Merge pull request #131 from mosaic-org/mosaic#130

fix: fixes #130 by adding overflowing_sub

src/terminal_pane/scroll.rs

@@ -266,7 +266,7 @@ impl CursorPosition {
         self.column_index += count;
     }
     pub fn move_backwards(&mut self, count: usize) {
-        self.column_index -= count;
+        self.column_index = u32::overflowing_sub(self.column_index as u32, count as u32).0 as usize;
     }
     pub fn move_to_next_linewrap(&mut self) {
         self.line_index.1 += 1;

src/tests/integration/compatibility.rs

@@ -461,3 +461,26 @@ pub fn git_diff_scrollup() {
         assert_snapshot!(snapshot);
     }
 }
+
+#[test]
+pub fn emacs_longbuf() {
+    let fake_win_size = PositionAndSize {
+        columns: 284,
+        rows: 60,
+        x: 0,
+        y: 0,
+    };
+    let fixture_name = "emacs_longbuf_tutorial";
+    let mut fake_input_output = get_fake_os_input(&fake_win_size, fixture_name);
+    fake_input_output.add_terminal_input(&[&COMMAND_TOGGLE, &COMMAND_TOGGLE, &QUIT]);
+    start(Box::new(fake_input_output.clone()), Opt::default());
+    let output_frames = fake_input_output
+        .stdout_writer
+        .output_frames
+        .lock()
+        .unwrap();
+    let snapshots = get_output_frame_snapshots(&output_frames, &fake_win_size);
+    for snapshot in snapshots {
+        assert_snapshot!(snapshot);
+    }
+}

src/tests/integration/snapshots/mosaic__tests__integration__compatibility__emacs_longbuf-2.snap

@@ -0,0 +1,64 @@
+---
+source: src/tests/integration/compatibility.rs
+expression: snapshot
+---
+➜  mosaic git:(mosaic#130) emacs                                                                                                                                                                                                                                                            
+➜  mosaic git:(mosaic#130) emacs -nw                                                                                                                                                                                                                                                        
+➜  mosaic git:(mosaic#130) exit                                                                                                                                                                                                                                                             
+█                                                                                                                                                                                                                                                                                           
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src/tests/integration/snapshots/mosaic__tests__integration__compatibility__emacs_longbuf-3.snap

@@ -0,0 +1,64 @@
+---
+source: src/tests/integration/compatibility.rs
+expression: snapshot
+---
+➜  mosaic git:(mosaic#130) emacs -nw                                                                                                                                                                                                                                                        
+➜  mosaic git:(mosaic#130) exit                                                                                                                                                                                                                                                             
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+Bye from Mosaic!█                                                                                                                                                                                                                                                                           

src/tests/integration/snapshots/mosaic__tests__integration__compatibility__emacs_longbuf.snap

@@ -0,0 +1,64 @@
+---
+source: src/tests/integration/compatibility.rs
+expression: snapshot
+---
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