410. How to set the background color of the column header of a treeview?

Problem

Suppose you would like to set the background color of the header of the Price column in the treeview as shown below:

How to set the background color of the column header of a treeview?


Solution

  • For those of you who have played with PHP-GTK2 for some time, you will know that setting the background of treeview header is not supported, yet. I'm sure one day it will. But at least for now, there is no method that allows you to do so directly.
  • However, by getting the pointer to the GtkButton that holds the treeview header, you can set the background color of that GtkButton, and hence the header.
  • I know there are some people that don't like this. They said it's not right accessing into the internal data structures. If you don't like this, then don't use this method.
  • However, if you're like me, who faced a client that doesn't take "no, it's not supported yet" for an answer, at least you have an immediate workable solution to set the background color of the treeview header!

Sample Code

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<?php
$window = new GtkWindow();
$window->set_size_request(400, 200);
$window->connect_simple('destroy', array('Gtk','main_quit'));
$window->add($vbox = new GtkVBox());

// display title
$title = new GtkLabel("Set the background color of treeview column header");
$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(new GtkLabel(), 0, 0);

// 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
    $scrolled_win = new GtkScrolledWindow();
    $scrolled_win->set_policy( Gtk::POLICY_AUTOMATIC,
        Gtk::POLICY_AUTOMATIC);
    $vbox->pack_start($scrolled_win);

    // Creates the list store
    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);

        if ($col==3) {
            $col_header_button = get_col_header_button($column); // note 1
            $col_header_button->modify_bg(Gtk::STATE_NORMAL, 
                GdkColor::parse('#ffff00')); // note 2
            $col_header_button->modify_bg(Gtk::STATE_PRELIGHT, 
                GdkColor::parse('#ffff00')); // note 2
        }
    }

    // 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 get_col_header_button($column) { // note 3
    $widget = $column->get_widget();
    $parent = $widget;
    while ($parent->get_name()!='GtkButton') {
        $widget = $parent;
        $parent = $widget->get_parent();
    }
    return $parent;
}

?>

Output

How to set the background color of the column header of a treeview?

 

Explanation

We make use of the code from How to display a 2D array in GtkTreeView - Part 5 - get user selection? to set up the base treeview.

What's new here:

  1. Get hold of the GtkButton that holds the treeview column header.
  2. Set the background color of the GtkButton. Note that I set both the NORMAL and PRELIGHT states to the same color. You could set them to different colors if you want.
  3. This is the function that returns you the pointer to the GtkButton holding the treeview column header.

Note

In the event that you find that the above sample code doesn't work, please refer to the following article: Setting the background color of buttons.

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