gtk-layer-shell: Use zone 0 to get reliable workarea sizing.

In a proper wlr-layer-shell implementation, exclusive zone 0
ensures the nemo-desktop window and icon layout are kept within
the desktop workarea (avoiding panels or other layer-shell clients
with zone > 0). Use this capability if available.

Author: mtwebster

src/nemo-blank-desktop-window.c

@@ -522,10 +522,13 @@ nemo_blank_desktop_window_update_geometry (NemoBlankDesktopWindow *window)
         GdkDisplay *display = gdk_display_get_default ();
         GdkMonitor *monitor = gdk_display_get_monitor (display, window->details->monitor);
 
+        DEBUG ("NemoBlankDesktopWindow: using layer-shell for monitor %d",
+               window->details->monitor);
+
         gtk_layer_set_layer (GTK_WINDOW (window), GTK_LAYER_SHELL_LAYER_BOTTOM);
         gtk_layer_set_namespace (GTK_WINDOW (window), "nemo-desktop");
         gtk_layer_set_keyboard_mode (GTK_WINDOW (window), GTK_LAYER_SHELL_KEYBOARD_MODE_NONE);
-        gtk_layer_set_exclusive_zone (GTK_WINDOW (window), -1);
+        gtk_layer_set_exclusive_zone (GTK_WINDOW (window), 0);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_TOP, TRUE);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_BOTTOM, TRUE);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_LEFT, TRUE);

src/nemo-desktop-manager.c

@@ -15,6 +15,10 @@
 #include <gdk/gdkx.h>
 #include <stdio.h>
 
+#ifdef HAVE_GTK_LAYER_SHELL
+#include <gtk-layer-shell.h>
+#endif
+
 #include "libnemo-private/nemo-action-manager.h"
 #include <libnemo-private/nemo-global-preferences.h>
 #include <libnemo-private/nemo-desktop-utils.h>
@@ -629,12 +633,16 @@ fallback_startup_idle_cb (NemoDesktopManager *manager)
 static gboolean
 is_cinnamon_desktop (void)
 {
+    const gchar *session_desktop = g_getenv ("XDG_SESSION_DESKTOP");
+    const gchar *desktop_session = g_getenv ("DESKTOP_SESSION");
 
-    if (g_strcmp0 (g_getenv ("XDG_SESSION_DESKTOP"), "cinnamon") == 0) {
+    if (session_desktop != NULL &&
+        g_strstr_len (session_desktop, -1, "cinnamon") != NULL) {
         return TRUE;
     }
 
-    if (g_strstr_len (g_getenv ("DESKTOP_SESSION"), -1, "cinnamon") != NULL) {
+    if (desktop_session != NULL &&
+        g_strstr_len (desktop_session, -1, "cinnamon") != NULL) {
         return TRUE;
     }
 
@@ -882,13 +890,24 @@ nemo_desktop_manager_get_margins (NemoDesktopManager *manager,
 {
     FETCH_PRIV (manager);
     GdkRectangle work_rect, geometry;
+    gboolean use_layer_shell = FALSE;
+
+#ifdef HAVE_GTK_LAYER_SHELL
+    use_layer_shell = gtk_layer_is_supported ();
+#endif
 
-    /* We don't use margins if we have reliable work area
-     * info (e.g. having an active Cinnamon session) */
+    DEBUG ("NemoDesktopManager get_margins: monitor=%d proxy_owned=%d other_desktop=%d use_layer_shell=%d",
+           monitor, priv->proxy_owned, priv->other_desktop, use_layer_shell);
+
+    /* When Cinnamon is running, we don't use margins because the window is
+     * sized to the work area (X11 mode) or the compositor sizes it to the
+     * workarea (layer-shell mode with exclusive_zone=0). */
 
     if (priv->proxy_owned && !priv->other_desktop) {
         *left = *right = *top = *bottom = 0;
 
+        DEBUG ("NemoDesktopManager get_margins: returning 0 margins (Cinnamon running)");
+
         return;
     }
 

src/nemo-desktop-window.c

@@ -358,10 +358,13 @@ nemo_desktop_window_update_geometry (NemoDesktopWindow *window)
         GdkDisplay *display = gdk_display_get_default ();
         GdkMonitor *monitor = gdk_display_get_monitor (display, window->details->monitor);
 
+        DEBUG ("NemoDesktopWindow: using layer-shell for monitor %d",
+               window->details->monitor);
+
         gtk_layer_set_layer (GTK_WINDOW (window), GTK_LAYER_SHELL_LAYER_BOTTOM);
         gtk_layer_set_namespace (GTK_WINDOW (window), "nemo-desktop");
         gtk_layer_set_keyboard_mode (GTK_WINDOW (window), GTK_LAYER_SHELL_KEYBOARD_MODE_ON_DEMAND);
-        gtk_layer_set_exclusive_zone (GTK_WINDOW (window), -1);
+        gtk_layer_set_exclusive_zone (GTK_WINDOW (window), 0);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_TOP, TRUE);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_BOTTOM, TRUE);
         gtk_layer_set_anchor (GTK_WINDOW (window), GTK_LAYER_SHELL_EDGE_LEFT, TRUE);