Use precise scrolling values

Since SDL 2.0.18, the amount scrolled horizontally or vertically is
exposed as a float (between 0 and 1). Forward a precise value to the
Android device when possible.

Refs <https://wiki.libsdl.org/SDL_MouseWheelEvent>
Fixes #3363 <https://github.com/Genymobile/scrcpy/issues/3363>
PR #3369 <https://github.com/Genymobile/scrcpy/pull/3369>

Signed-off-by: Romain Vimont <rom@rom1v.com>

app/meson.build

@@ -245,8 +245,8 @@ if get_option('buildtype') == 'debug'
             'src/util/str.c',
             'src/util/strbuf.c',
         ]],
-        ['test_buffer_util', [
-            'tests/test_buffer_util.c',
+        ['test_binary', [
+            'tests/test_binary.c',
         ]],
         ['test_cbuf', [
             'tests/test_cbuf.c',

app/src/control_msg.c

@@ -5,7 +5,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "util/buffer_util.h"
+#include "util/binary.h"
 #include "util/log.h"
 #include "util/str.h"
 
@@ -78,16 +78,6 @@ write_string(const char *utf8, size_t max_len, unsigned char *buf) {
     return 4 + len;
 }
 
-static uint16_t
-to_fixed_point_16(float f) {
-    assert(f >= 0.0f && f <= 1.0f);
-    uint32_t u = f * 0x1p16f; // 2^16
-    if (u >= 0xffff) {
-        u = 0xffff;
-    }
-    return (uint16_t) u;
-}
-
 size_t
 sc_control_msg_serialize(const struct sc_control_msg *msg, unsigned char *buf) {
     buf[0] = msg->type;
@@ -109,18 +99,20 @@ sc_control_msg_serialize(const struct sc_control_msg *msg, unsigned char *buf) {
             sc_write64be(&buf[2], msg->inject_touch_event.pointer_id);
             write_position(&buf[10], &msg->inject_touch_event.position);
             uint16_t pressure =
-                to_fixed_point_16(msg->inject_touch_event.pressure);
+                sc_float_to_u16fp(msg->inject_touch_event.pressure);
             sc_write16be(&buf[22], pressure);
             sc_write32be(&buf[24], msg->inject_touch_event.buttons);
             return 28;
         case SC_CONTROL_MSG_TYPE_INJECT_SCROLL_EVENT:
             write_position(&buf[1], &msg->inject_scroll_event.position);
-            sc_write32be(&buf[13],
-                             (uint32_t) msg->inject_scroll_event.hscroll);
-            sc_write32be(&buf[17],
-                             (uint32_t) msg->inject_scroll_event.vscroll);
-            sc_write32be(&buf[21], msg->inject_scroll_event.buttons);
-            return 25;
+            int16_t hscroll =
+                sc_float_to_i16fp(msg->inject_scroll_event.hscroll);
+            int16_t vscroll =
+                sc_float_to_i16fp(msg->inject_scroll_event.vscroll);
+            sc_write16be(&buf[13], (uint16_t) hscroll);
+            sc_write16be(&buf[15], (uint16_t) vscroll);
+            sc_write32be(&buf[17], msg->inject_scroll_event.buttons);
+            return 21;
         case SC_CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON:
             buf[1] = msg->inject_keycode.action;
             return 2;
@@ -191,8 +183,8 @@ sc_control_msg_log(const struct sc_control_msg *msg) {
             break;
         }
         case SC_CONTROL_MSG_TYPE_INJECT_SCROLL_EVENT:
-            LOG_CMSG("scroll position=%" PRIi32 ",%" PRIi32 " hscroll=%" PRIi32
-                         " vscroll=%" PRIi32 " buttons=%06lx",
+            LOG_CMSG("scroll position=%" PRIi32 ",%" PRIi32 " hscroll=%f"
+                         " vscroll=%f buttons=%06lx",
                      msg->inject_scroll_event.position.point.x,
                      msg->inject_scroll_event.position.point.y,
                      msg->inject_scroll_event.hscroll,

app/src/control_msg.h

@@ -68,8 +68,8 @@ struct sc_control_msg {
         } inject_touch_event;
         struct {
             struct sc_position position;
-            int32_t hscroll;
-            int32_t vscroll;
+            float hscroll;
+            float vscroll;
             enum android_motionevent_buttons buttons;
         } inject_scroll_event;
         struct {

app/src/demuxer.c

@@ -7,7 +7,7 @@
 #include "decoder.h"
 #include "events.h"
 #include "recorder.h"
-#include "util/buffer_util.h"
+#include "util/binary.h"
 #include "util/log.h"
 
