[nautilus/wip/antoniof/draw-shadow-directly] list-view: Draw shadow instead of doing style class changes

[António Fernandes <antoniof src gnome org>]

commit 18dd71d10e2960d62caf590724715973ac9e5684
Author: António Fernandes <antoniof gnome org>
Date:   Mon Feb 28 13:05:40 2022 +0000

    list-view: Draw shadow instead of doing style class changes

 src/nautilus-list-view.c | 55 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 37 insertions(+), 18 deletions(-)
---
diff --git a/src/nautilus-list-view.c b/src/nautilus-list-view.c
index 77278fab1..c1cef11f2 100644
--- a/src/nautilus-list-view.c
+++ b/src/nautilus-list-view.c
@@ -1578,16 +1578,6 @@ starred_cell_data_func (GtkTreeViewColumn *column,
     g_autofree gchar *text = NULL;
     g_autofree gchar *uri = NULL;
     NautilusFile *file;
-    GtkStyleContext *context;
-
-    /* The "thumbnail" style class is set before rendering each icon cell with
-     * a thumbnail. However, style classes are not applied to each cell, but
-     * alwyas to the whole GtkTreeView widget. So, before the star icon is
-     * rendered, we must ensure that the style is not set, otherwise the star
-     * icon is going to get the styles meant only for thumbnail icons.
-     */
-    context = gtk_widget_get_style_context (GTK_WIDGET (view));
-    gtk_style_context_remove_class (context, "thumbnail");
 
     gtk_tree_model_get (model, iter,
                         view->details->file_name_column_num, &text,
@@ -1659,10 +1649,6 @@ icon_cell_data_func (GtkTreeViewColumn *column,
                         &file,
                         -1);
 
-    /* Hack: Set/unset the style class in advance of rendering. This makes a
-     * major assumption that's all but clearly stated in the documentation of
-     * GtkCellLayout: that the DataFunc is called before rendering each cell.
-     */
     is_thumbnail = FALSE;
     if (zoom_level_is_enough_for_thumbnails (view) && file != NULL)
     {
@@ -1678,11 +1664,44 @@ icon_cell_data_func (GtkTreeViewColumn *column,
 
     if (is_thumbnail)
     {
+        cairo_surface_t *new_surface;
+        cairo_t *cr;
+
+        /* The shadow extends 1px up, 3px down, and 2px left and right.
+         *
+         *    *************************
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#                     #*
+         *    *#######################*
+         *    *#######################*
+         *    *************************
+         *
+         * Therefore, final surface is 4px taller and 4px wider, with the
+         * original icon starting at (2,1).
+         */
+        new_surface = cairo_surface_create_similar (surface,
+                                                    CAIRO_CONTENT_COLOR_ALPHA,
+                                                    cairo_image_surface_get_width (surface) + 4,
+                                                    cairo_image_surface_get_height (surface) + 4);
+        cr = cairo_create (new_surface);
+
+        gtk_style_context_save (context);
         gtk_style_context_add_class (context, "thumbnail");
-    }
-    else
-    {
-        gtk_style_context_remove_class (context, "thumbnail");
+        gtk_render_icon_surface (context, cr, surface, 2, 1);
+        gtk_style_context_restore (context);
+
+        cairo_destroy (cr);
+
+        cairo_surface_destroy (surface);
+        surface = new_surface;
     }
 
     g_object_set (renderer,