Improved handling of dt_dev_pixelpipe_change()

dt_dev_pixelpipe_change() calls the possibly costly dt_dev_pixelpipe_get_dimensions()
in all cases in addition to possibly syncing pipe nodes.

In dt_dev_process_image_job() we check for situations where we *must* call dt_dev_pixelpipe_change()
as we don't have the pipe dimensions available in addition to pipe->changed != DT_DEV_PIPE_UNCHANGED.

This leads to a significant performance gain due to less "pixelpipe-runs" just done to get the dimension.

In dt_dev_pixelpipe_change() we reduce the amount of syncing if possible as there is another active
dt_dev_pixelpipe_change_t flag that includes work to be done. Locking history is also done only if
required as nodes/parameters have been changed.

Some log improvements reducing misleading noise.

src/common/image.c

@@ -862,9 +862,9 @@ void dt_image_update_final_size(const dt_imgid_t imgid)
       dt_image_cache_write_release(darktable.image_cache, imgtmp, DT_IMAGE_CACHE_RELAXED);
       DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_METADATA_UPDATE);
       DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_DEVELOP_IMAGE_CHANGED);
+      dt_print(DT_DEBUG_PIPE, "updated final size for ID=%i to %ix%i", imgid, ww, hh);
     }
   }
-  dt_print(DT_DEBUG_PIPE, "[dt_image_update_final_size] for ID=%i, updated to %ix%i", imgid, ww, hh);
 }
 
 gboolean dt_image_get_final_size(const dt_imgid_t imgid, int *width, int *height)

src/develop/develop.c

@@ -346,6 +346,9 @@ void dt_dev_process_image_job(dt_develop_t *dev,
   dt_dev_pixelpipe_set_input(pipe, dev, (float *)buf.buf, buf.width, buf.height,
                              port ? 1.0 : buf.iscale);
 
+  // We require calculation of pixelpipe dimensions via dt_dev_pixelpipe_change() in these cases
+  const gboolean initial = pipe->loading || dev->image_force_reload || pipe->input_changed;
+
   if(pipe->loading)
   {
     // init pixel pipeline
@@ -398,10 +401,10 @@ void dt_dev_process_image_job(dt_develop_t *dev,
   if(port == &dev->full)
     pipe->input_timestamp = dev->timestamp;
 
-  // dt_dev_pixelpipe_change() will clear the changed value
-  const dt_dev_pixelpipe_change_t pipe_changed = pipe->changed;
-  // this locks dev->history_mutex.
-  dt_dev_pixelpipe_change(pipe, dev);
+  const gboolean pipe_changed = pipe->changed != DT_DEV_PIPE_UNCHANGED;
+  // dt_dev_pixelpipe_change() locks history mutex while syncing nodes and finally calculates dimensions
+  if(pipe_changed || initial || (port && port->pipe->loading))
+    dt_dev_pixelpipe_change(pipe, dev);
 
   float scale = 1.0f;
   int window_width = G_MAXINT;
@@ -414,7 +417,7 @@ void dt_dev_process_image_job(dt_develop_t *dev,
     // if just changed to an image with a different aspect ratio or
     // altered image orientation, the prior zoom xy could now be beyond
     // the image boundary
-    if(port->pipe->loading || pipe_changed != DT_DEV_PIPE_UNCHANGED)
+    if(port->pipe->loading || pipe_changed)
       dt_dev_zoom_move(port, DT_ZOOM_MOVE, 0.0f, 0, 0.0f, 0.0f, TRUE);
 
     // determine scale according to new dimensions

src/develop/pixelpipe_hb.c

@@ -632,39 +632,49 @@ void dt_dev_pixelpipe_synch_top(dt_dev_pixelpipe_t *pipe, dt_develop_t *dev)
 
