[FIX] web: better mode handling, prevent useless work in some cases

Before this commit, the way mode was handled was not optimal.  The end
result was correct (the widget were properly created/displayed in
edit/readonly as required), but useless work was done.  In particular,
if we have list/x2manys with widgets and modifiers, it could happen that
widgets were created in edit mode, then destroyed and recreated in
readonly mode.

This could happen in some important views, for example, any view with a
field many2many_tags with a readonly modifiers (pretty much all views
handling taxes)

In this commit, we add a 'editable' attribute to list renderer.  This is
necessary, because the list renderer is not actually editable when it is
in a x2many in a form view which is in readonly mode.  Also, we need to
manage the distinction between the fact that a list view is editable,
and the fact that some widgets are created in edit and other in readonly
mode, depending on modifiers, and on which line is being edited.

We also add a benchmark (courtesy of CHM) to be able to measure the
performance impact of edit/readonly/onchange in a larger form view.
Before this commit, running this form benchmark on my machine gave a
number of 0.4 op/sec, and after, it increases to 1.26 op/sec, so a
pretty large improvement.

1 files changed, 1 insertions, 1 deletions

diff --git a/addons/web/static/src/js/fields/relational_fields.js b/addons/web/static/src/js/fields/relational_fields.js
index 9cdadb1051a..73e474b0342 100644
--- a/addons/web/static/src/js/fields/relational_fields.js
+++ b/addons/web/static/src/js/fields/relational_fields.js
@@ -839,7 +839,7 @@ var FieldX2Many = AbstractField.extend({
             this.currentColInvisibleFields = this._evalColumnInvisibleFields();
             this.renderer = new ListRenderer(this, this.value, {
                 arch: arch,
-                mode: this.mode,
+                editable: this.mode === 'edit' && arch.attrs.editable,
                 addCreateLine: !this.isReadonly && this.activeActions.create,
                 addTrashIcon: !this.isReadonly && this.activeActions.delete,
                 viewType: viewType,