 #define SC_PACKET_HEADER_SIZE 12

app/src/device_msg.c

@@ -4,7 +4,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "util/buffer_util.h"
+#include "util/binary.h"
 #include "util/log.h"
 
 ssize_t

app/src/input_events.h

@@ -358,8 +358,8 @@ struct sc_mouse_click_event {
 
 struct sc_mouse_scroll_event {
     struct sc_position position;
-    int32_t hscroll;
-    int32_t vscroll;
+    float hscroll;
+    float vscroll;
     uint8_t buttons_state; // bitwise-OR of sc_mouse_button values
 };
 

app/src/input_manager.c

@@ -747,8 +747,13 @@ sc_input_manager_process_mouse_wheel(struct sc_input_manager *im,
             .point = sc_screen_convert_window_to_frame_coords(im->screen,
                                                               mouse_x, mouse_y),
         },
-        .hscroll = event->x,
-        .vscroll = event->y,
+#if SDL_VERSION_ATLEAST(2, 0, 18)
+        .hscroll = CLAMP(event->preciseX, -1.0f, 1.0f),
+        .vscroll = CLAMP(event->preciseY, -1.0f, 1.0f),
+#else
+        .hscroll = CLAMP(event->x, -1, 1),
+        .vscroll = CLAMP(event->y, -1, 1),
+#endif
         .buttons_state =
             sc_mouse_buttons_state_from_sdl(buttons, im->forward_all_clicks),
     };

app/src/util/binary.h

@@ -1,8 +1,9 @@
-#ifndef SC_BUFFER_UTIL_H
-#define SC_BUFFER_UTIL_H
+#ifndef SC_BINARY_H
+#define SC_BINARY_H
 
 #include "common.h"
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>
 
@@ -43,4 +44,33 @@ sc_read64be(const uint8_t *buf) {
     return ((uint64_t) msb << 32) | lsb;
 }
 
+/**
+ * Convert a float between 0 and 1 to an unsigned 16-bit fixed-point value
+ */
+static inline uint16_t
+sc_float_to_u16fp(float f) {
+    assert(f >= 0.0f && f <= 1.0f);
+    uint32_t u = f * 0x1p16f; // 2^16
+    if (u >= 0xffff) {
+        assert(u == 0x10000); // for f == 1.0f
+        u = 0xffff;
+    }
+    return (uint16_t) u;
+}
+
+/**
+ * Convert a float between -1 and 1 to a signed 16-bit fixed-point value
+ */
+static inline int16_t
+sc_float_to_i16fp(float f) {
+    assert(f >= -1.0f && f <= 1.0f);
+    int32_t i = f * 0x1p15f; // 2^15
+    assert(i >= -0x8000);
+    if (i >= 0x7fff) {
+        assert(i == 0x8000); // for f == 1.0f
+        i = 0x7fff;
+    }
+    return (int16_t) i;
+}
+
 #endif

