2e7851b166ce