From 9bb5b679b4292b7333360a2ae618f7b74124a096 Mon Sep 17 00:00:00 2001
From: "P. L. Lim" <2090236+pllim@users.noreply.github.com>
Date: Fri, 12 May 2023 20:53:26 -0400
Subject: [PATCH 1/2] Add center method to RangeSubsetState

---
 glue/core/subset.py            | 3 +++
 glue/core/tests/test_subset.py | 1 +
 2 files changed, 4 insertions(+)

diff --git a/glue/core/subset.py b/glue/core/subset.py
index 6d968455b..94ac01989 100644
--- a/glue/core/subset.py
+++ b/glue/core/subset.py
@@ -808,6 +808,9 @@ def to_mask(self, data, view=None):
         result = (x >= self.lo) & (x <= self.hi)
         return result
 
+    def center(self):
+        return (self.hi - self.lo) * 0.5 + self.lo
+
     def copy(self):
         return RangeSubsetState(self.lo, self.hi, self.att)
 
diff --git a/glue/core/tests/test_subset.py b/glue/core/tests/test_subset.py
index c9c1a9072..2b120e944 100644
--- a/glue/core/tests/test_subset.py
+++ b/glue/core/tests/test_subset.py
@@ -828,6 +828,7 @@ def test_range_subset_state(self):
 
         subset = self.data.new_subset()
         subset.subset_state = RangeSubsetState(1.1, 1.4, self.data.id['c'])
+        assert_allclose(subset.subset_state.center(), 1.25)
         assert_equal(self.data.subsets[0].to_mask(), [1, 1, 0, 0])
 
         data_clone = clone(self.data)

From 6699766c6fed34d83d1aecc13dc60ce043e06d17 Mon Sep 17 00:00:00 2001
From: "P. L. Lim" <2090236+pllim@users.noreply.github.com>
Date: Fri, 12 May 2023 21:04:40 -0400
Subject: [PATCH 2/2] Also implement move_to

---
 glue/core/subset.py            | 5 +++++
 glue/core/tests/test_subset.py | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/glue/core/subset.py b/glue/core/subset.py
index 94ac01989..8d8bc149e 100644
--- a/glue/core/subset.py
+++ b/glue/core/subset.py
@@ -811,6 +811,11 @@ def to_mask(self, data, view=None):
     def center(self):
         return (self.hi - self.lo) * 0.5 + self.lo
 
+    def move_to(self, new_cen):
+        dx = new_cen - self.center()
+        self.lo = self.lo + dx
+        self.hi = self.hi + dx
+
     def copy(self):
         return RangeSubsetState(self.lo, self.hi, self.att)
 
diff --git a/glue/core/tests/test_subset.py b/glue/core/tests/test_subset.py
index 2b120e944..45356072a 100644
--- a/glue/core/tests/test_subset.py
+++ b/glue/core/tests/test_subset.py
@@ -835,6 +835,11 @@ def test_range_subset_state(self):
 
         assert_equal(data_clone.subsets[0].to_mask(), [1, 1, 0, 0])
 
+        # Also test moving it.
+        subset.subset_state.move_to(2)
+        assert_allclose((subset.subset_state.lo, subset.subset_state.hi), (1.85, 2.15))
+        assert_allclose(subset.subset_state.center(), 2)
+
     def test_and_subset_state(self):
 
         subset = self.data.new_subset()