fix: handle multiline selection starting at trailing space (#5691)

CHANGELOG.md

@@ -68,6 +68,7 @@
 - Bugfix: Fixed emotes starting with ":" not tab-completing. (#5603)
 - Bugfix: Fixed 7TV emotes messing with Qt's HTML. (#5677)
 - Bugfix: Fixed incorrect messages getting replaced visually. (#5683)
+- Bugfix: Fixed rendering of multi-line selection that starts at a trailing space. (#5691)
 - Dev: Update Windows build from Qt 6.5.0 to Qt 6.7.1. (#5420)
 - Dev: Update vcpkg build Qt from 6.5.0 to 6.7.0, boost from 1.83.0 to 1.85.0, openssl from 3.1.3 to 3.3.0. (#5422)
 - Dev: Unsingletonize `ISoundController`. (#5462)

src/messages/layouts/MessageLayoutContainer.cpp

@@ -854,6 +854,18 @@ std::optional<size_t> MessageLayoutContainer::paintSelectionStart(
 {
     const auto selectionColor = getTheme()->messages.selection;
 
+    auto paintRemainingLines = [&](size_t startIndex) {
+        for (size_t i = startIndex; i < this->lines_.size(); i++)
+        {
+            const auto &line = this->lines_[i];
+            auto left = this->elements_[line.startIndex]->getRect().left();
+            auto right = this->elements_[line.endIndex - 1]->getRect().right();
+
+            this->paintSelectionRect(painter, line, left, right, yOffset,
+                                     selectionColor);
+        }
+    };
+
     // The selection starts in this message
     for (size_t lineIndex = 0; lineIndex < this->lines_.size(); lineIndex++)
     {
@@ -874,7 +886,17 @@ std::optional<size_t> MessageLayoutContainer::paintSelectionStart(
             auto right = this->elements_[line.endIndex - 1]->getRect().right();
             this->paintSelectionRect(painter, line, right, right, yOffset,
                                      selectionColor);
-            return std::nullopt;
+
+            if (selection.selectionMax.messageIndex != messageIndex)
+            {
+                // The selection does not end in this message
+                paintRemainingLines(lineIndex + 1);
+
+                return std::nullopt;
+            }
+
+            // The selection starts in this line, but ends in some next line or message
+            return {lineIndex + 1};
         }
 
         int x = this->elements_[line.startIndex]->getRect().left();
@@ -923,21 +945,9 @@ std::optional<size_t> MessageLayoutContainer::paintSelectionStart(
             if (selection.selectionMax.messageIndex != messageIndex)
             {
                 // The selection does not end in this message
-                for (size_t lineIndex2 = lineIndex + 1;
-                     lineIndex2 < this->lines_.size(); lineIndex2++)
-                {
-                    const auto &line2 = this->lines_[lineIndex2];
-                    auto left =
-                        this->elements_[line2.startIndex]->getRect().left();
-                    auto right =
-                        this->elements_[line2.endIndex - 1]->getRect().right();
-
-                    this->paintSelectionRect(painter, line2, left, right,
-                                             yOffset, selectionColor);
-                }
-
                 this->paintSelectionRect(painter, line, x, r, yOffset,
                                          selectionColor);
+                paintRemainingLines(lineIndex + 1);
 
                 return std::nullopt;
             }

src/messages/layouts/MessageLayoutContainer.hpp

@@ -283,7 +283,12 @@ struct MessageLayoutContainer {
     /**
      * Paint the selection start
      *
-     * Returns a line index if this message should also paint the selection end
+     * @returns A line index if the selection ends within this message but start
+     *          and end are on different lines. The returned index is the index 
+     *          of the first line where the selection starts at the beginning of
+     *          the line. This index should be passed to paintSelectionEnd().
+     *          If `std::nullopt` is returned, no further call to 
+     *          paintSelectionEnd() is necessary.
      */
     std::optional<size_t> paintSelectionStart(QPainter &painter,
                                               size_t messageIndex,