Add frame_x_center/frame_y_center variables for themes

Sometimes you want to position something (usually the title) to be centered
with respect to the entire frame instead of centered with respect to the
individual piece currently being drawn.

This patch adds frame_x_center and frame_y_center variables that represent
the X/Y centers of the frame in the coordinate system of the piece being
drawn.

The theme version is bumped from 3.0 to 3.1 (3.0 is just the new version
system, 3.1 will have all the features we add for Mutter-2.28.)
position expressions

https://bugzilla.gnome.org/show_bug.cgi?id=591842

4 files changed, 29 insertions, 1 deletions

diff --git a/doc/theme-format.txt b/doc/theme-format.txt
index bb79d4534..cefc31627 100644
--- a/doc/theme-format.txt
+++ b/doc/theme-format.txt
@@ -22,6 +22,16 @@ This document has separate sections for each format version. You may
 want to read the document in reverse order, since the base features
 are discussed under version 1.
 
+New Features in Theme Format Version 3.1
+========================================
+
+Additional predefined variables are added for positioning expressions:
+
+ frame_x_center: the X center of the entire frame, with respect to the
+     piece currently being drawn.
+ frame_y_center: the Y center of the entire frame, with respect to the
+     piece currently being drawn.
+
 New Features in Theme Format Version 3
 ======================================
 
diff --git a/src/ui/theme-parser.c b/src/ui/theme-parser.c
index 9dad99fbd..b2d8bf77d 100644
--- a/src/ui/theme-parser.c
+++ b/src/ui/theme-parser.c
@@ -38,7 +38,7 @@
  * look out for.
  */
 #define THEME_MAJOR_VERSION 3
-#define THEME_MINOR_VERSION 0
+#define THEME_MINOR_VERSION 1
 #define THEME_VERSION (1000 * THEME_MAJOR_VERSION + THEME_MINOR_VERSION)
 
 #define METACITY_THEME_FILENAME_FORMAT "metacity-theme-%d.xml"
diff --git a/src/ui/theme.c b/src/ui/theme.c
index 0bb43655a..367423371 100644
--- a/src/ui/theme.c
+++ b/src/ui/theme.c
@@ -2188,6 +2188,10 @@ pos_eval_get_variable (PosToken                  *t,
         *result = env->title_width;
       else if (t->d.v.name_quark == env->theme->quark_title_height)
         *result = env->title_height;
+      else if (t->d.v.name_quark == env->theme->quark_frame_x_center)
+        *result = env->frame_x_center;
+      else if (t->d.v.name_quark == env->theme->quark_frame_y_center)
+        *result = env->frame_y_center;
       else
         {
           g_set_error (err, META_THEME_ERROR,
@@ -2229,6 +2233,10 @@ pos_eval_get_variable (PosToken                  *t,
         *result = env->title_width;
       else if (strcmp (t->d.v.name, "title_height") == 0)
         *result = env->title_height;
+      else if (strcmp (t->d.v.name, "frame_x_center") == 0)
+        *result = env->frame_x_center;
+      else if (strcmp (t->d.v.name, "frame_y_center") == 0)
+        *result = env->frame_y_center;
       else
         {
           g_set_error (err, META_THEME_ERROR,
@@ -3437,6 +3445,8 @@ fill_env (MetaPositionExprEnv *env,
       env->right_width = info->fgeom->right_width;
       env->top_height = info->fgeom->top_height;
       env->bottom_height = info->fgeom->bottom_height;
+      env->frame_x_center = info->fgeom->width / 2 - logical_region.x;
+      env->frame_y_center = info->fgeom->height / 2 - logical_region.y;
     }
   else
     {
@@ -3444,6 +3454,8 @@ fill_env (MetaPositionExprEnv *env,
       env->right_width = 0;
       env->top_height = 0;
       env->bottom_height = 0;
+      env->frame_x_center = 0;
+      env->frame_y_center = 0;
     }
   
   env->mini_icon_width = info->mini_icon ? gdk_pixbuf_get_width (info->mini_icon) : 0;
@@ -4845,6 +4857,8 @@ meta_theme_new (void)
   theme->quark_icon_height = g_quark_from_static_string ("icon_height");
   theme->quark_title_width = g_quark_from_static_string ("title_width");
   theme->quark_title_height = g_quark_from_static_string ("title_height");
+  theme->quark_frame_x_center = g_quark_from_static_string ("frame_x_center");
+  theme->quark_frame_y_center = g_quark_from_static_string ("frame_y_center");
   return theme;
 }
 
diff --git a/src/ui/theme.h b/src/ui/theme.h
index ddf777d4d..02a61566a 100644
--- a/src/ui/theme.h
+++ b/src/ui/theme.h
@@ -819,6 +819,8 @@ struct _MetaTheme
   GQuark quark_icon_height;
   GQuark quark_title_width;
   GQuark quark_title_height;
+  GQuark quark_frame_x_center;
+  GQuark quark_frame_y_center;
 };
 
 struct _MetaPositionExprEnv
@@ -834,6 +836,8 @@ struct _MetaPositionExprEnv
   int bottom_height;
   int title_width;
   int title_height;
+  int frame_x_center;
+  int frame_y_center;
   int mini_icon_width;
   int mini_icon_height;
   int icon_width;