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Merged
ReenigneArcher merged 5 commits into from
Oct 16, 2026
+80 −28
Merged

fix(linux): send scroll to the mouse device that last moved #195

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a9189e0
test(linux): cover scrolling after absolute mouse motion
GabeDuarteM Oct 15, 2026
22e5a51
fix(linux): send scroll to the mouse device that last moved
GabeDuarteM Oct 15, 2026
91ba7e7
test(linux): wrap the libinput scroll assertion
GabeDuarteM Oct 15, 2026
b316f9f
test(linux): use using enum in the scroll routing test
GabeDuarteM Oct 15, 2026
6212871
docs(linux): document mouse wheel routing on UinputMouse
GabeDuarteM Oct 16, 2026
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33 changes: 20 additions & 13 deletions src/platform/linux/uhid_backend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1204,6 +1204,10 @@ namespace lvh::detail {
}
}

if (const auto status = enable_evdev_type(device, EV_REL, "relative mouse events"); !status.ok()) {
return status;
}

if (kind == UinputMouseDeviceKind::absolute) {
if (const auto status = enable_evdev_property(device, INPUT_PROP_DIRECT, "direct input"); !status.ok()) {
return status;
Expand All @@ -1217,17 +1221,15 @@ namespace lvh::detail {
return status;
}
auto y = make_absinfo(0, absolute_axis_max);
return enable_evdev_code(device, EV_ABS, ABS_Y, "absolute mouse axis", &y);
}

if (const auto status = enable_evdev_type(device, EV_REL, "relative mouse events"); !status.ok()) {
return status;
}

for (const auto code : {REL_X, REL_Y}) {
if (const auto status = enable_evdev_code(device, EV_REL, code, "relative mouse axis"); !status.ok()) {
if (const auto status = enable_evdev_code(device, EV_ABS, ABS_Y, "absolute mouse axis", &y); !status.ok()) {
return status;
}
} else {
for (const auto code : {REL_X, REL_Y}) {
if (const auto status = enable_evdev_code(device, EV_REL, code, "relative mouse axis"); !status.ok()) {
return status;
}
}
}

if (const auto status = enable_evdev_code(device, EV_REL, REL_WHEEL, "vertical scroll"); !status.ok()) {
Expand Down Expand Up @@ -1740,6 +1742,11 @@ namespace lvh::detail {

/**
* @brief Backend mouse backed by separate relative and absolute Linux uinput devices.
*
* Both devices expose legacy and available high-resolution wheel axes.
* Relative motion axes are exposed only by the relative device.
* Wheel events follow the last successful motion submission, defaulting
* to the relative device before any successful motion submission.
*/
class UinputMouse final: public BackendMouse {
public:
Expand Down Expand Up @@ -1935,19 +1942,19 @@ namespace lvh::detail {
std::uint16_t legacy_code,
std::optional<std::uint16_t> high_resolution_code
) {
auto &relative = device(UinputMouseDeviceKind::relative);
auto &target = device(last_motion_device_);
Comment thread
ReenigneArcher marked this conversation as resolved.
const auto converted = accumulated_legacy_scroll(remainder, distance);
if (converted.detents != 0) {
if (const auto status = relative.emit(EV_REL, legacy_code, converted.detents); !status.ok()) {
if (const auto status = target.emit(EV_REL, legacy_code, converted.detents); !status.ok()) {
return status;
}
}
if (high_resolution_code.has_value()) {
if (const auto status = relative.emit(EV_REL, *high_resolution_code, distance); !status.ok()) {
if (const auto status = target.emit(EV_REL, *high_resolution_code, distance); !status.ok()) {
return status;
}
}
if (const auto status = relative.synchronize(); !status.ok()) {
if (const auto status = target.synchronize(); !status.ok()) {
return status;
}
remainder = converted.remainder;
Expand Down
65 changes: 50 additions & 15 deletions tests/unit/test_linux_backend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,19 @@ namespace {
}
return pressed_codes;
}

std::vector<std::int32_t> relative_axis_values(
const std::vector<lvh::detail::test::LinuxInputEventRecord> &events,
std::uint16_t code
) {
std::vector<std::int32_t> values;
for (const auto &event : events) {
if (event.type == EV_REL && event.code == code) {
values.push_back(event.value);
}
}
return values;
}
} // namespace

TEST_F(LinuxBackendTest, TranslatesKeyboardKeys) {
Expand Down Expand Up @@ -748,6 +761,28 @@ TEST_F(LinuxBackendTest, PipeBackedUinputMouseRoutesMotionAndButtonsAcrossSplitD
}));
}

TEST_F(LinuxBackendTest, PipeBackedUinputMouseScrollsOnLastMotionDevice) {
using enum lvh::MouseEventKind;

const std::vector<lvh::MouseEvent> events {
{.kind = absolute_motion, .x = 50, .y = 25, .width = 100, .height = 100},
{.kind = vertical_scroll, .high_resolution_scroll = 120},
{.kind = horizontal_scroll, .high_resolution_scroll = -120},
{.kind = relative_motion, .x = 5, .y = -2},
{.kind = vertical_scroll, .high_resolution_scroll = -120},
};
const auto result = lvh::detail::test::linux_uinput_mouse_submit_split_pipe_sequence(events);
ASSERT_TRUE(result.status.ok()) << result.status.message();

EXPECT_EQ(relative_axis_values(result.absolute_events, REL_WHEEL), (std::vector<std::int32_t> {1}));
EXPECT_EQ(relative_axis_values(result.absolute_events, REL_HWHEEL), (std::vector<std::int32_t> {-1}));
EXPECT_EQ(relative_axis_values(result.relative_events, REL_WHEEL), (std::vector<std::int32_t> {-1}));
#if defined(REL_WHEEL_HI_RES)
EXPECT_EQ(relative_axis_values(result.absolute_events, REL_WHEEL_HI_RES), (std::vector<std::int32_t> {120}));
EXPECT_EQ(relative_axis_values(result.relative_events, REL_WHEEL_HI_RES), (std::vector<std::int32_t> {-120}));
#endif
}

