[gnome-photos/wip/rishi/zoom: 3/12] image-view: Support scrolling and zooming

[Debarshi Ray <debarshir src gnome org>]

commit 320487deb1343eadd2b3eb3b0704ad6466acd76d
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Mar 30 10:46:17 2017 +0200

    image-view: Support scrolling and zooming
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742662

 src/photos-image-view.c |  478 ++++++++++++++++++++++++++++++++++++++++++++---
 src/photos-image-view.h |    6 +
 2 files changed, 459 insertions(+), 25 deletions(-)
---
diff --git a/src/photos-image-view.c b/src/photos-image-view.c
index 60138af..8b99af3 100644
--- a/src/photos-image-view.c
+++ b/src/photos-image-view.c
@@ -29,6 +29,7 @@
 #include "photos-gegl.h"
 #include "photos-image-view.h"
 #include "photos-marshalers.h"
+#include "photos-utils.h"
 
 
 struct _PhotosImageView
@@ -36,8 +37,17 @@ struct _PhotosImageView
   GtkDrawingArea parent_instance;
   GeglBuffer *buffer;
   GeglNode *node;
+  GeglRectangle bbox_zoomed_old;
+  GtkAdjustment *hadjustment;
+  GtkAdjustment *vadjustment;
+  GtkAllocation allocation_scaled_old;
+  GtkScrollablePolicy hscroll_policy;
+  GtkScrollablePolicy vscroll_policy;
   cairo_region_t *bbox_region;
   cairo_region_t *region;
+  gboolean best_fit;
+  gdouble height;
+  gdouble width;
   gdouble x;
   gdouble x_scaled;
   gdouble y;
@@ -49,7 +59,12 @@ struct _PhotosImageView
 enum
 {
   PROP_0,
+  PROP_BEST_FIT,
+  PROP_HADJUSTMENT,
+  PROP_HSCROLL_POLICY,
   PROP_NODE,
+  PROP_VADJUSTMENT,
+  PROP_VSCROLL_POLICY,
   PROP_X,
   PROP_Y,
   PROP_ZOOM
@@ -65,7 +80,8 @@ enum
 static guint signals[LAST_SIGNAL] = { 0 };
 
 
-G_DEFINE_TYPE (PhotosImageView, photos_image_view, GTK_TYPE_DRAWING_AREA);
+G_DEFINE_TYPE_WITH_CODE (PhotosImageView, photos_image_view, GTK_TYPE_DRAWING_AREA,
+                         G_IMPLEMENT_INTERFACE (GTK_TYPE_SCROLLABLE, NULL));
 
 
 static void photos_image_view_computed (PhotosImageView *self, GeglRectangle *rect);
@@ -111,57 +127,221 @@ photos_image_view_update_region (PhotosImageView *self)
 
 
 static void
+photos_image_view_adjustment_value_changed (GtkAdjustment *adjustment, gpointer user_data)
+{
+  PhotosImageView *self = PHOTOS_IMAGE_VIEW (user_data);
+  gdouble value;
+  gint scale_factor;
+
+  g_return_if_fail (GTK_IS_ADJUSTMENT (adjustment));
+  g_return_if_fail (self->hadjustment == adjustment || self->vadjustment == adjustment);
+
+  if (self->node == NULL)
+    return;
+
+  if (!gtk_widget_get_realized (GTK_WIDGET (self)))
+    return;
+
+  if (self->best_fit)
+    return;
+
+  scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (self));
+
+  if (self->hadjustment == adjustment)
+    {
+      value = gtk_adjustment_get_value (self->hadjustment);
+      self->x = value;
+      self->x_scaled = self->x * (gdouble) scale_factor;
+    }
+  else
+    {
+      value = gtk_adjustment_get_value (self->vadjustment);
+      self->y = value;
+      self->y_scaled = self->y * (gdouble) scale_factor;
+    }
+
+  gtk_widget_queue_draw (GTK_WIDGET (self));
+}
+
+
+static void
+photos_image_view_set_hadjustment_values (PhotosImageView *self)
+{
+  GtkAllocation allocation;
+  gdouble page_increment;
+  gdouble page_size;
+  gdouble step_increment;
+  gdouble upper;
+  gdouble value;
+
+  gtk_widget_get_allocation (GTK_WIDGET (self), &allocation);
+
+  page_size = (gdouble) allocation.width;
+  page_increment = page_size * 0.9;
+  step_increment = page_size * 0.1;
+
+  upper = MAX ((gdouble) allocation.width, self->width);
+  g_return_if_fail (upper - page_size >= 0.0);
+
+  value = self->x;
+
+  gtk_adjustment_configure (self->hadjustment,
+                            value,
+                            0.0,
+                            upper,
+                            step_increment,
+                            page_increment,
+                            page_size);
+}
+
+
+static void
+photos_image_view_set_vadjustment_values (PhotosImageView *self)
+{
+  GtkAllocation allocation;
+  gdouble page_increment;
+  gdouble page_size;
+  gdouble step_increment;
+  gdouble upper;
+  gdouble value;
+
+  gtk_widget_get_allocation (GTK_WIDGET (self), &allocation);
+
+  page_size = (gdouble) allocation.height;
+  page_increment = page_size * 0.9;
+  step_increment = page_size * 0.1;
+
+  upper = MAX ((gdouble) allocation.height, self->height);
+  g_return_if_fail (upper - page_size >= 0.0);
+
+  value = self->y;
+
+  gtk_adjustment_configure (self->vadjustment,
+                            value,
+                            0.0,
+                            upper,
+                            step_increment,
+                            page_increment,
+                            page_size);
+}
+
+
+static void
 photos_image_view_update (PhotosImageView *self)
 {
   GeglRectangle bbox;
   GeglRectangle bbox_zoomed;
   GtkAllocation allocation;
-  gdouble zoom_scaled = 1.0;
   gint scale_factor;
   gint viewport_height_real;
   gint viewport_width_real;
 
