Output: fix possible assertion failure on enable

Currently if we disable an output due to a wlr-output-power-management
protocol request we do not update Output.lock_render_state properly.

This is fine if the output is also re-enabled using the
wlr-output-power-management protocol but causes an assertion failure
if it is re-enabled using wlr-output-management instead.

river/Output.zig

@@ -432,7 +432,7 @@ fn handleRequestState(listener: *wl.Listener(*wlr.Output.event.RequestState), ev
 pub fn applyState(output: *Output, state: *wlr.Output.State) error{CommitFailed}!void {
 
     // We need to be precise about this state change to make assertions
-    // in handleEnableDisable() possible.
+    // in updateLockRenderStateOnEnableDisable() possible.
     const enable_state_change = state.committed.enabled and
         (state.enabled != output.wlr_output.enabled);
 
@@ -452,6 +452,18 @@ pub fn applyState(output: *Output, state: *wlr.Output.State) error{CommitFailed}
 }
 
 fn handleEnableDisable(output: *Output) void {
+    output.updateLockRenderStateOnEnableDisable();
+
+    if (output.wlr_output.enabled) {
+        // Add the output to root.active_outputs and the output layout if it has not
+        // already been added.
+        server.root.activateOutput(output);
+    } else {
+        server.root.deactivateOutput(output);
+    }
+}
+
+pub fn updateLockRenderStateOnEnableDisable(output: *Output) void {
     // We can't assert the current state of normal_content/locked_content
     // here as this output may be newly created.
     if (output.wlr_output.enabled) {
@@ -467,16 +479,11 @@ fn handleEnableDisable(output: *Output) void {
                 output.locked_content.node.setEnabled(true);
             },
         }
-        // Add the output to root.active_outputs and the output layout if it has not
-        // already been added.
-        server.root.activateOutput(output);
     } else {
         // Disabling and re-enabling an output always blanks it.
         output.lock_render_state = .blanked;
         output.normal_content.node.setEnabled(false);
         output.locked_content.node.setEnabled(true);
-
-        server.root.deactivateOutput(output);
     }
 }
 

river/Root.zig

@@ -846,18 +846,37 @@ fn handlePowerManagerSetMode(
     _: *wl.Listener(*wlr.OutputPowerManagerV1.event.SetMode),
     event: *wlr.OutputPowerManagerV1.event.SetMode,
 ) void {
-    const enable = event.mode == .on;
+    // The output may have been destroyed, in which case there is nothing to do
+    const output = @as(?*Output, @ptrFromInt(event.output.data)) orelse return;
 
-    const log_text = if (enable) "Enabling" else "Disabling";
+    std.log.debug("client requested dpms {s} for output {s}", .{
-    std.log.scoped(.output_manager).debug(
+        @tagName(event.mode),
-        "{s} dpms for output {s}",
+        event.output.name,
-        .{ log_text, event.output.name },
+    });
-    );
 
-    event.output.enable(enable);
+    const requested = event.mode == .on;
-    event.output.commit() catch {
+
-        std.log.scoped(.server).err("output commit failed for {s}", .{event.output.name});
+    if (output.wlr_output.enabled == requested) {
-    };
+        std.log.debug("output {s} dpms is already {s}, ignoring request", .{
+            event.output.name,
+            @tagName(event.mode),
+        });
+        return;
+    }
+
+    {
+        var state = wlr.Output.State.init();
+        defer state.finish();
+
+        state.setEnabled(requested);
+
+        if (!output.wlr_output.commitState(&state)) {
+            std.log.scoped(.server).err("output commit failed for {s}", .{output.wlr_output.name});
+            return;
+        }
+    }
+
+    output.updateLockRenderStateOnEnableDisable();
 }
 
 fn handleSetGamma(