From 8409b74ec202aefba9e499ee8f87b07cbb0cf128 Mon Sep 17 00:00:00 2001
From: Derek Foreman <derek.foreman@collabora.com>
Date: Tue, 26 Jul 2022 16:17:17 -0500
Subject: [PATCH] libweston: Don't move outputs during enable

This is pretty counter-intuitive, and should probably happen outside of
the core in the front end while configuring the outputs.

Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
---
 compositor/main.c      | 36 ++++++++++++++++++++++++++++++++++++
 libweston/compositor.c | 13 +------------
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/compositor/main.c b/compositor/main.c
index c388d861..6eba91e7 100644
--- a/compositor/main.c
+++ b/compositor/main.c
@@ -1707,6 +1707,38 @@ wet_head_tracker_create(struct wet_compositor *compositor,
 	weston_head_add_destroy_listener(head, &track->head_destroy_listener);
 }
 
+/* Place output exactly to the right of the most recently enabled output.
+ *
+ * Historically, we haven't given much thought to output placement,
+ * simply adding outputs in a horizontal line as they're enabled. This
+ * function simply sets an output's x coordinate to the right of the
+ * most recently enabled output, and its y to zero.
+ *
+ * If you're adding new calls to this function, you're also not giving
+ * much thought to output placement, so please consider carefully if
+ * it's really doing what you want.
+ *
+ * You especially don't want to use this for any code that won't
+ * immediately enable the passed output.
+ */
+static void
+weston_output_lazy_align(struct weston_output *output)
+{
+	struct weston_compositor *c;
+	struct weston_output *peer;
+	int next_x = 0;
+
+	/* Put this output to the right of the most recently enabled output */
+	c = output->compositor;
+	if (!wl_list_empty(&c->output_list)) {
+		peer = container_of(c->output_list.prev,
+				    struct weston_output, link);
+		next_x = peer->x + peer->width;
+	}
+	output->x = next_x;
+	output->y = 0;
+}
+
 static void
 simple_head_enable(struct wet_compositor *wet, struct weston_head *head)
 {
@@ -1723,6 +1755,8 @@ simple_head_enable(struct wet_compositor *wet, struct weston_head *head)
 		return;
 	}
 
+	weston_output_lazy_align(output);
+
 	if (wet->simple_output_configure)
 		ret = wet->simple_output_configure(output);
 	if (ret < 0) {
@@ -2359,6 +2393,8 @@ drm_try_enable(struct weston_output *output,
 {
 	/* Try to enable, and detach heads one by one until it succeeds. */
 	while (!output->enabled) {
+		weston_output_lazy_align(output);
+
 		if (weston_output_enable(output) == 0)
 			return 0;
 
diff --git a/libweston/compositor.c b/libweston/compositor.c
index 9c1768d2..303f3aa9 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -7268,11 +7268,8 @@ weston_output_create_heads_string(struct weston_output *output)
 WL_EXPORT int
 weston_output_enable(struct weston_output *output)
 {
-	struct weston_compositor *c = output->compositor;
-	struct weston_output *iterator;
 	struct weston_head *head;
 	char *head_names;
-	int x = 0, y = 0;
 
 	if (output->enabled) {
 		weston_log("Error: attempt to enable an enabled output '%s'\n",
@@ -7297,20 +7294,12 @@ weston_output_enable(struct weston_output *output)
 		assert(head->model);
 	}
 
-	iterator = container_of(c->output_list.prev,
-				struct weston_output, link);
-
-	if (!wl_list_empty(&c->output_list))
-		x = iterator->x + iterator->width;
-
 	/* Make sure the scale is set up */
 	assert(output->scale);
 
 	/* Make sure we have a transform set */
 	assert(output->transform != UINT32_MAX);
 
-	output->x = x;
-	output->y = y;
 	output->dirty = 1;
 	output->original_scale = output->scale;
 
@@ -7319,7 +7308,7 @@ weston_output_enable(struct weston_output *output)
 
 	weston_output_transform_scale_init(output, output->transform, output->scale);
 
-	weston_output_init_geometry(output, x, y);
+	weston_output_init_geometry(output, output->x, output->y);
 	weston_output_damage(output);
 
 	wl_list_init(&output->animation_list);