+  g_object_freeze_notify (G_OBJECT (self));
+
   if (self->node == NULL)
-    return;
+    goto out;
 
-  g_return_if_fail (GEGL_IS_BUFFER (self->buffer));
+  g_assert_true (GEGL_IS_BUFFER (self->buffer));
 
   gtk_widget_get_allocation (GTK_WIDGET (self), &allocation);
 
-  if (allocation.width < 0 || allocation.height < 0)
-    return;
+  if (allocation.width <= 0 || allocation.height <= 0)
+    goto out;
 
   bbox = *gegl_buffer_get_extent (self->buffer);
   if (bbox.width < 0 || bbox.height < 0)
-    return;
+    goto out;
 
   scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (self));
   viewport_height_real = allocation.height * scale_factor;
   viewport_width_real = allocation.width * scale_factor;
 
-  if (bbox.height > viewport_height_real || bbox.width > viewport_width_real)
+  if (self->best_fit)
     {
-      gdouble height_ratio = bbox.height / (gdouble) viewport_height_real;
-      gdouble width_ratio = bbox.width / (gdouble) viewport_width_real;
-      gdouble max_ratio =  MAX (height_ratio, width_ratio);
+      gdouble zoom_scaled = 1.0;
 
-      zoom_scaled = 1.0 / max_ratio;
-    }
+      if (bbox.height > viewport_height_real || bbox.width > viewport_width_real)
+        {
+          gdouble height_ratio = bbox.height / (gdouble) viewport_height_real;
+          gdouble width_ratio = bbox.width / (gdouble) viewport_width_real;
+          gdouble max_ratio =  MAX (height_ratio, width_ratio);
+
+          zoom_scaled = 1.0 / max_ratio;
+        }
 
-  bbox_zoomed.width = (gint) (zoom_scaled * bbox.width + 0.5);
-  bbox_zoomed.height = (gint) (zoom_scaled * bbox.height + 0.5);
-  bbox_zoomed.x = (gint) (zoom_scaled * bbox.x + 0.5);
-  bbox_zoomed.y = (gint) (zoom_scaled * bbox.y + 0.5);
+      bbox_zoomed.width = (gint) (zoom_scaled * bbox.width + 0.5);
+      bbox_zoomed.height = (gint) (zoom_scaled * bbox.height + 0.5);
+      bbox_zoomed.x = (gint) (zoom_scaled * bbox.x + 0.5);
+      bbox_zoomed.y = (gint) (zoom_scaled * bbox.y + 0.5);
 
