Finally fix the selection/interaction paradigm in GUI

- global actions are available from the global menu,
- global actions are applied on app-wide selection, else on view-wide active images. Selection is remembered between app restarts and saved in database,
- only lighttable can register selections (as in: user input), either from thumbnail interaction or from key shortcuts/global menu
- interactions with thumbnails in filmstrip don't make app-mide selections, they only update active images for the views using them,
- darkroom clears the selection,
- global actions affecting images both in lighttable and darkroom are properly reloading the history in the darkroom development at completion

Meaning:
1. global actions doing write operations will only affect the currently-opened image when in darkroom, else the selection in lighttable. Any other behaviour is either (or both) unpredictable or unintuitive.
2. selection happens on mouse **click**, global menu **click**, global menu **shortcuts**, and key actions on thumbnail (to be re-implemented),
3. mouse-hover events refresh read-only displays, like EXIF and stuff.
4. copy-pasting histories, which is a cross-image operation, happens only in lighttable to make it predictable through possibly-hidden dangling selection in filmstrip.

Fix #284
Fix #350
Fix darktable-org#6025
Fix darktable-org#16850

That shitshow went on for much too long, thank you very much.

src/common/colorlabels.c

@@ -34,6 +34,27 @@ const char *dt_colorlabels_name[] = {
   NULL // termination
 };
 
+char * dt_colorlabels_get_name(const int label)
+{
+  switch(label)
+  {
+    case 0:
+      return _("red");
+    case 1:
+      return _("yellow");
+    case 2:
+      return _("green");
+    case 3:
+      return _("blue");
+    case 4:
+      return _("purple");
+    case 5:
+      return _("empty");
+    default:
+      return _("unknown/invalid");
+  }
+}
+
 typedef struct dt_undo_colorlabels_t
 {
   int imgid;
@@ -241,6 +262,7 @@ void dt_colorlabels_toggle_label_on_list(GList *list, const int color, const gbo
     dt_undo_end_group(darktable.undo);
   }
   dt_collection_hint_message(darktable.collection);
+  dt_toast_log(_("Color label set to %s"), dt_colorlabels_get_name(color));
 }
 
 int dt_colorlabels_check_label(const int imgid, const int color)

src/common/history.c

@@ -996,7 +996,7 @@ gboolean dt_history_paste_on_list(const GList *list, gboolean undo)
     return FALSE;
 
   if(undo) dt_undo_start_group(darktable.undo, DT_UNDO_LT_HISTORY);
-  for(GList *l = (GList *)list; l; l = g_list_next(l))
+  for(GList *l = g_list_first((GList *)list); l; l = g_list_next(l))
   {
     const int dest = GPOINTER_TO_INT(l->data);
     dt_history_copy_and_paste_on_image(darktable.view_manager->copy_paste.copied_imageid,
@@ -1020,20 +1020,17 @@ gboolean dt_history_paste_parts_on_list(const GList *list, gboolean undo)
   // at the time the dialog is started, some signals are sent and this in turn call
   // back dt_view_get_images_to_act_on() which free list and create a new one.
 
-  GList *l_copy = g_list_copy((GList *)list);
-
   // we launch the dialog
   const int res = dt_gui_hist_dialog_new(&(darktable.view_manager->copy_paste),
                                          darktable.view_manager->copy_paste.copied_imageid, FALSE);
 
   if(res != GTK_RESPONSE_OK)
   {
-    g_list_free(l_copy);
     return FALSE;
   }
 
   if(undo) dt_undo_start_group(darktable.undo, DT_UNDO_LT_HISTORY);
-  for (const GList *l = l_copy; l; l = g_list_next(l))
+  for (const GList *l = g_list_first((GList *)list); l; l = g_list_next(l))
   {
     const int dest = GPOINTER_TO_INT(l->data);
     dt_history_copy_and_paste_on_image(darktable.view_manager->copy_paste.copied_imageid,
@@ -1044,8 +1041,6 @@ gboolean dt_history_paste_parts_on_list(const GList *list, gboolean undo)
   }
   if(undo) dt_undo_end_group(darktable.undo);
 
-  g_list_free(l_copy);
-
   return TRUE;
 }
 
@@ -1056,7 +1051,7 @@ gboolean dt_history_delete_on_list(const GList *list, gboolean undo)
 
   if(undo) dt_undo_start_group(darktable.undo, DT_UNDO_LT_HISTORY);
 
