Footnote popup: allow using book font as popup font

Also move footnote popup settings into a submenu.

frontend/apps/reader/modules/readerlink.lua

@@ -275,7 +275,13 @@ The footnote content may be empty, truncated, or include other footnotes.
 
 From the footnote popup, you can jump to the footnote location in the book by swiping to the left.]]),
         })
+        local footnote_popup_settings_items = {}
         table.insert(menu_items.follow_links.sub_item_table, 5, {
+            text = _("Footnote popup settings"),
+            sub_item_table = footnote_popup_settings_items,
+            separator = true,
+        })
+        table.insert(footnote_popup_settings_items, {
             text = _("Show more links as footnotes"),
             enabled_func = function()
                 return isFootnoteLinkInPopupEnabled() and
@@ -287,8 +293,23 @@ From the footnote popup, you can jump to the footnote location in the book by sw
                     not isPreferFootnoteEnabled())
             end,
             help_text = _([[Loosen footnote detection rules to show more links as footnotes.]]),
+            separator = true,
+        })
+        table.insert(footnote_popup_settings_items, {
+            text = _("Use book font as popup font"),
+            enabled_func = function()
+                return isFootnoteLinkInPopupEnabled() and
+                    (isTapToFollowLinksOn() or isSwipeToFollowNearestLinkEnabled())
+            end,
+            checked_func = function()
+                return G_reader_settings:isTrue("footnote_popup_use_book_font")
+            end,
+            callback = function()
+                G_reader_settings:flipNilOrFalse("footnote_popup_use_book_font")
+            end,
+            help_text = _([[Display the footnote popup text with the font set as the document font (the book text may still render with a different font if the book uses embedded fonts).]]),
         })
-        table.insert(menu_items.follow_links.sub_item_table, 6, {
+        table.insert(footnote_popup_settings_items, {
             text = _("Set footnote popup font size"),
             enabled_func = function()
                 return isFootnoteLinkInPopupEnabled() and
@@ -358,7 +379,6 @@ The recommended value is -2.]]),
             help_text = _([[
 The footnote popup font adjusts to the font size you've set for the document.
 This allows you to specify how much smaller or larger it should be relative to the document font size.]]),
-            separator = true,
         })
     end
 end
@@ -1345,6 +1365,7 @@ function ReaderLink:showAsFootnotePopup(link, neglect_current_location)
     local popup
     popup = FootnoteWidget:new{
         html = html,
+        doc_font_name = self.ui.font.font_face,
         doc_font_size = Screen:scaleBySize(self.ui.font.font_size),
         doc_margins = self.ui.document:getPageMargins(),
         close_callback = close_callback,

frontend/ui/widget/footnotewidget.lua

@@ -21,26 +21,6 @@ local Screen = Device.screen
 local T = require("ffi/util").template
 local time = require("ui/time")
 
--- If we wanted to use the default font set for the book,
--- we'd need to add a few functions to crengine and cre.cpp
--- to get the font files paths (for each font, regular, italic,
--- bold...) so we can pass them to MuPDF with:
---   @font-face {
---       font-family: 'KOReader Footnote Font';
---       src: url("%1");
---   }
---   @font-face {
---       font-family: 'KOReader Footnote Font';
---       src: url("%2");
---       font-style: italic;
---   }
---   body {
---       font-family: 'KOReader Footnote Font';
---   }
--- But it looks quite fine if we use "Noto Sans": the difference in font look
--- (Sans, vs probably Serif in the book) will help noticing this is a KOReader
--- UI element, and somehow justify the difference in looks.
-
 -- Note: we can't use < or > in comments in the CSS, or MuPDF complains with:
 --   error: css syntax error: unterminated comment.
 -- So, HTML tags in comments are written upppercase (eg: <li> => LI)
@@ -53,6 +33,7 @@ local PAGE_CSS = [[
     font-family: '%5';
 }
 %6
+%7
 ]]
 
 -- Make default MuPDF styles (source/html/html-layout.c) a bit
@@ -62,7 +43,7 @@ local DEFAULT_CSS = [[
 body {
     margin: 0;                  /* MuPDF: margin: 1em */
     padding: 0;
-    line-height: 1.3;
+    line-height: 1.3;           /* MuPDF defaults to 1.2 */
     text-align: justify;
 }
 /* We keep left and right margin the same so it also displays as expected in RTL */
@@ -139,6 +120,7 @@ local FootnoteWidget = InputContainer:new{
     -- For the doc_* values, we expect to be provided with the real
     -- (already scaled) sizes in screen pixels
     doc_font_size = Screen:scaleBySize(18),
+    doc_font_name = nil,
     doc_margins = {
         left = Screen:scaleBySize(20),
         right = Screen:scaleBySize(20),
@@ -233,6 +215,38 @@ function FootnoteWidget:init()
         font_size = self.doc_font_size + (G_reader_settings:readSetting("footnote_popup_relative_font_size") or -2)
     end
 
+    local font_css = ""
+    if G_reader_settings:isTrue("footnote_popup_use_book_font") then
+        -- Note: we can't provide any base weight (as supported by crengine), as MuPDF
+        -- will use the bold font for anything with a weight > 400. We can only use the
+        -- font as-is, without its natural weight tweaked.
+        local seen_font_path = {}
+        for i=1, 4 do
+            local bold = i >= 3
+            local italic = i == 2 or i ==4
+            -- We assume the font is not from a collection, and ignore the index.
+            local font_path = cre.getFontFaceFilenameAndFaceIndex(self.doc_font_name, bold, italic)
+            -- crengine returns the regular filename when requesting a bold that
+            -- it has synthesized; but MuPDF would consider it as real bold and
+            -- would use it as-is: by not providing the fake bold font file path,
+            -- we let MuPDF itself synthesize the bold (and also italic if none
+            -- provided). So, keep track of what's been seen and used.
+            if font_path and not seen_font_path[font_path] then
+                seen_font_path[font_path] = true
+                font_css = font_css .. T("\n@font-face { font-family: 'KOReaderFootnoteFont'; src: url('%1')%2%3}",
+                            font_path,
+                            bold and "; font-weight: bold" or "",
+                            italic and "; font-style: italic" or "")
+            end
+        end
+        if font_css ~= "" then
+            -- If not using our standard font, override "line-height:1.3" (which is fine
+            -- with Noto Sans) to use something smaller (looks like MuPDF's default is 1.2
+            -- and we can't make it use the font natural line height...)
+            font_css = font_css .. "\nbody { font-family: 'KOReaderFootnoteFont'; line-height: 1.2 !important; }\n"
+        end
+    end
+
     -- We want to display the footnote text with the same margins as
     -- the document, but keep the scrollbar in the right margin, so
     -- both small footnotes (without scrollbar) and longer ones (with
@@ -245,8 +259,9 @@ function FootnoteWidget:init()
     if BD.mirroredUILayout() then
         html_left_margin, html_right_margin = html_right_margin, html_left_margin
     end
+
     local css = T(PAGE_CSS, "0", html_right_margin, "0", html_left_margin, -- top right bottom left
-                    self.font_face, DEFAULT_CSS)
+                    self.font_face, font_css, DEFAULT_CSS)
     if self.css then -- add any provided css
         css = css .. "\n" .. self.css
     end