BASIC WIDGETS in Font

Creator DataMatrix in Font BASIC WIDGETS

Listing 4-7. Integer and Floating-point Number Selection with Scales (scales.c) #include <gtk/gtk.h> int main (int argc, char *argv[]) { GtkWidget *window, *scale_int, *scale_float, *vbox; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_title (GTK_WINDOW (window), "Scales"); gtk_container_set_border_width (GTK_CONTAINER (window), 10); gtk_widget_set_size_request (window, 250, -1); /* Create a scale that scrolls integers and one that scrolls floating point. */ scale_int = gtk_hscale_new_with_range (0.0, 10.0, 1.0); scale_float = gtk_hscale_new_with_range (0.0, 1.0, 0.1); /* Set the number of decimal places to display for each widget. */ gtk_scale_set_digits (GTK_SCALE (scale_int), 0); gtk_scale_set_digits (GTK_SCALE (scale_float), 1); /* Set the position of the value with respect to the widget. */ gtk_scale_set_value_pos (GTK_SCALE (scale_int), GTK_POS_RIGHT); gtk_scale_set_value_pos (GTK_SCALE (scale_float), GTK_POS_LEFT); vbox = gtk_vbox_new (FALSE, 5); gtk_box_pack_start_defaults (GTK_BOX (vbox), scale_int); gtk_box_pack_start_defaults (GTK_BOX (vbox), scale_float); gtk_container_add (GTK_CONTAINER (window), vbox); gtk_widget_show_all (window); gtk_main (); return 0; } There are two ways to create new scale widgets. The first is with gtk_hscale_new() or gtk_vscale_new(), which accepts a GtkAdjustment that defines how the scale will work. GtkWidget *gtk_hscale_new (GtkAdjustment *adjustment); Alternatively, you can create scales with gtk_hscale_new_with_range() or gtk_vscale_new_with_range(). This function accepts the minimum value, the maximum value, and the step increment of the scale.

GtkWidget *gtk_hscale_new_with_range (gdouble minimum, gdouble maximum, gdouble step); Since the value of the scale is always stored as a gdouble, you will need to define the number of decimal places to show with gtk_scale_set_digits() if the default value is not what you want. The default number of decimal places is calculated based on the number of decimal places provided for the step increment. For example, if you provide a step increment of 0.01, two decimal places will be displayed by default. void gtk_scale_set_digits (GtkScale *scale, gint digits); Depending on what type of scale widget you are using, you may want to change where the value is displayed with gtk_scale_set_value_pos(). Positions are defined by the GtkPositionType enumeration, and they are GTK_POS_LEFT, GTK_POS_RIGHT, GTK_POS_TOP, and GTK_POS_BOTTOM. You can also use gtk_scale_set_draw_value() to hide the value from the user s view altogether. void gtk_scale_set_value_pos (GtkScale *scale, GtkPositionType pos); GtkScale is derived from a widget called GtkRange. This widget is an abstract type that provides the ability to handle an adjustment. Because of this, you should use gtk_range_get_value() to retrieve the current value of the scale. GtkRange also provides the value-changed signal, which is emitted when the user changes the position of the scale.

In the next few sections, you will be editing widget style properties, so it is time to learn about the GtkStyle structure and resource files. Resource files are external collections of style settings that can be loaded and applied to your application during runtime to allow for further customization.

Every GtkWidget has five public members, which are shown in the following code snippet. These are style information, size requisition, size allocation, a GdkWindow that is used to draw the widget on the screen, and a pointer to the parent widget. typedef struct { GtkStyle *style; GtkRequisition requisition; GtkAllocation allocation; GdkWindow *window; GtkWidget *parent; } GtkWidget;

The GtkStyle structure stores drawing information about the widget. The content of the structure follows: typedef struct { GdkColor fg[5] GdkColor bg[5] GdkColor light[5] GdkColor dark[5] GdkColor mid[5] GdkColor text[5] GdkColor base[5] GdkColor text_aa[5]; GdkColor black, white;

/* /* /* /* /* /* /* /* /*

The foreground color for most widgets. */ The background color for most widgets. */ Lighter colors used for creating widget shadows. */ Darker colors used for creating widget shadows. */ The color midway between light and dark. */ The text color for most text widgets. */ The background color used for text-editing widgets. */ Used for anti-aliased text colors. */ Colors that represent "Black" and "White". */ /* The default text font. */ /* Thickness of lines. */ /* Background image to use for a widget. */

PangoFontDescription *font_desc; gint xthickness, ythickness; GdkPixmap *bg_pixmap[5];

/* Graphics contexts that hold drawing properties for each color and state. */ GdkGC *fg_gc [5], *bg_gc [5], *light_gc[5], *dark_gc[5], *mid_gc[5], *text_gc[5], *base_gc[5], *text_aa_gc[5]; GdkGC *black_gc, *white_gc; } GtkStyle; There are many objects in the GtkStyle structure. Each of these will have a default value set by the user s style, so overriding them may not always be a good idea. However, if it is necessary, editing a widget s GtkStyle is a simple way to change how it is displayed. You will notice that many of the style properties are arrays of file elements. This is because each of these elements can have different values for one of the following five possible widget states: GTK_STATE_NORMAL: The widget during normal operation. GTK_STATE_ACTIVE: An active widget, such as when a toggle is depressed. GTK_STATE_PRELIGHT: A widget when the mouse pointer is over the widget; it will respond to button clicks. GTK_STATE_SELECTED: A widget when the widget or its text has been selected. GTK_STATE_INSENSITIVE: A widget is deactivated and will not respond to the user.