?? z177.html
字號:
</tr> </table> <p> Of course, a real callback would probably examine the contents of the event and take some action in response to some of them. </p> </div> <div class="SECT2"> <h2 class="SECT2"> <a name="Z182">A Canvas Example</a> </h2> <p> This section gives a brief example program, demonstrating the user of the canvas. It does not explain the particulars of the canvas items being created; see <a href="sec-itemreference.html">the section called <i> Standard Canvas Item Reference</i></a> for that. <a href= "z177.html#FIG-CANVAS-EXAMPLE">Figure 9</a> shows the example program in action. You can drag canvas items around the screen with the left mouse button; clicking an item with the Shift key held down destroys it. </p> <div class="FIGURE"> <a name="FIG-CANVAS-EXAMPLE"></a> <p> <img src="figures/canvas-example.png"> </p> <p> <b>Figure 9. Simple <tt class="CLASSNAME"> GnomeCanvas</tt> program</b> </p> </div> <p> Here is the code to create an antialiased canvas. Notice the call to <tt class="FUNCTION">gdk_rgb_init()</tt>; notice that the canvas's scroll region is set; finally, notice that the GdkRGB colormap and visual are pushed when creating the canvas. </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> #include <gnome.h>static gint delete_event_cb(GtkWidget* window, GdkEventAny* e, gpointer data);static void create_canvas_items(GtkWidget* canvas);int main(int argc, char* argv[]){ GtkWidget* window; GtkWidget* sw; GtkWidget* canvas; gnome_init("canvas-example", "0.0", argc, argv); gdk_rgb_init(); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); gtk_window_set_title(GTK_WINDOW(window), "Canvas Example"); gtk_window_set_policy(GTK_WINDOW(window), TRUE, TRUE, TRUE); gtk_signal_connect(GTK_OBJECT(window), "delete_event", GTK_SIGNAL_FUNC(delete_event_cb), NULL); sw = gtk_scrolled_window_new(NULL, NULL); gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(sw), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC); gtk_widget_push_visual(gdk_rgb_get_visual()); gtk_widget_push_colormap(gdk_rgb_get_cmap()); canvas = gnome_canvas_new_aa(); gtk_widget_pop_colormap(); gtk_widget_pop_visual(); gnome_canvas_set_scroll_region(GNOME_CANVAS(canvas), 0, 0, 600, 450); create_canvas_items(canvas); gtk_container_add(GTK_CONTAINER(sw), canvas); gtk_container_add(GTK_CONTAINER(window), sw); gtk_window_set_default_size(GTK_WINDOW(window), 300, 300); gtk_widget_show_all(window); gtk_main(); return 0;}static gint delete_event_cb(GtkWidget* window, GdkEventAny* e, gpointer data){ gtk_main_quit(); return FALSE;} </pre> </td> </tr> </table> <p> Once the canvas has been created, the program adds some items to it, and connects a simple callback to the item's <span class="SYMBOL">"event"</span> signal. Here's the code: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> static gintitem_event(GnomeCanvasItem *item, GdkEvent *event, gpointer data){ static double x, y; double new_x, new_y; GdkCursor *fleur; static int dragging; double item_x, item_y; item_x = event->button.x; item_y = event->button.y; gnome_canvas_item_w2i(item->parent, &item_x, &item_y); switch (event->type) { case GDK_BUTTON_PRESS: switch(event->button.button) { case 1: if (event->button.state & GDK_SHIFT_MASK) { gtk_object_destroy(GTK_OBJECT(item)); } else { x = item_x; y = item_y; fleur = gdk_cursor_new(GDK_FLEUR); gnome_canvas_item_grab(item, GDK_POINTER_MOTION_MASK | GDK_BUTTON_RELEASE_MASK, fleur, event->button.time); gdk_cursor_destroy(fleur); dragging = TRUE; } break; default: break; } break; case GDK_MOTION_NOTIFY: if (dragging && (event->motion.state & GDK_BUTTON1_MASK)) { new_x = item_x; new_y = item_y; gnome_canvas_item_move(item, new_x - x, new_y - y); x = new_x; y = new_y; } break; case GDK_BUTTON_RELEASE: gnome_canvas_item_ungrab(item, event->button.time); dragging = FALSE; break; default: break; } return FALSE;}static voidsetup_item(GnomeCanvasItem *item){ gtk_signal_connect(GTK_OBJECT(item), "event", (GtkSignalFunc) item_event, NULL);}static void create_canvas_items(GtkWidget* canvas){ GnomeCanvasPoints* points; GnomeCanvasGroup* group; GnomeCanvasItem* item; double affine[6]; group = gnome_canvas_root(GNOME_CANVAS(canvas)); /* A polygon */ points = gnome_canvas_points_new(14); points->coords[0] = 270.0; points->coords[1] = 330.0; points->coords[2] = 270.0; points->coords[3] = 430.0; points->coords[4] = 390.0; points->coords[5] = 430.0; points->coords[6] = 390.0; points->coords[7] = 330.0; points->coords[8] = 310.0; points->coords[9] = 330.0; points->coords[10] = 310.0; points->coords[11] = 390.0; points->coords[12] = 350.0; points->coords[13] = 390.0; points->coords[14] = 350.0; points->coords[15] = 370.0; points->coords[16] = 330.0; points->coords[17] = 370.0; points->coords[18] = 330.0; points->coords[19] = 350.0; points->coords[20] = 370.0; points->coords[21] = 350.0; points->coords[22] = 370.0; points->coords[23] = 410.0; points->coords[24] = 290.0; points->coords[25] = 410.0; points->coords[26] = 290.0; points->coords[27] = 330.0; item = gnome_canvas_item_new(group, gnome_canvas_polygon_get_type (), "points", points, "fill_color", "tan", "outline_color", "black", "width_units", 3.0, NULL); setup_item(item); gnome_canvas_points_unref(points); /* Translate the polygon */ art_affine_translate(affine, -150.0, -300.0); gnome_canvas_item_affine_relative(item, affine); /* A translucent rectangle */ setup_item (gnome_canvas_item_new (group, gnome_canvas_rect_get_type(), "x1", 90.0, "y1", 40.0, "x2", 180.0, "y2", 100.0, "fill_color_rgba", 0x3cb37180, "outline_color", "black", "width_units", 4.0, NULL)); /* A translucent ellipse */ setup_item (gnome_canvas_item_new (group, gnome_canvas_ellipse_get_type(), "x1", 210.0, "y1", 80.0, "x2", 280.0, "y2", 140.0, "fill_color_rgba", 0x5f9ea080, "outline_color", "black", "width_pixels", 0, NULL)); /* Create ellipses arranged in a line; they're manipulated as a single item. */ group = GNOME_CANVAS_GROUP (gnome_canvas_item_new (group, gnome_canvas_group_get_type(), "x", 0.0, "y", 0.0, NULL)); setup_item(GNOME_CANVAS_ITEM(group)); { double xpos = 20.0; while (xpos < 300.0) { gnome_canvas_item_new(group, gnome_canvas_ellipse_get_type(), "x1", xpos, "y1", 100.0, "x2", xpos + 10.0, "y2", 110.0, "fill_color_rgba", 0x0000FFFF, "outline_color_rgba", 0xFF, NULL); xpos += 15.0; } }} </pre> </td> </tr> </table> </div> </div> <div class="NAVFOOTER"> <br> <br> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="z174.html"><font color="#0000ff" size="2"><b> <<< Previous</b></font></a> </td> <td width="25%" colspan="2" bgcolor="#ffffff" align= "center"> <font color="#0000ff" size="2"><b><a href="ggad.html"> <font color="#0000ff" size="2"><b> Home</b></font></a></b></font> </td> <td width="25%" bgcolor="#ffffff" align="right"> <a href="sec-itemreference.html"><font color="#0000ff" size="2"><b>Next >>></b></font></a> </td> </tr> <tr> <td colspan="2" align="left"> <font color="#000000" size="2"><b>Basic Canvas Architecture</b></font> </td> <td colspan="2" align="right"> <font color="#000000" size="2"><b>Standard Canvas Item Reference</b></font> </td> </tr> </table> </div> </body></html>?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -