Remove flickering by updating auto-complete menu items in-place

Instead of deleting the current items and creating new ones.

include/SuggestionsPopup.hpp

@@ -53,11 +53,14 @@ class UserItem : public PopupItem
 public:
         UserItem(QWidget *parent, const QString &user_id);
         QString selectedText() const { return userId_; }
+        void updateItem(const QString &user_id);
 
 protected:
         void mousePressEvent(QMouseEvent *event) override;
 
 private:
+        void resolveAvatar(const QString &user_id);
+
         QLabel *userName_;
         QString userId_;
 };
@@ -69,6 +72,7 @@ class RoomItem : public PopupItem
 public:
         RoomItem(QWidget *parent, const RoomSearchResult &res);
         QString selectedText() const { return roomId_; }
+        void updateItem(const RoomSearchResult &res);
 
 protected:
         void mousePressEvent(QMouseEvent *event) override;
@@ -124,12 +128,16 @@ private:
         void resetSelection() { selectedItem_ = -1; }
         void selectFirstItem() { selectedItem_ = 0; }
         void selectLastItem() { selectedItem_ = layout_->count() - 1; }
-        void removeItems()
+        void removeLayoutItemsAfter(size_t startingPos)
         {
+                size_t posToRemove = layout_->count() - 1;
+
                 QLayoutItem *item;
-                while ((item = layout_->takeAt(0)) != 0) {
+                while (startingPos <= posToRemove && (item = layout_->takeAt(posToRemove)) != 0) {
                         delete item->widget();
                         delete item;
+
+                        posToRemove = layout_->count() - 1;
                 }
         }
 

src/SuggestionsPopup.cpp

@@ -5,7 +5,6 @@
 #include "SuggestionsPopup.hpp"
 #include "Utils.h"
 
-#include <QDebug>
 #include <QPaintEvent>
 #include <QPainter>
 #include <QStyleOption>
@@ -60,10 +59,39 @@ UserItem::UserItem(QWidget *parent, const QString &user_id)
         topLayout_->addWidget(avatar_);
         topLayout_->addWidget(userName_, 1);
 
-        AvatarProvider::resolve(ChatPage::instance()->currentRoom(),
-                                userId_,
-                                this,
-                                [this](const QImage &img) { avatar_->setImage(img); });
+        resolveAvatar(user_id);
+}
+
+void
+UserItem::updateItem(const QString &user_id)
+{
+        userId_ = user_id;
+
+        auto displayName = Cache::displayName(ChatPage::instance()->currentRoom(), userId_);
+
+        // If it's a matrix id we use the second letter.
+        if (displayName.size() > 1 && displayName.at(0) == '@')
+                avatar_->setLetter(QChar(displayName.at(1)));
+        else
+                avatar_->setLetter(utils::firstChar(displayName));
+
+        userName_->setText(displayName);
+        resolveAvatar(user_id);
+}
+
+void
+UserItem::resolveAvatar(const QString &user_id)
+{
+        AvatarProvider::resolve(
+          ChatPage::instance()->currentRoom(), userId_, this, [this, user_id](const QImage &img) {
+                  // The user on the widget when the avatar is resolved,
+                  // might be different from the user that made the call.
+                  if (user_id == userId_)
+                          avatar_->setImage(img);
+                  else
+                          // We try to resolve the avatar again.
+                          resolveAvatar(userId_);
+          });
 }
 
 void
@@ -96,6 +124,24 @@ RoomItem::RoomItem(QWidget *parent, const RoomSearchResult &res)
                 avatar_->setImage(res.img);
 }
 
+void
+RoomItem::updateItem(const RoomSearchResult &result)
+{
+        roomId_ = QString::fromStdString(std::move(result.room_id));
+
+        auto name =
+          QFontMetrics(QFont()).elidedText(QString::fromStdString(std::move(result.info.name)),
+                                           Qt::ElideRight,
+                                           parentWidget()->width() - 10);
+
+        roomName_->setText(name);
+
+        if (!result.img.isNull())
+                avatar_->setImage(result.img);
+        else
+                avatar_->setLetter(utils::firstChar(name));
+}
+
 void
 RoomItem::mousePressEvent(QMouseEvent *event)
 {
@@ -119,17 +165,33 @@ SuggestionsPopup::SuggestionsPopup(QWidget *parent)
 void
 SuggestionsPopup::addRooms(const std::vector<RoomSearchResult> &rooms)
 {
-        removeItems();
-
         if (rooms.empty()) {
                 hide();
                 return;
         }
 
-        for (const auto &r : rooms) {
-                auto room = new RoomItem(this, r);
-                layout_->addWidget(room);
-                connect(room, &RoomItem::clicked, this, &SuggestionsPopup::itemSelected);
+        const size_t layoutCount = layout_->count();
+        const size_t roomCount   = rooms.size();
+
+        // Remove the extra widgets from the layout.
+        if (roomCount < layoutCount)
+                removeLayoutItemsAfter(roomCount - 1);
+
+        for (size_t i = 0; i < roomCount; ++i) {
+                auto item = layout_->itemAt(i);
+
+                // Create a new widget if there isn't already one in that
+                // layout position.
+                if (!item) {
+                        auto room = new RoomItem(this, rooms.at(i));
+                        connect(room, &RoomItem::clicked, this, &SuggestionsPopup::itemSelected);
+                        layout_->addWidget(room);
+                } else {
+                        // Update the current widget with the new data.
+                        auto room = qobject_cast<RoomItem *>(item->widget());
+                        if (room)
+                                room->updateItem(rooms.at(i));
+                }
         }
 
         resetSelection();
@@ -143,24 +205,38 @@ SuggestionsPopup::addRooms(const std::vector<RoomSearchResult> &rooms)
 void
 SuggestionsPopup::addUsers(const QVector<SearchResult> &users)
 {
-        removeItems();
-
         if (users.isEmpty()) {
                 hide();
                 return;
         }
 
-        for (const auto &u : users) {
-                auto user = new UserItem(this, u.user_id);
-                layout_->addWidget(user);
-                connect(user, &UserItem::clicked, this, &SuggestionsPopup::itemSelected);
+        const size_t layoutCount = layout_->count();
+        const size_t userCount   = users.size();
+
+        // Remove the extra widgets from the layout.
+        if (userCount < layoutCount)
+                removeLayoutItemsAfter(userCount - 1);
+
+        for (size_t i = 0; i < userCount; ++i) {
+                auto item = layout_->itemAt(i);
+
+                // Create a new widget if there isn't already one in that
+                // layout position.
+                if (!item) {
+                        auto user = new UserItem(this, users.at(i).user_id);
+                        connect(user, &UserItem::clicked, this, &SuggestionsPopup::itemSelected);
+                        layout_->addWidget(user);
+                } else {
+                        // Update the current widget with the new data.
+                        auto userWidget = qobject_cast<UserItem *>(item->widget());
+                        if (userWidget)
+                                userWidget->updateItem(users.at(i).user_id);
+                }
         }
 
         resetSelection();
         adjustSize();
 
-        resize(geometry().width(), 40 * users.size());
-
         selectNextSuggestion();
 }