dndvbox.h

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/*
    Copyright (C) 2009 Paul Davis 

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#include <gtkmm/box.h>

#include "gtkmm2ext/visibility.h"
#include "gtkmm2ext/widget_state.h"

namespace Gtkmm2ext {

class /*LIBGTKMM2EXT_API*/ DnDVBoxChild
{
public:
        virtual ~DnDVBoxChild () {}
        
        virtual Gtk::Widget& widget () = 0;
        
        virtual Gtk::EventBox& action_widget () = 0;

        virtual std::string drag_text () const = 0;

        virtual void set_visual_state (VisualState, bool onoff) = 0;

        virtual bool is_selectable () const = 0;
};

template <class T>
class /*LIBGTKMM2EXT_API*/ DnDVBox : public Gtk::EventBox
{
public:
        DnDVBox () : _active (0), _drag_icon (0), _expecting_unwanted_button_event (false), _placeholder (0)
        {
                _targets.push_back (Gtk::TargetEntry ("processor"));

                add (_internal_vbox);
                add_events (
                        Gdk::KEY_PRESS_MASK | Gdk::KEY_RELEASE_MASK |
                        Gdk::ENTER_NOTIFY_MASK | Gdk::LEAVE_NOTIFY_MASK |
                        Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK
                        );

                signal_button_press_event().connect (sigc::bind (mem_fun (*this, &DnDVBox::button_press), (T *) 0));
                signal_button_release_event().connect (sigc::bind (mem_fun (*this, &DnDVBox::button_release), (T *) 0));
                signal_drag_motion().connect (mem_fun (*this, &DnDVBox::drag_motion));
                signal_drag_leave().connect (mem_fun (*this, &DnDVBox::drag_leave));

                _internal_vbox.show ();
                
                drag_dest_set (_targets);
                signal_drag_data_received().connect (mem_fun (*this, &DnDVBox::drag_data_received));
        }
        
        virtual ~DnDVBox ()
        {
                clear ();
                
                delete _drag_icon;
        }

        void add_child (T* child)
        {
                child->action_widget().drag_source_set (_targets);
                child->action_widget().signal_drag_begin().connect (sigc::bind (mem_fun (*this, &DnDVBox::drag_begin), child));
                child->action_widget().signal_drag_data_get().connect (sigc::bind (mem_fun (*this, &DnDVBox::drag_data_get), child));
                child->action_widget().signal_drag_end().connect (sigc::bind (mem_fun (*this, &DnDVBox::drag_end), child));
                child->action_widget().signal_button_press_event().connect (sigc::bind (mem_fun (*this, &DnDVBox::button_press), child));
                child->action_widget().signal_button_release_event().connect (sigc::bind (mem_fun (*this, &DnDVBox::button_release), child));
                
                _internal_vbox.pack_start (child->widget(), false, false);
                
                _children.push_back (child);
                child->widget().show ();
        }

        std::list<T*> children ()
        {
                std::list<T*> sorted_children;

                std::list<Gtk::Widget*> widget_children = _internal_vbox.get_children ();
                for (std::list<Gtk::Widget*>::iterator i = widget_children.begin(); i != widget_children.end(); ++i) {
                        T* c = child_from_widget (*i);

                        if (c) {
                                sorted_children.push_back (c);
                        }
                }

                return sorted_children;
        }

        std::list<T*> selection () const {
                return _selection;
        }

        void set_active (T* c) {
                T* old_active = _active;
                _active = c;
                if (old_active) {
                        setup_child_state (old_active);
                }
                if (_active) {
                        setup_child_state (_active);
                }
        }

        bool selected (T* child) const {
                return (find (_selection.begin(), _selection.end(), child) != _selection.end());
        }

        void clear ()
        {
                _selection.clear ();

                for (typename std::list<T*>::iterator i = _children.begin(); i != _children.end(); ++i) {
                        _internal_vbox.remove ((*i)->widget());
                        delete *i;
                }