-  self->zoom_scaled = zoom_scaled;
-  self->zoom = self->zoom_scaled / (gdouble) scale_factor;
+      self->zoom_scaled = zoom_scaled;
+      self->zoom = self->zoom_scaled / (gdouble) scale_factor;
+
+      self->x_scaled = (bbox_zoomed.width - viewport_width_real) / 2.0;
+      self->y_scaled = (bbox_zoomed.height - viewport_height_real) / 2.0;
+
+      g_object_notify (G_OBJECT (self), "zoom");
+    }
+  else
+    {
+      gdouble ratio_old;
+
+      bbox_zoomed.width = (gint) (self->zoom_scaled * bbox.width + 0.5);
+      bbox_zoomed.height = (gint) (self->zoom_scaled * bbox.height + 0.5);
+      bbox_zoomed.x = (gint) (self->zoom_scaled * bbox.x + 0.5);
+      bbox_zoomed.y = (gint) (self->zoom_scaled * bbox.y + 0.5);
+
+      if (bbox_zoomed.width > viewport_width_real)
+        {
+          ratio_old = (self->x_scaled
+                       + self->allocation_scaled_old.width / 2.0
+                       - (gdouble) self->bbox_zoomed_old.x)
+                      / (gdouble) self->bbox_zoomed_old.width;
+          self->x_scaled = ratio_old * (gdouble) bbox_zoomed.width - (viewport_width_real / 2.0);
+          self->x_scaled = CLAMP (self->x_scaled, 0.0, (gdouble) bbox_zoomed.width - viewport_width_real);
+        }
+      else
+        {
+          self->x_scaled = (bbox_zoomed.width - viewport_width_real) / 2.0;
+        }
+
+      if (bbox_zoomed.height > viewport_height_real)
+        {
+          ratio_old = (self->y_scaled
+                       + self->allocation_scaled_old.height / 2.0
+                       - (gdouble) self->bbox_zoomed_old.y)
+                      / (gdouble) self->bbox_zoomed_old.height;
+          self->y_scaled = ratio_old * (gdouble) bbox_zoomed.height - (viewport_height_real / 2.0);
+          self->y_scaled = CLAMP (self->y_scaled, 0.0, (gdouble) bbox_zoomed.height - viewport_height_real);
+        }
+      else
+        {
+          self->y_scaled = (bbox_zoomed.height - viewport_height_real) / 2.0;
+        }
+    }
 
-  /* At this point, viewport is definitely bigger than bbox_zoomed. */
-  self->x_scaled = (bbox_zoomed.width - viewport_width_real) / 2.0 + bbox_zoomed.x;
-  self->y_scaled = (bbox_zoomed.height - viewport_height_real) / 2.0 + bbox_zoomed.y;
+  self->x_scaled += (gdouble) bbox_zoomed.x;
+  self->y_scaled += (gdouble) bbox_zoomed.y;
 
   self->x = self->x_scaled / (gdouble) scale_factor;
   self->y = self->y_scaled / (gdouble) scale_factor;
+
+  self->height = (gdouble) bbox_zoomed.height / (gdouble) scale_factor;
+  self->width = (gdouble) bbox_zoomed.width / (gdouble) scale_factor;
+
+  g_signal_handlers_block_by_func (self->hadjustment, photos_image_view_adjustment_value_changed, self);
+  g_signal_handlers_block_by_func (self->vadjustment, photos_image_view_adjustment_value_changed, self);
+
+  photos_image_view_set_hadjustment_values (self);
+  photos_image_view_set_vadjustment_values (self);
+
+  g_signal_handlers_unblock_by_func (self->hadjustment, photos_image_view_adjustment_value_changed, self);
+  g_signal_handlers_unblock_by_func (self->vadjustment, photos_image_view_adjustment_value_changed, self);
+
+  self->bbox_zoomed_old = bbox_zoomed;
+
+ out:
+  g_object_thaw_notify (G_OBJECT (self));
 }
 
 
@@ -301,10 +481,93 @@ static void
 photos_image_view_size_allocate (GtkWidget *widget, GtkAllocation *allocation)
 {
   PhotosImageView *self = PHOTOS_IMAGE_VIEW (widget);
+  gint scale_factor;
 
