[balsa] balsa-index: improve expand and collapse

[Peter Bloomfield <peterb src gnome org>]

commit 9cbcd3c8b770762b904956192ab56587ee61f26d
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Fri Jan 17 18:16:01 2020 -0500

    balsa-index: improve expand and collapse
    
    If a message is being viewed, it should still be visible after
    View:Expand-all (Ctrl e) or View:Collapse-all (Ctrl l). This
    commit achieves that for Expand-all, and mostly for
    Collapse-all.
    
    Only mostly: if the viewed message is near the bottom of the
    message index, Collapse-all may leave it a few rows below the current
    view of the message index. Unfortunately, if the current sort
    order puts the latest threads at the bottom, those are the most
    likely to be viewed!
    
    * src/balsa-index.c (bndx_selection_changed_idle),
      (bndx_scroll_on_open_idle), (bndx_mailbox_row_inserted_idle),
      (bndx_expand_to_row_and_select), (bndx_mailbox_changed_idle):
      actually, gtk_tree_view_expand_to_path() doesn't do what we want: it
      expands to the row, and the row itself, so we use it instead on
      the parent of the row, using bndx_expand_to_row() again;
      (bndx_update_tree_idle), (balsa_index_update_tree): do the
      re-expansion in an idle handler, after the tree-view's layout
      has settled down;
      (bndx_expand_to_row): restore it, but using
      gtk_tree_view_expand_to_path() to expand to the row's parent.

 ChangeLog         | 27 +++++++++++++++++++++++++++
 src/balsa-index.c | 50 ++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 65 insertions(+), 12 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index efb0a1eb1..a5b00de8c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,30 @@
+2020-01-17  Peter Bloomfield  <pbloomfield bellsouth net>
+
+       balsa-index: improve expand and collapse
+
+       If a message is being viewed, it should still be visible after
+       View:Expand-all (Ctrl e) or View:Collapse-all (Ctrl l). This
+       commit achieves that for Expand-all, and mostly for
+       Collapse-all.
+
+       Only mostly: if the viewed message is near the bottom of the
+       message index, Collapse-all may leave it a few rows below the current
+       view of the message index. Unfortunately, if the current sort
+       order puts the latest threads at the bottom, those are the most
+       likely to be viewed!
+
+       * src/balsa-index.c (bndx_selection_changed_idle),
+       (bndx_scroll_on_open_idle), (bndx_mailbox_row_inserted_idle),
+       (bndx_expand_to_row_and_select), (bndx_mailbox_changed_idle):
+       actually, gtk_tree_view_expand_to_path() doesn't do what we want: it
+       expands to the row, and the row itself, so we use it instead on
+       the parent of the row, using bndx_expand_to_row() again;
+       (bndx_update_tree_idle), (balsa_index_update_tree): do the
+       re-expansion in an idle handler, after the tree-view's layout
+       has settled down;
+       (bndx_expand_to_row): restore it, but using
+       gtk_tree_view_expand_to_path() to expand to the row's parent.
+
 2020-01-16  Peter Bloomfield  <pbloomfield bellsouth net>
 
        balsa-index: Use gtk_tree_view_expand_to_path()
diff --git a/src/balsa-index.c b/src/balsa-index.c
index 0f4e3b167..f82a0d374 100644
--- a/src/balsa-index.c
+++ b/src/balsa-index.c
@@ -134,6 +134,7 @@ static gint balsa_index_signals[LAST_SIGNAL] = {
 };
 
 /* General helpers. */
+static void bndx_expand_to_row(BalsaIndex * index, GtkTreePath * path);
 static void bndx_select_row(BalsaIndex * index, GtkTreePath * path);
 
 /* Other callbacks. */
@@ -533,7 +534,7 @@ bndx_selection_changed_idle(BalsaIndex * bindex)
             msgno = 0;
         else {
             if (!gtk_tree_selection_path_is_selected(selection, path)) {
-                gtk_tree_view_expand_to_path(GTK_TREE_VIEW(bindex), path);
+                bndx_expand_to_row(bindex, path);
                 bndx_select_row(bindex, path);
             }
             gtk_tree_path_free(path);
@@ -856,7 +857,7 @@ bndx_scroll_on_open_idle(BalsaIndex *bindex)
         path = gtk_tree_path_new_from_indices(n_children - 1, -1);
     }
 
