実際に動かして動作を確認する

書き換えたwinmain.cをコンパイルして実行する。

起動したらすぐに終了しても大丈夫だ。それだけで十分な数のメッセージが取得できている。ここでそれぞれ取得されたログデータは次のとおり。

長くなるが、比較を行いたいのでそれぞれ記録されたデータの全容を記載しておく。

log1.txtのサンプル

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log2.txtのサンプル

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ここからわかるように、メッセージループからウィンドウプロシージャが呼ばれるというよりも、メッセージループもウィンドウプロシージャもそれぞれの仕組みに従ってイベントがファイアしている動きをしていることがわかる。似たような動きに見えるが、実際には異なるものとして扱った方が適切ということになりそうだ。

実際に動かして理解していくことが大切

Windows APIで提供されている構造体や関数は、Microsoft Docsにドキュメントがまとまっている。サンプルコードも多く掲載されているので、Windows APIの全体像は比較的つかみやすいだろう。

しかしながら、実際にどのように動作するかは自分で作って実際に試してみるのがお薦めだ。ドキュメントを読んだだけの理解では、自分の都合がよいように解釈していることがある。往々にして人間は自分にとって都合がよいように理解しがちなのだ。こんな感じで自分で動きを追ってみると、APIの全体像や構造がよく見えてくる。ぜひとも実際に試して動きを追ってみてもらえればと思う。

参考