|
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 (this article) - adds both vscrollbar and hscrollbar
- Part 5 - use only one scrollbar to control scaling of both axis
In this Part 4, we will combine the codes from Part 2 and Part 3 so that the users now have the vscrollbar for scaling the y-axis and the hscrollbar for scaling the x-axis as shown below:
Solution
- Please refer to Part 2 for the set up of vscrollbar.
- Please refer to Part 3 for the set up of hscrollbar.
Sample Code 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
| <?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 4: with both hscrollbar and vscrollbar");
$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);
global $hadj, $vadj;
$vadj = new GtkAdjustment(0.87, 0.87, 2, 0.1, .5);
$vscrollbar = new GtkVScrollbar($vadj);
$vscrollbar->connect('value-changed', 'on_value_changed');
$hbox->pack_start($vscrollbar, 0);
$hadj = new GtkAdjustment(0.5, 0.5, 2, 0.01, .5);
$hscrollbar = new GtkHScrollbar($hadj);
$hscrollbar->connect('value-changed', 'on_value_changed');
$vbox->pack_start($hscrollbar, 0);
$vadj->set_value(1);
$hadj->set_value(1);
$vadj->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,
|
- 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 synthesis of the codes from Part 2 and Part 3.
- Note that we can handle both scrollbars with just one signal handler.
- 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).
Related Links
User reviews There are no user reviews yet. Note: You have to be a registered member to leave a comment. Free registration here. |
