a GtkLabel widget, you need to change the background color of
its parent, i.e. the object that you pack it into.</para>
</sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I set the color and font of a GtkLabel using a
+ Resource File?</title>
+
+ <para>The widget name path constructed for a Label consists of
+ the widget names of its object hierarchy as well, e.g.</para>
+
+ <para><literallayout>
+ <literal>window (name: humphrey)</literal>
+ <literal> hbox</literal>
+ <literal> label (name: mylabel)</literal>
+ </literallayout></para>
+
+ <para>The widget path your pattern needs to match would be:
+ <literal>humphrey.GtkHBox.mylabel</literal></para>
+
+ <para>The resource file may look something like:</para>
+
+<programlisting role="C">
+style "title"
+{
+ fg[NORMAL] = {1.0, 0.0, 0.0}
+ font = "-adobe-helvetica-bold-r-normal--*-140-*-*-*-*-*-*"
+}
+widget "*mylabel" style "title"
+</programlisting>
+
+ <para>In your program, you would also need to give a name to
+ the Label widget, which can be done using:</para>
+
+<programlisting role="C">
+ label = gtk_label_new("Some Label Text");
+ gtk_widget_set_name(label, "mylabel");
+ gtk_widget_show(label);
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I configure Tooltips in a Resource File?</title>
+
+ <para>The tooltip's window is named "gtk-tooltips",
+ GtkTooltips in itself is not a GtkWidget (though a GtkObject)
+ and as such is not attempted to match any widget styles.</para>
+
+ <para>So, you resource file should look something like:</para>
+
+<programlisting role="C">
+style "postie"
+{
+ bg[NORMAL] = {1.0, 1.0, 0.0}
+}
+widget "gtk-tooltips*" style "postie"
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>I can't add more than (something like) 2000 chars in a
+ GtkEntry. What's wrong?</title>
+
+ <para>There is now a known problem in the GtkEntry widget. In
+ the <literal>gtk_entry_insert_text()</literal> function, the
+ following lines limit the number of chars in the entry to
+ 2047.</para>
+
+<programlisting role="C">
+ /* The algorithms here will work as long as, the text size (a
+ * multiple of 2), fits into a guint16 but we specify a shorter
+ * maximum length so that if the user pastes a very long text, there
+ * is not a long hang from the slow X_LOCALE functions. */
+
+ if (entry->text_max_length == 0)
+ max_length = 2047;
+ else
+ max_length = MIN (2047, entry->text_max_length);
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I make a GtkEntry widget activate on pressing
+ the Return key?</title>
+
+ <para>The Entry widget emits an 'activate' signal when you
+ press return in it. Just attach to the activate signal on the
+ entry and do whatever you want to do. Typical code would
+ be:</para>
+
+<programlisting role="C">
+ entry = gtk_entry_new();
+ gtk_signal_connect (GTK_OBJECT(entry), "activate",
+ GTK_SIGNAL_FUNC(entry_callback),
+ NULL);
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I validate/limit/filter the input to a
+ GtkEntry?</title>
+
+ <para>If you want to validate the text that a user enters into
+ a GtkEntry widget you can attach to the "insert_text" signal
+ of the entry, and modify the text within the callback
+ function. The example below forces all characters to
+ uppercase, and limits the range of characters to A-Z. Note
+ that the entry is cast to an object of type GtkEditable, from
+ which GtkEntry is derived.</para>
+
+<programlisting role="C">
+#include <ctype.h>
+#include <gtk/gtk.h>
+
+void insert_text_handler (GtkEntry *entry,
+ const gchar *text,
+ gint length,
+ gint *position,
+ gpointer data)
+{
+ GtkEditable *editable = GTK_EDITABLE(entry);
+ int i, count=0;
+ gchar *result = g_new (gchar, length);
+
+ for (i=0; i < length; i++) {
+ if (!isalpha(text[i]))
+ continue;
+ result[count++] = islower(text[i]) ? toupper(text[i]) : text[i];
+ }
+
+ if (count > 0) {
+ gtk_signal_handler_block_by_func (GTK_OBJECT (editable),
+ GTK_SIGNAL_FUNC (insert_text_handler),
+ data);
+ gtk_editable_insert_text (editable, result, count, position);
+ gtk_signal_handler_unblock_by_func (GTK_OBJECT (editable),
+ GTK_SIGNAL_FUNC (insert_text_handler),
+ data);
+ }
+ gtk_signal_emit_stop_by_name (GTK_OBJECT (editable), "insert_text");
+
+ g_free (result);
+}
+
+int main (int argc,
+ char *argv[])
+{
+ GtkWidget *window;
+ GtkWidget *entry;
+
+ gtk_init (&argc, &argv);
+
+ /* create a new window */
+ window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+ gtk_window_set_title(GTK_WINDOW (window), "GTK Entry");
+ gtk_signal_connect(GTK_OBJECT (window), "delete_event",
+ (GtkSignalFunc) gtk_exit, NULL);
+
+ entry = gtk_entry_new();
+ gtk_signal_connect(GTK_OBJECT(entry), "insert_text",
+ GTK_SIGNAL_FUNC(insert_text_handler),
+ NULL);
+ gtk_container_add(GTK_CONTAINER (window), entry);
+ gtk_widget_show(entry);
+
+ gtk_widget_show(window);
+
+ gtk_main();
+ return(0);
+}
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I use horizontal scrollbars with a GtkText
+ widget?</title>
+
+ <para>The short answer is that you can't. The current version
+ of the GtkText widget does not support horizontal
+ scrolling. There is an intention to completely rewrite the
+ GtkText widget, at which time this limitation will be
+ removed.</para>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I change the font of a GtkText widget?</title>
+
+ <para>There are a couple of ways of doing this. As GTK+ allows
+ the appearance of applications to be changed at run time using
+ resources you can use something like the following in the
+ appropriate file:</para>
+
+<programlisting role="C">
+style "text"
+{
+ font = "-adobe-helvetica-medium-r-normal--*-100-*-*-*-*-*-*"
+}
+</programlisting>
+
+ <para>Another way to do this is to load a font within your
+ program, and then use this in the functions for adding text to
+ the text widget. You can load a font using, for example:</para>
+
+<programlisting role="C">
+ GdkFont *font;
+ font = gdk_font_load("-adobe-helvetica-medium-r-normal--*-140-*-*-*-*-*-*");
+</programlisting>
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I set the cursor position in a GtkText
+ object?</title>
+
+ <para>Notice that the response is valid for any object that
+ inherits from the GtkEditable class.</para>
+
+ <para>Are you sure that you want to move the cursor position?
