TextWidget: adds getFittedText() (#5776)

bump base for xtext:getText().

frontend/ui/widget/textwidget.lua

@@ -201,6 +201,57 @@ function TextWidget:_measureWithXText()
     end
 end
 
+-- Returns the substring of text that fits in self.max_width
+-- The substring does not include the ellipsis that could
+-- be added when drawn.
+-- 2nd returned value is nil if no truncation, false when truncated
+-- and no ellipsis would be added, true if truncated and an ellipsis
+-- will be added (on the right or left of string in logical order,
+-- caller knows the side from the provided 'truncate_left').
+function TextWidget:getFittedText()
+    if not self.max_width then
+        return self.text, nil
+    end
+    self:updateSize()
+    if self._is_empty then
+        return "", nil
+    end
+    if not self.use_xtext then
+        if self._text_to_draw == self.text then
+            return self.text, nil
+        end
+        if not self.truncate_with_ellipsis then
+            return self._text_to_draw, false
+        end
+        -- ellipsis is 3 bytes
+        if self.truncate_left then
+            return self._text_to_draw:sub(3), true
+        else
+            return self._text_to_draw:sub(1, -4), true
+        end
+    end
+    if self._shape_start == 1 and self._shape_end == #self.text then
+        -- not truncated
+        return self.text, nil
+    end
+    local with_ellipsis = false
+    local start_idx, end_idx = self._shape_start, self._shape_end
+    if self._shape_idx_to_substitute_with_ellipsis then
+        with_ellipsis = true
+        if self.truncate_left then
+            start_idx = start_idx + 1
+        else
+            end_idx = end_idx - 1
+        end
+    end
+    -- These start and end indexes are in the internal unicode
+    -- string of the xtext object, and we can't use them as
+    -- indices of the UTF-8 self.text.
+    -- So, get the UTF-8 directly from xtext.
+    local text = self._xtext:getText(start_idx, end_idx)
+    return text, with_ellipsis
+end
+
 function TextWidget:getSize()
     self:updateSize()
     return Geom:new{