Add evdev_frame_append_one()

This is the most common usage, let's add a helper.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1245>

src/evdev-frame.h

@@ -476,6 +476,21 @@ evdev_frame_append(struct evdev_frame *frame,
 	return 0;
 }
 
+static inline int
+evdev_frame_append_one(struct evdev_frame *frame, evdev_usage_t usage, int32_t value)
+{
+	if (evdev_usage_eq(usage, EVDEV_SYN_REPORT))
+		return 0;
+
+	if (frame->count >= frame->max_size)
+		return -ENOMEM;
+
+	struct evdev_event *e = &frame->events[frame->count - 1];
+	*e = (struct evdev_event){ .usage = usage, .value = value };
+	frame->count++;
+	return 0;
+}
+
 static inline int
 evdev_frame_append_input_event(struct evdev_frame *frame,
 			       const struct input_event *event)

src/libinput-plugin-tablet-double-tool.c

@@ -122,18 +122,14 @@ double_tool_plugin_filter_frame(struct libinput_plugin *plugin,
 	}
 
 	if (filter & (PEN_IN_PROX | PEN_OUT_OF_PROX)) {
-		struct evdev_event event = {
+		evdev_frame_append_one(frame_out,
-			.usage = evdev_usage_from(EVDEV_BTN_TOOL_PEN),
+				       evdev_usage_from(EVDEV_BTN_TOOL_PEN),
-			.value = (filter & PEN_IN_PROX) ? 1 : 0,
+				       (filter & PEN_IN_PROX) ? 1 : 0);
-		};
-		evdev_frame_append(frame_out, &event, 1);
 	}
 	if (filter & (ERASER_IN_PROX | ERASER_OUT_OF_PROX)) {
-		struct evdev_event event = {
+		evdev_frame_append_one(frame_out,
-			.usage = evdev_usage_from(EVDEV_BTN_TOOL_RUBBER),
+				       evdev_usage_from(EVDEV_BTN_TOOL_RUBBER),
-			.value = (filter & ERASER_IN_PROX) ? 1 : 0,
+				       (filter & ERASER_IN_PROX) ? 1 : 0);
-		};
-		evdev_frame_append(frame_out, &event, 1);
 	}
 
 	return frame_out;

src/libinput-plugin-tablet-eraser-button.c

@@ -209,26 +209,20 @@ eraser_button_insert_frame(struct plugin_device *device,
 	}
 
 	if (filter & (PEN_IN_PROX | PEN_OUT_OF_PROX)) {
-		struct evdev_event event = {
+		evdev_frame_append_one(frame_out,
-			.usage = evdev_usage_from(EVDEV_BTN_TOOL_PEN),
+				       evdev_usage_from(EVDEV_BTN_TOOL_PEN),
-			.value = (filter & PEN_IN_PROX) ? 1 : 0,
+				       (filter & PEN_IN_PROX) ? 1 : 0);
-		};
-		evdev_frame_append(frame_out, &event, 1);
 	}
 	if (filter & (ERASER_IN_PROX | ERASER_OUT_OF_PROX)) {
-		struct evdev_event event = {
+		evdev_frame_append_one(frame_out,
-			.usage = evdev_usage_from(EVDEV_BTN_TOOL_RUBBER),
+				       evdev_usage_from(EVDEV_BTN_TOOL_RUBBER),
-			.value = (filter & ERASER_IN_PROX) ? 1 : 0,
+				       (filter & ERASER_IN_PROX) ? 1 : 0);
-		};
-		evdev_frame_append(frame_out, &event, 1);
 	}
 	if (filter & (BUTTON_UP | BUTTON_DOWN)) {
 		assert(button != NULL);
-		struct evdev_event event = {
+		evdev_frame_append_one(frame_out,
-			.usage = *button,
+				       *button,
-			.value = (filter & BUTTON_DOWN) ? 1 : 0,
+				       (filter & BUTTON_DOWN) ? 1 : 0);
-		};
-		evdev_frame_append(frame_out, &event, 1);
 	}
 
 	evdev_frame_set_time(frame_out, evdev_frame_get_time(frame_in));

src/libinput-plugin-tablet-proximity-timer.c

@@ -115,13 +115,9 @@ tablet_proximity_out_quirk_timer_func(struct libinput_plugin *plugin,
 	plugin_log_debug(device->parent->plugin,
 			 "%s: forcing proximity out after timeout\n",
 			 libinput_device_get_name(device->device));
-	const struct evdev_event prox_out_event = {
-		.usage = evdev_usage_from(EVDEV_BTN_TOOL_PEN),
-		.value = 0,
-	};
 
