Cache background color brush instead of recreating it at each screen
update.

dlls/riched20/editor.c

diff --git a/dlls/riched20/editor.c b/dlls/riched20/editor.c
index 2dfd581..a25a90d 100644
--- a/dlls/riched20/editor.c
+++ b/dlls/riched20/editor.c
@@ -821,6 +821,7 @@
   ed->nUDArrowX = -1;
   ed->nSequence = 0;
   ed->rgbBackColor = -1;
+  ed->hbrBackground = GetSysColorBrush(COLOR_WINDOW);
   ed->bCaretAtEnd = FALSE;
   ed->nEventMask = 0;
   ed->nModifyStep = 0;
@@ -926,7 +927,8 @@
     if (editor->pFontCache[i].hFont)
       DeleteObject(editor->pFontCache[i].hFont);
   }
-    
+  DeleteObject(editor->hbrBackground);
+
   FREE_OBJ(editor);
 }
 
@@ -1265,10 +1267,18 @@
   case EM_SETBKGNDCOLOR:
   {
     LRESULT lColor = ME_GetBackColor(editor);
+    if (editor->rgbBackColor != -1)
+      DeleteObject(editor->hbrBackground);
     if (wParam)
+    {
       editor->rgbBackColor = -1;
+      editor->hbrBackground = GetSysColorBrush(COLOR_WINDOW);
+    }
     else
+    {
       editor->rgbBackColor = lParam;
+      editor->hbrBackground = CreateSolidBrush(editor->rgbBackColor);
+    }
     if (editor->bRedraw)
     {
       InvalidateRect(hWnd, NULL, TRUE);
@@ -1792,12 +1802,9 @@
     {
       HDC hDC = (HDC)wParam;
       RECT rc;
-      COLORREF rgbBG = ME_GetBackColor(editor);
       if (GetUpdateRect(hWnd,&rc,TRUE))
       {
-        HBRUSH hbr = CreateSolidBrush(rgbBG);
-        FillRect(hDC, &rc, hbr);
-        DeleteObject(hbr);
+        FillRect(hDC, &rc, editor->hbrBackground);
       }
     }
     return 1;

dlls/riched20/editstr.h

diff --git a/dlls/riched20/editstr.h b/dlls/riched20/editstr.h
index 2e8f175..7a7398f 100644
--- a/dlls/riched20/editstr.h
+++ b/dlls/riched20/editstr.h
@@ -270,6 +270,7 @@
   int nSequence;
   int nOldSelFrom, nOldSelTo;
   COLORREF rgbBackColor;
+  HBRUSH hbrBackground;
   BOOL bCaretAtEnd;
   int nEventMask;
   int nModifyStep;

dlls/riched20/paint.c

diff --git a/dlls/riched20/paint.c b/dlls/riched20/paint.c
index 29420c6..e1c56b4 100644
--- a/dlls/riched20/paint.c
+++ b/dlls/riched20/paint.c
@@ -78,14 +78,11 @@
     }
 
     if (ye>ys) {
-      HBRUSH hbr;
-      hbr = CreateSolidBrush(ME_GetBackColor(c.editor));
       rc.left = xs;
       rc.top = ys;
       rc.right = xe;
       rc.bottom = ye;
-      FillRect(hDC, &rc, hbr);
-      DeleteObject(hbr);
+      FillRect(hDC, &rc, c.editor->hbrBackground);
     }
     if (ys == c.pt.y) /* don't overwrite the top bar */
       ys++;