   GTK_WIDGET_CLASS (photos_image_view_parent_class)->size_allocate (widget, allocation);
 
   photos_image_view_update (self);
+
+  scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (self));
+  self->allocation_scaled_old.height = allocation->height * scale_factor;
+  self->allocation_scaled_old.width = allocation->width * scale_factor;
+}
+
+
+static void
+photos_image_view_set_hadjustment (PhotosImageView *self, GtkAdjustment *hadjustment)
+{
+  if (hadjustment != NULL && self->hadjustment == hadjustment)
+    return;
+
+  if (self->hadjustment != NULL)
+    g_signal_handlers_disconnect_by_func (self->hadjustment, photos_image_view_adjustment_value_changed, 
self);
+
+  g_clear_object (&self->hadjustment);
+
+  if (hadjustment == NULL)
+    hadjustment = gtk_adjustment_new (0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
+
+  g_signal_connect_object (hadjustment,
+                           "value-changed",
+                           G_CALLBACK (photos_image_view_adjustment_value_changed),
+                           self,
+                           0);
+
+  self->hadjustment = g_object_ref_sink (hadjustment);
+  photos_image_view_set_hadjustment_values (self);
+
+  g_object_notify (G_OBJECT (self), "hadjustment");
+}
+
+
+static void
+photos_image_view_set_hscroll_policy (PhotosImageView *self, GtkScrollablePolicy hscroll_policy)
+{
+  if (self->hscroll_policy == hscroll_policy)
+    return;
+
+  self->hscroll_policy = hscroll_policy;
+  gtk_widget_queue_resize (GTK_WIDGET (self));
+  g_object_notify (G_OBJECT (self), "hscroll-policy");
+}
+
+
+static void
+photos_image_view_set_vadjustment (PhotosImageView *self, GtkAdjustment *vadjustment)
+{
+  if (vadjustment != NULL && self->vadjustment == vadjustment)
+    return;
+
+  if (self->vadjustment != NULL)
+    g_signal_handlers_disconnect_by_func (self->vadjustment, photos_image_view_adjustment_value_changed, 
self);
+
+  g_clear_object (&self->vadjustment);
+
+  if (vadjustment == NULL)
+    vadjustment = gtk_adjustment_new (0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
+
+  g_signal_connect_object (vadjustment,
+                           "value-changed",
+                           G_CALLBACK (photos_image_view_adjustment_value_changed),
+                           self,
+                           0);
+
+  self->vadjustment = g_object_ref_sink (vadjustment);
+  photos_image_view_set_vadjustment_values (self);
+
+  g_object_notify (G_OBJECT (self), "vadjustment");
+}
+
+
+static void
+photos_image_view_set_vscroll_policy (PhotosImageView *self, GtkScrollablePolicy vscroll_policy)
+{
+  if (self->vscroll_policy == vscroll_policy)
+    return;
+
+  self->vscroll_policy = vscroll_policy;
+  gtk_widget_queue_resize (GTK_WIDGET (self));
+  g_object_notify (G_OBJECT (self), "vscroll-policy");
 }
 
 
@@ -315,6 +578,8 @@ photos_image_view_dispose (GObject *object)
 
   g_clear_object (&self->buffer);
   g_clear_object (&self->node);
+  g_clear_object (&self->hadjustment);
+  g_clear_object (&self->vadjustment);
 
   G_OBJECT_CLASS (photos_image_view_parent_class)->dispose (object);
 }
@@ -339,10 +604,30 @@ photos_image_view_get_property (GObject *object, guint prop_id, GValue *value, G
 
   switch (prop_id)
     {
+    case PROP_BEST_FIT:
+      g_value_set_boolean (value, self->best_fit);
+      break;
+
+    case PROP_HADJUSTMENT:
+      g_value_set_object (value, self->hadjustment);
+      break;
+
+    case PROP_HSCROLL_POLICY:
+      g_value_set_enum (value, self->hscroll_policy);
+      break;
+
     case PROP_NODE:
       g_value_set_object (value, self->node);
       break;
 
+    case PROP_VADJUSTMENT:
+      g_value_set_object (value, self->vadjustment);
+      break;
+
+    case PROP_VSCROLL_POLICY:
+      g_value_set_enum (value, self->vscroll_policy);
+      break;
+
     case PROP_X:
       g_value_set_double (value, self->x);
       break;
@@ -369,6 +654,33 @@ photos_image_view_set_property (GObject *object, guint prop_id, const GValue *va
 
   switch (prop_id)
     {
+    case PROP_BEST_FIT:
+      {
+        gboolean best_fit;
+
+        best_fit = g_value_get_boolean (value);
+        photos_image_view_set_best_fit (self, best_fit);
+        break;
+      }
+
+    case PROP_HADJUSTMENT:
+      {
+        GtkAdjustment *hadjustment;
+
+        hadjustment = GTK_ADJUSTMENT (g_value_get_object (value));
+        photos_image_view_set_hadjustment (self, hadjustment);
+        break;
+      }
+
+    case PROP_HSCROLL_POLICY:
+      {
+        GtkScrollablePolicy hscroll_policy;
+
+        hscroll_policy = (GtkScrollablePolicy) g_value_get_enum (value);
+        photos_image_view_set_hscroll_policy (self, hscroll_policy);
+        break;
+      }
+
     case PROP_NODE:
       {
         GeglNode *node;
@@ -378,6 +690,33 @@ photos_image_view_set_property (GObject *object, guint prop_id, const GValue *va
         break;
       }
 
