feat: auto-below placement re-reads the live layout

2 files changed, 21 insertions, 0 deletions

diff --git a/deckit/display.py b/deckit/display.py
index 50fa3f6..c1a74b1 100644
--- a/deckit/display.py
+++ b/deckit/display.py
@@ -30,6 +30,12 @@ def tablet_resolution(cfg: dict, adb=None) -> str:
     return f"{w}x{h}"
 
 
+def below_position(ref: dict, resolution: str, scale=1) -> str:
+    """Center a monitor below `ref` (a hyprctl monitor dict)."""
+    width = round(int(re.match(r"(\d+)x", resolution).group(1)) / scale)
+    return f"{ref['x'] + (ref['width'] - width) // 2}x{ref['y'] + ref['height']}"
+
+
 def hypr_lua(cfg: dict) -> bool:
     mode = cfg.get("hyprland", "auto")
     if mode == "auto":
@@ -72,9 +78,14 @@ def setup_display(cfg: dict, run_cmd=None, popen=None) -> None:
     if not any(m["name"] == mon for m in monitors):
         run_cmd(["hyprctl", "output", "create", "headless", mon])
         time.sleep(1)
+    # Creating the output can re-flow the layout, so read it again.
+    monitors = json.loads(run_cmd(["hyprctl", "monitors", "-j"]) or "[]")
     mode = f"{tablet_resolution(cfg)}@{d.get('refresh', 60)}"
     pos = d.get("position", "auto-right")
     scale = d.get("scale", 1)
+    if pos in ("auto-below", "below"):
+        ref = next((m for m in monitors if m["name"] != mon), monitors[0])
+        pos = below_position(ref, mode, scale)
     if hypr_lua(cfg):
         run_cmd(["hyprctl", "eval",
                  f'hl.monitor({{output="{mon}", mode="{mode}", position="{pos}", scale={scale}}})'])
diff --git a/tests/test_display.py b/tests/test_display.py
index b69759a..7f90fe4 100644
--- a/tests/test_display.py
+++ b/tests/test_display.py
@@ -22,6 +22,16 @@ class Resolution(unittest.TestCase):
             "2560x1600")
 
 
+class Below(unittest.TestCase):
+    def test_centered_under_the_reference(self):
+        ref = {"x": 0, "y": 0, "width": 2560, "height": 1080}
+        self.assertEqual(display.below_position(ref, "1280x800"), "640x1080")
+
+    def test_honours_the_reference_offset(self):
+        ref = {"x": 0, "y": -540, "width": 2560, "height": 1080}
+        self.assertEqual(display.below_position(ref, "1280x800"), "640x540")
+
+
 class Swaybg(unittest.TestCase):
     def test_finds_the_image_for_an_output(self):
         root = Path(tempfile.mkdtemp())