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ext-iframe.js
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/**
* Copyright (c) 2020 Kaj Magnus Lindberg
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/** Talkyard injects this Javascript into external srcdoc=... iframes,
* to resize the iframe properly, and adjust margins.
*
* The embedding parent window doesn't know how tall this iframe with oEmbed
* stuff inside wants to be — so we postMessage() and tell it.
*
* We set body.margin = 0, otherwise e.g. Chrome has an 8px default margin.
* We set the top-bottom-margin of elems directly in <body> to '0 auto'
* to avoid scrollbars. E.g. Twitter otherwise include 10px top & bottom margin.
* 'auto' is to place in the middle.
*
* We don't really know when the oEmbed contents is done loading.
* So, we send a few messages — and if after a while, the oEmbed still
* doesn't have its final size, then, that's a weird oEmbed and someone
* else's problem (don't try to fix that).
*/
// TESTS_MISSING TyT037MKAH24 // create a LinkPrevwRendrEng that creates a 432 px
// tall div, with 20 px body margin, 20 px child div padding & margin, should
// become 432 px tall? (margin & padding removed)
(function(doc) { // Talkyard [OEMBHGHT]
function removePaddingAndMargin() {
try {
doc.body.style.margin = '0';
var chidren = doc.querySelectorAll('body > *');
for (var i = 0; i < chidren.length; ++i) {
// Unfortunately, this won't zero the margins of nested elems, and they
// can make the <html> taller than the <body>. [iframe_height]
var c = chidren[i];
c.style.margin = '0 auto';
c.style.padding = '0';
}
}
catch (ex) {
console.warn("Error removing padding or margin [TyEOEMBMARG]", ex);
}
}
var numSent = 0;
function sendHeightToParent() {
var height = 0;
// There's no body if an embedded-thing-<script> broke, no content appeared.
if (doc.body) {
removePaddingAndMargin();
// To get the real iframe height [iframe_height], one needs to look at each
// elem in the iframe, its position (could be absolute or relative, with top < 0)
// and add its margin-top and -bottom to its position?
//
// For example: Twitter's oEmbed has a <blockquote><p> with margin: 16px 0px,
// so unless the iframe is >= 16px taller than the <body>, there'll be
// scrollbars. I (KajMagnus) tried this in Chrome — yes if the iframe is less
// than body.scrollHeight + 16px, then, an Y scrollbar appears.
// And, I changed the <p>'s margin-top to 24px —> scrollbars appear unless
// the <iframe> is >= body.scrollHeight + 24px tall.
//
// See also: https://github.com/davidjbradshaw/iframe-resizer/
// blob/master/docs/parent_page/options.md#heightcalculationmethod
// > lowestElement: Loops though every element in the the DOM
// > and finds the lowest bottom point
// > most reliable way of determining the page height ... performance impact ...
// > ... checking the position of every element
//
// Instead of the above, we can send a hasScrollbar true/false to the parent?
// And then the parent makes the iframe taller, until scrollbars gone?
// Good enough. Fix later. For now, just this: [oemb_extr_height] instead.
height = doc.body.offsetHeight;
}
// Need to post to '*', because the domain of this srcdoc=... iframe is "null",
// i.e. different from the parent frame domain.
console.debug("Sending oEmbHeight: " + height + " [TyMOEMBHGHT]");
window.parent.postMessage(['oEmbHeight', height], '*');
numSent += 1;
if (numSent < 4) {
setTimeout(sendHeightToParent, numSent * 500);
}
}
// This sends a message after 500, 1000, 2000, 3500 ms, right.
setTimeout(sendHeightToParent, 500);
})(document);