Remember the focused window on tag changes

a. Adds a get_current_tag_number function to allow for above updates
and teaches get_current_layout(...) and arrange(...) to use it.
b. Adds an extra client_sel entry in struct Tag, updated on
focus(...), manage(...), and unmanage(...), and used in arrange(...).

client.c

@@ -349,6 +349,7 @@ client_detach(Client **head, Client *c)
 void
 focus(Client *c, Bool selscreen, awesome_config *awesomeconf)
 {
+    int tag;
     /* if c is NULL or invisible, take next client in the stack */
     if((!c && selscreen) || (c && !isvisible(c, awesomeconf->screen, awesomeconf->tags, awesomeconf->ntags)))
         for(c = *awesomeconf->clients; c && !isvisible(c, awesomeconf->screen, awesomeconf->tags, awesomeconf->ntags); c = c->next);
@@ -374,6 +375,8 @@ focus(Client *c, Bool selscreen, awesome_config *awesomeconf)
     if(!selscreen)
         return;
     *awesomeconf->client_sel = c;
+    if ((tag = get_current_tag_number(awesomeconf->tags, awesomeconf->ntags)) >= 0)
+        *awesomeconf->tags[tag].client_sel = c;
     drawstatusbar(awesomeconf);
     if(*awesomeconf->client_sel)
     {
@@ -425,7 +428,7 @@ loadprops(Client *c, int ntags)
 void
 manage(Window w, XWindowAttributes *wa, awesome_config *awesomeconf)
 {
-    int i;
+    int i, tag;
     Client *c, *t = NULL;
     Window trans;
     Status rettrans;
@@ -526,6 +529,9 @@ manage(Window w, XWindowAttributes *wa, awesome_config *awesomeconf)
     /* some windows require this */
     XMoveResizeWindow(c->display, c->win, c->x, c->y, c->w, c->h);
 
+    if((tag = get_current_tag_number(awesomeconf->tags, awesomeconf->ntags)) >= 0)
+        *awesomeconf->tags[tag].client_sel = c;
+
     /* rearrange to display new window */
     arrange(awesomeconf);
 }
@@ -649,6 +655,7 @@ void
 unmanage(Client *c, long state, awesome_config *awesomeconf)
 {
     XWindowChanges wc;
+    int tag;
 
     client_untab(c);
     wc.border_width = c->oldborder;
@@ -658,6 +665,9 @@ unmanage(Client *c, long state, awesome_config *awesomeconf)
     client_detach(awesomeconf->clients, c);
     if(*awesomeconf->client_sel == c)
         focus(NULL, True, awesomeconf);
+    for(tag = 0; tag < awesomeconf->ntags; tag++)
+        if(*awesomeconf->tags[tag].client_sel == c)
+            *awesomeconf->tags[tag].client_sel = NULL;
     XUngrabButton(c->display, AnyButton, AnyModifier, c->win);
     window_setstate(c->display, c->win, state);
     XSync(c->display, False);

config.c

@@ -362,6 +362,7 @@ parse_config(Display * disp, int scr,const char *confpatharg, awesome_config *aw
         awesomeconf->tags[i].name = a_strdup(cfg_title(cfgsectmp));
         awesomeconf->tags[i].selected = False;
         awesomeconf->tags[i].was_selected = False;
+        awesomeconf->tags[i].client_sel = p_new(Client *, 1);
         tmp = cfg_getstr(cfgsectmp, "layout");
         for(k = 0; k < awesomeconf->nlayouts; k++)
             if(awesomeconf->layouts[k].arrange == name_func_lookup(tmp, LayoutsList))

config.h

@@ -80,19 +80,6 @@ typedef struct
     int screen;
 } Statusbar;
 
-/** Tag type */
-typedef struct
-{
-    /** Tag name */
-    char *name;
-    /** True if selected */
-    Bool selected;
-    /** True if was selected before selecting others tags */
-    Bool was_selected;
-    /** Current tag layout */
-    Layout *layout;
-} Tag;
-
 typedef struct Client Client; 
 struct Client
 {
@@ -141,6 +128,21 @@ struct Client
     int phys_screen;
 };
 
+/** Tag type */
+typedef struct
+{
+    /** Tag name */
+    char *name;
+    /** True if selected */
+    Bool selected;
+    /** True if was selected before selecting others tags */
+    Bool was_selected;
+    /** Current tag layout */
+    Layout *layout;
+    /** Selected client on this tag */
+    Client **client_sel;
+} Tag;
+
 /** Main configuration structure */
 struct awesome_config
 {

layout.c

@@ -29,6 +29,22 @@
 #include "statusbar.h"
 #include "layouts/floating.h"
 
+/** Find the index of the first currently selected tag
+ * \param tags the array of tags to search
+ * \param ntags number of elements in above array
+ */
+int
+get_current_tag_number(Tag *tags, int ntags)
+{
+    int i;
+
+    for(i = 0; i < ntags; i++)
+        if(tags[i].selected == True)
+            return i;
+
+    return -1;
+}
+
 /** Arrange windows following current selected layout
  * \param disp display ref
  * \param awesomeconf awesome config
@@ -37,6 +53,7 @@ void
 arrange(awesome_config *awesomeconf)
 {
     Client *c;
+    int curtag;
 
     for(c = *awesomeconf->clients; c; c = c->next)
     {
@@ -46,20 +63,23 @@ arrange(awesome_config *awesomeconf)
         else if(c->screen == awesomeconf->screen)
             ban(c);
     }
-    get_current_layout(awesomeconf->tags, awesomeconf->ntags)->arrange(awesomeconf);
+    if ((curtag = get_current_tag_number(awesomeconf->tags, awesomeconf->ntags)) >= 0)
+    {
+        awesomeconf->tags[curtag].layout->arrange(awesomeconf);
+        focus(*awesomeconf->tags[curtag].client_sel, True, awesomeconf);
+    }
+    else
         focus(NULL, True, awesomeconf);
     restack(awesomeconf);
 }
 
-
 Layout *
 get_current_layout(Tag *tags, int ntags)
 {
-    int i;
+    int curtag;
 
-    for(i = 0; i < ntags; i++)
-        if(tags[i].selected)
-            return tags[i].layout;
+    if ((curtag = get_current_tag_number(tags, ntags)) >= 0)
+        return tags[curtag].layout;
 
     return NULL;
 }

layout.h

@@ -28,6 +28,7 @@
 
 void arrange(awesome_config *);
 Layout * get_current_layout(Tag *, int);
+int get_current_tag_number(Tag *, int);
 void restack(awesome_config *);
 void loadawesomeprops(awesome_config *);
 void saveawesomeprops(awesome_config *);