Add InputText:setText and avoid non-intuitive UI behavior after light toggle

frontend/ui/reader/readerfrontlight.lua

@@ -69,6 +69,7 @@ function ReaderFrontLight:onShowFlDialog()
 					text = _("Toggle"),
 					enabled = true,
 					callback = function()
+						self.fl_dialog.input:setText("")
 						fl:toggle()
 					end,
 				},

frontend/ui/widget/inputtext.lua

@@ -114,6 +114,12 @@ function InputText:getText()
 	return self.text
 end
 
+function InputText:setText(text)
+	self:StringToCharlist(text)
+	self:initTextBox()
+	UIManager:setDirty(self.parent, "partial")
+end
+
 function InputText:StringToCharlist(text)
 	if text == nil then return end
 	-- clear