-  for(GList *l = (GList *)list; l; l = g_list_next(l))
+  for(GList *l = g_list_first((GList *)list); l; l = g_list_next(l))
   {
     const int imgid = GPOINTER_TO_INT(l->data);
     dt_undo_lt_history_t *hist = dt_history_snapshot_item_init();

src/common/image.c

@@ -904,6 +904,8 @@ void dt_image_flip(const int32_t imgid, const int32_t cw)
                  dt_history_snapshot_undo_pop, dt_history_snapshot_undo_lt_history_data_free);
 
   dt_mipmap_cache_remove(darktable.mipmap_cache, imgid);
+
+  DT_DEBUG_CONTROL_SIGNAL_RAISE(darktable.signals, DT_SIGNAL_DEVELOP_MIPMAP_UPDATED, imgid);
 }
 
 /* About the image size ratio

src/common/ratings.c

@@ -40,6 +40,29 @@ typedef struct dt_undo_ratings_t
   int after;
 } dt_undo_ratings_t;
 
+char *dt_ratings_get_name(const int rating)
+{
+  switch(rating)
+  {
+    case 0:
+      return _("empty");
+    case 1:
+      return _("1 star");
+    case 2:
+      return _("2 stars");
+    case 3:
+      return _("3 stars");
+    case 4:
+      return _("4 stars");
+    case 5:
+      return _("5 stars");
+    case 6:
+      return _("rejected");
+    default:
+      return _("unknown/invalid");
+  }
+}
+
 int dt_ratings_get(const int imgid)
 {
   int stars = 0;
@@ -169,6 +192,7 @@ void dt_ratings_apply_on_list(GList *img, const int rating, const gboolean undo_
       dt_undo_end_group(darktable.undo);
     }
     dt_collection_hint_message(darktable.collection);
+    dt_toast_log(_("Rating set to %s"), dt_ratings_get_name(rating));
   }
 }
 

src/develop/dev_history.c

@@ -371,10 +371,6 @@ gboolean dt_history_copy_and_paste_on_image(const int32_t imgid, const int32_t d
     return 1;
   }
 
-  // be sure the current history is written before pasting some other history data
-  const dt_view_t *cv = dt_view_manager_get_current_view(darktable.view_manager);
-  if(cv->view((dt_view_t *)cv) == DT_VIEW_DARKROOM) dt_dev_write_history(darktable.develop);
-
   dt_undo_lt_history_t *hist = dt_history_snapshot_item_init();
   hist->imgid = dest_imgid;
   dt_history_snapshot_undo_create(hist->imgid, &hist->before, &hist->before_history_end);

src/dtgtk/thumbnail.c

@@ -700,6 +700,22 @@ static gboolean _event_main_press(GtkWidget *widget, GdkEventButton *event, gpoi
   dt_thumbnail_t *thumb = (dt_thumbnail_t *)user_data;
   dt_control_set_mouse_over_id(thumb->imgid);
 
+  // select on single or double click, whatever happens next
+  if(event->button == 1 && event->type == GDK_BUTTON_PRESS)
+  {
+    // Duplicate module uses that fucking thumbnail without a table...
+    if(thumb->table && thumb->table->mode == DT_THUMBTABLE_MODE_FILEMANAGER)
+    {
+      if(dt_modifier_is(event->state, 0))
+        dt_selection_select_single(darktable.selection, thumb->imgid);
+      else if(dt_modifier_is(event->state, GDK_CONTROL_MASK))
+        dt_selection_toggle(darktable.selection, thumb->imgid);
+      else if(dt_modifier_is(event->state, GDK_SHIFT_MASK))
+        dt_selection_select_range(darktable.selection, thumb->imgid);
+    }
+  }
+
+  // raise signal on double click
   if(event->button == 1 && event->type == GDK_2BUTTON_PRESS)
   {
     DT_DEBUG_CONTROL_SIGNAL_RAISE(darktable.signals, DT_SIGNAL_VIEWMANAGER_THUMBTABLE_ACTIVATE, thumb->imgid);
@@ -710,17 +726,6 @@ static gboolean _event_main_press(GtkWidget *widget, GdkEventButton *event, gpoi
 }
 static gboolean _event_main_release(GtkWidget *widget, GdkEventButton *event, gpointer user_data)
 {
-  dt_thumbnail_t *thumb = (dt_thumbnail_t *)user_data;
-
-  if(event->button == 1 && !thumb->moved)
-  {
-    if(dt_modifier_is(event->state, 0))
-      dt_selection_select_single(darktable.selection, thumb->imgid);
-    else if(dt_modifier_is(event->state, GDK_CONTROL_MASK))
-      dt_selection_toggle(darktable.selection, thumb->imgid);
-    else if(dt_modifier_is(event->state, GDK_SHIFT_MASK))
-      dt_selection_select_range(darktable.selection, thumb->imgid);
-  }
   return FALSE;
 }
 
