examples: Add "viewport" example program

Add an examples/ subdirectory, and a new simple-stack example program
which shows how to attach multiple views to the CogShell view stack
and switch among them.

examples/meson.build

@@ -0,0 +1,8 @@
+examples_c_args = ['-DG_LOG_DOMAIN="Cog-Example"']
+
+executable('viewport',
+    'viewport.c',
+    c_args: examples_c_args,
+    dependencies: cogcore_dep,
+    install: false,
+)

examples/viewport.c

@@ -0,0 +1,66 @@
+/*
+ * viewport.c
+ * Copyright (C) 2023 Igalia S.L.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "../core/cog.h"
+
+typedef struct {
+    CogViewport *views;
+    gsize        current_index;
+} TimeoutData;
+
+static gboolean
+on_timeout_tick(TimeoutData *data)
+{
+    if (++data->current_index >= cog_viewport_get_n_views(data->views))
+        data->current_index = 0;
+
+    CogView *view = cog_viewport_get_nth_view(data->views, data->current_index);
+    g_message("Set visible view %zu <%p>", data->current_index, view);
+    cog_viewport_set_visible_view(data->views, view);
+
+    return G_SOURCE_CONTINUE;
+}
+
+int
+main(int argc, char *argv[])
+{
+    if (argc < 2) {
+        g_printerr("Usage: %s <URL> [URL...]\n", argv[0]);
+        return EXIT_FAILURE;
+    }
+
+    g_set_prgname("view-stack");
+    cog_modules_add_directory(g_getenv("COG_MODULEDIR") ?: COG_MODULEDIR);
+
+    g_autoptr(GError)      error = NULL;
+    g_autoptr(CogShell)    shell = cog_shell_new(g_get_prgname(), FALSE);
+    g_autoptr(CogPlatform) platform = cog_platform_configure(NULL, NULL, "COG", shell, &error);
+    if (!platform)
+        g_error("Cannot configure platform: %s", error->message);
+
+    g_autoptr(GMainLoop) loop = g_main_loop_new(NULL, FALSE);
+
+    CogViewport *viewport = cog_shell_get_viewport(shell);
+
+    for (int i = 1; i < argc; i++) {
+        g_autoptr(CogView) view = cog_view_new(NULL);
+        cog_platform_init_web_view(platform, WEBKIT_WEB_VIEW(view));
+        cog_viewport_add(viewport, view);
+        webkit_web_view_load_uri(WEBKIT_WEB_VIEW(view), argv[i]);
+        g_message("Created view %p, URI %s", view, argv[i]);
+    }
+
+    TimeoutData data = {
+        .views = viewport,
+        .current_index = SIZE_MAX,
+    };
+    g_timeout_add_seconds(3, (GSourceFunc) on_timeout_tick, &data);
+    on_timeout_tick(&data);
+
+    g_main_loop_run(loop);
+    return EXIT_SUCCESS;
+}

meson.build

@@ -164,6 +164,10 @@ if get_option('documentation')
     subdir('docs')
 endif
 
+if get_option('examples')
+    subdir('examples')
+endif
+
 if with_programs
     subdir('launcher')
     if get_option('manpages')

meson_options.txt

@@ -16,6 +16,12 @@ option(
     value: true,
     description: 'build and install programs (cog, cogctl)'
 )
+option(
+    'examples',
+    type: 'boolean',
+    value: true,
+    description: 'build example programs'
+)
 option(
     'wpe_api',
     type: 'combo',