Footnote popups: allow setting an absolute font size

In the "Set footnote popup font size", allow toggling
between setting a relative (to the document) font size
and setting an absolute font size (that won't change
with the document font size).

frontend/apps/reader/modules/readerlink.lua

@@ -271,24 +271,64 @@ From the footnote popup, you can jump to the footnote location in the book by sw
             end,
             keep_menu_open = true,
             callback = function()
-                local SpinWidget = require("ui/widget/spinwidget")
-                UIManager:show(SpinWidget:new{
-                    width = math.floor(Screen:getWidth() * 0.75),
-                    value = G_reader_settings:readSetting("footnote_popup_relative_font_size") or -2,
-                    value_min = -10,
-                    value_max = 5,
-                    precision = "%+d",
-                    ok_text = _("Set font size"),
-                    title_text =  _("Set footnote popup font size"),
-                    info_text = _([[
+                local spin_widget
+                local get_font_size_widget
+                get_font_size_widget = function(show_absolute_font_size_widget)
+                    local SpinWidget = require("ui/widget/spinwidget")
+                    if show_absolute_font_size_widget then
+                        spin_widget = SpinWidget:new{
+                            width = math.floor(Screen:getWidth() * 0.75),
+                            value = G_reader_settings:readSetting("footnote_popup_absolute_font_size")
+                                            or Screen:scaleBySize(self.ui.font.font_size),
+                            value_min = 12,
+                            value_max = 255,
+                            precision = "%d",
+                            ok_text = _("Set font size"),
+                            title_text =  _("Set footnote popup font size"),
+                            info_text = _([[
+The footnote popup font can adjust to the font size you've set for the document, but you can specify here a fixed absolute font size to be used instead.]]),
+                            callback = function(spin)
+                                G_reader_settings:delSetting("footnote_popup_relative_font_size")
+                                G_reader_settings:saveSetting("footnote_popup_absolute_font_size", spin.value)
+                            end,
+                            extra_text = _("Set a relative font size instead"),
+                            extra_callback = function()
+                                UIManager:close(spin_widget)
+                                spin_widget = get_font_size_widget(false)
+                                UIManager:show(spin_widget)
+                            end,
+                        }
+                    else
+                        spin_widget = SpinWidget:new{
+                            width = math.floor(Screen:getWidth() * 0.75),
+                            value = G_reader_settings:readSetting("footnote_popup_relative_font_size") or -2,
+                            value_min = -10,
+                            value_max = 5,
+                            precision = "%+d",
+                            ok_text = _("Set font size"),
+                            title_text =  _("Set footnote popup font size"),
+                            info_text = _([[
 The footnote popup font adjusts to the font size you've set for the document.
 You can specify here how much smaller or larger it should be relative to the document font size.
 A negative value will make it smaller, while a positive one will make it larger.
 The recommended value is -2.]]),
-                    callback = function(spin)
-                        G_reader_settings:saveSetting("footnote_popup_relative_font_size", spin.value)
-                    end,
-                })
+                            callback = function(spin)
+                                G_reader_settings:delSetting("footnote_popup_absolute_font_size")
+                                G_reader_settings:saveSetting("footnote_popup_relative_font_size", spin.value)
+                            end,
+                            extra_text = _("Set an absolute font size instead"),
+                            extra_callback = function()
+                                UIManager:close(spin_widget)
+                                spin_widget = get_font_size_widget(true)
+                                UIManager:show(spin_widget)
+                            end,
+                        }
+                    end
+                    return spin_widget
+                end
+                local show_absolute_font_size_widget = G_reader_settings:readSetting("footnote_popup_absolute_font_size") ~= nil
+                spin_widget = get_font_size_widget(show_absolute_font_size_widget)
+                UIManager:show(spin_widget)
             end,
             help_text = _([[
 The footnote popup font adjusts to the font size you've set for the document.

frontend/ui/widget/footnotewidget.lua

@@ -225,7 +225,12 @@ function FootnoteWidget:init()
     -- We may use a font size a bit smaller than the document one (because
     -- footnotes are usually smaller, and because NotoSans is a bit on the
     -- larger size when compared to other fonts at the same size)
-    local font_size = self.doc_font_size + (G_reader_settings:readSetting("footnote_popup_relative_font_size") or -2)
+    local font_size = G_reader_settings:readSetting("footnote_popup_absolute_font_size")
+    if font_size then
+        font_size = Screen:scaleBySize(font_size)
+    else
+        font_size = self.doc_font_size + (G_reader_settings:readSetting("footnote_popup_relative_font_size") or -2)
+    end
 
     -- We want to display the footnote text with the same margins as
     -- the document, but keep the scrollbar in the right margin, so