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GTK入门导读(封装物件)



        
    4. 封装物件
    当我们制作一套软体, 您会希望在视窗内放超过一个以上的按钮. 我们第一个范例\"hello world\"仅用一个物件, 因此我们能够很简单使用gtk_container_add来\"封装\"该物件到视窗中. 但当您希够望放更多的物件到视窗中, 要如何控制它们的位置? 这里就要用到\"封装\"(Packing).

    4.1 Packing Boxes的理论
    大部份的封装是由产生boxes来达成的. 这些是看不见的widget containers, 我们可以用两种形式来将我们的物件封装进去, vertical box及horizontal box. 当我们封装物件到一个horizontal box时, 物件是依我们呼叫的顺序由右至左平行的被新增进去. 在vertical box, 物件是由上至下. 您可以将物件插入box, 也可以将boxes插入box, 任意的组合用以产生所想要的效果.

    要产生horizontal box,我们使用gtk_hbox_new(), 而vertical boxe使用gtk_vbox_new(). gtk_box_pack_start()及gtk_box_pack_end()函数是用来将物件放到containers里面. gtk_box_pack_start()函数会开始由左至右, 由上至下来封装物件. gtk_box_pack_end()则相反, 由下至上, 由右至左. 使用这些函数允许我们对右边或对左边较正, 而且可以用许多种方式来较正来取得所想要的效果. 一个object可以是另一个container或物件. 而且事实上, 许多物件本身也是containers. 像按钮就是, 不过我们一般只在按钮中用一个标签.

    使用这些呼叫, GTK知道要把物件放到那里去, 并且会自动缩放及其它比例上的调整. 还有许多其它选项可以控制如何将物件封装在一起. 正如您所想的, 这些方法可以给您许多的弹性来制作视窗.

    4.2 Boxes详述
    由於这样的弹性, packing boxes在一开始使用的话会有点搞糊涂. 还有许多其它的选项,一开始还看不太出来它们如何凑在一起. 最後您会知道, 他们基本上有五种不同的型式.





    每一行包含一个horizontal box (hbox)及好几个按钮. 所有按钮都是以同样的方式来包入hbox内.

    这是gtk_box_pack_start的宣告.


    void gtk_box_pack_start (GtkBox *box,
    GtkWidget *child,
    gint expand,
    gint fill,
    gint padding);

    第一个参数是您要把object放进去的box, 第二个是该object. 现在这些物件将会都是按钮.

    expand参数在gtk_box_pack_start()或gtk_box_pack_end()中控制物件如何在box中排列. expand = TRUE的话它们会填满box中所有额外的空间. expand = FALSE的话, 该box会缩小到刚好该物件的大小. 设expand=FALSE您可做好左右较正. 否则它们会填满整个box. 同样的效果可用tk_box_pack_start或pack_end functions来达成.

    fill参数在gtk_box_pack中控制额外空间. fill=TRUE该物件会自行产生额外空间, fill=FALSE则由box产生一个在物件周围的填白区域. 这只有在expand=TRUE时, 才会有作用.

    当产生一个新的box, 该函数看起来像这样:


    GtkWidget * gtk_hbox_new (gint homogeneous,
    gint spacing);

    homogeneous参数在gtk_hbox_new (and the same for gtk_vbox_new) 控制每个物件是否有同样的宽或高. 若homogeneous=TRUE, 则expand也会被开启.

    空白(spacing)及填白(padding)有什麽不同呢空白是加在物件之间, 填白只加在物件的一边. 看以下这张图可能会明白一点:



    这里是一些用来产生以上影像的程式. 我做了蛮多的注解, 希望您不会有问题. 将它编译然後玩玩它.


