127. How to drag and drop between a table and a list - Part 2 - in both directions?

Problem

You have set up selection of items by drag-and-drop from the table on the left to the list on the right in Part 1.

Now you would like to allow removal of selection by dragging from right to left. You would also like to eliminate any duplication of selection as shown below:

How to drag and drop between a table and a list - Part 2 - in both directions?


Solution

We add in support for drag-and-drop in both directions using exactly the same technique as outlined in the article How to drag and drop between 2 GtkTreeViews - Part 2 - in both directions?


Sample Code

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<?php
$window = new GtkWindow();
$window->set_size_request(400, 240);
$window->connect_simple('destroy', array('Gtk','main_quit'));
$window->add($vbox = new GtkVBox());

// display title
$title = new GtkLabel("Drag and Drop between a table and a list - Part 2
             drag-and-drop in both directions");
$title->modify_font(new PangoFontDescription("Times New Roman Italic 10"));
$title->modify_fg(Gtk::STATE_NORMAL, GdkColor::parse("#0000ff"));
$title->set_size_request(-1, 48);
$vbox->pack_start($title, false);

// setup table
$table = new GtkTable();
$data = array(
array('', 'header1', 'header2', 'header3'),
array('row0', 1, 2, 3),
array('row1', 4, 5, 6),
array('row2', 7, 8, 9),
array('row3', 10, 11, 12),
array('row4', 13, 14, 15));
display_table ($table, $data);

$hbox = new GtkHBox();
$vbox->pack_start($hbox);
$hbox->pack_start($table, 0, 0);
$hbox->pack_start(new GtkLabel(' '), 0 ,0);

// setup treeview
$data2 = array();
$view2 = display_treeview($hbox, $data2);
$view2->drag_dest_set(Gtk::DEST_DEFAULT_ALL,
    array( array( 'text/plain', 0, 0)),
    Gdk::ACTION_COPY|Gdk::ACTION_MOVE);
$view2->connect('drag-data-received', 'on_drop', $table);

// set up drag and drop in the other direction
$table->drag_dest_set(Gtk::DEST_DEFAULT_ALL, 
    array( array( 'text/plain', 0, 0)), 
    Gdk::ACTION_COPY|Gdk::ACTION_MOVE);  // note 1
$table->connect('drag-data-received', 'on_drop_right_to_left', $view2); // note 1
$view2->drag_source_set(Gdk::BUTTON1_MASK, 
    array( array( 'text/plain', 0, 0)), 
    Gdk::ACTION_COPY|Gdk::ACTION_MOVE); // note 2
$view2->connect('drag-data-get', 'on_drag_right_to_left'); // note 2

$window->show_all();
Gtk::main();

function display_table($table, $a) {
    for ($row=0; $row<count($a); ++$row) {
        for ($col=0; $col<count($a[$row]); ++$col) {
            $frame = new GtkFrame();
            $eventbox = new GtkEventBox();
            $frame->add($eventbox);
            $label = new GtkLabel($a[$row][$col]);
            $eventbox->add($label);
            if ($row==0) {
                $eventbox->modify_bg(Gtk::STATE_NORMAL,
                    GdkColor::parse("#FFCC66"));
            } elseif ($row%2==0) {
                $eventbox->modify_bg(Gtk::STATE_NORMAL,
                    GdkColor::parse("#CCFF99"));
            }
            $table->attach($frame, $col, $col+1, $row, $row+1,
                Gtk::FILL, Gtk::SHRINK, 0, 0);
            $eventbox->drag_source_set(Gdk::BUTTON1_MASK,
                array( array( 'text/plain', 0, 0)),
                   Gdk::ACTION_COPY|Gdk::ACTION_MOVE);
            $eventbox->connect('drag-data-get', 'on_drag',
                $row, $col, $a[$row][$col]);
        }
    }
}

function display_treeview($container, $data) {

    // Set up a scroll window
    $scrolled_win = new GtkScrolledWindow();
    $scrolled_win->set_policy( Gtk::POLICY_AUTOMATIC,
        Gtk::POLICY_AUTOMATIC);
    $container->pack_start($scrolled_win);

    // Creates the list store
    if (defined("GObject::TYPE_STRING")) {
         $model = new GtkListStore(GObject::TYPE_LONG, GObject::TYPE_LONG,
            GObject::TYPE_STRING);
    } else {
        $model = new GtkListStore(Gtk::TYPE_LONG, Gtk::TYPE_LONG,
            Gtk::TYPE_STRING);
    }
    $field_header = array('Row', 'Col', 'Value');
    $field_justification = array(0.5, 0.5, 0.0);

    // Creates the view to display the list store
    $view = new GtkTreeView($model);
    $scrolled_win->add($view);

