clutter布局之json［0722］

clutter布局可以使用一种源自json的语言
这样对程序日后的调整就方便了许多，下面给出两端源自官网的代码

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

#include <glib.h>

#include <clutter/clutter.h>

static ClutterScript *script = NULL;
static guint merge_id = 0;

static const gchar *test_unmerge =
"["
"  {"
"    \"id\" : \"main-stage\","
"    \"type\" : \"ClutterStage\","
"    \"children\" : [ \"blue-button\" ]"
"  },"
"  {"
"    \"id\" : \"blue-button\","
"    \"type\" : \"ClutterRectangle\","
"    \"color\" : \"#0000ffff\","
"    \"x\" : 350,"
"    \"y\" : 50,"
"    \"width\" : 100,"
"    \"height\" : 100,"
"    \"visible\" : true,"
"    \"reactive\" : true"
"  }"
"]";

static const gchar *test_behaviour =
"["
"  {"
"    \"id\" : \"main-timeline\","
"    \"type\" : \"ClutterTimeline\","
"    \"duration\" : 5000,"
"    \"loop\" : true"
"  },"
"  {"
"    \"id\"          : \"path-behaviour\","
"    \"type\"        : \"ClutterBehaviourPath\","
"    \"knots\"       : [ [ 50, 50 ],[100,100]],"
"    \"alpha\"       : {"
"      \"timeline\" : \"main-timeline\","
"      \"function\" : \"ramp_inc\""
"    }"
"  },"
"  {"
"    \"id\"          : \"rotate-behaviour\","
"    \"type\"        : \"ClutterBehaviourRotate\","
"    \"angle-start\" : 0.0,"
"    \"angle-end\"   : 360.0,"
"    \"axis\"        : \"y-axis\","
"    \"alpha\"       : {"
"      \"timeline\" : \"main-timeline\","
"      \"function\" : \"sine\""
"    }"
"  },"
"  {"
"    \"id\"            : \"fade-behaviour\","
"    \"type\"          : \"ClutterBehaviourOpacity\","
"    \"opacity-start\" : 255,"
"    \"opacity-end\"   : 0,"
"    \"alpha\"         : {"
"      \"timeline\" : \"main-timeline\","
"      \"function\" : \"ramp-inc\""
"    }"
"  }"
"]";

static gboolean
blue_button_press (ClutterActor       *actor,
                   ClutterButtonEvent *event,
                   gpointer            data)
{
  g_print ("[*] Pressed `%s'\n", clutter_get_script_id (G_OBJECT (actor)));
  g_print ("[*] Unmerging objects with merge id: %d\n", merge_id);

  clutter_script_unmerge_objects (script, merge_id);

  return TRUE;
}

static gboolean
red_button_press (ClutterActor *actor,
                  ClutterButtonEvent *event,
                  gpointer            data)
{
  GObject *timeline;

  g_print ("[*] Pressed `%s'\n", clutter_get_script_id (G_OBJECT (actor)));

  timeline = clutter_script_get_object (script, "main-timeline");
  g_assert (CLUTTER_IS_TIMELINE (timeline));

  if (!clutter_timeline_is_playing (CLUTTER_TIMELINE (timeline)))
    clutter_timeline_start (CLUTTER_TIMELINE (timeline));
  else
    clutter_timeline_pause (CLUTTER_TIMELINE (timeline));

  return TRUE;
}

int
main (int argc, char *argv[])
{
  GObject *stage, *blue_button, *red_button;
  GError *error = NULL;
  gint res;

  clutter_init (&argc, &argv);

  script = clutter_script_new ();
  g_assert (CLUTTER_IS_SCRIPT (script));

  clutter_script_load_from_data (script, test_behaviour, -1, &error);
  if (error)
    {
      g_print ("*** Error:\n"
               "***   %s\n", error->message);
      g_error_free (error);
      g_object_unref (script);
      return EXIT_FAILURE;
    }
  
  clutter_script_load_from_file (script, "test-script.json", &error);
  if (error)
    {
      g_print ("*** Error:\n"
               "***   %s\n", error->message);
      g_error_free (error);
      g_object_unref (script);
      return EXIT_FAILURE;
    }

  merge_id = clutter_script_load_from_data (script, test_unmerge, -1, &error);
  if (error)
    {
      g_print ("*** Error:\n"
               "***   %s\n", error->message);
      g_error_free (error);
      g_object_unref (script);
      return EXIT_FAILURE;
    }

 

  res = clutter_script_get_objects (script,
                                    "main-stage", &stage,
                                    "red-button", &red_button,
                                    "blue-button", &blue_button,
                                    NULL);
  g_assert (res == 3);

  clutter_actor_show (CLUTTER_ACTOR (stage));

  g_signal_connect (red_button,
                    "button-press-event", 
                    G_CALLBACK (red_button_press),
                    NULL);

  g_signal_connect (blue_button,
                    "button-press-event",
                    G_CALLBACK (blue_button_press),
                    NULL);

  clutter_main ();

  g_object_unref (script);

  return EXIT_SUCCESS;
}

上面这段为c的代码，下面给出外置布局文件的代码

{
  "Scene" : {
    "id" : "main-stage",
    "type" : "ClutterStage",
    "title" : "ClutterScript test",
    "color" : "white",
 
    "children" : [
      {
        "id" : "red-button",
        "type" : "ClutterRectangle",
        "color" : "#ff0000ff",
        "x" : 50, "y" : 50, "width" : 100, "height" : 100,
        "reactive" : true,
        "rotation" : [
          { "z-axis" : [ 45.0, [ 75, 75 ] ] }
        ],
        "behaviours" : [ "fade-behaviour", "path-behaviour" ],
 
      },
      
      {
        "id" : "green-button",
        "type" : "ClutterRectangle",
        "color" : "#00ff00ff",
        "border-width" : 5,
        "border-color" : "#00cc00ff",
        "x" : 200,
        "y" : 50,
        "width" : 100,
        "height" : 100,
        "reactive" : true,
    
      }, 
      {
        "id" : "red-hand",
        "type" : "ClutterTexture",
        "filename" : "star.png",
        "x" : 100,
        "y" : 100,
        "width" : "20mm",
        "keep-aspect-ratio" : true,
        "anchor-x" : 5,
        "anchor-y" : 5,
        "opacity" : 100,
        "behaviours" : [ "rotate-behaviour", "fade-behaviour" ]
      },
      {
        "id" : "red-hand-clone",
        "type" : "ClutterCloneTexture",
        "parent-texture" : "red-hand",
        "x" : 250,
        "y" : 150,
        "opacity" : 100,
      },
      {
        "id" : "label",
        "type" : "ClutterLabel",
        "x" : 50,
        "y" : 200,
        "width" : 400,
        "text" : "Clutter\tScript测试",
        "font-name" : "Sans 24px",
        "color" : "black",
        "alignment" : "center",
        "wrap" : false,
        "ellipsize" : "none",
        "rotation" : [
   
          { "z-axis" : [ 45.0, [ 0,0 ] ] } 
        ]
      }
    ]
  }
}

实际使用中发现使用json布局文件除了一般的布局之外还可以关联behavior等属性，这样就免除了
反复unref的麻烦，只需在最后unref掉script即可。
虽然官方手册中提到可以在布局文件中声明signal，但实际使用中发现这样做总是提示找不到相应的处理函数
［即使声明了G_MODULE_EXPORT也不行］或是提示段错误。
但无论怎样，这对于代码的简化还是很有帮助的。