@@ -1233,7 +1238,7 @@ GtkWidget *dt_thumbnail_create_widget(dt_thumbnail_t *thumb, float zoom_ratio)
 }
 
 dt_thumbnail_t *dt_thumbnail_new(int width, int height, float zoom_ratio, int imgid, int rowid,
-                                 dt_thumbnail_overlay_t over)
+                                 dt_thumbnail_overlay_t over, dt_thumbtable_t *table)
 {
   dt_thumbnail_t *thumb = calloc(1, sizeof(dt_thumbnail_t));
   thumb->width = width;
@@ -1243,6 +1248,7 @@ dt_thumbnail_t *dt_thumbnail_new(int width, int height, float zoom_ratio, int im
   thumb->over = over;
   thumb->zoom = 1.0f;
   thumb->expose_again_timeout_id = 0;
+  thumb->table = table;
 
   // we read and cache all the infos from dt_image_t that we need
   const dt_image_t *img = dt_image_cache_get(darktable.image_cache, thumb->imgid, 'r');

src/dtgtk/thumbnail.h

@@ -26,6 +26,8 @@
 #define MAX_STARS 5
 #define IMG_TO_FIT 0.0f
 
+struct dt_thumbtable_t;
+
 typedef enum dt_thumbnail_border_t
 {
   DT_THUMBNAIL_BORDER_NONE = 0,
@@ -113,10 +115,12 @@ typedef struct
 
   gboolean display_focus; // do we display rectangles to show focused part of the image
 
+  struct dt_thumbtable_t *table; // convenience reference to the parent
+
   gboolean busy; // should we show the busy message ?
 } dt_thumbnail_t;
 
-dt_thumbnail_t *dt_thumbnail_new(int width, int height, float zoom_ratio, int imgid, int rowid, dt_thumbnail_overlay_t over);
+dt_thumbnail_t *dt_thumbnail_new(int width, int height, float zoom_ratio, int imgid, int rowid, dt_thumbnail_overlay_t over, struct dt_thumbtable_t *table);
 void dt_thumbnail_destroy(dt_thumbnail_t *thumb);
 GtkWidget *dt_thumbnail_create_widget(dt_thumbnail_t *thumb, float zoom_ratio);
 void dt_thumbnail_resize(dt_thumbnail_t *thumb, int width, int height, gboolean force, float zoom_ratio);

src/dtgtk/thumbtable.c

@@ -402,7 +402,7 @@ static int _thumbs_load_needed(dt_thumbtable_t *table)
       {
         dt_thumbnail_t *thumb = dt_thumbnail_new(
             table->thumb_size, table->thumb_size, IMG_TO_FIT, sqlite3_column_int(stmt, 1),
-            sqlite3_column_int(stmt, 0), table->overlays);
+            sqlite3_column_int(stmt, 0), table->overlays, table);
 
         thumb->x = posx;
         thumb->y = posy;
@@ -452,7 +452,7 @@ static int _thumbs_load_needed(dt_thumbtable_t *table)
       {
         dt_thumbnail_t *thumb = dt_thumbnail_new
           (table->thumb_size, table->thumb_size, IMG_TO_FIT, sqlite3_column_int(stmt, 1),
-           sqlite3_column_int(stmt, 0), table->overlays);
+           sqlite3_column_int(stmt, 0), table->overlays, table);
 
         thumb->x = posx;
         thumb->y = posy;
@@ -1543,7 +1543,7 @@ void dt_thumbtable_full_redraw(dt_thumbtable_t *table, gboolean force)
       {
         // we create a completely new thumb
         dt_thumbnail_t *thumb
-            = dt_thumbnail_new(table->thumb_size, table->thumb_size, IMG_TO_FIT, nid, nrow, table->overlays);
+            = dt_thumbnail_new(table->thumb_size, table->thumb_size, IMG_TO_FIT, nid, nrow, table->overlays, table);
         thumb->x = posx;
         thumb->y = posy;
         newlist = g_list_prepend(newlist, thumb);