i3-companion: switch to Xlib to query XRandR state

bin/i3-companion

@@ -23,6 +23,8 @@ from i3ipc.aio import Connection
 from systemd import journal
 import ravel
 import dbussy
+from Xlib import display
+from Xlib.ext import randr
 
 
 def icon(font_number, char):
@@ -508,32 +510,37 @@ async def workspace_info(i3, event):
 
 
 @on(I3Event.OUTPUT, StartEvent)
-@static(last_setup={})
+@static(last_setup=None)
 @debounce(2)
 async def output_update(i3, event):
     """React to a XRandR change."""
-    proc = await asyncio.create_subprocess_exec(
-        "xrandr", "--current", stdout=asyncio.subprocess.PIPE
-    )
-    stdout, _ = await proc.communicate()
-    if proc.returncode != 0:
-        logger.warning(f"xrandr exited with {proc.returncode}")
-        return
-    stdout = stdout.decode("ascii")
-    xrandr_re = re.compile(
-        r"^"
-        r"(?P<output>\S+) connected"
-        r"(?: (?P<primary>primary))? "
-        r"(?P<geometry>\d+x\d+\+\d+\+\d+) "
-        r"\(.*?\) "
-        r"\d+mm x \d+mm"
-        r"$"
-    )
-    current_setup = {
-        mo.groups()
-        for mo in {xrandr_re.match(line) for line in stdout.split("\n")}
-        if mo
-    }
+
+    # Grab current setup. Synchronous, but it's short enough
+    d = display.Display()
+    screen = d.screen()
+    window = screen.root.create_window(0, 0, 1, 1, 1, screen.root_depth)
+    screen_resources = randr.get_screen_resources_current(window)
+    current_setup = set()
+    for output in screen_resources.outputs:
+        output_info = randr.get_output_info(
+            window, output, screen_resources.timestamp
+        )
+        if output_info.crtc == 0:
+            continue
+        crtc_info = randr.get_crtc_info(
+            window, output_info.crtc, output_info.timestamp
+        )
+        current_setup.add(
+            (
+                output_info.name,
+                crtc_info.width,
+                crtc_info.height,
+                crtc_info.x,
+                crtc_info.y,
+            )
+        )
+
+    # Compare to current setup
     if current_setup == output_update.last_setup:
         logger.debug("current xrandr setup unchanged")
         return
@@ -542,6 +549,7 @@ async def output_update(i3, event):
     if event is StartEvent:
         return
 
+    # Trigger changes
     logger.info("xrandr change detected")
     cmds = (
         "systemctl --user reload --no-block xsettingsd.service",