Add "integrate" node type complementary to "differentiate"

Makefile

@@ -12,7 +12,7 @@ CPPFLAGS += $(shell pkg-config --cflags $(DEPS))
 LDLIBS += $(shell pkg-config --libs $(DEPS))
 INTERP ?=
 MAIN = main
-OBJS = main.o events.o processing.o graph.o config.o event_code_names.o hash_table.o queue.o module_registry.o event_predicate.o nodes/getchar.o nodes/print.o nodes/evdev.o nodes/tee.o nodes/router.o nodes/modifiers.o nodes/modify_predicate.o nodes/uinput.o nodes/assign.o nodes/differentiate.o nodes/scale.o nodes/window.o
+OBJS = main.o events.o processing.o graph.o config.o event_code_names.o hash_table.o queue.o module_registry.o event_predicate.o nodes/getchar.o nodes/print.o nodes/evdev.o nodes/tee.o nodes/router.o nodes/modifiers.o nodes/modify_predicate.o nodes/uinput.o nodes/assign.o nodes/differentiate.o nodes/integrate.o nodes/scale.o nodes/window.o
 
 all: $(MAIN)
 

config.cfg

@@ -3,7 +3,8 @@ constants = {
 };
 
 enums = {
-	namespaces: ["stdin", "clickpad"];
+	namespaces: ["stdin", "clickpad", "variable"];
+	variables: ["num_touches"];
 };
 
 predicates = {
@@ -23,6 +24,17 @@ predicates = {
 			}
 		);
 	};
+	abs_event = {
+		type = "and";
+		args = (
+			"is_evdev",
+			{
+				type = "code_major";
+				min = "event_type.ABS";
+				max = "event_type.ABS";
+			}
+		);
+	};
 	btn_touch_event = {
 		type = "and";
 		args = (
@@ -34,6 +46,17 @@ predicates = {
 			}
 		);
 	};
+	touch_tracking_id = {
+		type = "and";
+		args = (
+			"abs_event",
+			{
+				type = "code_minor";
+				min = "absolute_axis.MT_TRACKING_ID";
+				max = "absolute_axis.MT_TRACKING_ID";
+			}
+		);
+	};
 	payload_zero = {
 		type = "payload";
 		min = 0;
@@ -44,6 +67,22 @@ predicates = {
 		min = 1;
 		max = 1;
 	};
+	payload_negative = {
+		type = "payload";
+		max = -1;
+	};
+	payload_nonnegative = {
+		type = "payload";
+		min = 0;
+	};
+	touch_start = {
+		type = "and";
+		args = ["touch_tracking_id", "payload_nonnegative"];
+	};
+	touch_end = {
+		type = "and";
+		args = ["touch_tracking_id", "payload_negative"];
+	};
 	touch_held = {
 		type = "accept";
 		inverted = 1;
@@ -78,7 +117,9 @@ nodes = {
 					type = "or";
 					inverted = 1;
 					args = ["key_event"];
-				}
+				},
+				"touch_start",
+				"touch_end"
 			);
 		};
 	};
@@ -116,6 +157,24 @@ nodes = {
 			);
 		};
 	};
+	set_one = {
+		type = "assign";
+		options = {
+			payload = 1;
+		};
+	};
+	count_touches = {
+		// This exact usecase may be implemented using events like button_event.TOOL_DOUBLETAP, button_event.TOOL_TRIPLETAP, button_event.TOOL_QUADTAP, button_event.TOOL_QUINTTAP
+		type = "integrate";
+	};
+	set_variable_num_touches = {
+		type = "assign";
+		options = {
+			namespace = "namespaces.variable";
+			major = "variables.num_touches";
+			minor = 0;
+		};
+	};
 };
 
 channels = ({
@@ -139,6 +198,21 @@ channels = ({
 }, {
 	from: ("clickpad", 1);
 	to: ("update_touch_held", 0);
+}, {
+	from: ("select_key_events", 2);  // touch_start
+	to: ("set_one", 0);
+}, {
+	from: ("set_one", 0);
+	to: ("count_touches", 0);
+}, {
+	from: ("select_key_events", 3);  // touch_end
+	to: ("count_touches", 1);
+}, {
+	from: ("count_touches", 0);
+	to: ("set_variable_num_touches", 0);
+}, {
+	from: ("set_variable_num_touches", 0);
+	to: ("print", 2);
 });
 
 // vim: ft=libconfig

nodes/integrate.c

@@ -0,0 +1,78 @@
+#include "../graph.h"
+#include "../module_registry.h"
+
+typedef struct {
+	GraphNode as_GraphNode;
+	int64_t total;
+} IntegrateGraphNode;
+
+static bool
+handle_event(EventPositionBase * self, EventNode * event)
+{
+	IntegrateGraphNode *node = DOWNCAST(IntegrateGraphNode, GraphNode, DOWNCAST(GraphNode, EventPositionBase, self));
+	size_t count = node->as_GraphNode.outputs.length;
+	if (!count) {
+		event_destroy(event);
+		return true;
+	}
+
+	int64_t total = node->total;
+	total += event->data.payload;
+	event->data.payload = total;
+	node->total = total;
+
+	graph_node_broadcast_forward_event(&node->as_GraphNode, event);
+	return true;
+}
+
+static GraphNode *
+create(GraphNodeSpecification * spec, GraphNodeConfig * config, InitializationEnvironment * env)
+{
+	(void) config;
+	(void) env;
+	IntegrateGraphNode * node = T_ALLOC(1, IntegrateGraphNode);
+	if (!node) {
+		return NULL;
+	}
+
+	int64_t initial = 0;
+	if (config->options) {
+		initial = env_resolve_constant(env, config_setting_get_member(config->options, "initial"));
+	}
+
+	*node = (IntegrateGraphNode) {
+		.as_GraphNode = {
+			.as_EventPositionBase = {
+				.handle_event = &handle_event,
+				.waiting_new_event = false,
+			},
+			.specification = spec,
+			.inputs = EMPTY_GRAPH_CHANNEL_LIST,
+			.outputs = EMPTY_GRAPH_CHANNEL_LIST,
+		},
+		.total = initial,
+	};
+	return &node->as_GraphNode;
+}
+
+static void destroy
+(GraphNodeSpecification * self, GraphNode * target)
+{
+	(void) self;
+	free(target);
+}
+
+GraphNodeSpecification nodespec_integrate = (GraphNodeSpecification) {
+	.create = &create,
+	.destroy = &destroy,
+	.register_io = NULL,
+	.name = "integrate",
+	.documentation = "Calculates a running sum of previous event payloads and replaces with it the current one\nAccepts events on any connector\nSends events on all connectors"
+	                 "\nOption 'initial' (optional): the initial partial sum value"
+	,
+};
+
+MODULE_CONSTRUCTOR(init)
+{
+	register_graph_node_specification(&nodespec_integrate);
+}