[fix] Update charpos in InputText after moving the cursor up/down. (#3874)

frontend/ui/widget/inputtext.lua

@@ -301,13 +301,13 @@ end
 
 function InputText:upLine()
     if self.text_widget.moveCursorUp then
-        self.text_widget:moveCursorUp()
+        self.charpos = self.text_widget:moveCursorUp()
     end
 end
 
 function InputText:downLine()
     if self.text_widget.moveCursorDown then
-        self.text_widget:moveCursorDown()
+        self.charpos = self.text_widget:moveCursorDown()
     end
 end
 

frontend/ui/widget/scrolltextwidget.lua

@@ -96,6 +96,14 @@ function ScrollTextWidget:moveCursor(x, y)
     return self.text_widget:moveCursor(x, y)
 end
 
+function ScrollTextWidget:moveCursorUp()
+    return self.text_widget:moveCursorUp();
+end
+
+function ScrollTextWidget:moveCursorDown()
+    return self.text_widget:moveCursorDown();
+end
+
 function ScrollTextWidget:scrollText(direction)
     if direction == 0 then return end
     local low, high

frontend/ui/widget/textboxwidget.lua

@@ -675,6 +675,7 @@ function TextBoxWidget:moveCursorUp()
     if charpos then
         self:moveCursorToCharpos(charpos)
     end
+    return charpos
 end
 
 function TextBoxWidget:moveCursorDown()
@@ -685,6 +686,7 @@ function TextBoxWidget:moveCursorDown()
     if charpos then
         self:moveCursorToCharpos(charpos)
     end
+    return charpos
 end
 
 function TextBoxWidget:paintTo(bb, x, y)