Now, nsTextEditState::GetValue uses TextEditor::OutputToString to get current value when editor has focus. nsTextEditState::UpdateOverlayTextVisibility uses this to check whether current value is empty. I think that OutputToString is expensive whether value is empty or not. So nsIPlainEditor might have to have hasText property for this.

HTMLInputElement::IsValueEmpty might require it since element::UpdateState uses nsTextEditState::GetValue to check empty string.

Comment on attachment 8866635 [details] Bug 1360154 - Part 1. DocumentIsBody should return bool, not nsresult. https://reviewboard.mozilla.org/r/138238/#review141436

Comment on attachment 8866636 [details] Bug 1360154 - Part 2. Add fast path to check whether valus is emtpy. https://reviewboard.mozilla.org/r/138240/#review141438 ::: dom/html/nsTextEditorState.h:184 (Diff revision 1) > // not changed the cursor won't move. > eSetValue_MoveCursorToEndIfValueChanged = 1 << 3, > }; > MOZ_MUST_USE bool SetValue(const nsAString& aValue, uint32_t aFlags); > void GetValue(nsAString& aValue, bool aIgnoreWrap) const; > + bool HasValue(); HasValue() is unclear to me. I think that HasNonEmptyValue(), IsEmpty() or something is better.

Pushed by m_kato@ga2.so-net.ne.jp: https://hg.mozilla.org/integration/autoland/rev/b508ea403285 Part 1. DocumentIsBody should return bool, not nsresult. r=masayuki https://hg.mozilla.org/integration/autoland/rev/fab114e7628c Part 2. Add fast path to check whether valus is emtpy. r=masayuki

https://hg.mozilla.org/mozilla-central/rev/b508ea403285 https://hg.mozilla.org/mozilla-central/rev/fab114e7628c