    4.3 封装示范程式


    #include \"gtk/gtk.h\"

    void
    destroy (GtkWidget *widget, gpointer *data)
    {
    gtk_main_quit ();
    }

    /* Make a new hbox filled with button-labels. Arguments for the
    * variables we\"re interested are passed in to this function.
    * We do not show the box, but do show everything inside. */
    GtkWidget *make_box (gint homogeneous, gint spacing,
    gint expand, gint fill, gint padding)
    {
    GtkWidget *box;
    GtkWidget *button;
    char padstr[80];

    /* create a new hbox with the appropriate homogeneous and spacing
    * settings */
    box = gtk_hbox_new (homogeneous, spacing);

    /* create a series of buttons with the appropriate settings */
    button = gtk_button_new_with_label (\"gtk_box_pack\");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    button = gtk_button_new_with_label (\"(box,\");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    button = gtk_button_new_with_label (\"button,\");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    /* create a button with the label depending on the value of
    * expand. */
    if (expand == TRUE)
    button = gtk_button_new_with_label (\"TRUE,\");
    else
    button = gtk_button_new_with_label (\"FALSE,\");

    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    /* This is the same as the button creation for \"expand\"
    * above, but uses the shorthand form. */
    button = gtk_button_new_with_label (fill ? \"TRUE,\" : \"FALSE,\");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    sprintf (padstr, \"%d);\", padding);

    button = gtk_button_new_with_label (padstr);
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);

    return box;
    }

    int
    main (int argc, char *argv[])
    {
    GtkWidget *window;
    GtkWidget *button;
    GtkWidget *box1;
    GtkWidget *box2;
    GtkWidget *separator;
    GtkWidget *label;
    GtkWidget *quitbox;
    int which;

    /* Our init, don\"t forget this! :) */
    gtk_init (&argc, &argv);

    if (argc != 2) {
    fprintf (stderr, \"usage: packbox num, where num is 1, 2, or 3.\\n\");
    /* this just does cleanup in GTK, and exits with an exit status of 1. */
    gtk_exit (1);
    }

    which = atoi (argv[1]);

    /* Create our window */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

    /* You should always remember to connect the destroy signal to the
    * main window. This is very important for proper intuitive
    * behavior */
    gtk_signal_connect (GTK_OBJECT (window), \"destroy\",
    GTK_SIGNAL_FUNC (destroy), NULL);
    gtk_container_border_width (GTK_CONTAINER (window), 10);

    /* We create a vertical box (vbox) to pack the horizontal boxes into.
    * This allows us to stack the horizontal boxes filled with buttons one
    * on top of the other in this vbox. */
    box1 = gtk_vbox_new (FALSE, 0);

    /* which example to show. These correspond to the pictures above. */
    switch (which) {
    case 1:
    /* create a new label. */
    label = gtk_label_new (\"gtk_hbox_new (FALSE, 0);\");

    /* Align the label to the left side. We\"ll discuss this function and
    * others in the section on Widget Attributes. */
    gtk_misc_set_alignment (GTK_MISC (label), 0, 0);

    /* Pack the label into the vertical box (vbox box1). Remember that
    * widgets added to a vbox will be packed one on top of the other in
    * order. */
    gtk_box_pack_start (GTK_BOX (box1), label, FALSE, FALSE, 0);

    /* show the label */
    gtk_widget_show (label);

    /* call our make box function - homogeneous = FALSE, spacing = 0,
    * expand = FALSE, fill = FALSE, padding = 0 */
    box2 = make_box (FALSE, 0, FALSE, FALSE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* call our make box function - homogeneous = FALSE, spacing = 0,
    * expand = FALSE, fill = FALSE, padding = 0 */
    box2 = make_box (FALSE, 0, TRUE, FALSE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (FALSE, 0, TRUE, TRUE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* creates a separator, we\"ll learn more about these later,
    * but they are quite simple. */
    separator = gtk_hseparator_new ();

    /* pack the separator into the vbox. Remember each of these
    * widgets are being packed into a vbox, so they\"ll be stacked
    * vertically. */
    gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 5);
    gtk_widget_show (separator);

    /* create another new label, and show it. */
    label = gtk_label_new (\"gtk_hbox_new (TRUE, 0);\");
    gtk_misc_set_alignment (GTK_MISC (label), 0, 0);
    gtk_box_pack_start (GTK_BOX (box1), label, FALSE, FALSE, 0);
    gtk_widget_show (label);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (TRUE, 0, TRUE, FALSE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (TRUE, 0, TRUE, TRUE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* another new separator. */
    separator = gtk_hseparator_new ();
    /* The last 3 arguments to gtk_box_pack_start are: expand, fill, padding. */
    gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 5);
    gtk_widget_show (separator);

    break;

    case 2:

