[gnome-todo] color-button: Use CSS to render color

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 31319a83c07c82f9e1f6d4b16c35a73b6e1b7c52
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed Feb 13 17:48:41 2019 -0200

    color-button: Use CSS to render color
    
    This allows us to use CSS effects such as filter,
    background-color and border-radius.

 src/theme/Adwaita.css          | 10 ++++++++
 src/widgets/gtd-color-button.c | 53 +++++++++++++++++++++++++++++++++++-------
 2 files changed, 54 insertions(+), 9 deletions(-)
---
diff --git a/src/theme/Adwaita.css b/src/theme/Adwaita.css
index 7009e02..a576cb7 100644
--- a/src/theme/Adwaita.css
+++ b/src/theme/Adwaita.css
@@ -129,6 +129,16 @@ image.color-circle-icon {
 
 
 /* Color button */
+colorbutton {
+    border-radius: 6px;
+    transition: 100ms;
+}
+
+colorbutton:hover {
+    filter: brightness(80%);
+    transition: 100ms;
+}
+
 colorbutton.dark image {
     color: white;
 }
diff --git a/src/widgets/gtd-color-button.c b/src/widgets/gtd-color-button.c
index 693f61d..5965950 100644
--- a/src/widgets/gtd-color-button.c
+++ b/src/widgets/gtd-color-button.c
@@ -29,6 +29,7 @@ struct _GtdColorButton
 {
   GtkWidget           parent;
 
+  GtkCssProvider     *css_provider;
   GdkRGBA             color;
 
   GtkWidget          *selected_icon;
@@ -116,14 +117,10 @@ gtd_color_button_snapshot (GtkWidget   *widget,
   width = gtk_widget_get_width (widget);
   height = gtk_widget_get_height (widget);
 
-  /* XXX: This API doesn't exist yet:
-   *
-   * gtk_snapshot_push_content_clip (snapshot, 0, 0, width, height);
-   */
-
-  gtk_snapshot_append_color (snapshot,
-                             &self->color,
-                             &GRAPHENE_RECT_INIT (0, 0, width, height));
+  gtk_snapshot_render_background (snapshot,
+                                  gtk_widget_get_style_context (widget),
+                                  0, 0,
+                                  width, height);
 
   gtk_widget_snapshot_child (widget, self->selected_icon, snapshot);
 }
@@ -157,6 +154,7 @@ gtd_color_button_finalize (GObject *object)
   GtdColorButton *self = (GtdColorButton *)object;
 
   g_clear_pointer (&self->selected_icon, gtk_widget_unparent);
+  g_clear_object (&self->css_provider);
 
   G_OBJECT_CLASS (gtd_color_button_parent_class)->finalize (object);
 }
@@ -255,18 +253,55 @@ void
 gtd_color_button_set_color (GtdColorButton *self,
                             const GdkRGBA  *color)
 {
+  g_autofree gchar *color_string = NULL;
+  g_autofree gchar *css_snippet = NULL;
+  g_autofree gchar *css_class = NULL;
   GtkStyleContext *context;
+  GQuark color_id;
 
   g_return_if_fail (GTD_IS_COLOR_BUTTON (self));
 
   if (gdk_rgba_equal (&self->color, color))
     return;
 
+  context = gtk_widget_get_style_context (GTK_WIDGET (self));
+
+  /* Remove the old CSS class */
+  if (self->css_provider)
+    {
+      g_autofree gchar *old_color_string = NULL;
+      g_autofree gchar *old_css_class = NULL;
+      GQuark old_color_id;
+
+      old_color_string = gdk_rgba_to_string (&self->color);
+      old_color_id = g_quark_from_string (old_color_string);
+      old_css_class = g_strdup_printf ("%d", old_color_id);
+
+      gtk_style_context_remove_class (context, old_css_class);
+    }
+
   self->color = *color;
   self->color.alpha = 1.0;
 
-  context = gtk_widget_get_style_context (GTK_WIDGET (self));
+  /* Eventually create the CSS provider */
+  if (!self->css_provider)
+    {
+      self->css_provider = gtk_css_provider_new ();
+      gtk_style_context_add_provider (context,
+                                      GTK_STYLE_PROVIDER (self->css_provider),
+                                      GTK_STYLE_PROVIDER_PRIORITY_USER);
+    }
+
+  color_string = gdk_rgba_to_string (color);
+  color_id = g_quark_from_string (color_string);
+  css_snippet = g_strdup_printf ("colorbutton.%d { background-color: %s; }", color_id, color_string);
+  gtk_css_provider_load_from_data (self->css_provider, css_snippet, -1);
+
+  /* Add the new CSS class */
+  css_class = g_strdup_printf ("%d", color_id);
+  gtk_style_context_add_class (context, css_class);
 
+  /* ... and adjust the icon color */
   if (INTENSITY (self->color.red, self->color.green, self->color.blue) > 0.5)
     {
       gtk_style_context_add_class (context, "light");