[gnome-photos] Add PhotosWidgetShader

[Debarshi Ray <debarshir src gnome org>]

commit 0617b3b87768f4a7e927c1d1be10d979611dc26a
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri Dec 4 02:28:31 2015 +0100

    Add PhotosWidgetShader
    
    Given a GtkWidget it will draw a RGBA(0,0,0,0.5) shadow over it. Unless
    you explicitly take a reference, it's lifetime will be restricted to
    that of the GtkWidget.

 src/Makefile.am            |    2 +
 src/photos-widget-shader.c |  227 ++++++++++++++++++++++++++++++++++++++++++++
 src/photos-widget-shader.h |   50 ++++++++++
 3 files changed, 279 insertions(+), 0 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 15c858f..2d1aabe 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -230,6 +230,8 @@ gnome_photos_SOURCES = \
        photos-view-container.h \
        photos-view-model.c \
        photos-view-model.h \
+       photos-widget-shader.c \
+       photos-widget-shader.h \
        photos-main.c \
        $(NULL)
 
diff --git a/src/photos-widget-shader.c b/src/photos-widget-shader.c
new file mode 100644
index 0000000..11224ba
--- /dev/null
+++ b/src/photos-widget-shader.c
@@ -0,0 +1,227 @@
+/*
+ * Photos - access, organize and share your photos on GNOME
+ * Copyright © 2015 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+
+#include "config.h"
+
+#include <cairo.h>
+
+#include "photos-widget-shader.h"
+
+
+struct _PhotosWidgetShader
+{
+  GInitiallyUnowned parent_instance;
+  GtkWidget *widget;
+  cairo_surface_t *surface;
+  gboolean active;
+};
+
+struct _PhotosWidgetShaderClass
+{
+  GInitiallyUnownedClass parent_class;
+};
+
+enum
+{
+  PROP_0,
+  PROP_ACTIVE,
+  PROP_WIDGET
+};
+
+
+G_DEFINE_TYPE (PhotosWidgetShader, photos_widget_shader, G_TYPE_INITIALLY_UNOWNED);
+
+
+static gboolean
+photos_widget_shader_draw (PhotosWidgetShader *self, cairo_t *cr)
+{
+  if (!self->active)
+    goto out;
+
+  cairo_save (cr);
+  cairo_set_source_surface (cr, self->surface, 0.0, 0.0);
+  cairo_paint (cr);
+  cairo_restore (cr);
+
+ out:
+  return GDK_EVENT_PROPAGATE;
+}
+
+
+static void
+photos_widget_shader_surface_create (PhotosWidgetShader *self)
+{
+  GdkRectangle allocation;
+  GdkWindow *window;
+  cairo_t *cr = NULL;
+
+  g_clear_pointer (&self->surface, (GDestroyNotify) cairo_surface_destroy);
+
+  if (self->widget == NULL)
+    goto out;
+
+  window = gtk_widget_get_window (self->widget);
+  if (window == NULL)
+    goto out;
+
+  gtk_widget_get_allocation (self->widget, &allocation);
+  self->surface = gdk_window_create_similar_surface (window,
+                                                     CAIRO_CONTENT_COLOR_ALPHA,
+                                                     allocation.width,
+                                                     allocation.height);
+
+  cr = cairo_create (self->surface);
+  cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
+  cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 0.5);
+  cairo_paint (cr);
+
+ out:
+  g_clear_pointer (&cr, (GDestroyNotify) cairo_destroy);
+}
+
+
+static void
+photos_widget_shader_size_allocate (PhotosWidgetShader *self)
+{
+  photos_widget_shader_surface_create (self);
+}
+
+
+static void
+photos_widget_shader_constructed (GObject *object)
+{
+  PhotosWidgetShader *self = PHOTOS_WIDGET_SHADER (object);
+
+  G_OBJECT_CLASS (photos_widget_shader_parent_class)->constructed (object);
+
+  photos_widget_shader_surface_create (self);
+
+  g_signal_connect_object (self->widget,
+                           "draw",
+                           G_CALLBACK (photos_widget_shader_draw),
+                           self,
+                           G_CONNECT_AFTER | G_CONNECT_SWAPPED);
+  g_signal_connect_object (self->widget,
+                           "size-allocate",
+                           G_CALLBACK (photos_widget_shader_size_allocate),
+                           self,
+                           G_CONNECT_SWAPPED);
+
+  g_object_ref_sink (self);
+}
+
+
+static void
+photos_widget_shader_finalize (GObject *object)
+{
+  PhotosWidgetShader *self = PHOTOS_WIDGET_SHADER (object);