app/tests/test_binary.c

@@ -0,0 +1,114 @@
+#include "common.h"
+
+#include <assert.h>
+
+#include "util/binary.h"
+
+static void test_write16be(void) {
+    uint16_t val = 0xABCD;
+    uint8_t buf[2];
+
+    sc_write16be(buf, val);
+
+    assert(buf[0] == 0xAB);
+    assert(buf[1] == 0xCD);
+}
+
+static void test_write32be(void) {
+    uint32_t val = 0xABCD1234;
+    uint8_t buf[4];
+
+    sc_write32be(buf, val);
+
+    assert(buf[0] == 0xAB);
+    assert(buf[1] == 0xCD);
+    assert(buf[2] == 0x12);
+    assert(buf[3] == 0x34);
+}
+
+static void test_write64be(void) {
+    uint64_t val = 0xABCD1234567890EF;
+    uint8_t buf[8];
+
+    sc_write64be(buf, val);
+
+    assert(buf[0] == 0xAB);
+    assert(buf[1] == 0xCD);
+    assert(buf[2] == 0x12);
+    assert(buf[3] == 0x34);
+    assert(buf[4] == 0x56);
+    assert(buf[5] == 0x78);
+    assert(buf[6] == 0x90);
+    assert(buf[7] == 0xEF);
+}
+
+static void test_read16be(void) {
+    uint8_t buf[2] = {0xAB, 0xCD};
+
+    uint16_t val = sc_read16be(buf);
+
+    assert(val == 0xABCD);
+}
+
+static void test_read32be(void) {
+    uint8_t buf[4] = {0xAB, 0xCD, 0x12, 0x34};
+
+    uint32_t val = sc_read32be(buf);
+
+    assert(val == 0xABCD1234);
+}
+
+static void test_read64be(void) {
+    uint8_t buf[8] = {0xAB, 0xCD, 0x12, 0x34,
+                      0x56, 0x78, 0x90, 0xEF};
+
+    uint64_t val = sc_read64be(buf);
+
+    assert(val == 0xABCD1234567890EF);
+}
+
+static void test_float_to_u16fp(void) {
+    assert(sc_float_to_u16fp(0.0f) == 0);
+    assert(sc_float_to_u16fp(0.03125f) == 0x800);
+    assert(sc_float_to_u16fp(0.0625f) == 0x1000);
+    assert(sc_float_to_u16fp(0.125f) == 0x2000);
+    assert(sc_float_to_u16fp(0.25f) == 0x4000);
+    assert(sc_float_to_u16fp(0.5f) == 0x8000);
+    assert(sc_float_to_u16fp(0.75f) == 0xc000);
+    assert(sc_float_to_u16fp(1.0f) == 0xffff);
+}
+
+static void test_float_to_i16fp(void) {
+    assert(sc_float_to_i16fp(0.0f) == 0);
+    assert(sc_float_to_i16fp(0.03125f) == 0x400);
+    assert(sc_float_to_i16fp(0.0625f) == 0x800);
+    assert(sc_float_to_i16fp(0.125f) == 0x1000);
+    assert(sc_float_to_i16fp(0.25f) == 0x2000);
+    assert(sc_float_to_i16fp(0.5f) == 0x4000);
+    assert(sc_float_to_i16fp(0.75f) == 0x6000);
+    assert(sc_float_to_i16fp(1.0f) == 0x7fff);
+
+    assert(sc_float_to_i16fp(-0.03125f) == -0x400);
+    assert(sc_float_to_i16fp(-0.0625f) == -0x800);
+    assert(sc_float_to_i16fp(-0.125f) == -0x1000);
+    assert(sc_float_to_i16fp(-0.25f) == -0x2000);
+    assert(sc_float_to_i16fp(-0.5f) == -0x4000);
+    assert(sc_float_to_i16fp(-0.75f) == -0x6000);
+    assert(sc_float_to_i16fp(-1.0f) == -0x8000);
+}
+
+int main(int argc, char *argv[]) {
+    (void) argc;
+    (void) argv;
+
+    test_write16be();
+    test_write32be();
+    test_write64be();
+    test_read16be();
+    test_read32be();
+    test_read64be();
+
+    test_float_to_u16fp();
+    test_float_to_i16fp();
+    return 0;
+}

app/tests/test_buffer_util.c

@@ -1,81 +0,0 @@
-#include "common.h"
-
-#include <assert.h>
-
-#include "util/buffer_util.h"
-
-static void test_buffer_write16be(void) {
-    uint16_t val = 0xABCD;
-    uint8_t buf[2];
-
-    sc_write16be(buf, val);
-
-    assert(buf[0] == 0xAB);
-    assert(buf[1] == 0xCD);
-}
-
-static void test_buffer_write32be(void) {
-    uint32_t val = 0xABCD1234;
-    uint8_t buf[4];
-
-    sc_write32be(buf, val);
-
-    assert(buf[0] == 0xAB);
-    assert(buf[1] == 0xCD);
-    assert(buf[2] == 0x12);
-    assert(buf[3] == 0x34);
-}
-
-static void test_buffer_write64be(void) {
-    uint64_t val = 0xABCD1234567890EF;
-    uint8_t buf[8];
-
-    sc_write64be(buf, val);
-
-    assert(buf[0] == 0xAB);
-    assert(buf[1] == 0xCD);
-    assert(buf[2] == 0x12);
-    assert(buf[3] == 0x34);
-    assert(buf[4] == 0x56);
-    assert(buf[5] == 0x78);
-    assert(buf[6] == 0x90);
-    assert(buf[7] == 0xEF);
-}
-
-static void test_buffer_read16be(void) {
-    uint8_t buf[2] = {0xAB, 0xCD};
-
-    uint16_t val = sc_read16be(buf);
-
-    assert(val == 0xABCD);
-}
-
-static void test_buffer_read32be(void) {
-    uint8_t buf[4] = {0xAB, 0xCD, 0x12, 0x34};
-
-    uint32_t val = sc_read32be(buf);
-
-    assert(val == 0xABCD1234);
-}
-
-static void test_buffer_read64be(void) {
-    uint8_t buf[8] = {0xAB, 0xCD, 0x12, 0x34,
-                      0x56, 0x78, 0x90, 0xEF};
-
-    uint64_t val = sc_read64be(buf);
-
-    assert(val == 0xABCD1234567890EF);
-}
-
-int main(int argc, char *argv[]) {
-    (void) argc;
-    (void) argv;
-
-    test_buffer_write16be();
-    test_buffer_write32be();
-    test_buffer_write64be();
-    test_buffer_read16be();
-    test_buffer_read32be();
-    test_buffer_read64be();
-    return 0;
-}