                _children.clear ();
                _active = 0;
        }

        void select_all ()
        {
                clear_selection ();
                for (typename std::list<T*>::iterator i = _children.begin(); i != _children.end(); ++i) {
                        add_to_selection (*i);
                }

                SelectionChanged (); /* EMIT SIGNAL */
        }

        void select_none ()
        {
                clear_selection ();

                SelectionChanged (); /* EMIT SIGNAL */
        }

        std::pair<T*, double> get_child_at_position (int y) const
        {
                T* before;
                T* after;

                std::pair<T*, double> r;
                
                r.second = get_children_around_position (y, &before, &r.first, &after);

                return r;
        }

        void set_spacing (int s) {
                _internal_vbox.set_spacing (s);
        }

        void remove_placeholder ()
        {
                if (_placeholder) {
                        _internal_vbox.remove (*_placeholder);
                        _placeholder = 0;
                }
        }

        int add_placeholder (double y)
        {
                return create_or_update_placeholder (get_child_at_position (y).second);
        }
        
        sigc::signal<void> Reordered;

        sigc::signal<bool, GdkEventButton*, T*> ButtonPress;

        sigc::signal<bool, GdkEventButton*, T*> ButtonRelease;

        sigc::signal<void, DnDVBox*, T*, Glib::RefPtr<Gdk::DragContext> const & > DropFromAnotherBox;
        sigc::signal<void> SelectionChanged;

private:

        double bottom_of_child_ignoring_placeholder (T* child) const
        {
                Gtk::Allocation const a = child->widget().get_allocation ();
                double bottom = a.get_y() + a.get_height();

                if (_placeholder) {
                        Gtk::Allocation const b = _placeholder->get_allocation ();
                        if (b.get_y() < a.get_y()) {
                                bottom -= (b.get_height () + _internal_vbox.get_spacing ());
                        }
                }

                return bottom;
        }
        
        double get_children_around_position (int y, T** before, T** at, T** after) const
        {
                if (_children.empty()) {
                        *before = *at = *after = 0;
                        return -1;
                }

                *before = 0;

                typename std::list<T*>::const_iterator j = _children.begin ();

                /* index of current child */
                int i = 0;
                /* top of current child */
                double top = 0;
                /* bottom of current child */
                double bottom = bottom_of_child_ignoring_placeholder (*j);

                while (y >= bottom && j != _children.end()) {

                        top = bottom;
                        
                        *before = *j;
                        ++i;
                        ++j;

                        if (j != _children.end()) {
                                bottom = bottom_of_child_ignoring_placeholder (*j);
                        }
                }

                if (j == _children.end()) {
                        *at = 0;
                        *after = 0;
                        return -1;
                }

                *at = *j;

                ++j;
                *after = j != _children.end() ? *j : 0;

                return i + ((y - top) / (bottom - top));
        }

        void drag_begin (Glib::RefPtr<Gdk::DragContext> const & context, T* child)
        {
                _drag_child = child;
                
                /* make up an icon for the drag */
                _drag_icon = new Gtk::Window (Gtk::WINDOW_POPUP);
                
                Gtk::Allocation a = child->action_widget().get_allocation ();
                _drag_icon->set_size_request (a.get_width(), a.get_height());
                
                _drag_icon->signal_expose_event().connect (sigc::mem_fun (*this, &DnDVBox::icon_expose));
                _drag_icon->set_name (get_name ());

                /* make the icon transparent if possible */
                Glib::RefPtr<Gdk::Screen const> s = _drag_icon->get_screen ();
                Glib::RefPtr<Gdk::Colormap const> c = s->get_rgba_colormap ();
                if (c) {
                        _drag_icon->set_colormap (c);
                }

                int w, h;
                _drag_icon->get_size (w, h);
                _drag_icon->drag_set_as_icon (context, w / 2, h / 2);
                
                _drag_source = this;
        }

        /* Draw the drag icon */
        bool icon_expose (GdkEventExpose*)
        {
                /* Just grab the child's widget and use that */

                int w, h;
                _drag_icon->get_size (w, h);

                cairo_t* cr = gdk_cairo_create (_drag_icon->get_window()->gobj ());