 void dt_dev_pixelpipe_change(dt_dev_pixelpipe_t *pipe, dt_develop_t *dev)
 {
-  dt_pthread_mutex_lock(&dev->history_mutex);
-
   dt_print_pipe(DT_DEBUG_PIPE, "pipe state changing",
-      pipe, NULL, DT_DEVICE_NONE, NULL, NULL, "%s%s%s%s",
+      pipe, NULL, DT_DEVICE_NONE, NULL, NULL, "%s%s%s%s%s",
       pipe->changed & DT_DEV_PIPE_ZOOMED      ? "zoomed, " : "",
       pipe->changed & DT_DEV_PIPE_TOP_CHANGED ? "top changed, " : "",
       pipe->changed & DT_DEV_PIPE_SYNCH       ? "synch all, " : "",
-      pipe->changed & DT_DEV_PIPE_REMOVE      ? "pipe remove" : "");
-  // case DT_DEV_PIPE_UNCHANGED: case DT_DEV_PIPE_ZOOMED:
-  if(pipe->changed & DT_DEV_PIPE_TOP_CHANGED)
-  {
-    // only top history item changed.
-    dt_dev_pixelpipe_synch_top(pipe, dev);
-  }
-  if(pipe->changed & DT_DEV_PIPE_SYNCH)
-  {
-    // pipeline topology remains intact, only change all params.
-    dt_dev_pixelpipe_synch_all(pipe, dev);
-  }
-  if(pipe->changed & DT_DEV_PIPE_REMOVE)
+      pipe->changed & DT_DEV_PIPE_REMOVE      ? "pipe remove" : "",
+      pipe->changed == DT_DEV_PIPE_UNCHANGED  ? "dimension" : "");
+
+  if(pipe->changed & (DT_DEV_PIPE_TOP_CHANGED | DT_DEV_PIPE_SYNCH | DT_DEV_PIPE_REMOVE))
   {
-    // modules have been added in between or removed. need to rebuild
-    // the whole pipeline.
-    dt_dev_pixelpipe_cleanup_nodes(pipe);
-    dt_dev_pixelpipe_create_nodes(pipe, dev);
-    dt_dev_pixelpipe_synch_all(pipe, dev);
+    dt_pthread_mutex_lock(&dev->history_mutex);
+
+    const gboolean sync_all = pipe->changed & (DT_DEV_PIPE_SYNCH | DT_DEV_PIPE_REMOVE);
+    const gboolean sync_remove = pipe->changed & DT_DEV_PIPE_REMOVE;
+
+    if((pipe->changed & DT_DEV_PIPE_TOP_CHANGED) && !sync_all)
+    {
+      // only top history item changed. Not required if we synch_all
+      dt_dev_pixelpipe_synch_top(pipe, dev);
+    }
+
+    if((pipe->changed & DT_DEV_PIPE_SYNCH) && !sync_remove)
+    {
+      // pipeline topology remains intact but change all params. Not required if we rebuild all nodes
+      dt_dev_pixelpipe_synch_all(pipe, dev);
+    }
+
+    if(pipe->changed & DT_DEV_PIPE_REMOVE)
+    {
+      // modules have been added in between or removed. need to rebuild the whole pipeline.
+      dt_dev_pixelpipe_cleanup_nodes(pipe);
+      dt_dev_pixelpipe_create_nodes(pipe, dev);
+      dt_dev_pixelpipe_synch_all(pipe, dev);
+    }
+
+    dt_pthread_mutex_unlock(&dev->history_mutex);
   }
-  pipe->changed = DT_DEV_PIPE_UNCHANGED;
-  dt_pthread_mutex_unlock(&dev->history_mutex);
+
   dt_dev_pixelpipe_get_dimensions(pipe, dev,
                                   pipe->iwidth, pipe->iheight,
                                   &pipe->processed_width,
                                   &pipe->processed_height);
+  pipe->changed = DT_DEV_PIPE_UNCHANGED;
 }
 
 void dt_dev_pixelpipe_usedetails(dt_dev_pixelpipe_t *pipe)
@@ -2903,6 +2913,8 @@ void dt_dev_pixelpipe_get_dimensions(dt_dev_pixelpipe_t *pipe,
 {
   dt_pthread_mutex_lock(&pipe->busy_mutex);
   dt_iop_roi_t roi_in = (dt_iop_roi_t){ 0, 0, width_in, height_in, 1.0 };
+  dt_print_pipe(DT_DEBUG_PIPE,
+                "get dimensions", pipe, NULL, DT_DEVICE_NONE, &roi_in, NULL, "ID=%i", pipe->image.id);
   dt_iop_roi_t roi_out;
   GList *modules = pipe->iop;
   GList *pieces = pipe->nodes;
@@ -2919,8 +2931,7 @@ void dt_dev_pixelpipe_get_dimensions(dt_dev_pixelpipe_t *pipe,
       module->modify_roi_out(module, piece, &roi_out, &roi_in);
       if((darktable.unmuted & DT_DEBUG_PIPE) && memcmp(&roi_out, &roi_in, sizeof(dt_iop_roi_t)))
       dt_print_pipe(DT_DEBUG_PIPE,
-                  "modify roi OUT", piece->pipe, module, DT_DEVICE_NONE, &roi_in, &roi_out, "ID=%i",
-                  pipe->image.id);
+                  "modify roi OUT", pipe, module, DT_DEVICE_NONE, &roi_in, &roi_out);
     }
     else
     {