Allow windows to be locked against WM-initiated opacity changes.
This uses a new non-standard hint, _NET_WM_WINDOW_OPACITY_LOCKED.

If the hint is present for the current window, then the window manager
SHOULD NOT alter its opacity from the current value of
_NET_WM_WINDOW_OPACITY (if it uses that hint), and opacity-setting tools
SHOULD NOT alter _NET_WM_WINDOW_OPACITY.

If the hint is absent, then the behaviour of xfwm4 without this patch is
maintained.

(Reason: opacity of windows which (contain sub-windows which) are used for
Xv overlays.)

Signed-off-by: Darren Salt <linux@youmustbejoking.demon.co.uk>

Index: src/display.c
===================================================================
--- src/display.c	(revision 22201)
+++ src/display.c	(working copy)
@@ -106,6 +106,7 @@
         "_NET_WM_MOVERESIZE",
         "_NET_WM_NAME",
         "_NET_WM_WINDOW_OPACITY",
+        "_NET_WM_WINDOW_OPACITY_LOCKED",
         "_NET_WM_STATE",
         "_NET_WM_STATE_ABOVE",
         "_NET_WM_STATE_BELOW",
Index: src/display.h
===================================================================
--- src/display.h	(revision 22201)
+++ src/display.h	(working copy)
@@ -117,6 +117,7 @@
     NET_WM_MOVERESIZE,
     NET_WM_NAME,
     NET_WM_WINDOW_OPACITY,
+    NET_WM_WINDOW_OPACITY_LOCKED,
     NET_WM_STATE,
     NET_WM_STATE_ABOVE,
     NET_WM_STATE_BELOW,
Index: src/events.c
===================================================================
--- src/events.c	(revision 22201)
+++ src/events.c	(working copy)
@@ -1823,6 +1823,11 @@
             }
             compositorWindowSetOpacity (display_info, c->frame, c->opacity);
         }
+        else if (ev->atom == display_info->atoms[NET_WM_WINDOW_OPACITY_LOCKED])
+        {
+            TRACE ("client \"%s\" (0x%lx) has received a net_wm_opacity_locked notify", c->name, c->window);
+            c->opacity_locked = getOpacityLock (display_info, c->window);
+        }
         else if ((screen_info->params->show_app_icon) &&
                  ((ev->atom == display_info->atoms[NET_WM_ICON]) ||
                   (ev->atom == display_info->atoms[KWM_WIN_ICON])))
Index: src/compositor.c
===================================================================
--- src/compositor.c	(revision 22201)
+++ src/compositor.c	(working copy)
@@ -99,6 +99,7 @@
     gboolean argb;
     gboolean skipped;
     gboolean native_opacity;
+    gboolean opacity_locked;
 
     Damage damage;
 #if HAVE_NAME_WINDOW_PIXMAP
@@ -1769,17 +1770,20 @@
     cw->native_opacity = FALSE;
     if (c)
     {
+        cw->opacity_locked = c->opacity_locked;
         cw->opacity = c->opacity;
         cw->native_opacity = WIN_IS_OPAQUE(cw);
     }
     else if (getOpacity (display_info, cw->id, &cw->opacity))
     {
         cw->native_opacity = WIN_IS_OPAQUE(cw);
+        cw->opacity_locked = getOpacityLock (display_info, cw->id);
     }
     else
     {
         cw->opacity = (double) (screen_info->params->popup_opacity / 100.0) * NET_WM_OPAQUE;
         cw->native_opacity = TRUE;
+        cw->opacity_locked = getOpacityLock (display_info, cw->id);
     }
 }
 
@@ -2146,6 +2150,20 @@
             }
         }
     }
+    else if (ev->atom == display_info->atoms[NET_WM_WINDOW_OPACITY_LOCKED])
+    {
+        CWindow *cw = find_cwindow_in_display (display_info, ev->window);
+        TRACE ("Opacity locking property changed for id 0x%lx", ev->window);
+
+        if (cw)
+        {
+            cw->opacity_locked = getOpacityLock (display_info, cw->id);
+            if (cw->c)
+            {
+                cw->c->opacity_locked = cw->opacity_locked;
+            }
+        }
+    }
     else
     {
         TRACE ("No compositor property changed for id 0x%lx", ev->window);
Index: src/client.c
===================================================================
--- src/client.c	(revision 22201)
+++ src/client.c	(working copy)
@@ -1629,6 +1629,8 @@
     c->opacity = NET_WM_OPAQUE;
     getOpacity (display_info, c->window, &c->opacity);
 