+    case PROP_VADJUSTMENT:
+      {
+        GtkAdjustment *vadjustment;
+
+        vadjustment = GTK_ADJUSTMENT (g_value_get_object (value));
+        photos_image_view_set_vadjustment (self, vadjustment);
+        break;
+      }
+
+    case PROP_VSCROLL_POLICY:
+      {
+        GtkScrollablePolicy vscroll_policy;
+
+        vscroll_policy = (GtkScrollablePolicy) g_value_get_enum (value);
+        photos_image_view_set_vscroll_policy (self, vscroll_policy);
+        break;
+      }
+
+    case PROP_ZOOM:
+      {
+        gdouble zoom;
+
+        zoom = g_value_get_double (value);
+        photos_image_view_set_zoom (self, zoom);
+        break;
+      }
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -393,11 +732,15 @@ photos_image_view_init (PhotosImageView *self)
   gtk_widget_add_events (GTK_WIDGET (self),
                          GDK_BUTTON_PRESS_MASK
                          | GDK_BUTTON_RELEASE_MASK
-                         | GDK_POINTER_MOTION_MASK);
+                         | GDK_POINTER_MOTION_MASK
+                         | GDK_SCROLL_MASK
+                         | GDK_SMOOTH_SCROLL_MASK);
 
   context = gtk_widget_get_style_context (GTK_WIDGET (self));
   gtk_style_context_add_class (context, GTK_STYLE_CLASS_VIEW);
   gtk_style_context_add_class (context, "content-view");
+
+  self->best_fit = TRUE;
 }
 
 
@@ -415,12 +758,24 @@ photos_image_view_class_init (PhotosImageViewClass *class)
   widget_class->size_allocate = photos_image_view_size_allocate;
 
   g_object_class_install_property (object_class,
+                                   PROP_BEST_FIT,
+                                   g_param_spec_boolean ("best-fit",
+                                                         "Best Fit",
+                                                         "Zoom and center the GeglNode to fit the widget's 
size",
+                                                         TRUE,
+                                                         G_PARAM_CONSTRUCT
+                                                         | G_PARAM_EXPLICIT_NOTIFY
+                                                         | G_PARAM_READWRITE));
+
+  g_object_class_install_property (object_class,
                                    PROP_NODE,
                                    g_param_spec_object ("node",
                                                         "GeglNode object",
                                                         "The GeglNode to render",
                                                         GEGL_TYPE_NODE,
-                                                        G_PARAM_CONSTRUCT | G_PARAM_READWRITE));
+                                                        G_PARAM_CONSTRUCT
+                                                        | G_PARAM_EXPLICIT_NOTIFY
+                                                        | G_PARAM_READWRITE));
 
   g_object_class_install_property (object_class,
                                    PROP_X,
@@ -450,7 +805,7 @@ photos_image_view_class_init (PhotosImageViewClass *class)
                                                         0.0,
                                                         100.0,
                                                         1.0,
-                                                        G_PARAM_READABLE));
+                                                        G_PARAM_EXPLICIT_NOTIFY | G_PARAM_READWRITE));
 
   signals[DRAW_BACKGROUND] = g_signal_new ("draw-background",
                                            G_TYPE_FROM_CLASS (class),
@@ -475,6 +830,11 @@ photos_image_view_class_init (PhotosImageViewClass *class)
                                         2,
                                         CAIRO_GOBJECT_TYPE_CONTEXT,
                                         GDK_TYPE_RECTANGLE);
+
+  g_object_class_override_property (object_class, PROP_HADJUSTMENT, "hadjustment");
+  g_object_class_override_property (object_class, PROP_HSCROLL_POLICY, "hscroll-policy");
+  g_object_class_override_property (object_class, PROP_VADJUSTMENT, "vadjustment");
+  g_object_class_override_property (object_class, PROP_VSCROLL_POLICY, "vscroll-policy");
 }
 