+
+  g_assert_null (self->widget);
+  g_clear_pointer (&self->surface, (GDestroyNotify) cairo_surface_destroy);
+
+  G_OBJECT_CLASS (photos_widget_shader_parent_class)->finalize (object);
+}
+
+
+static void
+photos_widget_shader_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
+{
+  PhotosWidgetShader *self = PHOTOS_WIDGET_SHADER (object);
+
+  switch (prop_id)
+    {
+    case PROP_ACTIVE:
+      {
+        gboolean active;
+
+        active = g_value_get_boolean (value);
+        photos_widget_shader_set_active (self, active);
+        break;
+      }
+
+    case PROP_WIDGET:
+      self->widget = GTK_WIDGET (g_value_get_object (value));
+      g_object_add_weak_pointer (G_OBJECT (self->widget), (gpointer *) &self->widget);
+      g_object_weak_ref (G_OBJECT (self->widget), (GWeakNotify) g_object_unref, self);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+
+static void
+photos_widget_shader_init (PhotosWidgetShader *self)
+{
+}
+
+
+static void
+photos_widget_shader_class_init (PhotosWidgetShaderClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->constructed = photos_widget_shader_constructed;
+  object_class->finalize = photos_widget_shader_finalize;
+  object_class->set_property = photos_widget_shader_set_property;
+
+  g_object_class_install_property (object_class,
+                                   PROP_ACTIVE,
+                                   g_param_spec_boolean ("active",
+                                                         "Active",
+                                                         "Whether the widget shader is active or not",
+                                                         FALSE,
+                                                         G_PARAM_WRITABLE));
+
+  g_object_class_install_property (object_class,
+                                   PROP_WIDGET,
+                                   g_param_spec_object ("widget",
+                                                        "Widget",
+                                                        "The target widget that is going to be shaded",
+                                                        GTK_TYPE_WIDGET,
+                                                        G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE));
+}
+
+
+PhotosWidgetShader *
+photos_widget_shader_new (GtkWidget *widget)
+{
+  g_return_val_if_fail (widget != NULL && GTK_IS_WIDGET (widget), NULL);
+  return g_object_new (PHOTOS_TYPE_WIDGET_SHADER, "widget", widget, NULL);
+}
+
+
+void
+photos_widget_shader_set_active (PhotosWidgetShader *self, gboolean active)
+{
+  if (self->active == active)
+    return;
+
+  self->active = active;
+  g_object_notify (G_OBJECT (self), "active");
+
+  if (self->widget == NULL)
+    return;
+
+  gtk_widget_queue_draw (self->widget);
+}
diff --git a/src/photos-widget-shader.h b/src/photos-widget-shader.h
new file mode 100644
index 0000000..0f5391f
--- /dev/null
+++ b/src/photos-widget-shader.h
@@ -0,0 +1,50 @@
+/*
+ * Photos - access, organize and share your photos on GNOME
+ * Copyright © 2015 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef PHOTOS_WIDGET_SHADER_H
+#define PHOTOS_WIDGET_SHADER_H
+
+#include <glib-object.h>
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define PHOTOS_TYPE_WIDGET_SHADER (photos_widget_shader_get_type ())
+
+#define PHOTOS_WIDGET_SHADER(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST ((obj), \
+   PHOTOS_TYPE_WIDGET_SHADER, PhotosWidgetShader))
+
+#define PHOTOS_IS_WIDGET_SHADER(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE ((obj), \
+   PHOTOS_TYPE_WIDGET_SHADER))
+
+typedef struct _PhotosWidgetShader      PhotosWidgetShader;
+typedef struct _PhotosWidgetShaderClass PhotosWidgetShaderClass;
+
+GType                  photos_widget_shader_get_type               (void) G_GNUC_CONST;
+
+PhotosWidgetShader    *photos_widget_shader_new                    (GtkWidget *widget);
+
+void                   photos_widget_shader_set_active             (PhotosWidgetShader *self, gboolean 
active);
+
+G_END_DECLS
+
+#endif /* PHOTOS_WIDGET_SHADER_H */