tests: Don't rely on build directory layout

Rather than having a hardcoded dependency on the build-directory layout,
use an explicit module-map environment variable, which rewrites requests
for modules and helper/libexec binaries to specific paths.

Pekka: This will help with migration to Meson where setting up the paths
according to autotools would be painful and unnecessary.

Emre: This should also help setting up the test suite after a
cross-compile.

Pekka: A caveat here is that this patch makes it slightly easier to load
external backends by abusing the module map. External backends are
specifically not supported in libweston.

Signed-off-by: Daniel Stone <daniels@collabora.com>

v2:

Fixed ivi_layout-test-plugin.c:wet_module_init().
Do not change the lookup name of ivi-layout.ivi.

Improved documentation of weston_module_path_from_env() and made it cope
with map strings that a) do not end with a semicolon, and b) have
multiple consecutive semicolons.

Let WESTON_MODULE_MAP be printed into the test log so that it is easier
to run tests manually.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emre Ucan <eucan@de.adit-jv.com>

Suggested by Emil: Use a variable for strlen(name).

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

compositor/main.c

@@ -652,7 +652,6 @@ weston_create_listening_socket(struct wl_display *display, const char *socket_na
 WL_EXPORT void *
 wet_load_module_entrypoint(const char *name, const char *entrypoint)
 {
-	const char *builddir = getenv("WESTON_BUILD_DIR");
 	char path[PATH_MAX];
 	void *module, *init;
 	size_t len;
@@ -661,10 +660,8 @@ wet_load_module_entrypoint(const char *name, const char *entrypoint)
 		return NULL;
 
 	if (name[0] != '/') {
-		if (builddir)
-			len = snprintf(path, sizeof path, "%s/.libs/%s", builddir,
-				       name);
-		else
+		len = weston_module_path_from_env(name, path, sizeof path);
+		if (len == 0)
 			len = snprintf(path, sizeof path, "%s/%s", MODULEDIR,
 				       name);
 	} else {
@@ -701,7 +698,6 @@ wet_load_module_entrypoint(const char *name, const char *entrypoint)
 	return init;
 }
 
-
 WL_EXPORT int
 wet_load_module(struct weston_compositor *compositor,
 	        const char *name, int *argc, char *argv[])
@@ -732,6 +728,24 @@ wet_load_shell(struct weston_compositor *compositor,
 	return 0;
 }
 
+WL_EXPORT char *
+wet_get_binary_path(const char *name)
+{
+	char path[PATH_MAX];
+	size_t len;
+
+	len = weston_module_path_from_env(name, path, sizeof path);
+	if (len > 0)
+		return strdup(path);
+
+	len = snprintf(path, sizeof path, "%s/%s",
+		       weston_config_get_libexec_dir(), name);
+	if (len >= sizeof path)
+		return NULL;
+
+	return strdup(path);
+}
+
 static int
 load_modules(struct weston_compositor *ec, const char *modules,
 	     int *argc, char *argv[], int32_t *xwayland)

compositor/text-backend.c

@@ -1047,14 +1047,10 @@ text_backend_configuration(struct text_backend *text_backend)
 	struct weston_config *config = wet_get_config(text_backend->compositor);
 	struct weston_config_section *section;
 	char *client;
-	int ret;
 
 	section = weston_config_get_section(config,
 					    "input-method", NULL, NULL);
-	ret = asprintf(&client, "%s/weston-keyboard",
-		       weston_config_get_libexec_dir());
-	if (ret < 0)
-		client = NULL;
+	client = wet_get_binary_path("weston-keyboard");
 	weston_config_section_get_string(section, "path",
 					 &text_backend->input_method.path,
 					 client);

compositor/weston-screenshooter.c

@@ -117,12 +117,10 @@ screenshooter_binding(struct weston_keyboard *keyboard,
 {
 	struct screenshooter *shooter = data;
 	char *screenshooter_exe;
-	int ret;
 
-	ret = asprintf(&screenshooter_exe, "%s/%s",
-		       weston_config_get_libexec_dir(),
-		       "/weston-screenshooter");
-	if (ret < 0) {
+
+	screenshooter_exe = wet_get_binary_path("weston-screenshooter");
+	if (!screenshooter_exe) {
 		weston_log("Could not construct screenshooter path.\n");
 		return;
 	}

compositor/weston.h

@@ -77,6 +77,9 @@ int
 module_init(struct weston_compositor *compositor,
 	    int *argc, char *argv[]);
 
+char *
+wet_get_binary_path(const char *name);
+
 int
 wet_load_xwayland(struct weston_compositor *comp);