From 8dec751a6d84335fb04288b8efab6dd5c90288d3 Mon Sep 17 00:00:00 2001
From: Isaac Freund <ifreund@ifreund.xyz>
Date: Fri, 9 Oct 2020 15:28:07 +0200
Subject: [PATCH] layer-shell: error on 0 dimension without anchors

The protocol requires clients to set opposing anchors when requesting
a width or height of 0.

The goal of this patch is not to break clients that rely on this
behavior but to improve the consistency of the layer shell ecosystem
through adherence to the protocol.
---
 types/wlr_layer_shell_v1.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/types/wlr_layer_shell_v1.c b/types/wlr_layer_shell_v1.c
index d83b22b8..bc681117 100644
--- a/types/wlr_layer_shell_v1.c
+++ b/types/wlr_layer_shell_v1.c
@@ -307,6 +307,26 @@ static void layer_surface_role_commit(struct wlr_surface *wlr_surface) {
 		return;
 	}
 
+	const uint32_t horiz = ZWLR_LAYER_SURFACE_V1_ANCHOR_LEFT |
+		ZWLR_LAYER_SURFACE_V1_ANCHOR_RIGHT;
+	if (surface->client_pending.desired_width == 0 &&
+		(surface->client_pending.anchor & horiz) != horiz) {
+		wl_resource_post_error(surface->resource,
+			ZWLR_LAYER_SURFACE_V1_ERROR_INVALID_SIZE,
+			"width 0 requested without setting left and right anchors");
+		return;
+	}
+
+	const uint32_t vert = ZWLR_LAYER_SURFACE_V1_ANCHOR_TOP |
+		ZWLR_LAYER_SURFACE_V1_ANCHOR_BOTTOM;
+	if (surface->client_pending.desired_height == 0 &&
+		(surface->client_pending.anchor & vert) != vert) {
+		wl_resource_post_error(surface->resource,
+			ZWLR_LAYER_SURFACE_V1_ERROR_INVALID_SIZE,
+			"height 0 requested without setting top and bottom anchors");
+		return;
+	}
+
 	if (surface->closed) {
 		// Ignore commits after the compositor has closed it
 		return;