magnification display accounts for display scale

Author: jcupitt

src/imageui.c

@@ -125,6 +125,7 @@ enum {
 	PROP_ZOOM,
 	PROP_X,
 	PROP_Y,
+	PROP_PIXEL_SIZE,
 
 	PROP_LAST
 };
@@ -194,6 +195,10 @@ imageui_property_name(guint prop_id)
 		return "Y";
 		break;
 
+	case PROP_PIXEL_SIZE:
+		return "PIXEL_SIZE";
+		break;
+
 	default:
 		return "<unknown>";
 	}
@@ -253,6 +258,11 @@ imageui_set_property(GObject *object,
 			"y", value);
 		break;
 
+	case PROP_PIXEL_SIZE:
+		g_object_set_property(G_OBJECT(imageui->imagedisplay),
+			"pixel-size", value);
+		break;
+
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
 		break;
@@ -296,6 +306,11 @@ imageui_get_property(GObject *object,
 		g_object_get_property(G_OBJECT(imageui->imagedisplay), "y", value);
 		break;
 
+	case PROP_PIXEL_SIZE:
+		g_object_get_property(G_OBJECT(imageui->imagedisplay), 
+			"pixel-size", value);
+		break;
+
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
 		break;
@@ -1011,6 +1026,13 @@ imageui_class_init(ImageuiClass *class)
 			-VIPS_MAX_COORD, VIPS_MAX_COORD, 0,
 			G_PARAM_READWRITE));
 
+	g_object_class_install_property(gobject_class, PROP_PIXEL_SIZE,
+		g_param_spec_double("pixel_size",
+			_("Pixel size"),
+			_("Size of hardware display pixels in gtk coordinates"),
+			0.0, 10.0, 0.0,
+			G_PARAM_READWRITE));
+
 	imageui_signals[SIG_CHANGED] = g_signal_new("changed",
 		G_TYPE_FROM_CLASS(class),
 		G_SIGNAL_RUN_LAST,

src/imagewindow.c

@@ -377,19 +377,29 @@ imagewindow_files_set(Imagewindow *win, char **files, int n_files)
 	}
 }
 
+/* Get the effective zoom, ie. the zoom considering the hardware pixel display
+ * density.
+ */
 double
 imagewindow_get_zoom(Imagewindow *win)
 {
 	double zoom;
-
 	if (win->imageui)
 		g_object_get(win->imageui,
 			"zoom", &zoom,
 			NULL);
 	else
 		zoom = 1.0;
 
-	return zoom;
+	double pixel_size;
+	if (win->imageui)
+		g_object_get(win->imageui,
+			"pixel_size", &pixel_size,
+			NULL);
+	else
+		pixel_size = 1.0;
+
+	return zoom / pixel_size;
 }
 
 void