[gnome-flashback] desktop: add dark css class if background is dark

[Alberts Muktupāvels <muktupavels src gnome org>]

commit aa2db881eb13c8a2d162671076051a0fa1ae4962
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Oct 30 13:28:27 2019 +0200

    desktop: add dark css class if background is dark

 gnome-flashback/libdesktop/gf-background.c     | 21 +++++++++++++++++
 gnome-flashback/libdesktop/gf-background.h     |  4 +++-
 gnome-flashback/libdesktop/gf-desktop-window.c | 31 ++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)
---
diff --git a/gnome-flashback/libdesktop/gf-background.c b/gnome-flashback/libdesktop/gf-background.c
index 5e88c02..4e95bf6 100644
--- a/gnome-flashback/libdesktop/gf-background.c
+++ b/gnome-flashback/libdesktop/gf-background.c
@@ -66,6 +66,7 @@ static GParamSpec *background_properties[LAST_PROP] = { NULL };
 enum
 {
   READY,
+  CHANGED,
 
   LAST_SIGNAL
 };
@@ -130,6 +131,8 @@ fade_cb (gpointer user_data)
   screen = gtk_widget_get_screen (self->window);
   gnome_bg_set_surface_as_root (screen, self->surface);
 
+  g_signal_emit (self, background_signals[CHANGED], 0);
+
   return G_SOURCE_REMOVE;
 }
 
@@ -179,6 +182,8 @@ change (GfBackground *self,
                                                TRUE);
 
       gnome_bg_set_surface_as_root (screen, self->surface);
+
+      g_signal_emit (self, background_signals[CHANGED], 0);
     }
 
   g_signal_emit (self, background_signals[READY], 0);
@@ -395,6 +400,10 @@ install_signals (void)
   background_signals[READY] =
     g_signal_new ("ready", GF_TYPE_BACKGROUND, G_SIGNAL_RUN_LAST,
                   0, NULL, NULL, NULL, G_TYPE_NONE, 0);
+
+  background_signals[CHANGED] =
+    g_signal_new ("changed", GF_TYPE_BACKGROUND, G_SIGNAL_RUN_LAST,
+                  0, NULL, NULL, NULL, G_TYPE_NONE, 0);
 }
 
 static void
@@ -425,3 +434,15 @@ gf_background_new (GtkWidget *window)
                        "window", window,
                        NULL);
 }
+
+gboolean
+gf_background_is_dark (GfBackground *self)
+{
+  int width;
+  int height;
+
+  width = gf_desktop_window_get_width (GF_DESKTOP_WINDOW (self->window));
+  height = gf_desktop_window_get_height (GF_DESKTOP_WINDOW (self->window));
+
+  return gnome_bg_is_dark (self->bg, width, height);
+}
diff --git a/gnome-flashback/libdesktop/gf-background.h b/gnome-flashback/libdesktop/gf-background.h
index a83593c..2aa466f 100644
--- a/gnome-flashback/libdesktop/gf-background.h
+++ b/gnome-flashback/libdesktop/gf-background.h
@@ -25,7 +25,9 @@ G_BEGIN_DECLS
 #define GF_TYPE_BACKGROUND (gf_background_get_type ())
 G_DECLARE_FINAL_TYPE (GfBackground, gf_background, GF, BACKGROUND, GObject)
 
-GfBackground *gf_background_new (GtkWidget *window);
+GfBackground *gf_background_new     (GtkWidget    *window);
+
+gboolean      gf_background_is_dark (GfBackground *self);
 
 G_END_DECLS
 
diff --git a/gnome-flashback/libdesktop/gf-desktop-window.c b/gnome-flashback/libdesktop/gf-desktop-window.c
index 1914099..b71a665 100644
--- a/gnome-flashback/libdesktop/gf-desktop-window.c
+++ b/gnome-flashback/libdesktop/gf-desktop-window.c
@@ -68,6 +68,25 @@ static guint window_signals[LAST_SIGNAL] = { 0 };
 
 G_DEFINE_TYPE (GfDesktopWindow, gf_desktop_window, GTK_TYPE_WINDOW)
 
+static void
+update_css_class (GfDesktopWindow *self)
+{
+  gboolean dark;
+  GtkStyleContext *context;
+
+  dark = FALSE;
+
+  if (self->background != NULL)
+    dark = gf_background_is_dark (self->background);
+
+  context = gtk_widget_get_style_context (GTK_WIDGET (self));
+
+  if (!dark)
+    gtk_style_context_remove_class (context, "dark");
+  else
+    gtk_style_context_add_class (context, "dark");
+}
+
 static void
 ensure_surface (GfDesktopWindow *self)
 {
@@ -80,6 +99,7 @@ ensure_surface (GfDesktopWindow *self)
 
   self->surface = gnome_bg_get_surface_from_root (screen);
   gtk_widget_queue_draw (widget);
+  update_css_class (self);
 }
 
 static GdkFilterReturn
@@ -177,6 +197,13 @@ ready_cb (GfBackground    *background,
   emit_ready (self);
 }
 
+static void
+changed_cb (GfBackground    *background,
+            GfDesktopWindow *self)
+{
+  update_css_class (self);
+}
+
 static void
 draw_background_changed (GfDesktopWindow *self)
 {
@@ -189,6 +216,10 @@ draw_background_changed (GfDesktopWindow *self)
       self->background = gf_background_new (GTK_WIDGET (self));
 
       g_signal_connect (self->background, "ready", G_CALLBACK (ready_cb), self);
+
+      g_signal_connect (self->background, "changed",
+                        G_CALLBACK (changed_cb),
+                        self);
     }
   else
     {