koreader/frontend/ui/data/css_tweaks.lua

--[[--
CSS tweaks must have the following attributes:
 - id: unique ID identifying this tweak, to be stored in settings
 - title: menu item title (must not be too long)
 - css: stylesheet text to append to external stylesheet
They may have the following optional attributes:
 - description: text displayed when holding on menu item
 - priority: higher numbers are appended after lower numbers
   (if not specified, default to 0)
]]

local _ = require("gettext")

local CssTweaks = {
    {
        title = _("Pages"),
        {
            id = "margin_body_0";
            title = _("Ignore publisher page margins"),
            description = _("Force page margins to be 0, and may allow KOReader's margin settings to work on books where they would not."),
            css = [[body { margin: 0 !important; }]],
        },
        {
            id = "margin_all_0";
            title = _("Ignore all publisher margins"),
            priority = 2,
            css = [[* { margin: 0 !important; }]],
            separator = true,
        },
        {
            id = "titles_page-break-before_avoid ";
            title = _("Avoid blank page on chapter start"),
            priority = 2, -- so it can override the one put back by publisher_page-break-before_avoid
            css = [[h1, h2, h3 { page-break-before: auto !important; }]],

        },
        {
            id = "docfragment_page-break-before_avoid ";
            title = _("Avoid blank page on chapter end"),
            priority = 2, -- so it can override the one put back by publisher_page-break-before_avoid
            css = [[DocFragment { page-break-before: auto !important; }]],
        },
        {
            id = "publisher_page-breaks_avoid ";
            title = _("Avoid publisher page breaks"),
            description = _("Disable all publisher page breaks, keeping only KOReader's epub.css ones.\nWhen combined with the two previous tweaks, all page-breaks are disabled."),
            css = [[
* { page-break-before: auto !important; page-break-after: auto !important; }
/* put back epub.css page-breaks */
DocFragment { page-break-before: always !important; }
h1, h2, h3 { page-break-before: always !important; page-break-after: avoid !important; }
h4, h5, h6 { page-break-after: avoid !important; }
            ]],
        },
    },
    {
        title = _("Text"),
        {
            title = _("Text alignment"),
            {
                id = "text_align_most_left",
                title = _("Left align most text"),
                description = _("Enforce left alignment of text in common text elements."),
                css = [[body, p, li { text-align: left !important; }]],
                priority = 2, -- so it overrides the justify below
            },
            {
                id = "text_align_all_left",
                title = _("Left align all elements"),
                description = _("Enforce left alignment of text in all elements."),
                css = [[* { text-align: left !important; }]],
                priority = 2, -- so it overrides the justify below
                separator = true,
            },
            {
                id = "text_align_most_justify",
                title = _("Justify most text"),
                description = _("Text justification is the default, but it may be overridden by publisher styles. This will re-enable it for most common text elements."),
                css = [[body, p, li { text-align: justify !important; }]],
            },
            {
                id = "text_align_all_justify",
                title = _("Justify all elements"),
                description = _("Text justification is the default, but it may be overridden by publisher styles. This will re-enable it for all elements, which may lose centering in some of them."),
                css = [[* { text-align: justify !important; }]],
            },
        },
        {
            title = _("Widows and orphans"),
            {
                title = _("About widow and orphan lines"),
                info_text = _([[
Widows and orphans are lines at the beginning or end of a paragraph, which are left dangling at the top or bottom of a page, separated from the rest of the paragraph.
The first line of a paragraph alone at the bottom of a page is called an orphan line.
The last line of a paragraph alone at the top of a page is called a widow line.

Some people (and publishers) don't like widows and orphans, and can avoid them with CSS rules.
To avoid widows and orphans, some lines have to be pushed to the next page to accompany what would otherwise be widows and orphans. This may leave some blank space at the bottom of the previous page, which might be more disturbing to others.