    // Creates the columns
    for ($col=0; $col<count($field_header); ++$col) {
        $cell_renderer = new GtkCellRendererText();
        $cell_renderer->set_property("xalign", $field_justification[$col]);
        $column = new GtkTreeViewColumn($field_header[$col],
            $cell_renderer, 'text', $col);
        $column->set_alignment($field_justification[$col]);
        $column->set_sort_column_id($col);

        // set the header font and color
        $label = new GtkLabel($field_header[$col]);
        $label->modify_font(new PangoFontDescription("Arial Bold"));
        $label->modify_fg(Gtk::STATE_NORMAL, GdkColor::parse("#0000FF"));
        $column->set_widget($label);
        $label->show();

        // setup self-defined function to display alternate row color
        $column->set_cell_data_func($cell_renderer, "format_col", $col);
        $view->append_column($column);
    }

    // pupulates the data
    for ($row=0; $row<count($data); ++$row) {
        $values = array();
        for ($col=0; $col<count($data[$row]); ++$col) {
            $values[] = $data[$row][$col];
        }
        $model->append($values);
    }
    return $view;
}

// display alternate row color
function format_col($column, $cell, $model, $iter, $col_num) {
    $path = $model->get_path($iter); // get the current path
    $row_num = $path[0]; // get the row number
    if ($col_num==3) {
        $amt = $model->get_value($iter, 3);
        $cell->set_property('text', '$'.number_format($amt,2));
    }
    $row_color = ($row_num%2==1) ? '#dddddd' : '#ffffff';
    $cell->set_property('cell-background', $row_color);
}

// process drag
function on_drag($widget, $context, $data, $info, $time, $row, $col, $value) {
    $drag_content = array('tree', $row, $col, $value); // note 3
    $data->set_text(serialize($drag_content));
}

// process drop
function on_drop($widget, $context, $x, $y, $data, $info, $time, $images) {
    // append the dragged item to the destination view
    $dragged_content = unserialize($data->data);
    if ($dragged_content[0]=='treeview') return; // note 4
    $dragged_row = $dragged_content[1];
    $dragged_col = $dragged_content[2];
    $model = $widget->get_model();
    $drag_src = array_shift($dragged_content);
    if (check_for_duplication($model, $dragged_row, $dragged_col)) {
        $model->append($dragged_content);
    }
}

// check for duplication
function check_for_duplication($model, $dragged_row, $dragged_col) { // note 5
    $total_rows = $model->iter_n_children(NULL);
    $found = 0;
    for ($i=0; $i<$total_rows; ++$i) {
        $iter = $model->get_iter($i);
        $row = $model->get_value($iter, 0);
        $col = $model->get_value($iter, 1);
        if ($row==$dragged_row && $col==$dragged_col) {
            $found = 1;
            echo "row $row and col $col already exists!\n";
            break;
        }
    }
    return ($found) ? 0 : 1;
}

// process drag on the right
function on_drag_right_to_left($widget, $context, $data, $info, $time) {// note 6
    $selection = $widget->get_selection();
    list($model, $iter) = $selection->get_selected();
    if ($iter==null) return;
    $row = $model->get_value($iter, 0);
    $col = $model->get_value($iter, 1);
    $value = $model->get_value($iter, 2);
    $data->set_text(serialize(array('treeview', $row, $col, $value))); // note 4
}

// process drop on the left
function on_drop_right_to_left($widget, $context,
    $x, $y, $data, $info, $time, $src_view) {// note 7
    // remove from src
    $data = unserialize($data->data);
    if ($data[0]=='tree') return; // note 3
    $src_selection = $src_view->get_selection();
    list($src_model, $src_iter) = $src_selection->get_selected();
    if ($src_iter==null) {
        return;
    }
    $src_model->remove($src_iter);
}

?>

Output

As shown above.

 

Explanation

This example make use of the code from the article How to drag and drop between 2 GtkTreeViews - Part 2 - in both directions?

This table on the left was direct from the article How to display a 2D array in table - Part 5?

What's new here:

  1. Set up drag on the right side (the tree view).
  2. Set up drop on the left side (the table). Note that the main purpose of the drag from right to left is remove selections from the left. As such, for this drop, it's set up on the GtkTable so that the user can drop anywhere on the table.
  3. Note that in this example we attached an additional information "tree" in the dragged data when the user starts dragging from the left. This is to allow us to know if the user dropped the data on the left instead of on the right.
  4. Similarly, we attached an additional information "treeview" in the dragged data when the user starts dragging from the right. This is to allow us to know if the user dropped the data on the right instead of on the left.
  5. Check for any duplication. We basically loop through the existing items in the treeview. If there's no duplication, we will add the new item.
  6. Process drag from the right.
  7. Process drop on the left.

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