autohide-window : add margins to the opposite edge if autohide is disabled

The margins being mostly a matter of style, this makes it so that if a margin is applied and autohide is disabled, space is reserved on both sides of the window.

However, wayfire 0.10.1 with gtk4-layer-shell 1.3 has a bug where auto
exclusive zone doesn’t account for the margin size, which causes shell
toplevels to go outside of the reserved space. Until this is fixed, on wayfire,
this patch only prevents overlap and doesn’t cause the intended behaviour

Wayfire issue : WayfireWM/wayfire#3038

Author: AKArien

src/util/wf-autohide-window.cpp

@@ -204,16 +204,35 @@ void WayfireAutohidingWindow::m_show_uncertain()
 
 void WayfireAutohidingWindow::update_position()
 {
-    /* Reset old anchors */
-    gtk_layer_set_anchor(this->gobj(), GTK_LAYER_SHELL_EDGE_TOP, false);
-    gtk_layer_set_anchor(this->gobj(), GTK_LAYER_SHELL_EDGE_BOTTOM, false);
-    gtk_layer_set_anchor(this->gobj(), GTK_LAYER_SHELL_EDGE_LEFT, false);
-    gtk_layer_set_anchor(this->gobj(), GTK_LAYER_SHELL_EDGE_RIGHT, false);
+    // reset anchors and margins
+    for (auto edge :
+     {GTK_LAYER_SHELL_EDGE_TOP, GTK_LAYER_SHELL_EDGE_BOTTOM, GTK_LAYER_SHELL_EDGE_LEFT,
+         GTK_LAYER_SHELL_EDGE_RIGHT})
+    {
+        gtk_layer_set_anchor(this->gobj(), edge, false);
+        gtk_layer_set_margin(this->gobj(), edge, 0);
+    }
 
     /* Set new anchor */
     GtkLayerShellEdge edge = get_anchor_edge(position);
     gtk_layer_set_anchor(this->gobj(), edge, true);
     gtk_layer_set_margin(this->gobj(), edge, edge_margin);
+    if (auto_exclusive_zone)
+    {
+        if (edge == GTK_LAYER_SHELL_EDGE_TOP)
+        {
+            gtk_layer_set_margin(this->gobj(), GTK_LAYER_SHELL_EDGE_BOTTOM, edge_margin);
+        } else if (edge == GTK_LAYER_SHELL_EDGE_BOTTOM)
+        {
+            gtk_layer_set_margin(this->gobj(), GTK_LAYER_SHELL_EDGE_TOP, edge_margin);
+        } else if (edge == GTK_LAYER_SHELL_EDGE_LEFT)
+        {
+            gtk_layer_set_margin(this->gobj(), GTK_LAYER_SHELL_EDGE_RIGHT, edge_margin);
+        } else if (edge == GTK_LAYER_SHELL_EDGE_RIGHT)
+        {
+            gtk_layer_set_margin(this->gobj(), GTK_LAYER_SHELL_EDGE_LEFT, edge_margin);
+        }
+    }
 
     if (full_span)
     {