    /* create a new label, remember box1 is a vbox as created
    * near the beginning of main() */
    label = gtk_label_new (\"gtk_hbox_new (FALSE, 10);\");
    gtk_misc_set_alignment (GTK_MISC (label), 0, 0);
    gtk_box_pack_start (GTK_BOX (box1), label, FALSE, FALSE, 0);
    gtk_widget_show (label);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (FALSE, 10, TRUE, FALSE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (FALSE, 10, TRUE, TRUE, 0);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    separator = gtk_hseparator_new ();
    /* The last 3 arguments to gtk_box_pack_start are: expand, fill, padding. */
    gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 5);
    gtk_widget_show (separator);

    label = gtk_label_new (\"gtk_hbox_new (FALSE, 0);\");
    gtk_misc_set_alignment (GTK_MISC (label), 0, 0);
    gtk_box_pack_start (GTK_BOX (box1), label, FALSE, FALSE, 0);
    gtk_widget_show (label);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (FALSE, 0, TRUE, FALSE, 10);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* Args are: homogeneous, spacing, expand, fill, padding */
    box2 = make_box (FALSE, 0, TRUE, TRUE, 10);
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    separator = gtk_hseparator_new ();
    /* The last 3 arguments to gtk_box_pack_start are: expand, fill, padding. */
    gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 5);
    gtk_widget_show (separator);
    break;

    case 3:

    /* This demonstrates the ability to use gtk_box_pack_end() to
    * right justify widgets. First, we create a new box as before. */
    box2 = make_box (FALSE, 0, FALSE, FALSE, 0);
    /* create the label that will be put at the end. */
    label = gtk_label_new (\"end\");
    /* pack it using gtk_box_pack_end(), so it is put on the right side
    * of the hbox created in the make_box() call. */
    gtk_box_pack_end (GTK_BOX (box2), label, FALSE, FALSE, 0);
    /* show the label. */
    gtk_widget_show (label);

    /* pack box2 into box1 (the vbox remember ? :) */
    gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, FALSE, 0);
    gtk_widget_show (box2);

    /* a separator for the bottom. */
    separator = gtk_hseparator_new ();
    /* this explicitly sets the separator to 400 pixels wide by 5 pixels
    * high. This is so the hbox we created will also be 400 pixels wide,
    * and the \"end\" label will be separated from the other labels in the
    * hbox. Otherwise, all the widgets in the hbox would be packed as
    * close together as possible. */
    gtk_widget_set_usize (separator, 400, 5);
    /* pack the separator into the vbox (box1) created near the start
    * of main() */
    gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 5);
    gtk_widget_show (separator);
    }

    /* Create another new hbox.. remember we can use as many as we need! */
    quitbox = gtk_hbox_new (FALSE, 0);

    /* Our quit button. */
    button = gtk_button_new_with_label (\"Quit\");

    /* setup the signal to destroy the window. Remember that this will send
    * the \"destroy\" signal to the window which will be caught by our signal
    * handler as defined above. */
    gtk_signal_connect_object (GTK_OBJECT (button), \"clicked\",
    GTK_SIGNAL_FUNC (gtk_widget_destroy),
    GTK_OBJECT (window));
    /* pack the button into the quitbox.
    * The last 3 arguments to gtk_box_pack_start are: expand, fill, padding. */
    gtk_box_pack_start (GTK_BOX (quitbox), button, TRUE, FALSE, 0);
    /* pack the quitbox into the vbox (box1) */
    gtk_box_pack_start (GTK_BOX (box1), quitbox, FALSE, FALSE, 0);

    /* pack the vbox (box1) which now contains all our widgets, into the
    * main window. */
    gtk_container_add (GTK_CONTAINER (window), box1);

    /* and show everything left */
    gtk_widget_show (button);
    gtk_widget_show (quitbox);

    gtk_widget_show (box1);
    /* Showing the window last so everything pops up at once. */
    gtk_widget_show (window);

    /* And of course, our main function. */
    gtk_main ();

    /* control returns here when gtk_main_quit() is called, but not when
    * gtk_exit is used. */

    return 0;
    }



    4.4 使用表格来封装
    我们来看看另一个封装的方法 - 用表格. 在很多状况下, 这是极其有用的.

