Fix white line at bottom of iframe kiwix/kiwix-tools#809

[zeyad-elkholy]

Fixes kiwix/kiwix-tools#809

I removed the hardcoded Javascript math that was calculating the iframe height with an arbitrary - 4 pixel offset. I replaced it with the CSS Flexbox approach (display: flex, flex: 1) on the html, body, and iframe elements to allow it to scale naturally without leaving a gap at the bottom.

[zeyad-elkholy]

Fixes kiwix/kiwix-tools#809

[david-cako]

🎉 sweet!!

I hope this works on all dependents of libkiwix, but it should. Looks like iOS and Android are webviews. Still could be scaffolding that gets changed with this, and I'm sure someone can test it!

[zeyad-elkholy]

i don't know to be honest but i don't see smth wrong in web, so check it on safari, it works in firefox

[Yizhen-Zheng]

I've verified this works perfectly on Safari.
Before:(notice the white line at the bottom

After:

[kelson42]

@zeyad-elkholy Thank you very much for your PR. I have assigned reviewers and will test things myself. Give us a few days to complete the review.

[Copilot]

Pull request overview

This PR aims to fix the bottom gap/white line caused by hardcoded iframe height calculations by switching the viewer layout to a CSS flexbox-based sizing approach.

Changes:

• Added inline flexbox CSS in static/viewer.html to make the iframe naturally fill remaining viewport height.
• Disabled the JavaScript-based iframe height calculation previously performed on viewport changes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
static/viewer.html	Adds inline flexbox rules intended to make the toolbar + iframe layout fill the viewport without a bottom gap.
static/skin/viewer.js	Comments out the resize-based iframe height math in handle_visual_viewport_change().

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[veloman-yunkan]

I didn't test the fix (leaving it to @kelson42). If testing doesn't reveal any problems and the fix is going to be merged then we should simply drop the handle_visual_viewport_change() function (as suggested by Copilot).

Also, the cacheids in the server unit-test must be updated.

[zeyad-elkholy]

@kelson42 @veloman-yunkan i removed handle_visual_viewport_change() and his calls and also updated the cache ids and SHA1 hash

[veloman-yunkan]

@kelson42 This PR should be merged as a single (squashed) commit.

[zeyad-elkholy]

@kelson42 could you review or merge the PR plz if u have time?