session-lock: properly handle disabled outputs

Outputs that are part of the layout but currently disabled (e.g. due
to use of wlr-output-power-management) are not correctly handled as
river currently waits for them to present a new locked frame before
sending the locked event.

This new frame never comes however since the output is disabled. Fix
this by maintaining the correct Output.lock_render_state as outputs
are enabled/disabled.

Additionally add missing maybeLock() calls to handle the case that all
outputs in the layout are disabled.

river/LockManager.zig

@@ -95,6 +95,8 @@ fn handleLock(listener: *wl.Listener(*wlr.SessionLockV1), lock: *wlr.SessionLock
         manager.lock_surfaces_timer.timerUpdate(200) catch {
             log.err("error setting lock surfaces timer, imperfect frames may be shown", .{});
             manager.state = .waiting_for_blank;
+            // This call is necessary in the case that all outputs in the layout are disabled.
+            manager.maybeLock();
         };
 
         {
@@ -138,6 +140,9 @@ fn handleLockSurfacesTimeout(manager: *LockManager) c_int {
         }
     }
 
+    // This call is necessary in the case that all outputs in the layout are disabled.
+    manager.maybeLock();
+
     return 0;
 }
 

river/Output.zig

@@ -507,6 +507,18 @@ fn handleEnable(listener: *wl.Listener(*wlr.Output), wlr_output: *wlr.Output) vo
     // Add the output to root.outputs and the output layout if it has not
     // already been added.
     if (wlr_output.enabled) server.root.addOutput(self);
+
+    if (wlr_output.enabled) {
+        switch (server.lock_manager.state) {
+            .unlocked => self.lock_render_state = .unlocked,
+            .waiting_for_lock_surfaces, .waiting_for_blank, .locked => {
+                assert(self.lock_render_state == .blanked);
+            },
+        }
+    } else {
+        // Disabling and re-enabling an output always blanks it.
+        self.lock_render_state = .blanked;
+    }
 }
 
 fn handleFrame(listener: *wl.Listener(*wlr.OutputDamage), _: *wlr.OutputDamage) void {