raise fullscreen windows on top of all other X11 windows

Note that this is ineffective for dunst’s notifications because dunst
re-raises them as soon as they get obscured. It does work for dzen2
however, which was the original use-case.

fixes #569

include/x.h

@@ -93,8 +93,12 @@ void x_push_changes(Con *con);
  * Raises the specified container in the internal stack of X windows. The
  * next call to x_push_changes() will make the change visible in X11.
  *
+ * If above_all is true, the X11 window will be raised to the top
+ * of the stack. This should only be used for precisely one fullscreen
+ * window per output.
+ *
  */
-void x_raise_con(Con *con);
+void x_raise_con(Con *con, bool above_all);
 
 /**
  * Sets the WM_NAME property (so, no UTF8, but used only for debugging anyways)

src/render.c

@@ -70,7 +70,7 @@ static void render_l_output(Con *con) {
     Con *fullscreen = con_get_fullscreen_con(ws, CF_OUTPUT);
     if (fullscreen) {
         fullscreen->rect = con->rect;
-        x_raise_con(fullscreen);
+        x_raise_con(fullscreen, true);
         render_con(fullscreen, true);
         return;
     }
@@ -110,7 +110,7 @@ static void render_l_output(Con *con) {
 
         DLOG("child at (%d, %d) with (%d x %d)\n",
                 child->rect.x, child->rect.y, child->rect.width, child->rect.height);
-        x_raise_con(child);
+        x_raise_con(child, false);
         render_con(child, false);
     }
 }
@@ -207,7 +207,7 @@ void render_con(Con *con, bool render_fullscreen) {
     }
     if (fullscreen) {
         fullscreen->rect = rect;
-        x_raise_con(fullscreen);
+        x_raise_con(fullscreen, false);
         render_con(fullscreen, true);
         return;
     }
@@ -298,7 +298,7 @@ void render_con(Con *con, bool render_fullscreen) {
                 }
                 DLOG("floating child at (%d,%d) with %d x %d\n",
                      child->rect.x, child->rect.y, child->rect.width, child->rect.height);
-                x_raise_con(child);
+                x_raise_con(child, false);
                 render_con(child, false);
             }
         }
@@ -407,7 +407,7 @@ void render_con(Con *con, bool render_fullscreen) {
 
         DLOG("child at (%d, %d) with (%d x %d)\n",
                 child->rect.x, child->rect.y, child->rect.width, child->rect.height);
-        x_raise_con(child);
+        x_raise_con(child, false);
         render_con(child, false);
         i++;
     }
@@ -415,7 +415,7 @@ void render_con(Con *con, bool render_fullscreen) {
     /* in a stacking or tabbed container, we ensure the focused client is raised */
     if (con->layout == L_STACKED || con->layout == L_TABBED) {
         TAILQ_FOREACH_REVERSE(child, &(con->focus_head), focus_head, focused)
-            x_raise_con(child);
+            x_raise_con(child, false);
         if ((child = TAILQ_FIRST(&(con->focus_head)))) {
             /* By rendering the stacked container again, we handle the case
              * that we have a non-leaf-container inside the stack. In that
@@ -429,7 +429,7 @@ void render_con(Con *con, bool render_fullscreen) {
              * top of every stack window. That way, when a new window is opened in
              * the stack, the old window will not obscure part of the decoration
              * (it’s unmapped afterwards). */
-            x_raise_con(con);
+            x_raise_con(con, false);
     }
     }
 }

src/x.c

@@ -36,6 +36,7 @@ typedef struct con_state {
     bool mapped;
     bool unmap_now;
     bool child_mapped;
+    bool above_all;
 
     /** The con for which this state is. */
     Con *con;
@@ -899,6 +900,10 @@ void x_push_changes(Con *con) {
 
             xcb_configure_window(conn, prev->id, mask, values);
         }
+        if (state->above_all) {
+            DLOG("above all: 0x%08x\n", state->id);
+            xcb_configure_window(conn, state->id, XCB_CONFIG_WINDOW_STACK_MODE, (uint32_t[]){ XCB_STACK_MODE_ABOVE });
+        }
         state->initial = false;
     }
 
@@ -1024,12 +1029,18 @@ void x_push_changes(Con *con) {
  * Raises the specified container in the internal stack of X windows. The
  * next call to x_push_changes() will make the change visible in X11.
  *
+ * If above_all is true, the X11 window will be raised to the top
+ * of the stack. This should only be used for precisely one fullscreen
+ * window per output.
+ *
  */
-void x_raise_con(Con *con) {
+void x_raise_con(Con *con, bool above_all) {
     con_state *state;
     state = state_for_frame(con->frame);
     //DLOG("raising in new stack: %p / %s / %s / xid %08x\n", con, con->name, con->window ? con->window->name_json : "", state->id);
 
+    state->above_all = above_all;
+
     CIRCLEQ_REMOVE(&state_head, state, state);
     CIRCLEQ_INSERT_HEAD(&state_head, state, state);
 }