Use QFontMetrics::elidedText over manual implementation (#4807)

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unversioned
 
+- Bugfix: Fixed a performance issue when displaying replies to certain messages. (#4807)
 - Bugfix: Fixed a data race when disconnecting from Twitch PubSub. (#4771)
 - Bugfix: Fixed `/shoutout` command not working with usernames starting with @'s (e.g. `/shoutout @forsen`). (#4800)
 - Dev: Fixed UTF16 encoding of `modes` file for the installer. (#4791)

src/messages/MessageElement.cpp

@@ -674,42 +674,16 @@ void SingleLineTextElement::addToContainer(MessageLayoutContainer &container,
             auto &parsedWord = parsedWords[0];
             if (parsedWord.type() == typeid(QString))
             {
-                int nextWidth =
+                if (!currentText.isEmpty())
-                    metrics.horizontalAdvance(currentText + word.text);
-
-                // see if the text fits in the current line
-                if (container.fitsInLine(nextWidth))
                 {
-                    currentText += (word.text + " ");
+                    currentText += ' ';
                 }
-                else
+                currentText += word.text;
+                QString prev = currentText;  // only increments the ref-count
+                currentText = metrics.elidedText(currentText, Qt::ElideRight,
+                                                 container.remainingWidth());
+                if (currentText != prev)
                 {
-                    // word overflows, try minimum truncation
-                    bool cutSuccess = false;
-                    for (size_t cut = 1; cut < word.text.length(); ++cut)
-                    {
-                        // Cut off n characters and append the ellipsis.
-                        // Try removing characters one by one until the word fits.
-                        QString truncatedWord =
-                            word.text.chopped(cut) + ellipsis;
-                        int newSize = metrics.horizontalAdvance(currentText +
-                                                                truncatedWord);
-                        if (container.fitsInLine(newSize))
-                        {
-                            currentText += (truncatedWord);
-
-                            cutSuccess = true;
-                            break;
-                        }
-                    }
-
-                    if (!cutSuccess)
-                    {
-                        // We weren't able to show any part of the current word, so
-                        // just append the ellipsis.
-                        currentText += ellipsis;
-                    }
-
                     break;
                 }
             }

src/messages/layouts/MessageLayoutContainer.cpp

@@ -424,11 +424,16 @@ bool MessageLayoutContainer::atStartOfLine()
 
 bool MessageLayoutContainer::fitsInLine(int _width)
 {
-    return this->currentX_ + _width <=
+    return _width <= this->remainingWidth();
-           (this->width_ - int(this->margin.left * this->scale_) -
+}
+
+int MessageLayoutContainer::remainingWidth() const
+{
+    return (this->width_ - int(this->margin.left * this->scale_) -
             int(this->margin.right * this->scale_) -
             (this->line_ + 1 == MAX_UNCOLLAPSED_LINES ? this->dotdotdotWidth_
-                                                      : 0));
+                                                      : 0)) -
+           this->currentX_;
 }
 
 void MessageLayoutContainer::end()

src/messages/layouts/MessageLayoutContainer.hpp

@@ -66,6 +66,7 @@ struct MessageLayoutContainer {
     void breakLine();
     bool atStartOfLine();
     bool fitsInLine(int width_);
+    int remainingWidth() const;
     // this method is called when a message has an RTL word
     // we need to reorder the words to be shown properly
     // however we don't we to reorder non-text elements like badges, timestamps, username