[FIX] mail, *: significantly reduce number of useless renders

* = hr_holidays, im_livechat, website_livechat

A huge amount of components where rendered for no reason, notably when typing a
new message (at every key press), which significantly slowed down the interface.

There were 2 causes to this number of renders:
- OWL rendering all children automatically, even if their props didn't change,
  unless `shouldUpdate` is overridden, which is now done.
- `useStore` selectors being way too generous in what they observed

task-2399731

closes odoo/odoo#62703

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/addons/website_livechat/static/src/components/discuss/discuss.js b/addons/website_livechat/static/src/components/discuss/discuss.js
index 18b41cea432..778b1513730 100644
--- a/addons/website_livechat/static/src/components/discuss/discuss.js
+++ b/addons/website_livechat/static/src/components/discuss/discuss.js
@@ -6,6 +6,24 @@ const components = {
     VisitorBanner: require('website_livechat/static/src/components/visitor_banner/visitor_banner.js'),
 };
 
+components.Discuss.patch('website_livechat/static/src/components/discuss/discuss.js', T =>
+    class extends T {
+
+        /**
+         * @override
+         */
+        _useStoreSelector(props) {
+            const res = super._useStoreSelector(...arguments);
+            const thread = res.thread;
+            const visitor = thread && thread.visitor;
+            return Object.assign({}, res, {
+                visitor,
+            });
+        }
+
+    }
+);
+
 Object.assign(components.Discuss.components, {
     VisitorBanner: components.VisitorBanner,
 });
diff --git a/addons/website_livechat/static/src/components/visitor_banner/visitor_banner.js b/addons/website_livechat/static/src/components/visitor_banner/visitor_banner.js
index 0b39134dcfc..4d0b95a82d0 100644
--- a/addons/website_livechat/static/src/components/visitor_banner/visitor_banner.js
+++ b/addons/website_livechat/static/src/components/visitor_banner/visitor_banner.js
@@ -14,7 +14,9 @@ class VisitorBanner extends Component {
         super(...args);
         useStore(props => {
             const visitor = this.env.models['website_livechat.visitor'].get(props.visitorLocalId);
+            const country = visitor && visitor.country;
             return {
+                country: country && country.__state,
                 visitor: visitor ? visitor.__state : undefined,
             };
         });