+ Most of the time, while the cursor position is good, the
+ insertion point does not match the cursor position. If this
+ apply to what you really want, then you should use the
+ <literal>gtk_text_set_point()</literal> function. If you want
+ to set the insertion point at the current cursor position, use
+ the following:</para>
+
+<programlisting role="C">
+ gtk_text_set_point(GTK_TEXT(text),
+ gtk_editable_get_position(GTK_EDITABLE(text)));
+</programlisting>
+
+ <para>If you want the insertion point to follow the cursor at
+ all time, you should probably catch the button press event,
+ and then move the insertion point. Be careful : you'll have to
+ catch it after the widget has changed the cursor position
+ though. Thomas Mailund Jensen proposed the following
+ code:</para>
+
+<programlisting role="C">
+static void
+insert_bar (GtkWidget *text)
+{
+ /* jump to cursor mark */
+ gtk_text_set_point (GTK_TEXT (text),
+ gtk_editable_get_position (GTK_EDITABLE (text)));
+ gtk_text_insert (GTK_TEXT (text), NULL, NULL, NULL,
+ "bar", strlen ("bar"));
+}
+
+int
+main (int argc, char *argv[])
+{
+ GtkWidget *window, *text;
+
+ gtk_init (&argc, &argv);
+
+ window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+ text = gtk_text_new (NULL, NULL);
+ gtk_text_set_editable (GTK_TEXT (text), TRUE);
+ gtk_container_add (GTK_CONTAINER (window), text);
+
+ /* connect after everything else */
+ gtk_signal_connect_after (GTK_OBJECT(text), "button_press_event",
+ GTK_SIGNAL_FUNC (insert_bar), NULL);
+
+ gtk_widget_show_all(window);
+ gtk_main();
+
+ return 0;
+}
+</programlisting>
+
+ <para>Now, if you really want to change the cursor position,
+ you should use the
+ <literal>gtk_editable_set_position()</literal>
+ function.</para>
+
+ </sect2>
+
+ </sect1>
+ </chapter>
+
+ <!-- ***************************************************************** -->
+ <chapter>
+ <title>About GDK</title>
+ <sect1>
+ <title></title>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>What is GDK?</title>
+
+ <para>GDK is basically a wrapper around the standard Xlib
+ function calls. If you are at all familiar with Xlib, a lot of
+ the functions in GDK will require little or no getting used
+ to. All functions are written to provide an way to access Xlib
+ functions in an easier and slightly more intuitive manner. In
+ addition, since GDK uses GLib (see below), it will be more
+ portable and safer to use on multiple platforms.</para>
+
+ <!-- Examples, anybody? I've been mulling some over. NF -->
+
+ </sect2>
+
+ <!-- ----------------------------------------------------------------- -->
+
+ <sect2>
+ <title>How do I use color allocation?</title>
+
+ <para>One of the nice things about GDK is that it's based on
+ top of Xlib; this is also a problem, especially in the area of
+ color management. If you want to use color in your program
+ (drawing a rectangle or such, your code should look something
+ like this:</para>
+
+<programlisting role="C">
+{
+ GdkColor *color;
+ int width, height;
+ GtkWidget *widget;
+ GdkGC *gc;
+
+ ...
+
+ /* first, create a GC to draw on */
+ gc = gdk_gc_new(widget->window);
+
+ /* find proper dimensions for rectangle */
+ gdk_window_get_size(widget->window, &width, &height);
+
+ /* the color we want to use */
+ color = (GdkColor *)malloc(sizeof(GdkColor));
+
+ /* red, green, and blue are passed values, indicating the RGB triple
+ * of the color we want to draw. Note that the values of the RGB components
+ * within the GdkColor are taken from 0 to 65535, not 0 to 255.
+ */
+ color->red = red * (65535/255);
+ color->green = green * (65535/255);
+ color->blue = blue * (65535/255);
+
+ /* the pixel value indicates the index in the colormap of the color.
+ * it is simply a combination of the RGB values we set earlier
+ */
+ color->pixel = (gulong)(red*65536 + green*256 + blue);
+
+ /* However, the pixel valule is only truly valid on 24-bit (TrueColor)
+ * displays. Therefore, this call is required so that GDK and X can
+ * give us the closest color available in the colormap
+ */
+ gdk_color_alloc(gtk_widget_get_colormap(widget), color);
+
+ /* set the foreground to our color */
+ gdk_gc_set_foreground(gc, color);
+
+ /* draw the rectangle */
+ gdk_draw_rectangle(widget->window, gc, 1, 0, 0, width, height);
+
+ ...
+}
+</programlisting>
+
+ </sect2>
</sect1>
</chapter>
projects / ~andy / gtk / commitdiff