[gtk+] Popover: Include window shadows in overshoot calcs

[Daniel Boles <dboles src gnome org>]

commit 12693c6fe31692d42552793a227d280917d35d6e
Author: Daniel Boles <dboles src gnome org>
Date:   Wed Aug 23 21:44:10 2017 +0100

    Popover: Include window shadows in overshoot calcs
    
    .update_position() enforces that non-Wayland platforms must position a
    Popover within its parent Window. We use the allocation of the Window
    to translate the position and check for overshoot on each of its sides.
    Calling Widget.get_allocation() of a CSD Window includes its shadows.
    
    But shadows were not excluded from the area in which we can position.
    Thus, Popovers could get positioned in the shadow of CSD windows, where,
    at least on X11, no input is received. Therefore, positioning a Popover
    over a shadow meant its child widgets within that area became unusable.
    
    Fix by calling Window.get_shadow() and including it in the overshoot on
    each side. This adjusts for how the allocation includes shadows, making
    overshoots with and without shadows the same. Thus, we avoid considering
    shadows as viable for positioning, favouring a side where input works.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786209

 gtk/gtkpopover.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkpopover.c b/gtk/gtkpopover.c
index f52d7b5..3f787fd 100644
--- a/gtk/gtkpopover.c
+++ b/gtk/gtkpopover.c
@@ -1099,6 +1099,7 @@ gtk_popover_update_position (GtkPopover *popover)
   GtkPopoverPrivate *priv = popover->priv;
   GtkWidget *widget = GTK_WIDGET (popover);
   GtkAllocation window_alloc;
+  GtkBorder window_shadow;
   GdkRectangle rect;
   GtkRequisition req;
   GtkPositionType pos;
@@ -1111,6 +1112,7 @@ gtk_popover_update_position (GtkPopover *popover)
 
   gtk_widget_get_preferred_size (widget, NULL, &req);
   gtk_widget_get_allocation (GTK_WIDGET (priv->window), &window_alloc);
+  _gtk_window_get_shadow_width (priv->window, &window_shadow);
   priv->final_position = priv->preferred_position;
 
   gtk_popover_get_pointing_to (popover, &rect);
@@ -1119,10 +1121,12 @@ gtk_popover_update_position (GtkPopover *popover)
 
   pos = get_effective_position (popover, priv->preferred_position);
 
-  overshoot[GTK_POS_TOP] = req.height - rect.y;
-  overshoot[GTK_POS_BOTTOM] = rect.y + rect.height + req.height - window_alloc.height;
-  overshoot[GTK_POS_LEFT] = req.width - rect.x;
-  overshoot[GTK_POS_RIGHT] = rect.x + rect.width + req.width - window_alloc.width;
+  overshoot[GTK_POS_TOP] = req.height - rect.y + window_shadow.top;
+  overshoot[GTK_POS_BOTTOM] = rect.y + rect.height + req.height - window_alloc.height
+                              + window_shadow.bottom;
+  overshoot[GTK_POS_LEFT] = req.width - rect.x + window_shadow.left;
+  overshoot[GTK_POS_RIGHT] = rect.x + rect.width + req.width - window_alloc.width
+                             + window_shadow.right;
 
 #ifdef GDK_WINDOWING_WAYLAND
   if (GDK_IS_WAYLAND_DISPLAY (gtk_widget_get_display (widget)) &&