app/tests/test_control_msg_serialize.c

@@ -132,14 +132,14 @@ static void test_serialize_inject_scroll_event(void) {
 
     unsigned char buf[SC_CONTROL_MSG_MAX_SIZE];
     size_t size = sc_control_msg_serialize(&msg, buf);
-    assert(size == 25);
+    assert(size == 21);
 
     const unsigned char expected[] = {
         SC_CONTROL_MSG_TYPE_INJECT_SCROLL_EVENT,
         0x00, 0x00, 0x01, 0x04, 0x00, 0x00, 0x04, 0x02, // 260 1026
         0x04, 0x38, 0x07, 0x80, // 1080 1920
-        0x00, 0x00, 0x00, 0x01, // 1
-        0xFF, 0xFF, 0xFF, 0xFF, // -1
+        0x7F, 0xFF, // 1 (float encoded as i16)
+        0x80, 0x00, // -1 (float encoded as i16)
         0x00, 0x00, 0x00, 0x01, // 1
     };
     assert(!memcmp(buf, expected, sizeof(expected)));

server/src/main/java/com/genymobile/scrcpy/Binary.java

@@ -0,0 +1,38 @@
+package com.genymobile.scrcpy;
+
+public final class Binary {
+    private Binary() {
+        // not instantiable
+    }
+
+    public static int toUnsigned(short value) {
+        return value & 0xffff;
+    }
+
+    public static int toUnsigned(byte value) {
+        return value & 0xff;
+    }
+
+    /**
+     * Convert unsigned 16-bit fixed-point to a float between 0 and 1
+     *
+     * @param value encoded value
+     * @return Float value between 0 and 1
+     */
+    public static float u16FixedPointToFloat(short value) {
+        int unsignedShort = Binary.toUnsigned(value);
+        // 0x1p16f is 2^16 as float
+        return unsignedShort == 0xffff ? 1f : (unsignedShort / 0x1p16f);
+    }
+
+    /**
+     * Convert signed 16-bit fixed-point to a float between -1 and 1
+     *
+     * @param value encoded value
+     * @return Float value between -1 and 1
+     */
+    public static float i16FixedPointToFloat(short value) {
+        // 0x1p15f is 2^15 as float
+        return value == 0x7fff ? 1f : (value / 0x1p15f);
+    }
+}

server/src/main/java/com/genymobile/scrcpy/ControlMessage.java

@@ -33,8 +33,8 @@ public final class ControlMessage {
     private long pointerId;
     private float pressure;
     private Position position;
-    private int hScroll;
-    private int vScroll;
+    private float hScroll;
+    private float vScroll;
     private int copyKey;
     private boolean paste;
     private int repeat;
@@ -71,7 +71,7 @@ public final class ControlMessage {
         return msg;
     }
 
-    public static ControlMessage createInjectScrollEvent(Position position, int hScroll, int vScroll, int buttons) {
+    public static ControlMessage createInjectScrollEvent(Position position, float hScroll, float vScroll, int buttons) {
         ControlMessage msg = new ControlMessage();
         msg.type = TYPE_INJECT_SCROLL_EVENT;
         msg.position = position;
@@ -156,11 +156,11 @@ public final class ControlMessage {
         return position;
     }
 
