filter: add a flat trackpoint accel

Previously, trackpoints got assigned the normal flat profile which does not
accommodate for the trackpoint magic multiplier *and* had a config range
that was too small if you take the multiplire indo account anyway.

Fix this by adding a trackpoint-specific flat accel that has a wider
configuration range and take sthe magic multiplier into account.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

meson.build

@@ -300,6 +300,7 @@ src_libfilter = [
 		'src/filter-touchpad-x230.c',
 		'src/filter-tablet.c',
 		'src/filter-trackpoint.c',
+		'src/filter-trackpoint-flat.c',
 ]
 libfilter = static_library('filter', src_libfilter,
 			   dependencies : [dep_udev, dep_libwacom],

src/evdev.c

@@ -1186,17 +1186,23 @@ static inline bool
 evdev_init_accel(struct evdev_device *device,
 		 enum libinput_config_accel_profile which)
 {
-	struct motion_filter *filter;
+	struct motion_filter *filter = NULL;
 
+	if (device->tags & EVDEV_TAG_TRACKPOINT) {
 		if (which == LIBINPUT_CONFIG_ACCEL_PROFILE_FLAT)
-		filter = create_pointer_accelerator_filter_flat(device->dpi);
-	else if (device->tags & EVDEV_TAG_TRACKPOINT)
+			filter = create_pointer_accelerator_filter_trackpoint_flat(device->trackpoint_multiplier);
+		else
 			filter = create_pointer_accelerator_filter_trackpoint(device->trackpoint_multiplier,
 									      device->use_velocity_averaging);
+	} else {
+		if (which == LIBINPUT_CONFIG_ACCEL_PROFILE_FLAT)
+			filter = create_pointer_accelerator_filter_flat(device->dpi);
 		else if (device->dpi < DEFAULT_MOUSE_DPI)
 			filter = create_pointer_accelerator_filter_linear_low_dpi(device->dpi,
 										  device->use_velocity_averaging);
-	else
+	}
+
+	if (!filter)
 		filter = create_pointer_accelerator_filter_linear(device->dpi,
 								  device->use_velocity_averaging);
 

src/filter-trackpoint-flat.c

@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2006-2009 Simon Thum
+ * Copyright © 2012 Jonas Ådahl
+ * Copyright © 2014-2015 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "filter.h"
+#include "libinput-util.h"
+#include "filter-private.h"
+
+struct trackpoint_flat_accelerator {
+	struct motion_filter base;
+
+	double speed_factor;
+	double multiplier;
+};
+
+static struct normalized_coords
+trackpoint_flat_filter(struct motion_filter *filter,
+		       const struct device_float_coords *unaccelerated,
+		       void *data, uint64_t time)
+{
+	struct trackpoint_flat_accelerator *accel_filter =
+		(struct trackpoint_flat_accelerator *) filter;
+	struct normalized_coords accelerated;
+
+	double factor = accel_filter->speed_factor;
+	double multiplier = accel_filter->multiplier;
+	accelerated.x = factor * multiplier * unaccelerated->x;
+	accelerated.y = factor * multiplier * unaccelerated->y;
+
+	return accelerated;
+}
+
+static struct normalized_coords
+trackpoint_flat_filter_noop(struct motion_filter *filter,
+			    const struct device_float_coords *unaccelerated,
+			    void *data, uint64_t time)
+{
+	/* We map the unaccelerated flat filter to have the same behavior as
+	 * the "accelerated" flat filter.
+	 * The filter by definition is flat, i.e. it does not actually
+	 * apply any acceleration (merely a constant factor) and we can assume
+	 * that a user wants all mouse movement to have the same speed, mapped
+	 * 1:1 to the input speed.
+	 *
+	 * Thus we apply the same factor to our non-accelerated motion - this way
+	 * things like button scrolling end up having the same movement as
+	 * pointer motion.
+	 */
+	return trackpoint_flat_filter(filter, unaccelerated, data, time);
+}
+
+/* Maps the [-1, 1] speed setting into a constant acceleration
+ * range. This isn't a linear scale, we keep 0 as the 'optimized'
+ * mid-point and scale down to 0 for setting -1 and up to 5 for
+ * setting 1. On the premise that if you want a faster cursor, it
+ * doesn't matter as much whether you have 0.56789 or 0.56790,
+ * but for lower settings it does because you may lose movements.
+ * *shrug*.
+ *
+ * Magic numbers calculated by MyCurveFit.com, data points were
+ *  0.0 0.0
+ *  0.1 0.1 (because we need 4 points)
+ *  1   1
+ *  2   5
+ *
+ *  This curve fits nicely into the range necessary.
+ */
+static inline double
+speed_factor(double s)
+{
+	s += 1; /* map to [0, 2] */
+	return 435837.2 + (0.04762636 - 435837.2)/(1 + pow(s/240.4549,
+							   2.377168));
+}
+
+static bool
+trackpoint_flat_set_speed(struct motion_filter *filter,
+			  double speed_adjustment)
+{
+	struct trackpoint_flat_accelerator *accel_filter =
+		(struct trackpoint_flat_accelerator *) filter;
+
+	assert(speed_adjustment >= -1.0 && speed_adjustment <= 1.0);
+
+	filter->speed_adjustment = speed_adjustment;
+	accel_filter->speed_factor = speed_factor(speed_adjustment);
+
+
+	return true;
+}
+
+static void
+trackpoint_flat_destroy(struct motion_filter *filter)
+{
+	struct trackpoint_flat_accelerator *accel_filter =
+		(struct trackpoint_flat_accelerator *) filter;
+
+	free(accel_filter);
+}
+
+static struct motion_filter_interface accelerator_interface_flat = {
+	.type = LIBINPUT_CONFIG_ACCEL_PROFILE_FLAT,
+	.filter = trackpoint_flat_filter,
+	.filter_constant = trackpoint_flat_filter_noop,
+	.restart = NULL,
+	.destroy = trackpoint_flat_destroy,
+	.set_speed = trackpoint_flat_set_speed,
+};
+
+struct motion_filter *
+create_pointer_accelerator_filter_trackpoint_flat(double multiplier)
+{
+	struct trackpoint_flat_accelerator *filter;
+
+	filter = zalloc(sizeof *filter);
+	filter->base.interface = &accelerator_interface_flat;
+	filter->multiplier = multiplier;
+
+	return &filter->base;
+}

src/filter.h

@@ -128,6 +128,9 @@ create_pointer_accelerator_filter_lenovo_x230(int dpi, bool use_velocity_averagi
 struct motion_filter *
 create_pointer_accelerator_filter_trackpoint(double multiplier, bool use_velocity_averaging);
 
+struct motion_filter *
+create_pointer_accelerator_filter_trackpoint_flat(double multiplier);
+
 struct motion_filter *
 create_pointer_accelerator_filter_tablet(int xres, int yres);