 
@@ -493,6 +853,14 @@ photos_image_view_new_from_node (GeglNode *node)
 }
 
 
+gboolean
+photos_image_view_get_best_fit (PhotosImageView *self)
+{
+  g_return_val_if_fail (PHOTOS_IS_IMAGE_VIEW (self), FALSE);
+  return self->best_fit;
+}
+
+
 GeglNode *
 photos_image_view_get_node (PhotosImageView *self)
 {
@@ -526,6 +894,28 @@ photos_image_view_get_zoom (PhotosImageView *self)
 
 
 void
+photos_image_view_set_best_fit (PhotosImageView *self, gboolean best_fit)
+{
+  g_return_if_fail (PHOTOS_IS_IMAGE_VIEW (self));
+
+  if (self->best_fit == best_fit)
+    return;
+
+  self->best_fit = best_fit;
+
+  if (self->best_fit)
+    {
+      self->zoom = 0.0;
+      self->zoom_scaled = 0.0;
+      gtk_widget_queue_resize (GTK_WIDGET (self));
+      g_object_notify (G_OBJECT (self), "zoom");
+    }
+
+  g_object_notify (G_OBJECT (self), "best-fit");
+}
+
+
+void
 photos_image_view_set_node (PhotosImageView *self, GeglNode *node)
 {
   g_return_if_fail (PHOTOS_IS_IMAGE_VIEW (self));
@@ -540,6 +930,17 @@ photos_image_view_set_node (PhotosImageView *self, GeglNode *node)
       g_signal_handlers_disconnect_by_func (self->node, photos_image_view_invalidated, self);
     }
 
+  self->allocation_scaled_old.height = 0;
+  self->allocation_scaled_old.width = 0;
+  self->best_fit = TRUE;
+  self->height = 0.0;
+  self->width = 0.0;
+  self->x = 0.0;
+  self->x_scaled = 0.0;
+  self->y = 0.0;
+  self->y_scaled = 0.0;
+  self->zoom = 0.0;
+  self->zoom_scaled = 0.0;
   g_clear_object (&self->buffer);
   g_clear_object (&self->node);
   g_clear_pointer (&self->bbox_region, (GDestroyNotify) cairo_region_destroy);
@@ -561,4 +962,31 @@ photos_image_view_set_node (PhotosImageView *self, GeglNode *node)
     }
 
   gtk_widget_queue_resize (GTK_WIDGET (self));
+
+  g_object_notify (G_OBJECT (self), "best-fit");
+  g_object_notify (G_OBJECT (self), "node");
+  g_object_notify (G_OBJECT (self), "zoom");
+}
+
+
+void
+photos_image_view_set_zoom (PhotosImageView *self, gdouble zoom)
+{
+  gint scale_factor;
+
+  g_return_if_fail (PHOTOS_IS_IMAGE_VIEW (self));
+
+  if (photos_utils_equal_double (self->zoom, zoom))
+    return;
+
+  self->best_fit = FALSE;
+  self->zoom = zoom;
+
+  scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (self));
+  self->zoom_scaled = self->zoom * scale_factor;
+
+  gtk_widget_queue_resize (GTK_WIDGET (self));
+
+  g_object_notify (G_OBJECT (self), "best-fit");
+  g_object_notify (G_OBJECT (self), "zoom");
 }
diff --git a/src/photos-image-view.h b/src/photos-image-view.h
index 0ba8708..5cf0e82 100644
--- a/src/photos-image-view.h
+++ b/src/photos-image-view.h
@@ -33,6 +33,8 @@ GtkWidget          *photos_image_view_new                (void);
 
 GtkWidget          *photos_image_view_new_from_node      (GeglNode *node);
 
+gboolean            photos_image_view_get_best_fit       (PhotosImageView *self);
+
 GeglNode           *photos_image_view_get_node           (PhotosImageView *self);
 
 gdouble             photos_image_view_get_x              (PhotosImageView *self);
@@ -41,8 +43,12 @@ gdouble             photos_image_view_get_y              (PhotosImageView *self)
 
 gdouble             photos_image_view_get_zoom           (PhotosImageView *self);
 
+void                photos_image_view_set_best_fit       (PhotosImageView *self, gboolean best_fit);
+
 void                photos_image_view_set_node           (PhotosImageView *self, GeglNode *node);
 
+void                photos_image_view_set_zoom           (PhotosImageView *self, gdouble zoom);
+
 G_END_DECLS
 
 #endif /* PHOTOS_IMAGE_VIEW_H */