Fixes for EXT-4689 (Long-word chat spam cripples fps and/or disconnects client)

Removed some unnecessary string copies in LLTextBase and LLNormalTextSegment by changing getWText() to return const LLWString& (instead of LLWString), and storing the result in a const LLWString& instead of an LLWString in places where the string doesn't need to be modified.

Made LLTextViewModel::getDisplay() also return const LLWString& instead of LLWString.

Removed a couple of unused local string variables in LLTextBase (the compiler flagged these after converting the local copies to const LLWString&).

3 files changed, 8 insertions, 10 deletions

diff --git a/indra/llui/lltextbase.cpp b/indra/llui/lltextbase.cpp
index a12b7793f7..259522a932 100644
--- a/indra/llui/lltextbase.cpp
+++ b/indra/llui/lltextbase.cpp
@@ -312,7 +312,6 @@ void LLTextBase::drawSelectionBackground()
 	// Draw selection even if we don't have keyboard focus for search/replace
 	if( hasSelection() && !mLineInfoList.empty())
 	{
-		LLWString text = getWText();
 		std::vector<LLRect> selection_rects;
 
 		S32 selection_left		= llmin( mSelectionStart, mSelectionEnd );
@@ -411,7 +410,7 @@ void LLTextBase::drawCursor()
 		&& gFocusMgr.getAppHasFocus()
 		&& !mReadOnly)
 	{
-		LLWString wtext = getWText();
+		const LLWString &wtext = getWText();
 		const llwchar* text = wtext.c_str();
 
 		LLRect cursor_rect = getLocalRectFromDocIndex(mCursorPos);
@@ -497,7 +496,6 @@ void LLTextBase::drawCursor()
 
 void LLTextBase::drawText()
 {
-	LLWString text = getWText();
 	const S32 text_len = getLength();
 	if( text_len <= 0 )
 	{
@@ -1116,7 +1114,6 @@ void LLTextBase::reflow(S32 start_index)
 		S32 line_start_index = 0;
 		const S32 text_available_width = mVisibleTextRect.getWidth() - mHPad;  // reserve room for margin
 		S32 remaining_pixels = text_available_width;
-		LLWString text(getWText());
 		S32 line_count = 0;
 
 		// find and erase line info structs starting at start_index and going to end of document
@@ -1759,7 +1756,7 @@ void LLTextBase::setWText(const LLWString& text)
 	setText(wstring_to_utf8str(text));
 }
 
-LLWString LLTextBase::getWText() const
+const LLWString& LLTextBase::getWText() const
 {
     return getViewModel()->getDisplay();
 }
@@ -2454,7 +2451,7 @@ bool LLNormalTextSegment::getDimensions(S32 first_char, S32 num_chars, S32& widt
 	if (num_chars > 0)
 	{
 		height = mFontHeight;
-		LLWString text = mEditor.getWText();
+		const LLWString &text = mEditor.getWText();
 		// if last character is a newline, then return true, forcing line break
 		llwchar last_char = text[mStart + first_char + num_chars - 1];
 		if (last_char == '\n')
@@ -2481,7 +2478,7 @@ bool LLNormalTextSegment::getDimensions(S32 first_char, S32 num_chars, S32& widt
 
 S32	LLNormalTextSegment::getOffset(S32 segment_local_x_coord, S32 start_offset, S32 num_chars, bool round) const
 {
-	LLWString text = mEditor.getWText();
+	const LLWString &text = mEditor.getWText();
 	return mStyle->getFont()->charFromPixelOffset(text.c_str(), mStart + start_offset,
 											   (F32)segment_local_x_coord,
 											   F32_MAX,
@@ -2491,7 +2488,7 @@ S32	LLNormalTextSegment::getOffset(S32 segment_local_x_coord, S32 start_offset,
 
 S32	LLNormalTextSegment::getNumChars(S32 num_pixels, S32 segment_offset, S32 line_offset, S32 max_chars) const
 {
-	LLWString text = mEditor.getWText();
+	const LLWString &text = mEditor.getWText();
 
 	LLUIImagePtr image = mStyle->getImage();
 	if( image.notNull())
diff --git a/indra/llui/lltextbase.h b/indra/llui/lltextbase.h
index 48d5478088..b5c7fab67a 100644
--- a/indra/llui/lltextbase.h
+++ b/indra/llui/lltextbase.h
@@ -145,7 +145,7 @@ public:
 
 	// wide-char versions
 	void					setWText(const LLWString& text);
-	LLWString       		getWText() const;
+	const LLWString&       	getWText() const;
 
 	void					appendText(const std::string &new_text, bool prepend_newline, const LLStyle::Params& input_params = LLStyle::Params());
 	// force reflow of text
diff --git a/indra/llui/llviewmodel.h b/indra/llui/llviewmodel.h
index c8a9b52cca..992365d44d 100644
--- a/indra/llui/llviewmodel.h
+++ b/indra/llui/llviewmodel.h
@@ -107,7 +107,8 @@ public:
 
 	// New functions
     /// Get the stored value in string form
-    LLWString getDisplay() const { return mDisplay; }
+    const LLWString& getDisplay() const { return mDisplay; }
+
     /**
      * Set the display string directly (see LLTextEditor). What the user is
      * editing is actually the LLWString value rather than the underlying