[visualization] AreaPickingEvent.getPointsIndices() returns wrong indices

My Environment:

• OS: Windows 11
• Compiler: MSVC2019_64
• PCL Version 1.12.1
• VTK 9.1.0
• Qt 5.15.2

Problem

I integrated the areapickingevent under the visualization module in my Qt program, and tried to get the point cloud index of my selected area through getPointsIndices. But after I visualized the resulting point cloud, I found that the point cloud index was wrong.

The green box in the picture above is the part I selected.

The green box in the above picture is the result of the selected point cloud visualization.

Code

void PCL_test::pp_callback_AreaSelect(const pcl::visualization::AreaPickingEvent& event, void* args)
{
	PCL_test* p = (PCL_test*)args;
	std::vector<int > indices;
	if (event.getPointsIndices(indices) == -1)
		return;

	p->selected_3D_points->clear();

	qDebug() << "Pointcloud area size: " << indices.size() << endl;
	for (int i = 0; i < indices.size(); ++i)
	{
		qDebug() << "Selected point[" << i + 1 << "] indice" << indices[i] << ":" << p->cloudptr->points.at(indices[i]).x << ", " << p->cloudptr->points.at(indices[i]).y << ", " << p->cloudptr->points.at(indices[i]).z << endl;
		p->selected_3D_points->points.push_back(p->cloudptr->points.at(indices[i]));
	}
	//qDebug() << "Select points size: " << p->selected_3D_points->width << "*" << p->selected_3D_points->height << endl;

	//*p->cloudptr = *p->selected_3D_points;
	pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZI> cloud_color(p->selected_3D_points, 0, 255, 0);
	p->cloud_viewer->removeShape("pick");
	p->cloud_viewer->addPointCloud(p->selected_3D_points, cloud_color, "pick");
	p->cloud_viewer->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "pick");
	p->ui.qvtkwidget_cloudviewer->update();
}

Additional context
I found that getPointsIndices does not have any parameters for viewing angle settings, and I don't know what other factors will affect the accuracy of point cloud selection. In addition, I would like to add that I did not see any specific point cloud selection operation instructions in the official documentation, such as "press x first, then use the left mouse button to select, and then press x to visualize the selection results". I hope the official can add more detailed introductions in subsequent updates. Thanks a lot.

Start with pcl::visualization::AreaPickingEvent::getPointsIndices and the pp_callback_AreaSelect callback shown in the issue. Reproduce the area selection using the documented visualization interaction, then compare returned indices with the selected point cloud and review the AreaPickingEvent documentation. Done means the indices match the selected area and the required selection steps are documented.