input_filter: accelerate relative motion events

repos/os/run/input_filter.run

@@ -306,6 +306,51 @@ append config {
 			<expect_release code="BTN_MIDDLE"/>
 
 
+			<message string="accleration of relative motion events"/>
+
+			<!-- linear acceleration -->
+			<filter_config>
+				<input label="usb"/>
+				<output>
+					<accelerate max="100" curve="0" sensitivity_percent="200">
+						<input name="usb"/>
+					</accelerate>
+				</output>
+			</filter_config>
+			<sleep ms="100"/>
+			<usb>
+				<motion rx="1"/>
+				<motion rx="20"/>
+				<motion rx="100"/>
+				<motion rx="-100"/>
+			</usb>
+			<expect_motion rx="1"/>
+			<expect_motion rx="35"/>
+			<expect_motion rx="178"/>
+			<expect_motion rx="-178"/>
+
+			<!-- non-linear acceleration -->
+			<filter_config>
+				<input label="usb"/>
+				<output>
+					<accelerate max="100" curve="127" sensitivity_percent="200">
+						<input name="usb"/>
+					</accelerate>
+				</output>
+			</filter_config>
+			<sleep ms="100"/>
+			<usb>
+				<motion rx="1"/>
+				<motion rx="20"/>
+				<motion rx="100"/>
+				<motion rx="-100"/>
+			</usb>
+			<expect_motion rx="1"/>
+			<expect_motion rx="23"/>
+			<expect_motion rx="191"/>
+			<expect_motion rx="-191"/>
+
+
 			<message string="survive deeply nested config"/>
 
 			<deep_filter_config depth="50"/>

repos/os/src/server/input_filter/README

@@ -54,6 +54,16 @@ one of the following filters:
   such that pointer movements are inhibited while the wheel emulation is
   active. All other events are passed along unmodified.
 
+:<accelerate>:
+
+  Applies acceleration to relative motion values. The 'max' attribute
+  defines the maximum value added to the incoming motion values. The
+  'sensitivity_percent' attribute scales incoming motion values before
+  applying the (potentially non-linear) acceleration function. The 'curve'
+  attribute defines the degree of non-linearity of the acceleration. The value
+  "0" corresponds to a linear function whereas the maximum value "255" applies
+  a curved function. The default value is "127".
+
 
 Character generator rules
 -------------------------

repos/os/src/server/input_filter/accelerate_source.h

@@ -0,0 +1,121 @@
+/*
+ * \brief  Input-event source that accelerates relative motion events
+ * \author Norman Feske
+ * \date   2017-11-03
+ */
+
+/*
+ * Copyright (C) 2017 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INPUT_FILTER__ACCELERATE_SOURCE_H_
+#define _INPUT_FILTER__ACCELERATE_SOURCE_H_
+
+/* Genode includes */
+#include <util/bezier.h>
+#include <input/keycodes.h>
+
+/* local includes */
+#include <source.h>
+#include <key_code_by_name.h>
+
+namespace Input_filter { class Accelerate_source; }
+
+
+class Input_filter::Accelerate_source : public Source, Source::Sink
+{
+	private:
+
+		Owner _owner;
+
+		Source &_source;
+
+		Source::Sink &_destination;
+
+		/**
+		 * Look-up table used for the non-linear acceleration of motion values
+		 */
+		struct Lut
+		{
+			unsigned char values[256];
+
+			Lut(long curve)
+			{
+				/* clamp parameter to valid range */
+				curve = min(255, max(0, curve));
+
+				auto fill_segment = [&] (long x1, long y1, long x2, long y2)
+				{
+					for (long i = x1 >> 8; i <= (x2 >> 8); i++) values[i] = y1 >> 8;
+				};
+
+				long const x0 = 0,           y0 = 0,   x1 = curve, y1 = 0,
+				           x2 = 255 - curve, y2 = 255, x3 = 255,   y3 = 255;
+
+				bezier(x0<<8, y0<<8, x1<<8, y1<<8, x2<<8, y2<<8, x3<<8, y3<<8,
+				       fill_segment, 8);
+			}
+		};
+
+		Lut const _lut;
+
+		/**
+		 * Scale factor applied to incoming motion values before they are
+		 * used as index into the LUT.
+		 */
+		long const _sensitivity_percent;
+
+		/**
+		 * Scale factor of values obtained from the LUT. It corresponds to the
+		 * maximum increase of motion values.
+		 */
+		long const _max;
+
+		long _apply_acceleration(long v) const
+		{
+			long const sign  = (v < 0) ? -1 : 1,
+			           index = max(0, min(255, (sign*v*_sensitivity_percent)/100)),
+			           accel = (_lut.values[index]*_max)/256;
+
+			return v + sign*accel;
+		}
+
+		/**
+		 * Sink interface
+		 */
+		void submit_event(Input::Event const &event) override
+		{
+			/* forward unrelated events */
+			if (!event.relative_motion()) {
+				_destination.submit_event(event);
+				return;
+			}
+
+			_destination.submit_event(Input::Event(Input::Event::MOTION, 0, 0, 0,
+			                                       _apply_acceleration(event.rx()),
+			                                       _apply_acceleration(event.ry())));
+		}
+
+	public:
+
+		static char const *name() { return "accelerate"; }
+
+		Accelerate_source(Owner &owner, Xml_node config, Source::Sink &destination,
+		                  Source::Factory &factory)
+		:
+			Source(owner),
+			_owner(factory),
+			_source(factory.create_source(_owner, input_sub_node(config), *this)),
+			_destination(destination),
+			_lut                (config.attribute_value("curve", 127L)),
+			_sensitivity_percent(config.attribute_value("sensitivity_percent", 100L)),
+			_max                (config.attribute_value("max", 20L))
+		{ }
+
+		void generate() override { _source.generate(); }
+};
+
+#endif /* _INPUT_FILTER__ACCELERATE_SOURCE_H_ */

repos/os/src/server/input_filter/main.cc

@@ -25,6 +25,7 @@
 #include <merge_source.h>
 #include <chargen_source.h>
 #include <button_scroll_source.h>
+#include <accelerate_source.h>
 
 namespace Input_filter { struct Main; }
 
@@ -254,6 +255,9 @@ struct Input_filter::Main : Input_connection::Avail_handler,
 		if (node.type() == Button_scroll_source::name())
 			return *new (_heap) Button_scroll_source(owner, node, sink, *this);
 
+		if (node.type() == Accelerate_source::name())
+			return *new (_heap) Accelerate_source(owner, node, sink, *this);
+
 		warning("unknown <", node.type(), "> input-source node type");
 		throw Source::Invalid_config();
 	}

repos/os/src/server/input_filter/source.h

@@ -42,7 +42,8 @@ class Input_filter::Source
 			    || node.type() == "remap"
 			    || node.type() == "chargen"
 			    || node.type() == "merge"
-			    || node.type() == "button-scroll";
+			    || node.type() == "button-scroll"
+			    || node.type() == "accelerate";
 
 			return false;
 		}