modules/*: instantiate and use setups

Now modules allocate and return an opaque setup pointer in
res_setup when they implement a setup method.

Defaults are utilized when ${module}_create_context() receives a
NULL setup.  The default setup used in this case should match the
defaults/preferred values emitted by the module's setup method.
But performing setup should always be optional, so a NULL setup
provided to create_context() is to be expected.

No cleanup of these setup instances is currently performed, so
it's a small memory leak for now.  Since these are opaque and may
contain nested references to other allocations, simply using
free() somewhere in the frontend is insufficient.  There will
probably need to be something like a til_module_t.setup_free()
method added in the future which modules may assign libc's free()
to when appropriate, or their own more elaborate version.

Lifecycle for the settings is very simple; the setup method
returns an instance, the caller is expected to free it when no
longer needed (once free is implemented).  The create_context
consumer of a given setup must make its own copy of the settings
if necessary, and may not keep a reference - it must assume the
setup will be freed immediately after create_context() returns.
This enables the ability to reuse a setup instance across
multiple create_context() calls if desired, one can imagine
something like running the same module with the same settings
multiple times across multiple displays for instance.  If the
module has significant entropy the output will differ despite
being configured identically...

With this commit one may change settings for any of the modules
*while* the modules are actively rendering a given context, and
the settings should *not* be visible.  They should only affect
the context they're supplied to.

1 files changed, 23 insertions, 15 deletions

diff --git a/src/modules/compose/compose.c b/src/modules/compose/compose.c
index adf638c..da9215b 100644
--- a/src/modules/compose/compose.c
+++ b/src/modules/compose/compose.c
@@ -36,13 +36,19 @@ typedef struct compose_context_t {
 	compose_layer_t		layers[];
 } compose_context_t;
 
+typedef struct compose_setup_t {
+	size_t			n_layers;
+	char			*layers[];
+} compose_setup_t;
+
 static void * compose_create_context(unsigned ticks, unsigned num_cpus, void *setup);
 static void compose_destroy_context(void *context);
 static void compose_prepare_frame(void *context, unsigned ticks, unsigned n_cpus, til_fb_fragment_t *fragment, til_fragmenter_t *res_fragmenter);
 static int compose_setup(const til_settings_t *settings, til_setting_t **res_setting, const til_setting_desc_t **res_desc, void **res_setup);
 
-static char	*compose_default_layers[] = { "drizzle", "stars", "spiro", "plato", NULL };
-static char	**compose_layers;
+static compose_setup_t compose_default_setup = {
+	.layers = { "drizzle", "stars", "spiro", "plato", NULL },
+};
 
 
 til_module_t	compose_module = {
@@ -57,14 +63,13 @@ til_module_t	compose_module = {
 
 static void * compose_create_context(unsigned ticks, unsigned num_cpus, void *setup)
 {
-	char			**layers = compose_default_layers;
 	compose_context_t	*ctxt;
-	int			n;
+	size_t			n;
 
-	if (compose_layers)
-		layers = compose_layers;
+	if (!setup)
+		setup = &compose_default_setup;
 
-	for (n = 0; layers[n]; n++);
+	for (n = 0; ((compose_setup_t *)setup)->layers[n]; n++);
 
 	ctxt = calloc(1, sizeof(compose_context_t) + n * sizeof(compose_layer_t));
 	if (!ctxt)
@@ -75,7 +80,7 @@ static void * compose_create_context(unsigned ticks, unsigned num_cpus, void *se
 	for (int i = 0; i < n; i++) {
 		const til_module_t	*module;
 
-		module = til_lookup_module(layers[i]);
+		module = til_lookup_module(((compose_setup_t *)setup)->layers[i]);
 
 		ctxt->layers[i].module = module;
 		(void) til_module_create_context(module, ticks, NULL, &ctxt->layers[i].module_ctxt);
@@ -127,7 +132,8 @@ static int compose_setup(const til_settings_t *settings, til_setting_t **res_set
 		return r;
 
 	/* turn layers colon-separated list into a null-terminated array of strings */
-	{
+	if (res_setup) {
+		compose_setup_t		*setup = NULL;
 		const til_module_t	**modules;
 		size_t			n_modules;
 		char			*toklayers, *layer;
@@ -144,8 +150,8 @@ static int compose_setup(const til_settings_t *settings, til_setting_t **res_set
 			return -EINVAL;
 
 		do {
-			char	**new;
-			size_t	i;
+			compose_setup_t	*new;
+			size_t		i;
 
 			/* other meta-modules like montage and rtv may need to
 			 * have some consideration here, but for now I'm just
@@ -163,16 +169,18 @@ static int compose_setup(const til_settings_t *settings, til_setting_t **res_set
 			if (i >= n_modules)
 				return -EINVAL;
 
-			new = realloc(compose_layers, n * sizeof(*compose_layers));
+			new = realloc(setup, sizeof(*setup) + n * sizeof(*setup->layers));
 			if (!new)
 				return -ENOMEM;
 
-			new[n - 2] = layer;
-			new[n - 1] = NULL;
+			new->layers[n - 2] = layer;
+			new->layers[n - 1] = NULL;
 			n++;
 
-			compose_layers = new;
+			setup = new;
 		} while (layer = strtok(NULL, ":"));
+
+		*res_setup = setup;
 	}
 
 	return 0;