-    public int getHScroll() {
+    public float getHScroll() {
         return hScroll;
     }
 
-    public int getVScroll() {
+    public float getVScroll() {
         return vScroll;
     }
 

server/src/main/java/com/genymobile/scrcpy/ControlMessageReader.java

@@ -10,7 +10,7 @@ public class ControlMessageReader {
 
     static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 13;
     static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 27;
-    static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 24;
+    static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
     static final int BACK_OR_SCREEN_ON_LENGTH = 1;
     static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
     static final int GET_CLIPBOARD_LENGTH = 1;
@@ -103,7 +103,7 @@ public class ControlMessageReader {
         if (buffer.remaining() < INJECT_KEYCODE_PAYLOAD_LENGTH) {
             return null;
         }
-        int action = toUnsigned(buffer.get());
+        int action = Binary.toUnsigned(buffer.get());
         int keycode = buffer.getInt();
         int repeat = buffer.getInt();
         int metaState = buffer.getInt();
@@ -136,13 +136,10 @@ public class ControlMessageReader {
         if (buffer.remaining() < INJECT_TOUCH_EVENT_PAYLOAD_LENGTH) {
             return null;
         }
-        int action = toUnsigned(buffer.get());
+        int action = Binary.toUnsigned(buffer.get());
         long pointerId = buffer.getLong();
         Position position = readPosition(buffer);
-        // 16 bits fixed-point
-        int pressureInt = toUnsigned(buffer.getShort());
-        // convert it to a float between 0 and 1 (0x1p16f is 2^16 as float)
-        float pressure = pressureInt == 0xffff ? 1f : (pressureInt / 0x1p16f);
+        float pressure = Binary.u16FixedPointToFloat(buffer.getShort());
         int buttons = buffer.getInt();
         return ControlMessage.createInjectTouchEvent(action, pointerId, position, pressure, buttons);
     }
@@ -152,8 +149,8 @@ public class ControlMessageReader {
             return null;
         }
         Position position = readPosition(buffer);
-        int hScroll = buffer.getInt();
-        int vScroll = buffer.getInt();
+        float hScroll = Binary.i16FixedPointToFloat(buffer.getShort());
+        float vScroll = Binary.i16FixedPointToFloat(buffer.getShort());
         int buttons = buffer.getInt();
         return ControlMessage.createInjectScrollEvent(position, hScroll, vScroll, buttons);
     }
@@ -162,7 +159,7 @@ public class ControlMessageReader {
         if (buffer.remaining() < BACK_OR_SCREEN_ON_LENGTH) {
             return null;
         }
-        int action = toUnsigned(buffer.get());
+        int action = Binary.toUnsigned(buffer.get());
         return ControlMessage.createBackOrScreenOn(action);
     }
 
@@ -170,7 +167,7 @@ public class ControlMessageReader {
         if (buffer.remaining() < GET_CLIPBOARD_LENGTH) {
             return null;
         }
-        int copyKey = toUnsigned(buffer.get());
+        int copyKey = Binary.toUnsigned(buffer.get());
         return ControlMessage.createGetClipboard(copyKey);
     }
 
@@ -198,16 +195,8 @@ public class ControlMessageReader {
     private static Position readPosition(ByteBuffer buffer) {
         int x = buffer.getInt();
         int y = buffer.getInt();
-        int screenWidth = toUnsigned(buffer.getShort());
-        int screenHeight = toUnsigned(buffer.getShort());
+        int screenWidth = Binary.toUnsigned(buffer.getShort());
+        int screenHeight = Binary.toUnsigned(buffer.getShort());
         return new Position(x, y, screenWidth, screenHeight);
     }
-
-    private static int toUnsigned(short value) {
-        return value & 0xffff;
-    }
-
-    private static int toUnsigned(byte value) {
-        return value & 0xff;
-    }
 }

server/src/main/java/com/genymobile/scrcpy/Controller.java

@@ -223,7 +223,7 @@ public class Controller {
         return device.injectEvent(event, Device.INJECT_MODE_ASYNC);
     }
 
