qt5下自定义QGraphicsItem在场景中拖动吸附算法

#include "designAttach.h" CBorderAttach::CBorderAttach(QList<QGraphicsItem *> item_list, QPointF offset, QRectF sel_rect, int attach_interval) { _offset = offset; _sel_rect = sel_rect; _attach_interval = attach_interval; QRectF actual_rect = _sel_rect; actual_rect.moveTopLeft(actual_rect.topLeft() + offset); QRectF snap_rect = actual_rect; snap_rect.adjusted(-_attach_interval, -_attach_interval, _attach_interval, _attach_interval); QVector<CBorderLine> vec_border; qreal x1, y1, x2, y2; snap_rect.getCoords(&x1, &y1, &x2, &y2); for (int i = 0; i < item_list.size(); i++) { QGraphicsItem* item = item_list[i]; QRectF item_rect = item->sceneBoundingRect(); CBorderLine line; qreal left = item_rect.left(); if (x1 <= left && left <= x2) { double left_gap = qAbs(actual_rect.left() - left); double right_gap = qAbs(actual_rect.right() - left); if (left_gap <= _attach_interval) { line._dir = EBorder_Left; line._pos = left; if (!vec_border.contains(line)) { vec_border.push_back(line); } } else if (right_gap <= _attach_interval) { line._dir = EBorder_Right; line._pos = left; if (!vec_border.contains(line)) { vec_border.push_back(line); } } } qreal right = item_rect.right(); if (x1 <= right && right <= x2) { double left_gap = qAbs(actual_rect.left() - right); double right_gap = qAbs(actual_rect.right() - right); if (left_gap <= _attach_interval) { line._dir = EBorder_Left; line._pos = right; if (!vec_border.contains(line)) { vec_border.push_back(line); } } else if (right_gap <= _attach_interval) { line._dir = EBorder_Right; line._pos = right; if (!vec_border.contains(line)) { vec_border.push_back(line); } } } qreal top = item_rect.top(); if (y1 <= top && top <= y2) { double top_gap = qAbs(actual_rect.top() - top); double bottom_gap = qAbs(actual_rect.bottom() - top); if (top_gap <= _attach_interval) { line._dir = EBorder_Top; line._pos = top; if (!vec_border.contains(line)) { vec_border.push_back(line); } } else if (bottom_gap <= _attach_interval) { line._dir = EBorder_Bottom; line._pos = top; if (!vec_border.contains(line)) { vec_border.push_back(line); } } } qreal bottom = item_rect.bottom(); if (y1 <= bottom && bottom <= y2) { double top_gap = qAbs(actual_rect.top() - bottom); double bottom_gap = qAbs(actual_rect.bottom() - bottom); if (top_gap <= _attach_interval) { line._dir = EBorder_Top; line._pos = bottom; if (!vec_border.contains(line)) { vec_border.push_back(line); } } else if (bottom_gap <= _attach_interval) { line._dir = EBorder_Bottom; line._pos = bottom; if (!vec_border.contains(line)) { vec_border.push_back(line); } } } } _vec_border = vec_border; } QVector<CBorderLine> CBorderAttach::GetBorder(EBorder dir) { QVector<CBorderLine> vec_line; for (int i = 0; i < _vec_border.size(); i++) { CBorderLine line = _vec_border.at(i); if (line._dir == dir) { vec_line.push_back(line); } } return vec_line; } QPointF CBorderAttach::Calculate() { QPointF calc_point = _offset; if (_vec_border.size()) { QVector<CBorderLine> vec_left_line = GetBorder(EBorder_Left); qSort(vec_left_line); QVector<CBorderLine> vec_right_line = GetBorder(EBorder_Right); qSort(vec_right_line); QVector<CBorderLine> vec_top_line = GetBorder(EBorder_Top); qSort(vec_top_line); QVector<CBorderLine> vec_buttom_line = GetBorder(EBorder_Bottom); qSort(vec_buttom_line); if (vec_left_line.size()) { calc_point.setX(vec_left_line[0]._pos - _sel_rect.left()); } else if (vec_right_line.size()) { calc_point.setX(vec_right_line[0]._pos - _sel_rect.left() - _sel_rect.width()); } if (vec_top_line.size()) { calc_point.setY(vec_top_line[0]._pos - _sel_rect.top()); } else if (vec_buttom_line.size()) { calc_point.setY(vec_buttom_line[0]._pos - _sel_rect.top() - _sel_rect.height()); } } return calc_point; }