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fix(linux/input): emulate relative mouse movement from absolute coordinates #5529

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fix(linux/input): emulate relative mouse movement from absolute coordinates #5529

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35 changes: 34 additions & 1 deletion src/input.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -270,6 +270,12 @@ namespace input {

input::touch_port_t touch_port; ///< Touch coordinate bounds for the current stream.

bool abs_mouse_initialized = false; ///< Whether the absolute mouse baseline is set.
float last_abs_x = 0; ///< Last absolute mouse X in host coordinates.
float last_abs_y = 0; ///< Last absolute mouse Y in host coordinates.
float abs_mouse_frac_x = 0; ///< Accumulated fractional X delta.
float abs_mouse_frac_y = 0; ///< Accumulated fractional Y delta.

int32_t accumulated_vscroll_delta; ///< Accumulated vscroll delta.
int32_t accumulated_hscroll_delta; ///< Accumulated hscroll delta.
};
Expand Down Expand Up @@ -830,7 +836,34 @@ namespace input {
touch_port_dim_y
};

platf::abs_mouse(platf_input, abs_port, tpcoords->first, tpcoords->second);
// Emulate relative mouse movement from absolute coordinates.
// Absolute motion arrives as PointerMotionAbsolute in the compositor, which
// moves the cursor but does NOT update the screen magnifier focal point
// (pop-os/cosmic-comp #2760). The first event still places the cursor
// absolutely; subsequent events are converted to relative deltas so the
// magnifier tracks the cursor.
if (input->abs_mouse_initialized) {
// Accumulate fractional deltas so slow (sub-pixel) motion still produces
// cursor movement on both axes instead of being truncated to zero.
input->abs_mouse_frac_x += tpcoords->first - input->last_abs_x;
input->abs_mouse_frac_y += tpcoords->second - input->last_abs_y;

auto delta_x = (int)input->abs_mouse_frac_x;
auto delta_y = (int)input->abs_mouse_frac_y;

input->abs_mouse_frac_x -= delta_x;
input->abs_mouse_frac_y -= delta_y;

if (delta_x || delta_y) {
platf::move_mouse(platf_input, delta_x, delta_y);
}
} else {
platf::abs_mouse(platf_input, abs_port, tpcoords->first, tpcoords->second);
input->abs_mouse_initialized = true;
}

input->last_abs_x = tpcoords->first;
input->last_abs_y = tpcoords->second;
}

/**
Expand Down