                Glib::RefPtr<Gdk::Pixmap> p = _drag_child->action_widget().get_snapshot();
                gdk_cairo_set_source_pixmap (cr, p->gobj(), 0, 0);
                cairo_rectangle (cr, 0, 0, w, h);
                cairo_fill (cr);
                cairo_destroy (cr);
                
                return false;
        }
        
        void drag_data_get (Glib::RefPtr<Gdk::DragContext> const &, Gtk::SelectionData & selection_data, guint, guint, T* child)
        {
                selection_data.set (selection_data.get_target(), 8, (const guchar *) &child, sizeof (&child));
        }
        
        void drag_data_received (
                Glib::RefPtr<Gdk::DragContext> const & context, int /*x*/, int y, Gtk::SelectionData const & selection_data, guint /*info*/, guint time
                )
        {
                /* work out where it was dropped */
                std::pair<T*, double> const drop = get_child_at_position (y);
                
                if (_drag_source == this) {

                        /* dropped from ourselves onto ourselves */

                        T* child = *((T * const *) selection_data.get_data());

                        if (drop.first == 0) {
                                _internal_vbox.reorder_child (child->widget(), -1);
                        } else {

                                /* where in the list this child should be dropped */
                                int target = drop.second + 0.5;
                                
                                /* find out whether the child was `picked up' from before the drop position */
                                int n = 0;
                                typename std::list<T*>::const_iterator i = _children.begin ();
                                while (i != _children.end() && *i != child && n < target) {
                                        ++i;
                                        ++n;
                                }
                                
                                /* if so, adjust the drop position to account for this */
                                if (n < target) {
                                        --target;
                                }
                                
                                _internal_vbox.reorder_child (child->widget(), target);
                        }
                        
                } else {
                        
                        /* drag started in another DnDVBox; raise a signal to say what happened */
                        
                        std::list<T*> dropped = _drag_source->selection ();
                        DropFromAnotherBox (_drag_source, drop.first, context);
                }
                
                context->drag_finish (false, false, time);
        }
        
        void drag_end (Glib::RefPtr<Gdk::DragContext> const &, T *)
        {
                delete _drag_icon;
                _drag_icon = 0;
                
                _drag_child = 0;
                remove_placeholder ();

                Reordered (); /* EMIT SIGNAL */
        }

        int create_or_update_placeholder (double c)
        {
                if (_placeholder == 0) {
                        _placeholder = manage (new Gtk::Label (""));
                        _internal_vbox.pack_start (*_placeholder, false, false);
                        _placeholder->show ();
                }

                /* round up the index, unless we're off the end of the children */
                int const n = c < 0 ? -1 : int (c + 0.5);
                _internal_vbox.reorder_child (*_placeholder, n);
                return n;
        }

        bool drag_motion (Glib::RefPtr<Gdk::DragContext> const &, int /*x*/, int y, guint)
        {
                if (_children.empty ()) {
                        return false;
                }

                T* before;
                T* at;
                T* after;

                /* decide where we currently are */
                double const c = get_children_around_position (y, &before, &at, &after);

                /* whether we're in the top or bottom half of the child that we're over */
                bool top_half = (c - int (c)) < 0.5;

                /* Note that when checking on whether to remove a placeholder, we never do
                   so if _drag_child is 0 as this means that the child being dragged is
                   coming from a different DnDVBox, so it will never be the same as any
                   of our children.
                */

                if (top_half && _drag_child && (before == _drag_child || at == _drag_child)) {
                        /* dropping here would have no effect, so remove the visual cue */
                        remove_placeholder ();
                        return false;
                }

                if (!top_half && _drag_child && (at == _drag_child || after == _drag_child)) {
                        /* dropping here would have no effect, so remove the visual cue */
                        remove_placeholder ();
                        return false;
                }

                create_or_update_placeholder (c);
                return false;
        }

        void drag_leave (Glib::RefPtr<Gdk::DragContext> const &, guint)
        {
                remove_placeholder ();
        }

        bool button_press (GdkEventButton* ev, T* child)
        {
                if (_expecting_unwanted_button_event == true && child == 0) {
                        _expecting_unwanted_button_event = false;
                        return true;
                }

                if (child) {
                        _expecting_unwanted_button_event = true;
                }
                        
                if (ev->button == 1 || ev->button == 3) {

                        if (!selected (child)) {

                                if ((ev->state & Gdk::SHIFT_MASK) && !_selection.empty()) {

                                        /* Shift-click; select all between the clicked child and any existing selections */

