don't recalc subset of already available buffer

- when zooming in to multiples of 100%
- and then moving around within the region calculated at lower zoom level
- when switching on filmstrip or increasing left panel at fixed zoom level
- right panel resizing still triggers recalc elsewhere
- would allow calculating larger than needed region after move to prevent immediate update after first few pixels move

Author: dterrahe

src/develop/develop.c

@@ -2803,17 +2803,10 @@ void dt_dev_zoom_move(dt_dev_viewport_t *port,
      && old_closeup == port->closeup)
     return;
 
+  if(port->widget)
+    dt_control_queue_redraw_widget(port->widget);
   if(port == &dev->full)
-  {
-    dt_dev_invalidate(dev); // FIXME not needed? redraw should determines if needs new calculation
-    dt_control_queue_redraw_center();
     dt_control_navigation_redraw();
-  }
-  else if(port == &dev->preview2 && dev->second_wnd)
-  {
-    dev->preview2.pipe->status = DT_DEV_PIXELPIPE_DIRTY;
-    dt_control_queue_redraw_widget(dev->second_wnd);
-  }
 }
 
 void dt_dev_get_pointer_zoom_pos(dt_dev_viewport_t *port,

src/views/darkroom.c

@@ -465,10 +465,6 @@ void expose(
     dev->gui_synch = FALSE;
   }
 
-  if(_full_request(dev)) dt_dev_process_image(dev);
-  if(_preview_request(dev)) dt_dev_process_preview(dev);
-  if(_preview2_request(dev)) dt_dev_process_preview2(dev);
-
   float pzx = 0.0f, pzy = 0.0f, zoom_scale = 0.0f;
   dt_dev_get_pointer_zoom_pos(port, pointerx, pointery, &pzx, &pzy, &zoom_scale);
 
@@ -620,6 +616,10 @@ void expose(
     g_free(load_txt);
   }
 
+  if(_full_request(dev)) dt_dev_process_image(dev);
+  if(_preview_request(dev)) dt_dev_process_preview(dev);
+  if(_preview2_request(dev)) dt_dev_process_preview2(dev);
+
   /* if we are in full preview mode, we don"t want anything else than the image */
   if(dev->full_preview)
     return;
@@ -3396,8 +3396,6 @@ static gboolean _second_window_draw_callback(GtkWidget *widget,
 {
   cairo_set_source_rgb(cri, 0.2, 0.2, 0.2);
 
-  if(_preview2_request(dev)) dt_dev_process_preview2(dev);
-
   if(dev->preview2.pipe->backbuf)  // do we have an image?
   {
     // draw image
@@ -3408,6 +3406,8 @@ static gboolean _second_window_draw_callback(GtkWidget *widget,
                         &dev->preview2, DT_WINDOW_SECOND);
   }
 
+  if(_preview2_request(dev)) dt_dev_process_preview2(dev);
+
   return TRUE;
 }
 

src/views/view.c

@@ -1739,10 +1739,19 @@ void dt_view_paint_surface(cairo_t *cr,
   cairo_scale(cr, zoom_scale, zoom_scale);
 
   const double back_scale = (buf_scale == 0 ? 1.0 : backbuf_scale / buf_scale) * (1<<closeup) / ppd;
+  const double trans_x = (offset_x - zoom_x) * processed_width * buf_scale - 0.5 * buf_width;
+  const double trans_y = (offset_y - zoom_y) * processed_height * buf_scale - 0.5 * buf_height;
 
   if(dev->preview_pipe->output_imgid == dev->image_storage.id
+     && (port->pipe->output_imgid != dev->image_storage.id
+         || backbuf_scale != buf_scale
+         || floor(maxw / 2 / back_scale) - 1 > MIN(- trans_x, trans_x + buf_width)
+         || floor(maxh / 2 / back_scale) - 1 > MIN(- trans_y, trans_y + buf_height))
      && (port == &dev->full || port == &dev->preview2))
   {
+    if(port->pipe->status == DT_DEV_PIXELPIPE_VALID)
+      port->pipe->status = DT_DEV_PIXELPIPE_DIRTY;
+
     // draw preview
     float wd = processed_width * dev->preview_pipe->processed_width / MAX(1, dev->full.pipe->processed_width);
     float ht = processed_height * dev->preview_pipe->processed_width / MAX(1, dev->full.pipe->processed_width);
@@ -1784,9 +1793,7 @@ void dt_view_paint_surface(cairo_t *cr,
          buf_zoom_x, buf_zoom_y,
          offset_x, offset_y);
     cairo_scale(cr, back_scale / zoom_scale, back_scale / zoom_scale);
-    cairo_translate(cr, (offset_x - zoom_x) * processed_width * buf_scale - 0.5 * buf_width,
-                        (offset_y - zoom_y) * processed_height * buf_scale - 0.5 * buf_height);
-
+    cairo_translate(cr, trans_x, trans_y);
     cairo_surface_t *surface = dt_view_create_surface(buf, buf_width, buf_height);
     cairo_set_source_surface(cr, surface, 0, 0);
     cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_FAST);