Fix console not keeping scroll position when backlog is full

The console was not keeping its current scoll position if entries from the backlog are removed due to being recycled when new entries are added. For this purpose, a callback function is added to the ringbuffer to handle popped items, so the scrolling position of the console can be updated based on the number of lines of the removed backlog entries.

src/engine/shared/ringbuffer.cpp

@@ -123,11 +123,21 @@ void *CRingBufferBase::Allocate(int Size)
 	return (void *)(pBlock + 1);
 }
 
+void CRingBufferBase::SetPopCallback(std::function<void(void *pCurrent)> PopCallback)
+{
+	m_PopCallback = std::move(PopCallback);
+}
+
 int CRingBufferBase::PopFirst()
 {
 	if(m_pConsume->m_Free)
 		return 0;
 
+	if(m_PopCallback)
+	{
+		m_PopCallback(m_pConsume + 1);
+	}
+
 	// set the free flag
 	m_pConsume->m_Free = 1;
 

src/engine/shared/ringbuffer.h

@@ -5,6 +5,8 @@
 
 #include <base/system.h>
 
+#include <functional>
+
 class CRingBufferBase
 {
 	class CItem
@@ -25,6 +27,8 @@ class CRingBufferBase
 	int m_Size;
 	int m_Flags;
 
+	std::function<void(void *pCurrent)> m_PopCallback = nullptr;
+
 	CItem *NextBlock(CItem *pItem);
 	CItem *PrevBlock(CItem *pItem);
 	CItem *MergeBack(CItem *pItem);
@@ -39,6 +43,7 @@ protected:
 
 	void Init(void *pMemory, int Size, int Flags);
 	int PopFirst();
+	void SetPopCallback(const std::function<void(void *pCurrent)> PopCallback);
 
 public:
 	enum
@@ -55,6 +60,12 @@ class CTypedRingBuffer : public CRingBufferBase
 public:
 	T *Allocate(int Size) { return (T *)CRingBufferBase::Allocate(Size); }
 	int PopFirst() { return CRingBufferBase::PopFirst(); }
+	void SetPopCallback(std::function<void(T *pCurrent)> PopCallback)
+	{
+		CRingBufferBase::SetPopCallback([PopCallback](void *pCurrent) {
+			PopCallback((T *)pCurrent);
+		});
+	}
 
 	T *Prev(T *pCurrent) { return (T *)CRingBufferBase::Prev(pCurrent); }
 	T *Next(T *pCurrent) { return (T *)CRingBufferBase::Next(pCurrent); }

src/game/client/components/console.cpp

@@ -208,6 +208,13 @@ CGameConsole::CInstance::CInstance(int Type)
 
 	m_IsCommand = false;
 
+	m_Backlog.SetPopCallback([this](CBacklogEntry *pEntry) {
+		if(pEntry->m_LineCount != -1)
+		{
+			m_NewLineCounter -= pEntry->m_LineCount;
+		}
+	});
+
 	m_Input.SetClipboardLineCallback([this](const char *pStr) { ExecuteLine(pStr); });
 
 	m_CurrentMatchIndex = -1;
@@ -1135,7 +1142,7 @@ void CGameConsole::OnRender()
 		}
 
 		pConsole->PumpBacklogPending();
-		if(pConsole->m_NewLineCounter > 0)
+		if(pConsole->m_NewLineCounter != 0)
 		{
 			pConsole->UpdateSearch();
 
@@ -1145,6 +1152,8 @@ void CGameConsole::OnRender()
 				pConsole->m_BacklogCurLine += pConsole->m_NewLineCounter;
 				pConsole->m_BacklogLastActiveLine += pConsole->m_NewLineCounter;
 			}
+			if(pConsole->m_NewLineCounter < 0)
+				pConsole->m_NewLineCounter = 0;
 		}
 
 		// render console log (current entry, status, wrap lines)