From c857042b45c64a63166ffd7ba6cafa4e950329b4 Mon Sep 17 00:00:00 2001
From: Philipp Zabel <p.zabel@pengutronix.de>
Date: Thu, 11 Mar 2021 16:22:26 +0100
Subject: [PATCH] backend-vnc: enable multi-backend support

Insert the backend into the weston_compositor::backend_list instead
of setting weston_compositor::backend. The compositor uses this to
determine whether the backend is capable of being loaded simultaneously
with other backends.

To stay backwards compatible, the VNC backend can be loaded as primary
backend. It also supports being loaded as secondary backend.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 libweston/backend-vnc/vnc.c | 65 +++++++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 24 deletions(-)

diff --git a/libweston/backend-vnc/vnc.c b/libweston/backend-vnc/vnc.c
index c91d429f..8865eb82 100644
--- a/libweston/backend-vnc/vnc.c
+++ b/libweston/backend-vnc/vnc.c
@@ -874,6 +874,8 @@ vnc_destroy(struct weston_backend *base)
 	struct weston_compositor *ec = backend->compositor;
 	struct weston_head *head, *next;
 
+	wl_list_remove(&backend->base.link);
+
 	wl_event_source_remove(backend->aml_event);
 
 	aml_unref(backend->aml);
@@ -1144,6 +1146,8 @@ vnc_backend_create(struct weston_compositor *compositor,
 	if (backend == NULL)
 		return NULL;
 
+	wl_list_init(&backend->base.link);
+
 	backend->compositor = compositor;
 	backend->base.shutdown = vnc_shutdown;
 	backend->base.destroy = vnc_destroy;
@@ -1155,7 +1159,7 @@ vnc_backend_create(struct weston_compositor *compositor,
 							 "Debug messages from VNC backend\n",
 							 NULL, NULL, NULL);
 
-	compositor->backend = &backend->base;
+	wl_list_insert(&compositor->backend_list, &backend->base.link);
 
 	backend->base.supported_presentation_clocks =
 			WESTON_PRESENTATION_CLOCKS_SOFTWARE;
@@ -1163,30 +1167,31 @@ vnc_backend_create(struct weston_compositor *compositor,
 	backend->formats_count = ARRAY_LENGTH(vnc_formats);
 	backend->formats = pixel_format_get_array(vnc_formats,
 						  backend->formats_count);
-
-	switch (config->renderer) {
-	case WESTON_RENDERER_AUTO:
-	case WESTON_RENDERER_PIXMAN:
-		if (weston_compositor_init_renderer(compositor,
-						    WESTON_RENDERER_PIXMAN,
-						    NULL) < 0)
+	if (!compositor->renderer) {
+		switch (config->renderer) {
+		case WESTON_RENDERER_AUTO:
+		case WESTON_RENDERER_PIXMAN:
+			if (weston_compositor_init_renderer(compositor,
+							    WESTON_RENDERER_PIXMAN,
+							    NULL) < 0)
+				goto err_compositor;
+			break;
+		case WESTON_RENDERER_GL: {
+			const struct gl_renderer_display_options options = {
+				.egl_platform = EGL_PLATFORM_SURFACELESS_MESA,
+				.formats = backend->formats,
+				.formats_count = backend->formats_count,
+			};
+			if (weston_compositor_init_renderer(compositor,
+							    WESTON_RENDERER_GL,
+							    &options.base) < 0)
+				goto err_compositor;
+			break;
+		}
+		default:
+			weston_log("Unsupported renderer requested\n");
 			goto err_compositor;
-		break;
-	case WESTON_RENDERER_GL: {
-		const struct gl_renderer_display_options options = {
-			.egl_platform = EGL_PLATFORM_SURFACELESS_MESA,
-			.formats = backend->formats,
-			.formats_count = backend->formats_count,
-		};
-		if (weston_compositor_init_renderer(compositor,
-						    WESTON_RENDERER_GL,
-						    &options.base) < 0)
-			goto err_compositor;
-		break;
-	}
-	default:
-		weston_log("Unsupported renderer requested\n");
-		goto err_compositor;
+		}
 	}
 
 	vnc_head_create(backend, "vnc");
@@ -1266,6 +1271,7 @@ err_output:
 	wl_list_for_each_safe(base, next, &compositor->head_list, compositor_link)
 		vnc_head_destroy(base);
 err_compositor:
+	wl_list_remove(&backend->base.link);
 	free(backend);
 	return NULL;
 }
@@ -1294,6 +1300,17 @@ weston_backend_init(struct weston_compositor *compositor,
 		return -1;
 	}
 
+	if (compositor->renderer) {
+		switch (compositor->renderer->type) {
+		case WESTON_RENDERER_PIXMAN:
+		case WESTON_RENDERER_GL:
+			break;
+		default:
+			weston_log("Renderer not supported by VNC backend\n");
+			return -1;
+		}
+	}
+
 	config_init_to_defaults(&config);
 	memcpy(&config, config_base, config_base->struct_size);