171: support for non-scrollable text editor (#188)

Co-authored-by: Gyuri Majercsik <gyuri@fluttech.com>

lib/widgets/editor.dart

@@ -1043,7 +1043,6 @@ class RenderEditableContainerBox extends RenderBox
 
   @override
   void performLayout() {
-    assert(!constraints.hasBoundedHeight);
     assert(constraints.hasBoundedWidth);
     _resolvePadding();
     assert(_resolvedPadding != null);

lib/widgets/raw_editor.dart

@@ -1008,9 +1008,11 @@ class RawEditorState extends EditorState
 
     _showCaretOnScreenScheduled = true;
     SchedulerBinding.instance!.addPostFrameCallback((_) {
+      if (widget.scrollable) {
         _showCaretOnScreenScheduled = false;
 
-      final viewport = RenderAbstractViewport.of(getRenderEditor())!;
+        final viewport = RenderAbstractViewport.of(getRenderEditor());
+
         final editorOffset = getRenderEditor()!
             .localToGlobal(const Offset(0, 0), ancestor: viewport);
         final offsetInViewport = _scrollController!.offset + editorOffset.dy;
@@ -1028,6 +1030,7 @@ class RawEditorState extends EditorState
             curve: Curves.fastOutSlowIn,
           );
         }
+      }
     });
   }