 	_unref_(evdev_frame) *prox_out_frame = evdev_frame_new(2);
-	evdev_frame_append(prox_out_frame, &prox_out_event, 1);
+	evdev_frame_append_one(prox_out_frame, evdev_usage_from(EVDEV_BTN_TOOL_PEN), 0);
 	evdev_frame_set_time(prox_out_frame, now);
 
 	libinput_plugin_prepend_evdev_frame(device->parent->plugin,
@@ -215,16 +211,10 @@ proximity_timer_plugin_device_handle_frame(struct libinput_plugin *libinput_plug
 			return;
 		}
 	} else if (device->proximity_out_forced) {
-		struct evdev_event pen_in_event = {
-			.usage = evdev_usage_from(EVDEV_BTN_TOOL_PEN),
-			.value = 1,
-		};
 		plugin_log_debug(libinput_plugin,
 				 "%s: forcing proximity in\n",
 				 libinput_device_get_name(device->device));
-		evdev_frame_append(frame,
+		evdev_frame_append_one(frame, evdev_usage_from(EVDEV_BTN_TOOL_PEN), 1);
-				   &pen_in_event,
-				   1); /* libinput's event frame will have space */
 		device->proximity_out_forced = false;
 		proximity_timer_plugin_set_timer(device, time);
 	}

test/test-utils.c

@@ -3005,6 +3005,52 @@ START_TEST(evdev_frames)
 		/* We never appended a timestamp */
 		litest_assert_int_eq(evdev_frame_get_time(frame), 0U);
 	}
+	{
+		struct evdev_event events[] = {
+			{
+				.usage = U(EVDEV_ABS_X),
+				.value = 1,
+			},
+			{
+				.usage = U(EVDEV_ABS_Y),
+				.value = 2,
+			},
+			{
+				.usage = U(EVDEV_SYN_REPORT),
+				.value = 0,
+			},
+		};
+
+		_unref_(evdev_frame) *frame = evdev_frame_new(3);
+		int rc = evdev_frame_append_one(frame, U(EVDEV_ABS_X), 1);
+		litest_assert_neg_errno_success(rc);
+		rc = evdev_frame_append_one(frame, U(EVDEV_ABS_Y), 2);
+		litest_assert_neg_errno_success(rc);
+		rc = evdev_frame_append_one(frame, U(EV_SYN), 0);
+		litest_assert_neg_errno_success(rc);
+
+		litest_assert_int_eq(evdev_frame_get_count(frame),
+				     ARRAY_LENGTH(events));
+		litest_assert_int_eq(frame->max_size, ARRAY_LENGTH(events));
+
+		size_t nevents;
+		rc = memcmp(evdev_frame_get_events(frame, &nevents),
+			    events,
+			    sizeof(events));
+		litest_assert_int_eq(rc, 0);
+		litest_assert_int_eq(nevents, ARRAY_LENGTH(events));
+
+		/* Already full, can't append */
+		rc = evdev_frame_append_one(frame, U(EVDEV_ABS_Z), 1);
+		litest_assert_int_eq(rc, -ENOMEM);
+
+		/* Appending SYN_REPORT is a noop */
+		rc = evdev_frame_append_one(frame, U(EVDEV_SYN_REPORT), 0);
+		litest_assert_neg_errno_success(rc);
+		litest_assert_int_eq(evdev_frame_get_count(frame),
+				     ARRAY_LENGTH(events));
+		litest_assert_int_eq(frame->max_size, ARRAY_LENGTH(events));
+	}
 }
 END_TEST