+    c->opacity_locked = getOpacityLock (display_info, c->window);
+
     /* Timeout for blinking on urgency */
     c->blink_timeout_id = 0;
 
@@ -2865,7 +2867,7 @@
    screen_info = c->screen_info;
    display_info = screen_info->display_info;
 
-   if ( c->opacity > OPACITY_SET_MIN )
+   if ( c->opacity > OPACITY_SET_MIN && !c->opacity_locked )
    {
         c->opacity -= OPACITY_SET_STEP;
         compositorWindowSetOpacity (display_info, c->frame, c->opacity);
@@ -2881,7 +2883,7 @@
    screen_info = c->screen_info;
    display_info = screen_info->display_info;
 
-   if ( c->opacity < NET_WM_OPAQUE )
+   if ( c->opacity < NET_WM_OPAQUE && !c->opacity_locked )
    {
         c->opacity += OPACITY_SET_STEP;
 
@@ -3534,7 +3536,7 @@
 #endif /* SHOW_POSITION */
 
     /* Set window translucent while moving, looks nice */
-    if ((screen_info->params->move_opacity < 100) && !(screen_info->params->box_move))
+    if ((screen_info->params->move_opacity < 100) && !(screen_info->params->box_move) && !c->opacity_locked)
     {
         compositorWindowSetOpacity (display_info, c->frame, 
             (guint) (c->opacity * (double) (screen_info->params->move_opacity / 100.0)));
@@ -4014,7 +4016,7 @@
 #endif /* SHOW_POSITION */
 
     /* Set window translucent while resizing, doesn't looks too nice  :( */
-    if ((screen_info->params->resize_opacity < 100) && !(screen_info->params->box_resize))
+    if ((screen_info->params->resize_opacity < 100) && !(screen_info->params->box_resize) && !c->opacity_locked)
     {
         compositorWindowSetOpacity (display_info, c->frame, 
             (guint) (c->opacity * (double) (screen_info->params->resize_opacity / 100.0)));
Index: src/client.h
===================================================================
--- src/client.h	(revision 22201)
+++ src/client.h	(working copy)
@@ -269,6 +269,7 @@
     ClientPixmapCache pm_cache;
     /* Opacity for the compositor */
     guint opacity;
+    gboolean opacity_locked;
     
 #ifdef HAVE_LIBSTARTUP_NOTIFICATION
     /* Startup notification */
Index: src/hints.c
===================================================================
--- src/hints.c	(revision 22201)
+++ src/hints.c	(working copy)
@@ -1103,6 +1103,18 @@
 }
 
 gboolean
+getOpacityLock (DisplayInfo *display_info, Window window)
+{
+    long val;
+
+    g_return_val_if_fail (window != None, FALSE);
+    TRACE ("entering getOpacityLock");
+
+    /* only presence/absence matters */
+    return !!getHint (display_info, window, NET_WM_WINDOW_OPACITY_LOCKED, &val);
+}
+
+gboolean
 setCompositingManagerOwner (DisplayInfo *display_info, Window root, Window w)
 {
     XClientMessageEvent ev;
Index: src/hints.h
===================================================================
--- src/hints.h	(revision 22201)
+++ src/hints.h	(working copy)
@@ -176,6 +176,7 @@
 gboolean getKDEIcon (DisplayInfo *, Window, Pixmap *, Pixmap *);
 gboolean getRGBIconData (DisplayInfo *, Window, unsigned long **, unsigned long *);
 gboolean getOpacity (DisplayInfo *, Window, guint *);
+gboolean getOpacityLock (DisplayInfo *, Window);
 gboolean setCompositingManagerOwner (DisplayInfo *, Window , Window);
 
 #ifdef ENABLE_KDE_SYSTRAY_PROXY