Remove unused variables, Refactor in MessageLayout

[dnsge]

Pull request checklist:

• CHANGELOG.md was updated, if applicable

No changelog entry needed in my opinion

Description

• Moves layoutCount_ and bufferUpdatedCount_ debug counters to an ifdef block in MessageLayout
• Removes unused variable MessageLayout::collapsedHeight_
• Replaces std::shared_ptr<MessageLayoutContainer> container_ with MessageLayoutContainer container_ in MessageLayout
  • The container never escapes nor can be null so it made no sense to be in a shared_ptr
• Replaces std::shared_ptr<QPixmap> buffer_ with std::unique_ptr<QPixmap> buffer_ in MessageLayout
  • The buffer never escapes so I replaced it with a unique_ptr instead
• Extracts buffer creation logic to MessageLayout::ensureBuffer

Why? While scrolling on a debug build, my Chatterino crashed with the following stack trace:

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0xff76443500e54f18 -> 0x0000443500e54f18 (possible pointer authentication failure)
Exception Codes:       0x0000000000000001, 0xff76443500e54f18
Exception Note:        EXC_CORPSE_NOTIFY

Termination Reason:    Namespace SIGNAL, Code 11 Segmentation fault: 11
Terminating Process:   exc handler [4395]

VM Region Info: 0x443500e54f18 is not in any region.  Bytes after previous region: 74513402646297  Bytes before following region: 30558677283048
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      commpage (reserved)        1000000000-7000000000   [384.0G] ---/--- SM=NUL  ...(unallocated)
--->  GAP OF 0x5f9000000000 BYTES
      MALLOC_NANO              600000000000-600008000000 [128.0M] rw-/rwx SM=PRV  

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   chatterino                    	       0x1012b0ba4 std::__1::shared_ptr<chatterino::MessageLayoutContainer>::operator->() const + 12 (memory:2872)
1   chatterino                    	       0x1012b0b88 chatterino::MessageLayout::getHeight() const + 28 (MessageLayout.cpp:70)
2   chatterino                    	       0x101b8f87c chatterino::ChannelView::wheelEvent(QWheelEvent*) + 376 (ChannelView.cpp:1376)
3   QtWidgets                     	       0x1096c4404 QWidget::event(QEvent*) + 128
4   QtWidgets                     	       0x10968e740 QApplicationPrivate::notify_helper(QObject*, QEvent*) + 292
5   QtWidgets                     	       0x109690de4 QApplication::notify(QObject*, QEvent*) + 5424
6   QtCore                        	       0x10aead6e4 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 208

Ostensibly caused by the MessageLayoutContainer in the MessageLayout being null. I suppose this could be caused by a race condition in which the destructor was in progress and the layout container had been deleted, but not the layout? Not sure. Regardless, while investigating, I noticed that the MessageLayoutContainer didn't need to be a pointer at all. I also noticed the other few things that I included in this PR.

Feel free to say that this doesn't matter/shouldn't be changed. Though, I think extracting the debug counters to an ifdef and removing the unused variable should be a change made anyway.

[Nerixyz]

You might be able to do QPixmap buffer_; here and use QPixmap::isNull. This would remove another indirection, because a QPixmap is essentially another shared-pointer and constructing a null-pixmap is cheap. You then need to avoid using the QPixmap's copy-constructor, since this potentially copies the pixmap-data.

[pajlada]

follow-up pr, but can be explored if someone wants

[pajlada]

Good refactor, easy to follow 👍