diff --git a/TODO.md b/TODO.md
index d946df8d..df63cd86 100644
--- a/TODO.md
+++ b/TODO.md
@@ -7,6 +7,7 @@ https://zhuanlan.zhihu.com/p/39369370
 - [ ] High DPI for Direct2D (GDI will blur)
 - [ ] Window Icon
 - [x] Use another way to create focus rectangle bitmap mask for Direct2D
+- [ ] Fix combo dropdown hidden in topmost window
 - [ ] **Update Release**
 - [ ] New default control templates with animation, written in XML generated C++ code.
 - [ ] A window can be called to update all its controls' and components' template
diff --git a/TODO_ParserGen.md b/TODO_ParserGen.md
index 6869334c..4a64cd98 100644
--- a/TODO_ParserGen.md
+++ b/TODO_ParserGen.md
@@ -1,3 +1,4 @@
+# Goal
 * Parsing
     * No need to specify allow ambiguity or not
     * Calculate ambiguous **Parse** cases, pointing out which AST need to support ambiguity
@@ -11,3 +12,50 @@
     * Generate **ToString** algorithm
 * AST
     * Low overhead AST with reflection
+
+# AST Definition (compatible with Workflow)
+```
+class CLASS_NAME [: BASE_CLASS]
+{
+  var FIELD_NAME : TYPE;
+  ...
+}
+```
+
+## Configurations
+- Include files in generated C++ header
+- Depended AST definition files
+- Visitors selected to generate
+- Optional reflection support
+
+## Types
+- `Token`: In the previous version, `Token` is a value type, now it is a reference type.
+- `CLASS_NAME`: Another class.
+- `TYPE[]`: Array, whose element is not allowed to be another array.
+
+## MISC
+- Define a `ToString` algorithm with customizable configurations.
+
+# Lexical Analyzer
+- Pair name with regular expressions.
+- Extendable tokens.
+  - For example, recognize `R"[^\s(]\(` and invoke a callback function to determine the end of the string
+- Pair a name with the token subset, and give a default name to a token full set
+
+# Error Messages
+- Generate error messages in C++ code
+
+# Syntax Analyzer
+- Priority of loops:
+  - `+[ RULE ]` means only if `RULE` does not succeed, the result of not having `RULE` is kept.
+  - `-[ RULE ]` means only if skipping `RULE` makes the clause not able to parse, the result of having RULE is not discarded.
+  - `[ RULE ]` means keep both result
+  - `+{ RULE }`, `-{ RULE }`, `{ RULE }` are similar, but `{ RULE }` may generate more than two results, meanwhile others only generate one result.
+- Being able to change token subset during parsing.
+- Being able to specify a error message when a certain action fails.
+- Generate SAX-like parser, with a default handler to create AST.
+
+## High level steps
+- Name each progresses in all branches in all rules, including rule names as start progresses, as states.
+- Build DFA per rule, merging all branches with priority, assuming **rule-input**s are different from **token-input**s.
+- Add push-state, pop-state, remove **rule-input** transitions.