348. How to scroll to newly inserted item in a linear list using GtkTreeView - Part 2 - setting GtkAdjustment of GtkScrolledWindow?

Problem

This is in response to vlada's post titled "Automatic scrolling".

He has inserted some items in a linear list using GtkTreeView, and he would like to the treeview to automatically scroll to the newly inserted item.

In Part 1, we make use of the mathod GtkTreeView::scroll_to_cell().

In this Part 2, we achieve the same effect by setting GtkAdjustment of GtkScrolledWindow as shown below:

How to scroll to newly inserted item in a linear list using GtkTreeView - Part 2 - setting GtkAdjustment of GtkScrolledWindow?


Solution


Sample Code

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<?php
$window = new GtkWindow();
$window->set_size_request(400, 210);
$window->connect_simple('destroy', array('Gtk','main_quit'));
$window->add($vbox = new GtkVBox());

// display title
$title = new GtkLabel("          Scroll to newly inserted item in linear list\n".
"Part 2 - setting GtkAdjustment of GtkScrolledWindow");
$title->modify_font(new PangoFontDescription("Times New Roman Italic 10"));
$title->modify_fg(Gtk::STATE_NORMAL, GdkColor::parse("#0000ff"));
$title->set_size_request(-1, 40);
$vbox->pack_start($title, 0, 0);

$vbox->pack_start($hbox = new GtkHBox(), 0, 0);
$button = new GtkButton('Insert New Item');
$hbox->pack_start($button, 0, 0);
$button->connect('clicked', 'on_click');

// the 2D table
$data = array(
array('row0', 'item 42', 2, 3.1),
array('row1', 'item 36', 20, 6.21),
array('row2', 'item 21', 8, 9.36),
array('row3', 'item 10', 11, 12.4),
array('row4', 'item 7', 5, 15.5),
array('row5', 'item 4', 17, 18.6),
array('row6', 'item 3', 20, 21.73));

display_table($vbox, $data);

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

function display_table($vbox, $data) {

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

    // Creates the list store
    global $view, $model;
    if (defined("GObject::TYPE_STRING")) {
        $model = new GtkListStore(GObject::TYPE_STRING, GObject::TYPE_STRING,
            GObject::TYPE_LONG, GObject::TYPE_DOUBLE);
    } else {
        $model = new GtkListStore(Gtk::TYPE_STRING, Gtk::TYPE_STRING,
            Gtk::TYPE_LONG, Gtk::TYPE_DOUBLE);
    }
    $field_header = array('Row #', 'Description', 'Qty', 'Price');
    $field_justification = array(0.0, 0.0, 0.5, 1.0);

    // 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);
    }

    $selection = $view->get_selection();
    $selection->connect('changed', 'on_selection');
}

// self-defined function to format the price column
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);
}

// the function that is called when user selects a row
function on_selection($selection) {
    list($model, $iter) = $selection->get_selected();
    $desc = $model->get_value($iter, 1);
    $qty = $model->get_value($iter, 2);
    $price = $model->get_value($iter, 3);
    print "You have selected $desc: $qty ($price)\n";
}

function on_click($button) {
    global $model;
    $n = $model->iter_n_children(NULL);
    $model->append(array("row$n", "item $n",
        rand(1,20), sqrt(rand(1,100))));

    global $scrolled_win;
    $adj = $scrolled_win->get_vadjustment(); // note 1
    $adj->set_value($adj->upper); // note 2
}

?>

Output

As shown above.

 

Explanation

The above code is based on How to scroll to newly inserted item in a linear list using GtkTreeView - Part 1 - using GtkTreeView scroll_to_cell?

What's new here:

  1. Get the vadjustment.
  2. Scroll to the last row by setting the vadjustment to the upper boundary (i.e. the maximum value)

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