                                        bool selecting = false;
                                        bool done = false;
                                        for (typename std::list<T*>::const_iterator i = _children.begin(); i != _children.end(); ++i) {

                                                bool const was_selected = selected (*i);

                                                if (selecting && !was_selected) {
                                                        add_to_selection (*i);
                                                }
                                                
                                                if (!selecting && !done) {
                                                        if (selected (*i)) {
                                                                selecting = true;
                                                        } else if (*i == child) {
                                                                selecting = true;
                                                                add_to_selection (child);
                                                        }
                                                } else if (selecting) {
                                                        if (was_selected || *i == child) {
                                                                selecting = false;
                                                                done = true;
                                                        }
                                                }
                                        }

                                } else {
                                                
                                        if ((ev->state & Gdk::CONTROL_MASK) == 0) {
                                                clear_selection ();
                                        }
                                        
                                        if (child) {
                                                add_to_selection (child);
                                        }

                                }
                                
                                SelectionChanged (); /* EMIT SIGNAL */
                                
                        } else {
                                /* XXX THIS NEEDS GENERALIZING FOR OS X */
                                if (ev->button == 1 && (ev->state & Gdk::CONTROL_MASK)) {
                                        if (child && selected (child)) {
                                                remove_from_selection (child);
                                                SelectionChanged (); /* EMIT SIGNAL */
                                        }
                                }
                        }
                }

                return ButtonPress (ev, child); /* EMIT SIGNAL */
        }
        
        bool button_release (GdkEventButton* ev, T* child)
        {
                if (_expecting_unwanted_button_event == true && child == 0) {
                        _expecting_unwanted_button_event = false;
                        return true;
                }

                if (child) {
                        _expecting_unwanted_button_event = true;
                }

                return ButtonRelease (ev, child); /* EMIT SIGNAL */
        }

        void setup_child_state (T* c)
        {
                assert (c);
                c->set_visual_state (Selected, (selected (c) || (_active == c)));
        }

        void clear_selection ()
        {
                std::list<T*> old_selection = _selection;
                _selection.clear ();
                for (typename std::list<T*>::iterator i = old_selection.begin(); i != old_selection.end(); ++i) {
                        setup_child_state (*i);
                }
        }
        
        void add_to_selection (T* child)
        {
                if ( !child->is_selectable() )
                        return;
                _selection.push_back (child);
                setup_child_state (child);
        }

        void remove_from_selection (T* child)
        {
                typename std::list<T*>::iterator x = find (_selection.begin(), _selection.end(), child);
                if (x != _selection.end()) {
                        T* c = *x;
                        _selection.erase (x);
                        setup_child_state (c);
                }
        }
                
        T* child_from_widget (Gtk::Widget const * w) const
        {
                typename std::list<T*>::const_iterator i = _children.begin();
                while (i != _children.end() && &(*i)->widget() != w) {
                        ++i;
                }
                
                if (i == _children.end()) {
                        return 0;
                }

                return *i;
        }
        
        Gtk::VBox _internal_vbox;
        std::list<Gtk::TargetEntry> _targets;
        std::list<T*> _children;
        std::list<T*> _selection;
        T* _active;
        Gtk::Window* _drag_icon;
        bool _expecting_unwanted_button_event;
        Gtk::Label* _placeholder;
        T* _drag_child;
        
        static DnDVBox* _drag_source;
        
};

template <class T>
DnDVBox<T>* DnDVBox<T>::_drag_source = 0;
        
}