Fix saved cursor handling

This resolves several problems with handling of the saved cursor when
switching between primary and alternate screen. Additionally ref-tests
are also added for all common interactions to make sure the behavior
does not regress.

The behavior is based on XTerm's behavior except for interaction with
`reset`. XTerm does not reset the alternate screen's saved cursor on
`reset`, but VTE does. Since a `reset` should reset as much as possible,
Alacritty copies VTE here instead of XTerm.

CHANGELOG.md

@@ -56,6 +56,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Incorrectly deleted lines when increasing width with a prompt wrapped using spaces
 - Documentation for class in `--help` missing information on setting general class
 - Linewrap tracking when switching between primary and alternate screen buffer
+- Preservation of the alternate screen's saved cursor when swapping to primary screen and back
 
 ## 0.4.3
 

alacritty_terminal/src/term/mod.rs

@@ -1062,18 +1062,16 @@ impl<T> Term<T> {
 
     /// Swap primary and alternate screen buffer.
     pub fn swap_alt(&mut self) {
-        if self.mode.contains(TermMode::ALT_SCREEN) {
-            let template = self.grid.cursor.template;
-            self.grid.region_mut(..).each(|c| c.reset(&template));
+        if !self.mode.contains(TermMode::ALT_SCREEN) {
+            // Set alt screen cursor to the current primary screen cursor.
+            self.inactive_grid.cursor = self.grid.cursor;
 
-            self.inactive_grid.cursor = self.inactive_grid.saved_cursor;
-            self.grid.cursor = self.grid.saved_cursor;
-        } else {
-            self.inactive_grid.saved_cursor = self.inactive_grid.cursor;
+            // Drop information about the primary screens saved cursor.
             self.grid.saved_cursor = self.grid.cursor;
 
-            // Reset wrapline status flag.
-            self.inactive_grid.cursor.input_needs_wrap = false;
+            // Reset alternate screen contents.
+            let template = self.inactive_grid.cursor.template;
+            self.inactive_grid.region_mut(..).each(|c| c.reset(&template));
         }
 
         mem::swap(&mut self.grid, &mut self.inactive_grid);

alacritty_terminal/tests/ref.rs

@@ -64,6 +64,8 @@ ref_tests! {
     clear_underline
     region_scroll_down
     wrapline_alt_toggle
+    saved_cursor
+    saved_cursor_alt
 }
 
 fn read_u8<P>(path: P) -> Vec<u8>

alacritty_terminal/tests/ref/saved_cursor/alacritty.recording

@@ -0,0 +1,8 @@
+[undeadleech@archhq saved_cursor]$ echo -e "\e7 \e(0 test \e8 xxx"
+7 (0 test 8 xxx
+[undeadleech@archhq saved_cursor]$ echo -e "\e[?1049h \e(0 test \e[?1049l xxx"
+[?1049h (0 test [?1049l xxx
+[undeadleech@archhq saved_cursor]$ echo -e "\e7 \e(0 \e[?1049h test \e[?1049l \e8 xxx"
+7 (0 [?1049h test [?1049l 8 xxx
+[undeadleech@archhq saved_cursor]$ exit
+exit

alacritty_terminal/tests/ref/saved_cursor/config.json

@@ -0,0 +1 @@
+{"history_size":0}

alacritty_terminal/tests/ref/saved_cursor/size.json

@@ -0,0 +1 @@
+{"width":1259.0,"height":683.0,"cell_width":9.0,"cell_height":19.0,"padding_x":4.0,"padding_y":9.0,"dpr":1.1666666666666667}

alacritty_terminal/tests/ref/saved_cursor_alt/alacritty.recording

@@ -0,0 +1,4 @@
+[undeadleech@archhq saved_cursor_alt]$ echo -e "\e(0\e[10;$(tput cols)H \e[?1049h\e7 \e[?1049l \e(B\e[H \e[?1049h test\e8xxx"
+(0 [?1049h7 [?1049l (B [?1049h test8xxx
+[undeadleech@archhq saved_cursor_alt]$ exit
+exit

alacritty_terminal/tests/ref/saved_cursor_alt/config.json

@@ -0,0 +1 @@
+{"history_size":0}

alacritty_terminal/tests/ref/saved_cursor_alt/size.json

@@ -0,0 +1 @@
+{"width":1259.0,"height":683.0,"cell_width":9.0,"cell_height":19.0,"padding_x":4.0,"padding_y":9.0,"dpr":1.1666666666666667}