Button: reduce font size to avoid truncation (#8078)

If the button text would be truncated, try to avoid
it by reducing the font size, and even switching to
a 2-lines TextBoxWidget.
TextBoxWidget: fix possible glyphs truncations when
a small line_height is used. Also avoid some bad
result from getFontSizeToFitHeight(), possible due
to some rounding errors.

frontend/ui/widget/button.lua

@@ -25,6 +25,7 @@ local GestureRange = require("ui/gesturerange")
 local IconWidget = require("ui/widget/iconwidget")
 local InputContainer = require("ui/widget/container/inputcontainer")
 local Size = require("ui/size")
+local TextBoxWidget = require("ui/widget/textboxwidget")
 local TextWidget = require("ui/widget/textwidget")
 local UIManager = require("ui/uimanager")
 local _ = require("gettext")
@@ -52,6 +53,7 @@ local Button = InputContainer:new{
     padding_v = nil,
     width = nil,
     max_width = nil,
+    avoid_text_truncation = true,
     text_font_face = "cfont",
     text_font_size = 20,
     text_font_bold = true,
@@ -77,13 +79,51 @@ function Button:init()
     end
 
     if self.text then
+        local max_width = self.max_width and self.max_width - 2*self.padding_h - 2*self.margin - 2*self.bordersize or nil
         self.label_widget = TextWidget:new{
             text = self.text,
-            max_width = self.max_width and self.max_width - 2*self.padding_h - 2*self.margin - 2*self.bordersize or nil,
+            max_width = max_width,
             fgcolor = self.enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY,
             bold = self.text_font_bold,
             face = Font:getFace(self.text_font_face, self.text_font_size)
         }
+        self.did_truncation_tweaks = false
+        if self.avoid_text_truncation and self.label_widget:isTruncated() then
+            self.did_truncation_tweaks = true
+            local max_height = self.label_widget:getSize().h
+            local font_size_2_lines = TextBoxWidget:getFontSizeToFitHeight(max_height, 2, 0)
+            while self.label_widget:isTruncated() do
+                local new_size = self.label_widget.face.orig_size - 1
+                if new_size < font_size_2_lines then
+                    -- Switch to a 2-lines TextBoxWidget
+                    self.label_widget:free()
+                    self.label_widget = TextBoxWidget:new{
+                        text = self.text,
+                        line_height = 0,
+                        alignment = "center",
+                        width = max_width,
+                        height = max_height,
+                        height_adjust = true,
+                        height_overflow_show_ellipsis = true,
+                        fgcolor = self.enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY,
+                        bold = self.text_font_bold,
+                        face = Font:getFace(self.text_font_face, font_size_2_lines)
+                    }
+                    break
+                end
+                if new_size < 8 then -- don't go too small
+                    break
+                end
+                self.label_widget:free()
+                self.label_widget = TextWidget:new{
+                    text = self.text,
+                    max_width = max_width,
+                    fgcolor = self.enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY,
+                    bold = self.text_font_bold,
+                    face = Font:getFace(self.text_font_face, new_size)
+                }
+            end
+        end
     else
         self.label_widget = IconWidget:new{
             icon = self.icon,
@@ -150,7 +190,7 @@ end
 function Button:setText(text, width)
     if text ~= self.text then
         -- Don't trash the frame if we're already a text button, and we're keeping the geometry intact
-        if self.text and width and width == self.width then
+        if self.text and width and width == self.width and not self.did_truncation_tweaks then
             self.text = text
             self.label_widget:setText(text)
         else

frontend/ui/widget/textboxwidget.lua

@@ -118,6 +118,20 @@ function TextBoxWidget:init()
     end
 
     self.line_height_px = Math.round( (1 + self.line_height) * self.face.size )
+    -- Get accurate initial baseline and possible height overflow (so our bb
+    -- is tall enough to draw glyphs with descender larger than line height)
+    local face_height, face_ascender = self.face.ftface:getHeightAndAscender()
+    local line_heights_diff = math.floor(self.line_height_px - face_height)
+    if line_heights_diff >= 0 then
+        -- Glyphs will fit in our line_height_px: adjust baseline.
+        self.line_glyph_baseline = math.floor(face_ascender + line_heights_diff/2)
+        self.line_glyph_extra_height = 0
+    else
+        -- Glyphs may be taller than our line_height_px
+        self.line_glyph_baseline = math.floor(face_ascender)
+        self.line_glyph_extra_height = -line_heights_diff
+    end
+
     self.cursor_line = LineWidget:new{
         dimen = Geom:new{
             w = Size.line.medium,
@@ -753,13 +767,13 @@ end
 
 ---- Lays out text.
 function TextBoxWidget:_renderText(start_row_idx, end_row_idx)
-    local font_height = self.face.size
     if start_row_idx < 1 then start_row_idx = 1 end
     if end_row_idx > #self.vertical_string_list then end_row_idx = #self.vertical_string_list end
     local row_count = end_row_idx == 0 and 1 or end_row_idx - start_row_idx + 1
     -- We need a bb with the full height (even if we display only a few lines, we
     -- may have to draw an image bigger than these lines)
     local h = self.height or self.line_height_px * row_count
+    h = h + self.line_glyph_extra_height
     if self._bb then self._bb:free() end
     local bbtype = nil
     if self.line_num_to_image and self.line_num_to_image[start_row_idx] then
@@ -767,8 +781,8 @@ function TextBoxWidget:_renderText(start_row_idx, end_row_idx)
     end
     self._bb = Blitbuffer.new(self.width, h, bbtype)
     self._bb:fill(Blitbuffer.COLOR_WHITE)
-    local y = font_height
 
+    local y = self.line_glyph_baseline
     if self.use_xtext then
         for i = start_row_idx, end_row_idx do
             local line = self.vertical_string_list[i]
@@ -1056,9 +1070,12 @@ function TextBoxWidget:getFontSizeToFitHeight(height_px, nb_lines, line_height_e
     end
     -- We do the revert of what's done in :init():
     --   self.line_height_px = Math.round( (1 + self.line_height) * self.face.size )
-    local font_size = height_px / nb_lines / (1 + line_height_em)
-    font_size = font_size * 1000000 / Screen:scaleBySize(1000000) -- invert scaleBySize
-    return math.floor(font_size)
+    local face_size = height_px / nb_lines / (1 + line_height_em)
+    local font_size = math.floor(face_size * 1000000 / Screen:scaleBySize(1000000)) -- invert scaleBySize
+    if Screen:scaleBySize(font_size) > face_size then -- be really sure we won't get it larger
+        font_size = font_size - 1
+    end
+    return font_size
 end
 
 function TextBoxWidget:getCharPos()
@@ -1067,11 +1084,7 @@ function TextBoxWidget:getCharPos()
 end
 
 function TextBoxWidget:getSize()
-    if self.width and self.height then
-        return Geom:new{ w = self.width, h = self.height}
-    else
-        return Geom:new{ w = self.width, h = self._bb:getHeight()}
-    end
+    return Geom:new{ w = self.width, h = self._bb:getHeight()}
 end
 
 function TextBoxWidget:paintTo(bb, x, y)