-    gtk_tree_view_expand_to_path(GTK_TREE_VIEW(bindex), path);
+    bndx_expand_to_row(bindex, path);
     gtk_tree_view_scroll_to_cell(tree_view, path, NULL, FALSE, 0, 0);
 
     view_on_open =
@@ -914,7 +915,7 @@ bndx_mailbox_row_inserted_idle(struct bndx_mailbox_row_inserted_info *info)
     GtkTreePath *path;
     if (libbalsa_mailbox_msgno_find(info->mailbox, info->msgno,
                                     &path, NULL)) {
-        gtk_tree_view_expand_to_path(GTK_TREE_VIEW(info->index), path);
+        bndx_expand_to_row(info->index, path);
         gtk_tree_path_free(path);
     }
     g_object_unref(info->mailbox);
@@ -1324,7 +1325,7 @@ bndx_expand_to_row_and_select(BalsaIndex * index, GtkTreeIter * iter)
     GtkTreePath *path;
 
     path = gtk_tree_model_get_path(model, iter);
-    gtk_tree_view_expand_to_path(GTK_TREE_VIEW(index), path);
+    bndx_expand_to_row(index, path);
     bndx_select_row(index, path);
     gtk_tree_path_free(path);
 }
@@ -1396,7 +1397,7 @@ bndx_mailbox_changed_idle(BalsaIndex * bindex)
     if (bndx_find_current_msgno(bindex, &path, NULL)) {
         /* The thread containing the current message may have been
          * collapsed by rethreading; re-expand it. */
-        gtk_tree_view_expand_to_path(GTK_TREE_VIEW(bindex), path);
+        bndx_expand_to_row(bindex, path);
         gtk_tree_path_free(path);
     }
 
@@ -2040,6 +2041,23 @@ sendmsg_window_destroy_cb(GtkWidget * widget, gpointer data)
     balsa_window_enable_continue(balsa_app.main_window);
 }
 
+static gboolean
+bndx_update_tree_idle(BalsaIndex *bindex)
+{
+    GtkTreeIter iter;
+
+    if (bndx_find_current_msgno(bindex, NULL, &iter))
+        bndx_expand_to_row_and_select(bindex, &iter);
+    else
+        balsa_index_ensure_visible(bindex);
+
+    bndx_changed_find_row(bindex);
+
+    g_object_unref(bindex);
+
+    return G_SOURCE_REMOVE;
+}
+
 void
 balsa_index_update_tree(BalsaIndex * index, gboolean expand)
 /* Remarks: In the "collapse" case, we still expand current thread to the
@@ -2047,7 +2065,6 @@ balsa_index_update_tree(BalsaIndex * index, gboolean expand)
            approach would be to change preview, e.g. to top of thread. */
 {
     GtkTreeView *tree_view = GTK_TREE_VIEW(index);
-    GtkTreeIter iter;
 
     if (expand) {
         g_signal_handler_block(index, index->row_expanded_id);
@@ -2064,12 +2081,7 @@ balsa_index_update_tree(BalsaIndex * index, gboolean expand)
      * overhead is slight
      * select is needed in both cases, as a previous collapse could have
      * deselected the current message */
-    if (bndx_find_current_msgno(index, NULL, &iter))
-        bndx_expand_to_row_and_select(index, &iter);
-    else
-        balsa_index_ensure_visible(index);
-
-    bndx_changed_find_row(index);
+    g_idle_add((GSourceFunc) bndx_update_tree_idle, g_object_ref(index));
 }
 
 /* balsa_index_set_thread_messages: public method. */
@@ -2177,6 +2189,20 @@ balsa_index_transfer(BalsaIndex *index, GArray * msgnos,
 }
 
 /* General helpers. */
+static void
+bndx_expand_to_row(BalsaIndex * bindex, GtkTreePath * path)
+{
+    gint depth = gtk_tree_path_get_depth(path);
+
+    if (depth > 1) {
+        gint *indices = gtk_tree_path_get_indices(path);
+        gint last_index = indices[depth - 1];
+
+        gtk_tree_path_up(path);
+        gtk_tree_view_expand_to_path(GTK_TREE_VIEW(bindex), path);
+        gtk_tree_path_append_index(path, last_index);
+    }
+}
 
 static void
 bndx_changed_find_row(BalsaIndex * index)