WindowClone: Fix some warnings on allocate (#2610)

- outer_rect.width can be 0 in which case the clone_scale_factor is nan which leads to us allocating a size of nan. Therefore set the scale to 1 if the width is 0.
- clone isn't a child of us so don't allocate it
- bound the window title max width by its min width. The calculated max width could even be less than 0 which lead to allocating a negative size.

Author: leolost2605

src/Widgets/MultitaskingView/WindowClone.vala

@@ -310,7 +310,7 @@ public class Gala.WindowClone : ActorTarget, RootTarget {
 
         var input_rect = window.get_buffer_rect ();
         var outer_rect = window.get_frame_rect ();
-        var clone_scale_factor = width / outer_rect.width;
+        var clone_scale_factor = outer_rect.width != 0 ? width / outer_rect.width : 1f;
 
         // Compensate for invisible borders of the texture
         float clone_x = (input_rect.x - outer_rect.x) * clone_scale_factor;
@@ -327,12 +327,6 @@ public class Gala.WindowClone : ActorTarget, RootTarget {
 
         clone.set_scale (clone_scale_factor, clone_scale_factor);
 
-        float clone_width, clone_height;
-        clone.get_preferred_size (null, null, out clone_width, out clone_height);
-
-        var clone_alloc = InternalUtils.actor_box_from_rect (0, 0, clone_width, clone_height);
-        clone.allocate (clone_alloc);
-
         Clutter.ActorBox shape_alloc = {
             -ACTIVE_SHAPE_SIZE,
             -ACTIVE_SHAPE_SIZE,
@@ -364,11 +358,12 @@ public class Gala.WindowClone : ActorTarget, RootTarget {
         var monitor_index = display.get_monitor_index_for_rect (Mtk.Rectangle.from_graphene_rect (rect, ROUND));
         var monitor_scale = display.get_monitor_scale (monitor_index);
 
-        float window_title_max_width = box.get_width () - Utils.scale_to_int (TITLE_MAX_WIDTH_MARGIN, monitor_scale);
-        float window_title_height, window_title_nat_width;
-        window_title.get_preferred_size (null, null, out window_title_nat_width, out window_title_height);
+        float window_title_min_width, window_title_nat_width, window_title_height;
+        window_title.get_preferred_size (out window_title_min_width, null, out window_title_nat_width, out window_title_height);
+
+        float window_title_max_width = float.max (window_title_min_width, box.get_width () - Utils.scale_to_int (TITLE_MAX_WIDTH_MARGIN, monitor_scale));
 
-        var window_title_width = window_title_nat_width.clamp (0, window_title_max_width);
+        var window_title_width = float.min (window_title_nat_width, window_title_max_width);
 
         float window_title_x = (box.get_width () - window_title_width) / 2;
         float window_title_y = (window_icon.visible ? window_icon_y : box.get_height ()) - (window_title_height / 2) - Utils.scale_to_int (18, monitor_scale);