    使用表格, 我们产生格线来将物件放入. 物件会照我们安排的位置排入.

    我们第一个要看的是gtk_table_new这个函数:


    GtkWidget* gtk_table_new (gint rows,
    gint columns,
    gint homogeneous);

    第一个参数是多少列, 第二个是多少栏.

    homogeneous参数用来决定表格如何来定大小. 若homogeneous为TRUE, table boxes会被重定为在其中最大物件的大小. 若homogeneous为FALSE, 则其大小为, \"高\"为列中最高的物件, 及\"宽\"栏中最宽的物件大小.

    列及栏的编号为从0到n. n是我们在gtk_table_new中所指定的值. 所以, 如果您指定rows = 2及columns = 2, 整个排列会看起来像这样:


    0 1 2
    0+----------+----------+
    | | |
    1+----------+----------+
    | | |
    2+----------+----------+

    坐标系统开始於左上角. 要把物件放进box中, 可用以下函数:


    void gtk_table_attach (GtkTable *table,
    GtkWidget *child,
    gint left_attach,
    gint right_attach,
    gint top_attach,
    gint bottom_attach,
    gint xoptions,
    gint yoptions,
    gint xpadding,
    gint ypadding);

    第一个参数(\"table\")是您才刚产生的表格, 而第二个(\"child\")是您想放进去的物件.

    而left_attach及right_attach参数指定要把物件放在那里, 及用多少个boxes. 如果您想要用右下角的表格, 可以这样填表. left_attach = 1, right_attach = 2, top_attach = 1, bottom_attach = 2.

    现在, 如果您想要物件来使用上面2x2的表格, 您可以使用left_attach = 0, right_attach =2, top_attach = 0, bottom_attach = 1.

    xoptions及yoptions是用来指定封装选项, 可以同时组合多个选项(用or).

    这些选项是:

    GTK_FILL - 如果table box大过物件, 且GTK_FILL 被指定了, 该物件会扩展成使用所有可用的空间.
    GTK_SHRINK - 如果table widget小於该物件, (一般是使用者缩放该视窗), 那麽该物件将会一直被挤压到看不见为止. 如果GTK_SHRINK被指定了, 该物件会跟著table一起缩小.
    GTK_EXPAND - 这会使table本身扩展, 并利用视窗中所有可用空间.
    填空就像boxes, 产生一个在物件周边空白的区域.

    gtk_table_attach()有许多选项. 这里有个捷径:


    void gtk_table_attach_defaults (GtkTable *table,
    GtkWidget *widget,
    gint left_attach,
    gint right_attach,
    gint top_attach,
    gint bottom_attach);

    X及Y选项内定为GTK_FILL | GTK_EXPAND, X及Y填空则设为0. 其馀的参数则相同於以上的函数.

    我们另外有gtk_table_set_row_spacing()及gtk_table_set_col_spacing(). 这些会在指定的栏及列插入空白.


    void gtk_table_set_row_spacing (GtkTable *table,
    gint row,
    gint spacing);


    void gtk_table_set_col_spacing (GtkTable *table,
    gint column,
    gint spacing);

    对栏来说, 空格是在栏的右边. 而列则是在下面.

    您也可以用以下函数来产生固定的空格.


    void gtk_table_set_row_spacings (GtkTable *table,
    gint spacing);

    及,

    void gtk_table_set_col_spacings (GtkTable *table,
    gint spacing);

    使用这些函数, 其最後一栏及最後一列并没有空格存在.


    4.5 Table Packing范例
    目前并无说明, 请参照testgtk.c

    发布人:netbull 来自:Linux开发指南