terminal/new: fix issue with resizing when cursor is in blank trailing

cell

src/terminal/Screen.zig

@@ -6556,6 +6556,7 @@ test "Screen: resize (no reflow) more cols with scrollback scrolled up" {
     try testing.expectEqual(@as(usize, 2), s.cursor.y);
 }
 
+// X
 // https://github.com/mitchellh/ghostty/issues/1159
 test "Screen: resize (no reflow) less cols with scrollback scrolled up" {
     const testing = std.testing;
@@ -6583,6 +6584,11 @@ test "Screen: resize (no reflow) less cols with scrollback scrolled up" {
         defer alloc.free(contents);
         try testing.expectEqualStrings(str, contents);
     }
+    {
+        const contents = try s.testString(alloc, .active);
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("6\n7\n8", contents);
+    }
 
     // Cursor remains at bottom
     try testing.expectEqual(@as(usize, 1), s.cursor.x);

src/terminal/new/PageList.zig

@@ -760,6 +760,29 @@ fn reflowPage(
                 // Move both our cursors forward
                 src_cursor.cursorForward();
                 dst_cursor.cursorForward();
+            } else cursor: {
+                // We made it through all our source columns. As a final edge
+                // case, if our cursor is in one of the blanks, we update it
+                // to the edge of this page.
+
+                // If we have no trailing empty cells, it can't be in the blanks.
+                if (trailing_empty == 0) break :cursor;
+
+                // If we have no cursor, nothing to update.
+                const c = cursor orelse break :cursor;
+                const offset = c.offset orelse break :cursor;
+
+                // If our cursor is on this page, and our x is greater than
+                // our end, we update to the edge.
+                if (&offset.page.data == src_cursor.page and
+                    offset.row_offset == src_cursor.y and
+                    c.x >= cols_len)
+                {
+                    c.offset = .{
+                        .page = dst_node,
+                        .row_offset = dst_cursor.y,
+                    };
+                }
             }
         } else {
             // We made it through all our source rows, we're done.
@@ -3297,6 +3320,68 @@ test "PageList resize reflow less cols cursor in unchanged row" {
     try testing.expectEqual(@as(size.CellCountInt, 0), cursor.y);
 }
 
+test "PageList resize reflow less cols cursor in blank cell" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 6, 2, null);
+    defer s.deinit();
+    try testing.expect(s.pages.first == s.pages.last);
+    const page = &s.pages.first.?.data;
+    for (0..s.rows) |y| {
+        for (0..2) |x| {
+            const rac = page.getRowAndCell(x, y);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = @intCast(x) },
+            };
+        }
+    }
+
+    // Set our cursor to be in a blank cell
+    var cursor: Resize.Cursor = .{ .x = 2, .y = 0 };
+
+    // Resize
+    try s.resize(.{ .cols = 4, .reflow = true, .cursor = &cursor });
+    try testing.expectEqual(@as(usize, 4), s.cols);
+    try testing.expectEqual(@as(usize, 2), s.totalRows());
+
+    // Our cursor should move to the first row
+    try testing.expectEqual(@as(size.CellCountInt, 2), cursor.x);
+    try testing.expectEqual(@as(size.CellCountInt, 0), cursor.y);
+}
+
+test "PageList resize reflow less cols cursor in final blank cell" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 6, 2, null);
+    defer s.deinit();
+    try testing.expect(s.pages.first == s.pages.last);
+    const page = &s.pages.first.?.data;
+    for (0..s.rows) |y| {
+        for (0..2) |x| {
+            const rac = page.getRowAndCell(x, y);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = @intCast(x) },
+            };
+        }
+    }
+
+    // Set our cursor to be in the final cell of our resized
+    var cursor: Resize.Cursor = .{ .x = 3, .y = 0 };
+
+    // Resize
+    try s.resize(.{ .cols = 4, .reflow = true, .cursor = &cursor });
+    try testing.expectEqual(@as(usize, 4), s.cols);
+    try testing.expectEqual(@as(usize, 2), s.totalRows());
+
+    // Our cursor should move to the first row
+    try testing.expectEqual(@as(size.CellCountInt, 3), cursor.x);
+    try testing.expectEqual(@as(size.CellCountInt, 0), cursor.y);
+}
+
 test "PageList resize reflow less cols blank lines" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/new/Screen.zig

@@ -2258,6 +2258,51 @@ test "Screen: resize (no reflow) more cols with scrollback scrolled up" {
     try testing.expectEqual(@as(size.CellCountInt, 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, 5, 3, 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(size.CellCountInt, 1), s.cursor.x);
+    try testing.expectEqual(@as(size.CellCountInt, 2), s.cursor.y);
+
+    s.scroll(.{ .delta_row = -4 });
+    {
+        const contents = try s.dumpStringAlloc(alloc, .{ .viewport = .{} });
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("2\n3\n4", contents);
+    }
+
+    try s.resize(4, 3);
+    {
+        const contents = try s.dumpStringAlloc(alloc, .{ .screen = .{} });
+        defer alloc.free(contents);
+        try testing.expectEqualStrings(str, contents);
+    }
+    {
+        const contents = try s.dumpStringAlloc(alloc, .{ .active = .{} });
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("6\n7\n8", contents);
+    }
+
+    // Cursor remains at bottom
+    try testing.expectEqual(@as(size.CellCountInt, 1), s.cursor.x);
+    try testing.expectEqual(@as(size.CellCountInt, 2), s.cursor.y);
+
+    // Old implementation doesn't do this but it makes sense to me:
+    // {
+    //     const contents = try s.dumpStringAlloc(alloc, .{ .viewport = .{} });
+    //     defer alloc.free(contents);
+    //     try testing.expectEqualStrings("2\n3\n4", contents);
+    // }
+}
+
 test "Screen: resize more cols with reflow that fits full width" {
     const testing = std.testing;
     const alloc = testing.allocator;