InfoMessage: avoid overflowing screen height with long messages

When no height= provided, and the InfoMessage would overflow
screen height when some long message is provided, decrease the
font size until the widget fit.

frontend/apps/reader/modules/readerstyletweak.lua

@@ -439,13 +439,11 @@ You can enable individual tweaks on this book with a tap, or view more details a
                 callback = function()
                     UIManager:show(InfoMessage:new{
                         text = item.info_text,
-                        face = Font:getFace(item.smaller_font and "x_smallinfofont" or "smallinfofont"),
                     })
                 end,
                 hold_callback = function()
                     UIManager:show(InfoMessage:new{
                         text = item.info_text,
-                        face = Font:getFace(item.smaller_font and "x_smallinfofont" or "smallinfofont"),
                     })
                 end,
                 separator = item.separator,

frontend/ui/data/css_tweaks.lua

@@ -263,7 +263,6 @@ width: 100% !important;
             title = _("Alternative TOC hints"),
             {
                 title = _("About alternative TOC"),
-                smaller_font = true,
                 info_text = _([[
 An alternative table of content can be built with a long-press on the "Table of content" menu item.
 

frontend/ui/font.lua

@@ -117,11 +117,13 @@ function Font:getFace(font, size)
         end
         --- Freetype font face wrapper object
         -- @table FontFaceObj
+        -- @field orig_font font name requested
         -- @field size size of the font face (after scaled by screen size)
         -- @field orig_size raw size of the font face (before scale)
         -- @field ftface font face object from freetype
         -- @field hash hash key for this font face
         face_obj = {
+            orig_font = font,
             size = size,
             orig_size = orig_size,
             ftface = face,

frontend/ui/widget/infomessage.lua

@@ -129,21 +129,46 @@ function InfoMessage:init()
             width = text_width,
         }
     end
-    self.movable = MovableContainer:new{
-        FrameContainer:new{
-            background = Blitbuffer.COLOR_WHITE,
-            HorizontalGroup:new{
-                align = "center",
-                image_widget,
-                HorizontalSpan:new{ width = (self.show_icon and Size.span.horizontal_default or 0) },
-                text_widget,
-            }
+    local frame = FrameContainer:new{
+        background = Blitbuffer.COLOR_WHITE,
+        HorizontalGroup:new{
+            align = "center",
+            image_widget,
+            HorizontalSpan:new{ width = (self.show_icon and Size.span.horizontal_default or 0) },
+            text_widget,
         }
     }
+    self.movable = MovableContainer:new{
+        frame,
+    }
     self[1] = CenterContainer:new{
         dimen = Screen:getSize(),
         self.movable,
     }
+    if not self.height then
+        -- Reduce font size until widget fit screen height if needed
+        local cur_size = frame:getSize()
+        if cur_size and cur_size.h > 0.95 * Screen:getHeight() then
+            local orig_font = text_widget.face.orig_font
+            local orig_size = text_widget.face.orig_size
+            local real_size = text_widget.face.size
+            if orig_size > 10 then -- don't go too small
+                while true do
+                    orig_size = orig_size - 1
+                    self.face = Font:getFace(orig_font, orig_size)
+                    -- scaleBySize() in Font:getFace() may give the same
+                    -- real font size even if we decreased orig_size,
+                    -- so check we really got a smaller real font size
+                    if self.face.size < real_size then
+                        break
+                    end
+                end
+                -- re-init this widget
+                self:free()
+                self:init()
+            end
+        end
+    end
 end
 
 function InfoMessage:onCloseWidget()