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Problem This is in response to Paamayim's post titled 'smooth scrolling for a gtkimage drawing'.
He has set up a bar graph and wants to allow the user to dynamically change the scale of the x-axis and y-axis through the scrollbars as shown below.
As there are quite a number of techniques involved, to make it easier to follow, I've spread the techniques over 5 parts:
- Part 1 - adds the vscrollbar
- Part 2 - aligns the graph to bottom left
- Part 3 - adds the hscrollbar
- Part 4 - adds both vscrollbar and hscrollbar
- Part 5 (this article) - use only one scrollbar to control scaling of both axis
Part 5: After playing with the code from Part 4 for a while, I find that it might be more convenient for the user to have only one scroll bar to scale both the x- and y-axis together as shown below:
Solution
- Please refer to Part 2 for the set up of vscrollbar.
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| <?php
$window = new GtkWindow();
$window->set_title($argv[0]);
$window->connect_simple('destroy', array('Gtk','main_quit'));
$window->add($vbox = new GtkVBox());
// display title
$title = new GtkLabel("Dynamically scale a bar graph using scrollbars\n".
"Part 5: x- and y-directions with only one scrollbar");
$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);
$title->set_justify(Gtk::JUSTIFY_CENTER);
$alignment = new GtkAlignment(0.5, 0, 0, 0);
$alignment->add($title);
$vbox->pack_start($alignment, 0, 0);
$vbox->pack_start(new GtkLabel(), 0, 0);
setup_bargraph($vbox);
$window->show_all();
Gtk::main();
function setup_bargraph($vbox) {
global $img;
$vbox->pack_start($hbox = new GtkHBox());
$hbox->pack_start($vbox2 = new GtkVBox());
$img = new GtkImage();
$vbox2->pack_start(new GtkVBox());
$vbox2->pack_start($hbox2 = new GtkHBox(), 0);
$hbox2->pack_start($img, 0);
$adj = new GtkAdjustment(0.87, 0.87, 2, 0.1, .5);
$vscrollbar = new GtkVScrollbar($adj);
$vscrollbar->connect('value-changed', 'on_value_changed');
$hbox->pack_start($vscrollbar, 0);
$adj->set_value(1);
$adj->value_changed();
$hbox->set_size_request(600, 400);
}
function draw_bargraph($x_scale, $y_scale) {
global $img;
$max_width = 360 * $x_scale;
$max_height = 200 * $y_scale;
$margin = 40;
$im = imagecreate($max_width, $max_height);
$white = imagecolorallocate($im,255,255,255);
$black = imagecolorallocate($im,0,0,0);
$blue = imagecolorallocate($im,0,0,255);
$data = array('120','160','300','240');
imageline($im, 10, 5, 10, $max_height-$margin, $black );
imageline($im, 10, $max_height-$margin,
$max_width-$margin, $max_height-$margin, $black );
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- Note that this is only 70% of the sample code. You have to be a registered member to see the entire sample code. Please login or register.
- Registration is free and immediate.
- Have some doubt about the registration? Please read this forum article.
Explanation The above code is a modification of the codes from Part 4.
- Get the value of the vscrollbar and use this for both the scaling of the x- and y-axis.
- Redraw the bar graph.
Note
This example serves mainly to illustrate the use of GtkAdjustment and GtkVScrollbar. I will leave it to you to optimize and polish the gd2 portion (for the display of the bar graph).
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March 08, 2008 8:51am
July 03, 2008 10:09am