c - 找出一个 C 循环

Question

这是默认的 gnome 屏幕保护程序之一 - “个人幻灯片”。它显示来自某个位置的图片，图片之间暂停约 10 秒。有人知道它是如何循环和暂停的吗？

我正在尝试增加延迟，但我犹豫要不要添加 sleep() 而不首先知道它是如何做到的。

谢谢

#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <glib.h>
#include <glib/gi18n.h>
#include <glib/gstdio.h>
#include <gtk/gtk.h>

#include "gs-theme-window.h"
#include "gs-theme-engine.h"
#include "gste-slideshow.h"

#include "xdg-user-dir-lookup.h"

int
main (int argc, char **argv)
{
        GSThemeEngine *engine;
        GtkWidget     *window;
        GError        *error;
        gboolean       ret;
        char          *location = NULL;
        char          *background_color = NULL;
        gboolean       sort_images = FALSE;
        gboolean       no_stretch = FALSE;
        GOptionEntry  entries [] = {
                { "location", 0, 0, G_OPTION_ARG_STRING, &location,
                  N_("Location to get images from"), N_("PATH") },
                { "background-color", 0, 0, G_OPTION_ARG_STRING, &background_color,
                  N_("Color to use for images background"), N_("\"#rrggbb\"") },
                { "sort-images", 0, 0, G_OPTION_ARG_NONE, &sort_images,
                  N_("Do not randomize pictures from location"), NULL },
                { "no-stretch", 0, 0, G_OPTION_ARG_NONE, &no_stretch,
                  N_("Do not try to stretch images on screen"), NULL },
                { NULL }
        };

        bindtextdomain (GETTEXT_PACKAGE, GNOMELOCALEDIR);
        bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
        textdomain (GETTEXT_PACKAGE);

        error = NULL;

        g_thread_init (NULL);
        ret = gtk_init_with_args (&argc, &argv,
                                  NULL,
                                  entries,
                                  NULL,
                                  &error);
        if (! ret) {
                g_message ("%s", error->message);
                g_error_free (error);
                exit (1);
        }

        g_chdir (g_get_home_dir ());

        g_set_prgname ("slideshow");

        window = gs_theme_window_new ();
        g_signal_connect (G_OBJECT (window), "delete-event",
                          G_CALLBACK (gtk_main_quit), NULL);

        engine = g_object_new (GSTE_TYPE_SLIDESHOW, NULL);

        if (location == NULL) {
                location = xdg_user_dir_lookup ("PICTURES");
                if (location == NULL ||
                    strcmp (location, "/tmp") == 0 ||
                    strcmp (location, g_get_home_dir ()) == 0) {
                        free (location);
                        location = g_build_filename (g_get_home_dir (), "Pictures", NULL);
                }
        }

        if (location != NULL) {
                g_object_set (engine, "images-location", location, NULL);
        }

        if (sort_images) {
                g_object_set (engine, "sort-images", sort_images, NULL);
        }

        if (background_color != NULL) {
                g_object_set (engine, "background-color", background_color, NULL);
        }

        if (no_stretch) {
                g_object_set (engine, "no-stretch", no_stretch, NULL);
        }

        gtk_container_add (GTK_CONTAINER (window), GTK_WIDGET (engine));

        gtk_widget_show (GTK_WIDGET (engine));

        gtk_window_set_default_size (GTK_WINDOW (window), 640, 480);
        gtk_widget_show (window);

        gtk_main ();

        return 0;
}

Answer 1

看起来这个程序正在使用 GStreamer 的幻灯片引擎。这是由变量 engine 指向的。 GStreamer 是一个媒体处理框架，具有许多可重用的音频和视频组件。在这种情况下，幻灯片引擎从目录中读取图像并显示它们。

您可以看到程序使用 g_object_set 调整引擎的各种设置。也许您可以调整另一个设置来更改延迟？

编辑:幻灯片放映的相关来源是 gste-slideshow.c .看起来关键是 start_new_load 函数，通常用 IMAGE_LOAD_TIMEOUT 调用，一个常量设置为 10000(毫秒)。似乎没有任何方法可以从外部设置此值。