Bug 1048752. Part 27: Remove obsolete caret state logic and just Sche…

…dulePaint as needed. r=tn

This is the core of the whole patch set.

Now GetPaintGeometry/PaintCaret figure out on their own almost all the state
they need every time we paint. So when caret flags change, all we need
to do is SchedulePaint. We don't need to fiddle with mDrawn and most of the
logic in DrawCaret is obsolete. (In fact, it was duplicated by GetGeometry
and friends, and we're removing that duplication.) EraseCaret, CheckCaretState
and UpdateCaretPosition are also obsolete.

We need to have GetPaintGeometry/PaintCaret choose the correct content node
and offset, either getting them from the Selection or using specific data set by
DrawAtPosition. This logic, plus a bit of other code shared between them, is
put into the helper GetFrameAndOffset.

--HG--
extra : rebase_source : e777605dd2507ae043e9f82d0a30e23aa06e0c12

editor/libeditor/nsEditorEventListener.cpp

@@ -695,11 +695,7 @@ nsEditorEventListener::DragOver(nsIDOMDragEvent* aDragEvent)
       nsresult rv = aDragEvent->GetRangeOffset(&offset);
       NS_ENSURE_SUCCESS(rv, rv);
 
-      // to avoid flicker, we could track the node and offset to see if we moved
-      if (mCaret)
-        mCaret->EraseCaret();
-
-      //mCaret->SetCaretVisible(true);   // make sure it's visible
+      mCaret->SetVisible(true);
       mCaret->DrawAtPosition(parent, offset);
     }
   }
@@ -713,7 +709,7 @@ nsEditorEventListener::DragOver(nsIDOMDragEvent* aDragEvent)
 
     if (mCaret)
     {
-      mCaret->EraseCaret();
+      mCaret->SetVisible(false);
     }
   }
 
@@ -725,7 +721,6 @@ nsEditorEventListener::CleanupDragDropCaret()
 {
   if (mCaret)
   {
-    mCaret->EraseCaret();
     mCaret->SetVisible(false);    // hide it, so that it turns off its timer
 
     nsCOMPtr<nsIPresShell> presShell = GetPresShell();