[gthumb] hi-dpi: do not treat low quality as high quality

[Paolo Bacchilega <paobac src gnome org>]

commit 3a22267fd1c2dfafbc5fe3672e4a105f2b5262eb
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Fri Oct 27 12:31:11 2017 +0200

    hi-dpi: do not treat low quality as high quality
    
    [bug #779340]

 gthumb/gth-image-dragger.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/gthumb/gth-image-dragger.c b/gthumb/gth-image-dragger.c
index aad7630..cce716d 100644
--- a/gthumb/gth-image-dragger.c
+++ b/gthumb/gth-image-dragger.c
@@ -281,6 +281,7 @@ gth_image_dragger_draw (GthImageViewerTool *self,
        }
        else {
                double zoom = gth_image_viewer_get_zoom (viewer);
+               int    screen_scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (viewer));
 
                gth_image_viewer_paint_region (viewer,
                                               cr,
@@ -288,7 +289,7 @@ gth_image_dragger_draw (GthImageViewerTool *self,
                                               viewer->image_area.x,
                                               viewer->image_area.y,
                                               &viewer->visible_area,
-                                              (gth_image_viewer_get_zoom_quality (viewer) == 
GTH_ZOOM_QUALITY_HIGH) && (zoom > 1.0) && (zoom <= MAX_ZOOM_LEVEL_FOR_HIGH_QUALITY) ? CAIRO_FILTER_BILINEAR : 
CAIRO_FILTER_FAST);
+                                              (gth_image_viewer_get_zoom_quality (viewer) == 
GTH_ZOOM_QUALITY_HIGH) && (zoom * screen_scale_factor > 1.0) && (zoom <= MAX_ZOOM_LEVEL_FOR_HIGH_QUALITY) ? 
CAIRO_FILTER_BILINEAR : CAIRO_FILTER_FAST);
        }
 
        gth_image_viewer_apply_painters (viewer, cr);
@@ -520,7 +521,7 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
 
        screen_scale_factor = gtk_widget_get_scale_factor (GTK_WIDGET (self->priv->viewer));
 
-       if ((screen_scale_factor == 1) && (gth_image_viewer_get_zoom_quality_filter (self->priv->viewer) == 
CAIRO_FILTER_FAST)) {
+       if (gth_image_viewer_get_zoom_quality_filter (self->priv->viewer) == CAIRO_FILTER_FAST) {
                gtk_widget_queue_draw (GTK_WIDGET (self->priv->viewer));
                return;
        }
@@ -533,7 +534,7 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
        image_height = cairo_image_surface_get_height (image);
        zoom_from_image = (double) new_width / image_width;
 
-       if ((screen_scale_factor == 1) && (zoom_from_image >= 1.0)) {
+       if (zoom_from_image >= 1.0) {
                gtk_widget_queue_draw (GTK_WIDGET (self->priv->viewer));
                return;
        }