Merge pull request #1160 from mitchellh/cursor-scroll

terminal: resize cols should treat old cursor pos as active point

src/terminal/Screen.zig

@@ -2734,7 +2734,7 @@ pub fn resize(self: *Screen, rows: usize, cols: usize) !void {
 
         // Convert our cursor coordinates to screen coordinates because
         // we may have to reflow the cursor if the line it is on is unwrapped.
-        const cursor_pos = (point.Viewport{
+        const cursor_pos = (point.Active{
             .x = old.cursor.x,
             .y = old.cursor.y,
         }).toScreen(&old);
@@ -2948,7 +2948,7 @@ pub fn resize(self: *Screen, rows: usize, cols: usize) !void {
 
         // Convert our cursor coordinates to screen coordinates because
         // we may have to reflow the cursor if the line it is on is moved.
-        const cursor_pos = (point.Viewport{
+        const cursor_pos = (point.Active{
             .x = old.cursor.x,
             .y = old.cursor.y,
         }).toScreen(&old);
@@ -6372,6 +6372,72 @@ test "Screen: resize more cols perfect split" {
     try s.resize(3, 10);
 }
 
+// https://github.com/mitchellh/ghostty/issues/1159
+test "Screen: resize (no reflow) more cols with scrollback scrolled up" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 3, 5, 5);
+    defer s.deinit();
+    const str = "1\n2\n3\n4\n5\n6\n7\n8";
+    try s.testWriteString(str);
+
+    // Cursor at bottom
+    try testing.expectEqual(@as(usize, 1), s.cursor.x);
+    try testing.expectEqual(@as(usize, 2), s.cursor.y);
+
+    try s.scroll(.{ .viewport = -4 });
+    {
+        const contents = try s.testString(alloc, .viewport);
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("2\n3\n4", contents);
+    }
+
+    try s.resize(3, 8);
+    {
+        const contents = try s.testString(alloc, .screen);
+        defer alloc.free(contents);
+        try testing.expectEqualStrings(str, contents);
+    }
+
+    // Cursor remains at bottom
+    try testing.expectEqual(@as(usize, 1), s.cursor.x);
+    try testing.expectEqual(@as(usize, 2), s.cursor.y);
+}
+
+// https://github.com/mitchellh/ghostty/issues/1159
+test "Screen: resize (no reflow) less cols with scrollback scrolled up" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 3, 5, 5);
+    defer s.deinit();
+    const str = "1\n2\n3\n4\n5\n6\n7\n8";
+    try s.testWriteString(str);
+
+    // Cursor at bottom
+    try testing.expectEqual(@as(usize, 1), s.cursor.x);
+    try testing.expectEqual(@as(usize, 2), s.cursor.y);
+
+    try s.scroll(.{ .viewport = -4 });
+    {
+        const contents = try s.testString(alloc, .viewport);
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("2\n3\n4", contents);
+    }
+
+    try s.resize(3, 4);
+    {
+        const contents = try s.testString(alloc, .screen);
+        defer alloc.free(contents);
+        try testing.expectEqualStrings(str, contents);
+    }
+
+    // Cursor remains at bottom
+    try testing.expectEqual(@as(usize, 1), s.cursor.x);
+    try testing.expectEqual(@as(usize, 2), s.cursor.y);
+}
+
 test "Screen: resize more cols no reflow preserves semantic prompt" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/point.zig

@@ -6,6 +6,34 @@ const Screen = terminal.Screen;
 // use different types so that we can lean on type-safety to get the
 // exact expected type of point.
 
+/// Active is a point within the active part of the screen.
+pub const Active = struct {
+    x: usize = 0,
+    y: usize = 0,
+
+    pub fn toScreen(self: Active, screen: *const Screen) ScreenPoint {
+        return .{
+            .x = self.x,
+            .y = screen.history + self.y,
+        };
+    }
+
+    test "toScreen with scrollback" {
+        const testing = std.testing;
+        const alloc = testing.allocator;
+
+        var s = try Screen.init(alloc, 3, 5, 3);
+        defer s.deinit();
+        const str = "1\n2\n3\n4\n5\n6\n7\n8";
+        try s.testWriteString(str);
+
+        try testing.expectEqual(ScreenPoint{
+            .x = 1,
+            .y = 5,
+        }, (Active{ .x = 1, .y = 2 }).toScreen(&s));
+    }
+};
+
 /// Viewport is a point within the viewport of the screen.
 pub const Viewport = struct {
     x: usize = 0,