From 7ebd067a95886392b3894bed0d4a0c50de475b59 Mon Sep 17 00:00:00 2001
From: poire-z <poire-z@users.noreply.github.com>
Date: Fri, 12 Jul 2024 13:34:47 +0200
Subject: [PATCH] Footnote popup: fix XHTML handling (#12158)

Latest MuPDF update changed HTML parsing, and use a better
HTML5 parser, which may cause some issues with the XHTML
we get from crengine.
So, for footnote popups, be sure we use MuPDF's XHTML parser.
---
 frontend/ui/widget/footnotewidget.lua   |  3 +++
 frontend/ui/widget/htmlboxwidget.lua    | 10 ++++++++--
 frontend/ui/widget/scrollhtmlwidget.lua |  3 ++-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/frontend/ui/widget/footnotewidget.lua b/frontend/ui/widget/footnotewidget.lua
index 22b13625f..2ca88535d 100644
--- a/frontend/ui/widget/footnotewidget.lua
+++ b/frontend/ui/widget/footnotewidget.lua
@@ -293,8 +293,11 @@ function FootnoteWidget:init()
     local padding_bottom = Size.padding.large
     local htmlwidget_height = self.height - padding_top - padding_bottom
 
+    -- We always get balanced XHTML from crengine for HTML snippets, so we
+    -- pass is_xhtml=true to avoid side effects from MuPDF's HTML5 parser.
     self.htmlwidget = ScrollHtmlWidget:new{
         html_body = self.html,
+        is_xhtml = true,
         css = css,
         default_font_size = font_size,
         width = htmlwidget_width,
diff --git a/frontend/ui/widget/htmlboxwidget.lua b/frontend/ui/widget/htmlboxwidget.lua
index 02a1cc48c..447d89472 100644
--- a/frontend/ui/widget/htmlboxwidget.lua
+++ b/frontend/ui/widget/htmlboxwidget.lua
@@ -36,7 +36,7 @@ function HtmlBoxWidget:init()
     end
 end
 
-function HtmlBoxWidget:setContent(body, css, default_font_size)
+function HtmlBoxWidget:setContent(body, css, default_font_size, is_xhtml)
     -- fz_set_user_css is tied to the context instead of the document so to easily support multiple
     -- HTML dictionaries with different CSS, we embed the stylesheet into the HTML instead of using
     -- that function.
@@ -51,8 +51,14 @@ function HtmlBoxWidget:setContent(body, css, default_font_size)
     -- https://bugs.ghostscript.com/show_bug.cgi?id=698351
     html = html:gsub("%<br ?/?%>", "&nbsp;<div></div>")
 
+    -- We can provide some "magic"/"mimetype" to Mupdf.openDocumentFromText():
+    -- - "html" will get MuPDF to use its bundled gumbo-parser to parse HTML5 according to the specs.
+    -- - "xhtml" will get MuPDF to use its own XML parser, and if it fails, to switch to gumbo-parser.
+    -- When we know the body is balanced XHTML, it's safer to use "xhtml" to avoid the HTML5
+    -- rules to trigger (ie. <title><p>123</p></title>, which is valid in FB2 snippets, parsed
+    -- as title>p, while gumbo-parse would consider "<p>123</p>" as being plain text).
     local ok
-    ok, self.document = pcall(Mupdf.openDocumentFromText, html, "html")
+    ok, self.document = pcall(Mupdf.openDocumentFromText, html, is_xhtml and "xhtml" or "html")
     if not ok then
         -- self.document contains the error
         logger.warn("HTML loading error:", self.document)
diff --git a/frontend/ui/widget/scrollhtmlwidget.lua b/frontend/ui/widget/scrollhtmlwidget.lua
index ce5e5372a..038bd84ac 100644
--- a/frontend/ui/widget/scrollhtmlwidget.lua
+++ b/frontend/ui/widget/scrollhtmlwidget.lua
@@ -17,6 +17,7 @@ local Screen = Device.screen
 
 local ScrollHtmlWidget = InputContainer:extend{
     html_body = nil,
+    is_xhtml = false,
     css = nil,
     default_font_size = Screen:scaleBySize(24), -- same as infofont
     htmlbox_widget = nil,
@@ -39,7 +40,7 @@ function ScrollHtmlWidget:init()
         html_link_tapped_callback = self.html_link_tapped_callback,
     }
 
-    self.htmlbox_widget:setContent(self.html_body, self.css, self.default_font_size)
+    self.htmlbox_widget:setContent(self.html_body, self.css, self.default_font_size, self.is_xhtml)
 
     self.v_scroll_bar = VerticalScrollBar:new{
         enable = self.htmlbox_widget.page_count > 1,