-    private boolean injectScroll(Position position, int hScroll, int vScroll, int buttons) {
+    private boolean injectScroll(Position position, float hScroll, float vScroll, int buttons) {
         long now = SystemClock.uptimeMillis();
         Point point = device.getPhysicalPoint(position);
         if (point == null) {

server/src/test/java/com/genymobile/scrcpy/BinaryTest.java

@@ -0,0 +1,42 @@
+package com.genymobile.scrcpy;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BinaryTest {
+
+    @Test
+    public void testU16FixedPointToFloat() {
+        final float delta = 0.0f; // on these values, there MUST be no rounding error
+        Assert.assertEquals(0.0f, Binary.u16FixedPointToFloat((short) 0), delta);
+        Assert.assertEquals(0.03125f, Binary.u16FixedPointToFloat((short) 0x800), delta);
+        Assert.assertEquals(0.0625f, Binary.u16FixedPointToFloat((short) 0x1000), delta);
+        Assert.assertEquals(0.125f, Binary.u16FixedPointToFloat((short) 0x2000), delta);
+        Assert.assertEquals(0.25f, Binary.u16FixedPointToFloat((short) 0x4000), delta);
+        Assert.assertEquals(0.5f, Binary.u16FixedPointToFloat((short) 0x8000), delta);
+        Assert.assertEquals(0.75f, Binary.u16FixedPointToFloat((short) 0xc000), delta);
+        Assert.assertEquals(1.0f, Binary.u16FixedPointToFloat((short) 0xffff), delta);
+    }
+
+    @Test
+    public void testI16FixedPointToFloat() {
+        final float delta = 0.0f; // on these values, there MUST be no rounding error
+
+        Assert.assertEquals(0.0f, Binary.i16FixedPointToFloat((short) 0), delta);
+        Assert.assertEquals(0.03125f, Binary.i16FixedPointToFloat((short) 0x400), delta);
+        Assert.assertEquals(0.0625f, Binary.i16FixedPointToFloat((short) 0x800), delta);
+        Assert.assertEquals(0.125f, Binary.i16FixedPointToFloat((short) 0x1000), delta);
+        Assert.assertEquals(0.25f, Binary.i16FixedPointToFloat((short) 0x2000), delta);
+        Assert.assertEquals(0.5f, Binary.i16FixedPointToFloat((short) 0x4000), delta);
+        Assert.assertEquals(0.75f, Binary.i16FixedPointToFloat((short) 0x6000), delta);
+        Assert.assertEquals(1.0f, Binary.i16FixedPointToFloat((short) 0x7fff), delta);
+
+        Assert.assertEquals(-0.03125f, Binary.i16FixedPointToFloat((short) -0x400), delta);
+        Assert.assertEquals(-0.0625f, Binary.i16FixedPointToFloat((short) -0x800), delta);
+        Assert.assertEquals(-0.125f, Binary.i16FixedPointToFloat((short) -0x1000), delta);
+        Assert.assertEquals(-0.25f, Binary.i16FixedPointToFloat((short) -0x2000), delta);
+        Assert.assertEquals(-0.5f, Binary.i16FixedPointToFloat((short) -0x4000), delta);
+        Assert.assertEquals(-0.75f, Binary.i16FixedPointToFloat((short) -0x6000), delta);
+        Assert.assertEquals(-1.0f, Binary.i16FixedPointToFloat((short) -0x8000), delta);
+    }
+}

server/src/test/java/com/genymobile/scrcpy/ControlMessageReaderTest.java

@@ -126,8 +126,8 @@ public class ControlMessageReaderTest {
         dos.writeInt(1026);
         dos.writeShort(1080);
         dos.writeShort(1920);
-        dos.writeInt(1);
-        dos.writeInt(-1);
+        dos.writeShort(0); // 0.0f encoded as i16
+        dos.writeShort(0x8000); // -1.0f encoded as i16
         dos.writeInt(1);
 
         byte[] packet = bos.toByteArray();
@@ -143,8 +143,8 @@ public class ControlMessageReaderTest {
         Assert.assertEquals(1026, event.getPosition().getPoint().getY());
         Assert.assertEquals(1080, event.getPosition().getScreenSize().getWidth());
         Assert.assertEquals(1920, event.getPosition().getScreenSize().getHeight());
-        Assert.assertEquals(1, event.getHScroll());
-        Assert.assertEquals(-1, event.getVScroll());
+        Assert.assertEquals(0f, event.getHScroll(), 0f);
+        Assert.assertEquals(-1f, event.getVScroll(), 0f);
         Assert.assertEquals(1, event.getButtons());
     }