client: rework and document opacity field

Signed-off-by: Julien Danjou <julien@danjou.info>

client.c

@@ -1155,9 +1155,14 @@ luaA_client_newindex(lua_State *L)
         widget_invalidate_cache((*c)->screen, WIDGET_CACHE_CLIENTS);
         break;
       case A_TK_OPACITY:
+        if(lua_isnil(L, 3))
+            window_opacity_set((*c)->win, -1);
+        else
+        {
             d = luaL_checknumber(L, 3);
-        if(d == -1 || (d >= 0 && d <= 1))
+            if(d >= 0 && d <= 1)
-            window_trans_set((*c)->win, d);
+                window_opacity_set((*c)->win, d);
+        }
         break;
       case A_TK_FLOATING:
         client_setfloating(*c, luaA_checkboolean(L, 3));
@@ -1245,6 +1250,7 @@ luaA_client_newindex(lua_State *L)
  * \lfield titlebar The client titlebar.
  * \lfield urgent The client urgent state.
  * \lfield focus The focused client.
+ * \lfield opacity The client opacity between 0 and 1.
  */
 static int
 luaA_client_index(lua_State *L)
@@ -1258,6 +1264,7 @@ luaA_client_index(lua_State *L)
     xutil_class_hint_t hint;
     xcb_get_property_cookie_t prop_c;
     xcb_get_property_reply_t *prop_r = NULL;
+    double d;
 
     if((*c)->invalid)
         luaL_error(L, "client is invalid\n");
@@ -1321,6 +1328,12 @@ luaA_client_index(lua_State *L)
       case A_TK_ICON_PATH:
         lua_pushstring(L, (*c)->icon_path);
         break;
+      case A_TK_OPACITY:
+        if((d = window_opacity_get((*c)->win)) >= 0)
+            lua_pushnumber(L, d);
+        else
+            return 0;
+        break;
       case A_TK_FLOATING:
         lua_pushboolean(L, (*c)->isfloating);
         break;

window.c

@@ -153,12 +153,42 @@ window_root_buttons_grab(xcb_window_t root)
     }
 }
 
-/** Set transparency of a window.
+/** Get the opacity of a window.
+ * \param The window.
+ * \return The opacity, between 0 and 1 or -1 or no opacity set.
+ */
+double
+window_opacity_get(xcb_window_t win)
+{
+    xcb_get_property_cookie_t prop_c;
+    xcb_get_property_reply_t *prop_r;
+
+    prop_c = xcb_get_property_unchecked(globalconf.connection, false, win,
+                                        _NET_WM_WINDOW_OPACITY, CARDINAL, 0L, 1L);
+
+    prop_r = xcb_get_property_reply(globalconf.connection, prop_c, NULL);
+
+    if(!prop_r || !prop_r->value_len || prop_r->format != 32)
+        goto bailout;
+
+    if(prop_r->value_len)
+    {
+        unsigned int *data = xcb_get_property_value(prop_r);
+        printf("result %d\n", *data);
+        return (double) *data / (double) 0xffffffff;
+    }
+
+  bailout:
+    p_delete(&prop_r);
+    return -1;
+}
+
+/** Set opacity of a window.
  * \param win The window.
  * \param opacity Opacity of the window, between 0 and 1.
  */
 void
-window_trans_set(xcb_window_t win, double opacity)
+window_opacity_set(xcb_window_t win, double opacity)
 {
     unsigned int real_opacity = 0xffffffff;
 

window.h

@@ -30,7 +30,8 @@ long window_state_get_reply(xcb_get_property_cookie_t);
 void window_configure(xcb_window_t, area_t, int);
 void window_buttons_grab(xcb_window_t, xcb_window_t, button_t *);
 void window_root_buttons_grab(xcb_window_t);
-void window_trans_set(xcb_window_t, double);
+double window_opacity_get(xcb_window_t);
+void window_opacity_set(xcb_window_t, double);
 
 #endif
 // vim: filetype=c:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80