The default is to allow widows and orphans.
These tweaks allow you to change this behavior, and to override publisher rules.]]),
                separator = true,
            },
            -- To avoid duplicating these 2 tweaks into 2 others for ignoring publisher rules,
            -- we apply the rules to BODY without !important (so they can still be overriden
            -- by publisher rules applied to BODY), and to DocFragment with !important (so
            -- that with "* {widows/orphans: inherit !important}", all elements will inherit
            -- from the DocFragment rules.
            -- This trick will work with EPUB, but not with single file HTML.
            {
                id = "widows_orphans_avoid";
                title = _("Avoid widows and orphans"),
                description = _("Avoid widow and orphan lines, allowing for some possible blank space at the bottom of pages."),
                css = [[
body { orphans: 2; widows: 2; }
DocFragment {
    orphans: 2 !important;
    widows:  2 !important;
}
                ]],
                priority = 2, -- so it overrides the * inherit below for DocFragment
            },
            {
                id = "widows_avoid_orphans_allow";
                title = _("Avoid widows but allow orphans"),
                description = _([[
Avoid widow lines, but allow orphan lines, allowing for some possible blank space at the bottom of pages.
Allowing orphans avoids ambiguous blank space at the bottom of a page, which could otherwise be confused with real spacing between paragraphs.]]),
                css = [[
body { orphans: 1; widows: 2; }
DocFragment {
    orphans: 1 !important;
    widows:  2 !important;
}
                ]],
                priority = 2, -- so it overrides the * inherit below for DocFragment
                separator = true,
            },
            {
                id = "widows_orphans_all_inherit";
                title = _("Ignore publisher orphan and widow rules"),
                description = _("Disable orphan and widow rules specified in embedded styles."),
                css = [[
* {
    orphans: inherit !important;
    widows:  inherit !important;
}
                ]],
            },
        },
        {
            id = "sub_sup_smaller";
            title = _("Smaller sub- and superscript"),
            description = _("Prevent sub- and superscript from affecting line-height."),
            priority = 5, -- so we can override "font_size_all_inherit"
            -- https://friendsofepub.github.io/eBookTricks/
            -- https://github.com/koreader/koreader/issues/3923#issuecomment-386510294
            css = [[
sup { font-size: 50% !important; vertical-align: super !important; }
sub { font-size: 50% !important; vertical-align: sub !important; }
            ]],
            separator = true,
        },
        {
            id = "hyphenate_all_auto";
            title = _("Allow hyphenation on all text"),
            description = _("Allow hyphenation to happen on all text (except headings), in case the publisher has disabled it."),
            css = [[
* { hyphens: auto !important; }
h1, h2, h3, h4, h5, h6 { hyphens: none !important; }
            ]],
        },
        {
            id = "lineheight_all_inherit";
            title = _("Ignore publisher line heights"),
            description = _("Disable line-height specified in embedded styles, and may allow KOReader's line spacing settings to work on books where they would not."),
            css = [[* { line-height: inherit !important; }]],
        },
        {
            id = "font_family_all_inherit";
            title = _("Ignore publisher font families"),
            description = _("Disable font-family specified in embedded styles."),
            -- we have to use this trick, font-family handling by crengine is a bit complex
            css = [[* { font-family: "NoSuchFont" !important; }]],
        },
        {
            id = "font_size_all_inherit";
            title = _("Ignore publisher font sizes"),
            description = _("Disable font-size specified in embedded styles."),
            css = [[* { font-size: inherit !important; }]],
        },
    },
    {
        title = _("Paragraphs"),
        {
            id = "paragraph_web_browser_style";
            title = _("Generic web browser paragraph style"),
            description = _([[
Display paragraphs as browsers do, in full-block style without indentation or justification, discarding KOReader's book paragraph style.
This might be needed with some documents that expect this style as the default, and only use CSS when it needs to diverge from this default.]]),
            priority = -1,
            css = [[
p {
    text-align: left;
    text-indent: 0;
    margin-top: 1em;
    margin-bottom: 1em;
}
            ]],
            separator = true,
        },
        {
            id = "paragraph_no_indent";
            title = _("No indentation on first paragraph line"),
            description = _("Do not indent the first line of paragraphs."),
            css = [[p { text-indent: 0 !important; }]],
        },
        {
