Triple click in text editor now uses last mouse position for validity

Previously, you would be able to double click a word, followed by
single-clicking another word on the same line, which would select the
entire line. Now, it will only select the whole line if the mouse
position has remained the same after the double click. This mimicks the
behavior in most third party text editors.

Fixes #51312.

scene/gui/text_edit.cpp

@@ -2246,7 +2246,10 @@ void TextEdit::_gui_input(const Ref<InputEvent> &p_gui_input) {
 					selection.selecting_column = col;
 				}
 
-				if (!mb->is_double_click() && (OS::get_singleton()->get_ticks_msec() - last_dblclk) < 600 && cursor.line == prev_line) {
+				const int triple_click_timeout = 600;
+				const int triple_click_tolerance = 5;
+
+				if (!mb->is_double_click() && (OS::get_singleton()->get_ticks_msec() - last_dblclk) < triple_click_timeout && mb->get_position().distance_to(last_dblclk_pos) < triple_click_tolerance) {
 					// Triple-click select line.
 					selection.selecting_mode = SelectionMode::SELECTION_MODE_LINE;
 					_update_selection_mode_line();
@@ -2256,6 +2259,7 @@ void TextEdit::_gui_input(const Ref<InputEvent> &p_gui_input) {
 					selection.selecting_mode = SelectionMode::SELECTION_MODE_WORD;
 					_update_selection_mode_word();
 					last_dblclk = OS::get_singleton()->get_ticks_msec();
+					last_dblclk_pos = mb->get_position();
 				}
 
 				update();

scene/gui/text_edit.h

@@ -308,6 +308,7 @@ class TextEdit : public Control {
 	String lookup_symbol_word;
 
 	uint64_t last_dblclk = 0;
+	Vector2 last_dblclk_pos;
 
 	Timer *idle_detect;
 	Timer *click_select_held;