[gthumb] dragger: do not update the scaled image if the zoom didn't change

[Paolo Bacchilega <paobac src gnome org>]

commit f682c21244b1a5e7a7721eedb40d9320ed959e8c
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sat Oct 12 20:06:06 2013 +0200

    dragger: do not update the scaled image if the zoom didn't change

 gthumb/gth-image-dragger.c |   47 ++++++++++++++++++++++++-------------------
 1 files changed, 26 insertions(+), 21 deletions(-)
---
diff --git a/gthumb/gth-image-dragger.c b/gthumb/gth-image-dragger.c
index 0b3fe27..0c14c8f 100644
--- a/gthumb/gth-image-dragger.c
+++ b/gthumb/gth-image-dragger.c
@@ -35,6 +35,7 @@ struct _GthImageDraggerPrivate {
        GthImageViewer  *viewer;
        gboolean         draggable;
        cairo_surface_t *scaled;
+       double           scaled_zoom;
        GthTask         *scale_task;
 };
 
@@ -84,6 +85,7 @@ gth_image_dragger_init (GthImageDragger *dragger)
 {
        dragger->priv = G_TYPE_INSTANCE_GET_PRIVATE (dragger, GTH_TYPE_IMAGE_DRAGGER, GthImageDraggerPrivate);
        dragger->priv->scaled = NULL;
+       dragger->priv->scaled_zoom = 0;
        dragger->priv->scale_task = NULL;
        dragger->priv->viewer = NULL;
        dragger->priv->draggable = FALSE;
@@ -401,19 +403,20 @@ static void
 _gth_image_dragger_update_scaled_image (GthImageDragger *self)
 {
        cairo_surface_t *image;
+       double           zoom;
        int              image_width, image_height;
        int              original_width, original_height;
-       double           zoom;
        int              new_width, new_height;
        scale_filter_t   filter;
 
+       self->priv->scaled_zoom = 0;
+       _cairo_clear_surface (&self->priv->scaled);
+
        if (self->priv->scale_task != NULL) {
                gth_task_cancel (self->priv->scale_task);
                self->priv->scale_task = NULL;
        }
 
-       _cairo_clear_surface (&self->priv->scaled);
-
        if (self->priv->viewer == NULL)
                return;
 
@@ -424,13 +427,6 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
        if ((image == NULL) || (cairo_surface_status (image) != CAIRO_STATUS_SUCCESS))
                return;
 
-       image_width = cairo_image_surface_get_width (image);
-       image_height = cairo_image_surface_get_height (image);
-       gth_image_viewer_get_original_size (self->priv->viewer, &original_width, &original_height);
-
-       if ((original_width != image_width) || (original_height != image_height))
-               return;
-
        if (gth_image_viewer_get_zoom_quality (self->priv->viewer) == GTH_ZOOM_QUALITY_LOW)
                return;
 
@@ -438,33 +434,42 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
        if (zoom >= 1.0)
                return;
 
-       new_width = zoom * image_width;
-       new_height = zoom * image_height;
+       image_width = cairo_image_surface_get_width (image);
+       image_height = cairo_image_surface_get_height (image);
+       gth_image_viewer_get_original_size (self->priv->viewer, &original_width, &original_height);
+       new_width = zoom * original_width;
+       new_height = zoom * original_height;
 
-       if (image_width * image_height > SIZE_TOO_BIG_FOR_SCALE_BILINEAR) {
-               self->priv->scaled = _cairo_image_surface_scale_nearest (image, new_width, new_height);
-               filter = SCALE_FILTER_BOX;
-       }
-       else {
+       if (image_width * image_height <= SIZE_TOO_BIG_FOR_SCALE_BILINEAR) {
                self->priv->scaled = _cairo_image_surface_scale_bilinear (image, new_width, new_height);
                filter = SCALE_FILTER_TRIANGLE;
        }
+       else
+               filter = SCALE_FILTER_BOX;
 
+       self->priv->scaled_zoom = zoom;
        _gth_image_dragger_create_scaled_high_quality (self, image, new_width, new_height, filter);
 }
 
 
 static void
-gth_image_dragger_image_changed (GthImageViewerTool *self)
+gth_image_dragger_image_changed (GthImageViewerTool *base)
 {
-       _gth_image_dragger_update_scaled_image (GTH_IMAGE_DRAGGER (self));
+       _gth_image_dragger_update_scaled_image (GTH_IMAGE_DRAGGER (base));
 }
 
 
 static void
-gth_image_dragger_zoom_changed (GthImageViewerTool *self)
+gth_image_dragger_zoom_changed (GthImageViewerTool *base)
 {
-       _gth_image_dragger_update_scaled_image (GTH_IMAGE_DRAGGER (self));
+       GthImageDragger *self = GTH_IMAGE_DRAGGER (base);
+
+       if ((self->priv->viewer == NULL)
+               || (gth_image_viewer_get_zoom_quality (self->priv->viewer) == GTH_ZOOM_QUALITY_LOW)
+               || (self->priv->scaled_zoom != gth_image_viewer_get_zoom (self->priv->viewer)))
+       {
+               _gth_image_dragger_update_scaled_image (self);
+       }
 }