Make TextArea on_cursor_change include old cursor

Also add tests for TextArea `on_cursor_change` callback

docs/dev/Lua API.rst

@@ -5525,6 +5525,7 @@ Attributes:
 * ``init_text``: The initial text content for the text area.
 
 * ``init_cursor``: The initial cursor position within the text content.
+  If not specified, defaults to end of the text (length of ``init_text``).
 
 * ``text_pen``: Optional pen used to draw the text.
 
@@ -5536,8 +5537,8 @@ Attributes:
 * ``on_text_change``: Callback function called whenever the text changes.
   The function signature should be ``on_text_change(new_text)``.
 
-* ``on_cursor_change``: Callback function called whenever the cursor
-  position changes. The function signature should be ``on_cursor_change(new_cursor_pos)``.
+* ``on_cursor_change``: Callback function called whenever the cursor position changes.
+  Expected function signature is ``on_cursor_change(new_cursor, old_cursor)``.
 
 * ``one_line_mode``: Boolean attribute that, when set to ``true``,
   disables multi-line text features and restricts the text area to a single line.

library/lua/gui/widgets/text_area.lua

@@ -81,7 +81,7 @@ function TextArea:clearHistory()
     return self.text_area.history:clear()
 end
 
-function TextArea:onCursorChange(cursor)
+function TextArea:onCursorChange(cursor, old_cursor)
     local x, y = self.text_area.wrapped_text:indexToCoords(
         self.text_area.cursor
     )
@@ -95,7 +95,7 @@ function TextArea:onCursorChange(cursor)
     end
 
     if self.on_cursor_change then
-        self.on_cursor_change(cursor)
+        self.on_cursor_change(cursor, old_cursor)
     end
 end
 

library/lua/gui/widgets/text_area/text_area_content.lua

@@ -80,6 +80,8 @@ function TextAreaContent:recomputeLines()
 end
 
 function TextAreaContent:setCursor(cursor_offset)
+    local old_cursor = self.cursor
+
     self.cursor = math.max(
         1,
         math.min(#self.text + 1, cursor_offset)
@@ -92,8 +94,8 @@ function TextAreaContent:setCursor(cursor_offset)
     self.sel_end = nil
     self.last_cursor_x = nil
 
-    if self.on_cursor_change then
-        self.on_cursor_change(self.cursor)
+    if self.on_cursor_change and self.cursor ~= old_cursor then
+        self.on_cursor_change(self.cursor, old_cursor)
     end
 end