            id = "paragraph_indent";
            title = _("Indentation on first paragraph line"),
            description = _("Indentation on the first line of a paragraph is the default, but it may be overridden by publisher styles. This will force KOReader's defaults on common elements."),
            css = [[
p { text-indent: 1.2em !important; }
body, h1, h2, h3, h4, h5, h6, div, li, td, th { text-indent: 0 !important; }
            ]],
            separator = true,
        },
        {
            id = "paragraph_whitespace";
            title = _("Spacing between paragraphs"),
            description = _("Add a line of whitespace between paragraphs."),
            css = [[p + p { margin-top: 1em !important; }]],
        },
        {
            id = "paragraph_whitespace_half";
            title = _("Spacing between paragraphs (half)"),
            description = _("Add half a line of whitespace between paragraphs."),
            css = [[p + p { margin-top: .5em !important; }]],
        },
        {
            id = "paragraph_no_whitespace";
            title = _("No spacing between paragraphs"),
            description = _("No whitespace between paragraphs is the default, but it may be overridden by publisher styles. This will re-enable it for paragraphs and list items."),
            css = [[p, li { margin-top: 0 !important; margin-bottom: 0 !important; }]],
        },
    },
    {
        title = _("Tables"),
        {
            id = "table_full_width";
            title = _("Full-width tables"),
            description = _("Make table expand to the full width of the page. (Tables with small content now use only the width needed to display that content. This restores the previous behavior.)"),
            css = [[table { width: 100% !important; }]],
        },
        {
            id = "table_td_width_auto";
            title = _("Ignore publisher table and cell widths"),
            description = _("Ignore table and cells widths specified by the publisher, and let the engine decide the most appropriate widths."),
            css = [[table, td, th { width: auto !important; }]],
        },
        {
            id = "table_margin_left_right_auto";
            title = _("Center small tables"),
            description = _("Horizontally center tables that do not use the full page width."),
            css = [[table { margin-left: auto !important; margin-right: auto !important; }]],
            separator = true,
        },
        {
            id = "td_vertical_align_none";
            title = _("Ignore publisher vertical alignment in tables"),
            -- Using "vertical-align: top" would vertical-align children text nodes to top.
            -- "vertical-align: baseline" has no meaning in table rendering, and is as fine
            css = [[td { vertical-align: baseline !important; }]],
        },
        {
            id = "table_row_odd_even";
            title = _("Alternate background color of table rows"),
            css = [[
tr:nth-child(odd)  { background-color: #EEE !important; }
tr:nth-child(even) { background-color: #CCC !important; }
            ]],
        },
        {
            id = "table_force_border";
            title = _("Show borders on all tables"),
            css = [[
table, tcaption, tr, th, td { border: black solid 1px; border-collapse: collapse; }
            ]],
        },
    },
    {
        title = _("Links"),
        {
            id = "a_black";
            title = _("Links always black"),
            css = [[a { color: black !important; }]],
        },
        {
            id = "a_blue";
            title = _("Links always blue"),
            css = [[a { color: blue !important; }]],
            separator = true,
        },
        {
            id = "a_bold";
            title = _("Links always bold"),
            css = [[a { font-weight: bold !important; }]],
        },
        {
            id = "a_not_bold";
            title = _("Links never bold"),
            css = [[a { font-weight: normal !important; }]],
        },
    },
    {
        title = _("Images"),
        {
            id = "image_full_width";
            title = _("Full-width images"),
            description = _("Useful for books containing only images, when they are smaller than your screen. May stretch images in some cases."),
            -- This helped me once with a book. Will mess with aspect ratio
            -- when images have a style="width: NNpx; heigh: NNpx"
            css = [[
img {
text-align: center !important;
text-indent: 0px !important;
display: block !important;
width: 100% !important;
}
            ]],
        },
        {
            id = "image_valign_middle";
            title = _("Vertically center-align images relative to text"),
            css = [[img { vertical-align: middle; }]],
        },
    },
    {
        title = _("Miscellaneous"),
        {
            title = _("Alternative TOC hints"),
            {
                title = _("About alternative TOC"),
                info_text = _([[
An alternative table of contents can be built with a long-press on the "Table of contents" menu item.