TEST_F(LinuxBackendTest, PipeBackedUinputMouseAccumulatesLegacyScrollDetentsPerAxis) {
const std::vector<lvh::MouseEvent> events {
{.kind = lvh::MouseEventKind::vertical_scroll, .high_resolution_scroll = 60},
Expand All @@ -758,23 +793,13 @@ TEST_F(LinuxBackendTest, PipeBackedUinputMouseAccumulatesLegacyScrollDetentsPerA
const auto result = lvh::detail::test::linux_uinput_mouse_submit_pipe_sequence(events);
ASSERT_TRUE(result.status.ok()) << result.status.message();

const auto event_values = [&result](std::uint16_t code) {
std::vector<std::int32_t> values;
for (const auto &event : result.events) {
if (event.type == EV_REL && event.code == code) {
values.push_back(event.value);
}
}
return values;
};

EXPECT_EQ(event_values(REL_WHEEL), (std::vector<std::int32_t> {1}));
EXPECT_EQ(event_values(REL_HWHEEL), (std::vector<std::int32_t> {-1}));
EXPECT_EQ(relative_axis_values(result.events, REL_WHEEL), (std::vector<std::int32_t> {1}));
EXPECT_EQ(relative_axis_values(result.events, REL_HWHEEL), (std::vector<std::int32_t> {-1}));
#if defined(REL_WHEEL_HI_RES)
EXPECT_EQ(event_values(REL_WHEEL_HI_RES), (std::vector<std::int32_t> {60, 60}));
EXPECT_EQ(relative_axis_values(result.events, REL_WHEEL_HI_RES), (std::vector<std::int32_t> {60, 60}));
#endif
#if defined(REL_HWHEEL_HI_RES)
EXPECT_EQ(event_values(REL_HWHEEL_HI_RES), (std::vector<std::int32_t> {-60, -60}));
EXPECT_EQ(relative_axis_values(result.events, REL_HWHEEL_HI_RES), (std::vector<std::int32_t> {-60, -60}));
#endif
EXPECT_EQ(
std::ranges::count_if(result.events, [](const auto &event) {
Expand Down Expand Up @@ -1352,10 +1377,20 @@ TEST_F(LinuxBackendTest, FakeUinputConstructionCoversCapabilitiesAndFailureBranc
const auto absolute_mouse = lvh::detail::test::linux_uinput_create_fake_absolute_mouse_device();
ASSERT_TRUE(absolute_mouse.status.ok()) << absolute_mouse.status.message();
EXPECT_TRUE(has_type(absolute_mouse, EV_KEY));
EXPECT_FALSE(has_type(absolute_mouse, EV_REL));
EXPECT_TRUE(has_type(absolute_mouse, EV_REL));
EXPECT_TRUE(has_type(absolute_mouse, EV_ABS));
EXPECT_TRUE(has_property(absolute_mouse, INPUT_PROP_DIRECT));
EXPECT_NE(find_code(absolute_mouse, EV_KEY, BTN_LEFT), nullptr);
EXPECT_EQ(find_code(absolute_mouse, EV_REL, REL_X), nullptr);
EXPECT_EQ(find_code(absolute_mouse, EV_REL, REL_Y), nullptr);
EXPECT_NE(find_code(absolute_mouse, EV_REL, REL_WHEEL), nullptr);
EXPECT_NE(find_code(absolute_mouse, EV_REL, REL_HWHEEL), nullptr);
#if defined(REL_WHEEL_HI_RES)
EXPECT_NE(find_code(absolute_mouse, EV_REL, REL_WHEEL_HI_RES), nullptr);
#endif
#if defined(REL_HWHEEL_HI_RES)
EXPECT_NE(find_code(absolute_mouse, EV_REL, REL_HWHEEL_HI_RES), nullptr);
#endif
const auto *mouse_x = find_code(absolute_mouse, EV_ABS, ABS_X);
ASSERT_NE(mouse_x, nullptr);
EXPECT_TRUE(mouse_x->has_absinfo);
Expand Down
10 changes: 10 additions & 0 deletions tests/unit/test_linux_consumers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1341,6 +1341,16 @@ TEST_F(LinuxConsumerTest, LibinputSeesSplitUinputMouseMotionAndButtons) {
EXPECT_NEAR(libinput_event_pointer_get_absolute_x_transformed(pointer_event, 100), 75.0, 0.1);
EXPECT_NEAR(libinput_event_pointer_get_absolute_y_transformed(pointer_event, 100), 75.0, 0.1);

ASSERT_TRUE(created.mouse->vertical_scroll(120).ok());
event = wait_for_libinput_event(absolute_context.get(), {LIBINPUT_EVENT_POINTER_SCROLL_WHEEL});
ASSERT_NE(event.get(), nullptr);
pointer_event = libinput_event_get_pointer_event(event.get());
ASSERT_NE(pointer_event, nullptr);
EXPECT_DOUBLE_EQ(
libinput_event_pointer_get_scroll_value_v120(pointer_event, LIBINPUT_POINTER_AXIS_SCROLL_VERTICAL),
-120.0
);

ASSERT_TRUE(created.mouse->button(lvh::MouseButton::middle, true).ok());
event = wait_for_libinput_event(absolute_context.get(), {LIBINPUT_EVENT_POINTER_BUTTON});
ASSERT_NE(event.get(), nullptr);
Expand Down
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