CalendarFilterModel.cpp

#include "CalendarFilterModel.h"
#include <QTableView>
#include <QDebug>
#include <QStyledItemDelegate>

QObject* find_child_by_class(QObject* parent, const QString& class_name) {
  foreach(QObject* object, parent->findChildren<QObject*>()) {
    if (object->metaObject()->className() == class_name) {
      return object;
    }
  }
  return 0;
}

CalendarFilterModel::CalendarFilterModel(QCalendarWidget* p_calendar) :
  QSortFilterProxyModel(p_calendar), calendar(p_calendar)
{
  QAbstractItemModel* source_model = static_cast<QAbstractItemModel*>(find_child_by_class(calendar, "QCalendarModel"));
  setSourceModel(source_model);
  if (!source_model) {
    qFatal("failed to find source model");
    return;
  }
  QTableView* view = static_cast<QTableView*>(find_child_by_class(calendar, "QCalendarView"));
  if (!view) {
    qFatal("failed to find view");
    return;
  }
  view->setModel(this);
  view->setItemDelegate(new QStyledItemDelegate());
}

Qt::ItemFlags CalendarFilterModel::flags(const QModelIndex &index) const {
  Qt::ItemFlags v = QSortFilterProxyModel::flags(index);
  qDebug() << "flags" << v;
  return v;
}

QVariant CalendarFilterModel::data(const QModelIndex &index, int role) const {
  qDebug() << "data" << role;
  if (role == Qt::BackgroundColorRole) {
    return Qt::green;
  }
  qDebug() << QSortFilterProxyModel::data(index, role);
  return QSortFilterProxyModel::data(index, role);
}

void CalendarFilterModel::set_disabled_dates(const QList<QDate> &dates) {
  emit layoutAboutToBeChanged();
  disabled_dates = dates;
  emit layoutChanged();
}

CalendarFilterModel.h

#ifndef CALENDARFILTERMODEL_H
#define CALENDARFILTERMODEL_H

#include <QSortFilterProxyModel>
#include <QCalendarWidget>
#include <qitemselectionmodel.h>

class CalendarFilterModel : public QSortFilterProxyModel {
  Q_OBJECT
public:
  explicit CalendarFilterModel(QCalendarWidget* p_calendar);
  Qt::ItemFlags flags(const QModelIndex &index) const;
  QVariant data(const QModelIndex &index, int role) const;

  void set_disabled_dates(const QList<QDate>& dates);



  QDate referenceDate() const;
  QDate dateForCell(int row, int column) const;
private:
  QCalendarWidget* calendar;
  QList<QDate> disabled_dates;
  
};

#endif // CALENDARFILTERMODEL_H

MainWindow.cpp

// in the main window constructor
CalendarFilterModel* m = new CalendarFilterModel(ui->calendarWidget);