// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2026 Martino Ferrari

// The Qt adapter's pointer translation, driven directly. The widget's cached
// pointer anchor is a plain value with no toolkit dependency (see
// adapters/qt6/qt_pointer.hpp) precisely so the one thing a screenshot cannot show
// -- which pixel space a drag delta is in -- is testable without a QApplication, a
// window or a display.
#include "harness.hpp"

#include <qt6/qt_pointer.hpp>

#include <cmath>

// The defect this pins: the anchor used to be cached in *device* pixels while the
// next event's delta was a raw difference of device positions, so a DPR change
// between two move events -- the window dragged onto a monitor with a different
// scale factor mid-drag -- mixed two pixel spaces. At 1.0 -> 1.25 a logical
// position of 500 produced a spurious 125 device-pixel delta, which
// `Controller::pan` applies as a fraction of the range span and which also clears
// auto scale: a scale change mid-drag would move the plot by 125 pixels' worth of
// data and silently disarm a live axis.
PLOT_TEST(pointer_anchor_survives_a_dpr_change_between_move_events) {
  plot::qt::PointerAnchor anchor;

  // The press caches a logical position while the window is on the 1.0 display.
  anchor.set({500.0f, 300.0f});

  // The next move arrives after the window moved to the 1.25 display, at the same
  // logical position: the pointer has not moved, so the delta must be zero -- not
  // 500 * 1.25 - 500 * 1.0 = 125 device pixels, which is what comparing two device
  // positions across the scale change reported.
  const plot::Vec2 still = anchor.device_delta({500.0f, 300.0f}, 1.25);
  PLOT_CHECK_NEAR(still.x, 0.0, 1e-6);
  PLOT_CHECK_NEAR(still.y, 0.0, 1e-6);

  // A real movement is the logical delta scaled by the ratio in effect now, in both
  // directions.
  const plot::Vec2 moved = anchor.device_delta({503.0f, 295.0f}, 1.25);
  PLOT_CHECK_NEAR(moved.x, 3.0 * 1.25, 1e-6);
  PLOT_CHECK_NEAR(moved.y, -5.0 * 1.25, 1e-6);

  // And the anchor follows the sample it just reported: the following move is
  // measured from there, at whatever ratio that event carries.
  anchor.set({503.0f, 295.0f});
  const plot::Vec2 unchanged = anchor.device_delta({503.0f, 295.0f}, 1.0);
  PLOT_CHECK_NEAR(unchanged.x, 0.0, 1e-6);
  PLOT_CHECK_NEAR(unchanged.y, 0.0, 1e-6);
}

// The first sample of a gesture has no anchor to measure from, so its delta is
// zero however far the position is from the origin: the first motion of a drag
// must never include the jump to where the drag began.
PLOT_TEST(pointer_anchor_reports_no_movement_before_its_first_sample) {
  plot::qt::PointerAnchor anchor;
  const plot::Vec2 delta = anchor.device_delta({500.0f, 300.0f}, 1.25);
  PLOT_CHECK_NEAR(delta.x, 0.0, 1e-9);
  PLOT_CHECK_NEAR(delta.y, 0.0, 1e-9);
}