The TOC will be built from document headings <H1> to <H6>. Some of these can be ignored with the tweaks available here.
If the document contains no headings, or all are ignored, the alternative TOC will be built from document fragments and will point to the start of each individual HTML file in the EPUB.

Hints can be set to other non-heading elements in a user style tweak, so they can be used as TOC items. Since this would be quite book-specific, please see the final tweak for some examples.

After applying these tweaks, the alternative TOC needs to be rebuilt by long-pressing "Table of contents" twice: once to restore the original TOC, and once to build the alternative TOC again.]]),
                separator = true,
            },
            {
                id = "alt_toc_ignore_h_all";
                title = _("Ignore all <H1> to <H6>"),
                css = [[h1, h2, h3, h4, h5, h6 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h1";
                title = _("Ignore <H1>"),
                css = [[h1 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h2";
                title = _("Ignore <H2>"),
                css = [[h2 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h3";
                title = _("Ignore <H3>"),
                css = [[h3 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h4";
                title = _("Ignore <H4>"),
                css = [[h4 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h5";
                title = _("Ignore <H5>"),
                css = [[h5 { -cr-hint: toc-ignore; }]],
            },
            {
                id = "alt_toc_ignore_h6";
                title = _("Ignore <H6>"),
                css = [[h6 { -cr-hint: toc-ignore; }]],
                separator = true,
            },
            {
                id = "alt_toc_level_example";
                title = _("Example of book specific TOC hints"),
                description = _([[
If headings or document fragments do not result in a usable TOC, you can inspect the HTML and look for elements that contain chapter titles. Then you can set hints to their class names.
This is just an example, that will need to be adapted into a user style tweak.]]),
                css = [[
.book_n    { -cr-hint: toc-level1; }
.part_n    { -cr-hint: toc-level2; }
.chap_tit  { -cr-hint: toc-level3; }
.chap_tit1 { -cr-hint: toc-level3; }
                ]],
            },
        },
        {
            title = _("In-page footnotes"),
            {
                id = "footnote-inpage_epub";
                title = _("In-page EPUB footnotes"),
                description = _([[
Show EPUB footnote text at the bottom of pages that contain links to them.
This only works with footnotes that have specific attributes set by the publisher.]]),
                css = [[
*[type~="note"],
*[type~="footnote"],
*[type~="rearnote"],
*[role~="doc-note"],
*[role~="doc-footnote"],
*[role~="doc-rearnote"]
{
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
}
                ]],
            },
            {
                id = "footnote-inpage_epub_smaller";
                title = _("In-page EPUB footnotes (smaller)"),
                description = _([[
Show EPUB footnote text at the bottom of pages that contain links to them.
This only works with footnotes that have specific attributes set by the publisher.]]),
                css = [[
*[type~="note"],
*[type~="footnote"],
*[type~="rearnote"],
*[role~="doc-note"],
*[role~="doc-footnote"],
*[role~="doc-rearnote"]
{
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
    font-size: 80% !important;
}
                ]],
                separator = true,
            },
            {
                id = "footnote-inpage_wikipedia";
                title = _("In-page Wikipedia footnotes"),
                description = _([[Show footnotes at the bottom of pages in Wikipedia EPUBs.]]),
                css = [[
ol.references > li {
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
}
/* hide backlinks */
ol.references > li > .noprint { display: none; }
ol.references > li > .mw-cite-backlink { display: none; }
                ]],
            },
            {
                id = "footnote-inpage_wikipedia_smaller";
                title = _("In-page Wikipedia footnotes (smaller)"),
                description = _([[Show footnotes at the bottom of pages in Wikipedia EPUBs.]]),
                css = [[
ol.references > li {
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
    font-size: 80% !important;
}
/* hide backlinks */
ol.references > li > .noprint { display: none; }
ol.references > li > .mw-cite-backlink { display: none; }
                ]],
                separator = true,
            },
            -- We can add other classic class names to the 2 following
            -- tweaks (except when named 'calibreN', as the N number is
            -- usually random across books).
            {
                id = "footnote-inpage_classic_classnames";
                title = _("In-page classic classname footnotes"),
                description = _([[
Show footnotes with classic class names at the bottom of pages.
This tweak can be duplicated as a user style tweak when books contain footnotes wrapped with other class names.]]),
                css = [[
.footnote, .note, .note1, .ntb
{
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
}
                ]],
            },
            {
                id = "footnote-inpage_classic_classnames_smaller";
                title = _("In-page classic classname footnotes (smaller)"),
                description = _([[
Show footnotes with classic classname at the bottom of pages.
This tweak can be duplicated as a user style tweak when books contain footnotes wrapped with other class names.]]),
                css = [[
.footnote, .note, .note1, .ntb
{
    -cr-hint: footnote-inpage;
    margin-top: 0 !important;
    margin-bottom: 0 !important;
    font-size: 80% !important;
}
                ]],
            },
        },
        {
            id = "epub_switch_show_case";
            title = _("Toggle alternative EPUB content"),
            description = _([[
The EPUB3 format allows a
<epub:switch> <epub:case> <epub:default>
construct to provide alternative content to engines that support optional features.
KOReader currently falls back to hiding all <epub:case> content and shows the <epub:default> content (usually an image).
This tweak toggles this behavior, and may show the <epub:case> content as plain text.]]),
            css = [[
switch > case    { display: inline; }
switch > default { display: none; }
            ]],
        },
    },
    -- No current need for workarounds
    -- {
    --     title = _("Workarounds"),
    -- },
}

return CssTweaks