scrolllists were incredibly slow to render. This included the friends and groups lists. Should be much faster now due to not thrashing the bound texture quite as much. Also ui elements are culled on the cpu side if they are out of the current scissor region. list cells also had no clip logic, so added to that as well.

indra/llui/llscrolllistitem.cpp

@@ -28,6 +28,7 @@
 #include "linden_common.h"
 
 #include "llscrolllistitem.h"
+#include "llview.h"
 
 
 //---------------------------------------------------------------------------
@@ -116,32 +117,73 @@ std::string LLScrollListItem::getContentsCSV() const
 }
 
 
-void LLScrollListItem::draw(const LLRect& rect, const LLColor4& fg_color, const LLColor4& bg_color, const LLColor4& highlight_color, S32 column_padding)
+bool LLScrollListItem::draw(const U32 pass, const LLRect& rect, const LLColor4& fg_color, const LLColor4& bg_color, const LLColor4& highlight_color, S32 column_padding)
 {
+	const U32 num_cols = (U32)getNumColumns();
+
 	// draw background rect
-	gGL.getTexUnit(0)->unbind(LLTexUnit::TT_TEXTURE);
-	LLRect bg_rect = rect;
-	gl_rect_2d( bg_rect, bg_color );
-
-	S32 cur_x = rect.mLeft;
-	S32 num_cols = getNumColumns();
-	S32 cur_col = 0;
-
-	for (LLScrollListCell* cell = getColumn(0); cur_col < num_cols; cell = getColumn(++cur_col))
+	if (pass == 0)
 	{
-		// Two ways a cell could be hidden
-		if (cell->getWidth() < 0
-			|| !cell->getVisible()) continue;
-
-		LLUI::pushMatrix();
-		{
-			LLUI::translate((F32) cur_x, (F32) rect.mBottom);
-
-			cell->draw( fg_color, highlight_color );
-		}
-		LLUI::popMatrix();
-
-		cur_x += cell->getWidth() + column_padding;
+		gGL.getTexUnit(0)->unbind(LLTexUnit::TT_TEXTURE);
+		gl_rect_2d(rect, bg_color);
+		return true;
 	}
+	// Draw column (pass - 1)
+	else if (pass <= num_cols)
+	{
+		LLScrollListCell* cur_cell = getColumn(pass - 1);
+		if (!cur_cell)
+		{
+			return false;
+		}
+		// Two ways a cell could be hidden
+		else if (cur_cell->getWidth() && cur_cell->getVisible())
+		{
+			// Iterate over cells to the left and calculate offset.
+			S32 offset = rect.mLeft;
+			for (U32 i = 0; i < (pass - 1); ++i)
+			{
+				LLScrollListCell* cell = getColumn(i);
+				if (!cell)
+				{
+					return false; // Shouldn't happen.
+				}
+				if (cell->getVisible() && cell->getWidth())
+				{
+					// Only apply padding if cell is visible and has width.
+					offset += cell->getWidth() + column_padding;
+				}
+			}
+			// Do not draw if not on screen.
+			// Only care about horizontal bounds. This draw call wont even occur if this row is entirely off screen.
+			LLRect clip_rect = LLUI::getRootView()->getRect();
+			if (LLGLState<GL_SCISSOR_TEST>::isEnabled())
+			{
+				LLRect scissor = gGL.getScissor();
+				scissor.mLeft /= LLUI::getScaleFactor().mV[VX];
+				scissor.mTop /= LLUI::getScaleFactor().mV[VY];
+				scissor.mRight /= LLUI::getScaleFactor().mV[VX];
+				scissor.mBottom /= LLUI::getScaleFactor().mV[VY];
+				clip_rect.intersectWith(scissor);
+			}
+			if (offset + LLFontGL::sCurOrigin.mX >= clip_rect.mRight)
+			{
+				// Went off the right edge of the screen. Don't bother with any more columns.
+				return false;
+			}
+			// Draw if not off the left edge of screen. If it is off the left edge, still return true if other colums remain.
+			if (offset + LLFontGL::sCurOrigin.mX + cur_cell->getWidth() > clip_rect.mLeft)
+			{
+				LLUI::pushMatrix();
+				{
+					LLUI::translate((F32)offset, (F32)rect.mBottom);
+					cur_cell->draw(fg_color, highlight_color);
+				}
+				LLUI::popMatrix();
+			}
+		}
+		return pass != getNumColumns();
+	}
+	return false;
 }