Centre image at start (or on zoom reset)

This just sets the scroll bars to the middle position, which is not
necessarily the middle of the detector.  Still, it's better than
starting at the edge every time.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/crystfelimageview.c b/src/crystfelimageview.c
index 795d628c..96f49803 100644
--- a/src/crystfelimageview.c
+++ b/src/crystfelimageview.c
@@ -739,6 +739,7 @@ GtkWidget *crystfel_image_view_new()
 	iv->refl_box_size = 1.0;
 	iv->label_refls = 1;
 	iv->need_rerender = 0;
+	iv->need_recentre = 0;
 
 	g_signal_connect(G_OBJECT(iv), "destroy",
 	                 G_CALLBACK(destroy_sig), iv);
@@ -911,6 +912,15 @@ static double auto_scale_top(const struct image *image)
 }
 
 
+static void center_adjustment(GtkAdjustment *adj)
+{
+	double min = gtk_adjustment_get_lower(adj);
+	double max = gtk_adjustment_get_upper(adj);
+	double page = gtk_adjustment_get_page_size(adj);
+	gtk_adjustment_set_value(adj, min+(max-min-page)/2.0);
+}
+
+
 static int rerender_image(CrystFELImageView *iv)
 {
 	int i;
@@ -956,6 +966,11 @@ static int rerender_image(CrystFELImageView *iv)
 		iv->zoom = 1.0/iv->image->detgeom->panels[0].pixel_pitch;
 	}
 	configure_scroll_adjustments(iv);
+	if ( iv->need_recentre ) {
+		center_adjustment(iv->hadj);
+		center_adjustment(iv->vadj);
+		iv->need_recentre = 0;
+	}
 
 	iv->need_rerender = 0;
 	redraw(iv);
@@ -980,6 +995,7 @@ void crystfel_image_view_reset_zoom(CrystFELImageView *iv)
 	iv->detector_w = 1.0;
 	iv->detector_h = 1.0;
 	iv->zoom = -1.0;
+	iv->need_recentre = 1;
 	iv->need_rerender = 1;
 	redraw(iv);
 }