From 252bd4eb41691d279957528c7aad8610cf242914 Mon Sep 17 00:00:00 2001
From: Lephe <sebastien.michelland@protonmail.com>
Date: Tue, 8 Nov 2022 22:22:21 +0100
Subject: [PATCH] keydev: add low-level filter for async keyboard handlers

---
 include/gint/drivers/keydev.h | 17 +++++++++++++++++
 src/keysc/keydev.c            | 13 +++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/gint/drivers/keydev.h b/include/gint/drivers/keydev.h
index 39132cd..40defec 100644
--- a/include/gint/drivers/keydev.h
+++ b/include/gint/drivers/keydev.h
@@ -10,6 +10,7 @@ extern "C" {
 #endif
 
 #include <gint/keyboard.h>
+#include <stdbool.h>
 
 /* Size of the buffer event queue */
 #define KEYBOARD_QUEUE_SIZE 32
@@ -128,6 +129,9 @@ typedef struct {
 
 } GPACKEDENUM keydev_transform_t;
 
+/* keydev_async_filter_t: Low-level asynchronous event filter. */
+typedef bool (*keydev_async_filter_t)(key_event_t event);
+
 /* keydev_t: Keyboard device
 
    This structure represents the state and settings of a keyboard device that
@@ -159,6 +163,13 @@ typedef struct {
 	/* Event transforms */
 	keydev_transform_t tr;
 
+	/* Asynchronous event filter. This is a low-level filter which is
+	   called when events are generated to process and filter them. It
+	   provides the unique ability to run keyboard-triggered code even if
+	   the program's main thread is busy, for instance running some sort of
+	   infinite loop. */
+	keydev_async_filter_t async_filter;
+
 	// <Delayed Modifiers>
 
 	/* delayed_* is set when the delayed modifier is active (after a press/
@@ -250,6 +261,12 @@ key_event_t keydev_unqueue_event(keydev_t *d);
    must be terminated by a 0 keycode. */
 bool keydev_idle(keydev_t *d, ...);
 
+/* keydev_async_filter(): Obtain current async filter */
+keydev_async_filter_t keydev_async_filter(keydev_t const *d);
+
+/* keydev_set_async_filter(): Set low-level async filter */
+void keydev_set_async_filter(keydev_t *d, keydev_async_filter_t filter);
+
 //---
 //	High-level API to read from the device
 //---
diff --git a/src/keysc/keydev.c b/src/keysc/keydev.c
index 05052ba..4242ed2 100644
--- a/src/keysc/keydev.c
+++ b/src/keysc/keydev.c
@@ -31,6 +31,9 @@ static int standard_repeater(GUNUSED int key, GUNUSED int duration, int count)
    Returns false if the event cannot be pushed. */
 bool keydev_queue_push(keydev_t *d, key_event_t ev)
 {
+	if(d->async_filter && !d->async_filter(ev))
+		return true;
+
 	int next = (d->queue_end + 1) % KEYBOARD_QUEUE_SIZE;
 	if(next == d->queue_next)
 	{
@@ -147,6 +150,16 @@ void keydev_tick(keydev_t *d, uint us)
 	}
 }
 
+keydev_async_filter_t keydev_async_filter(keydev_t const *d)
+{
+	return d->async_filter;
+}
+
+void keydev_set_async_filter(keydev_t *d, keydev_async_filter_t filter)
+{
+	d->async_filter = filter;
+}
+
 //---
 // Keyboard event generation
 //---