use peekmessage instead of get to prevent blocking game loop

hw3d/App.cpp

@@ -4,30 +4,21 @@
 
 App::App()
 	:
-	wnd( 800,600,"The Donkey Fart Box")
+	wnd( 800,600,"The Donkey Fart Box" )
 {}
 
 int App::Go()
 {
-	MSG msg;
-	BOOL gResult;
-	while( (gResult = GetMessage( &msg,nullptr,0,0 )) > 0 )
+	while( true )
 	{
-		// TranslateMessage will post auxilliary WM_CHAR messages from key msgs
-		TranslateMessage( &msg );
-		DispatchMessage( &msg );
-
-		DoFrame();
-	}
-
-	// check if GetMessage call itself borked
-	if( gResult == -1 )
+		// process all messages pending, but to not block for new messages
+		if( const auto ecode = Window::ProcessMessages() )
 		{
-		throw CHWND_LAST_EXCEPT();
+			// if return optional has value, means we're quitting so return exit code
+			return *ecode;
+		}
+		DoFrame();
 	}
-
-	// wParam here is the value passed to PostQuitMessage
-	return msg.wParam;
 }
 
 void App::DoFrame()

hw3d/Window.cpp

@@ -112,6 +112,28 @@ void Window::SetTitle( const std::string& title )
 	}
 }
 
+std::optional<int> Window::ProcessMessages()
+{
+	MSG msg;
+	// while queue has messages, remove and dispatch them (but do not block on empty queue)
+	while( PeekMessage( &msg,nullptr,0,0,PM_REMOVE ) )
+	{
+		// check for quit because peekmessage does not signal this via return val
+		if( msg.message == WM_QUIT )
+		{
+			// return optional wrapping int (arg to PostQuitMessage is in wparam) signals quit
+			return msg.wParam;
+		}
+
+		// TranslateMessage will post auxilliary WM_CHAR messages from key msgs
+		TranslateMessage( &msg );
+		DispatchMessage( &msg );
+	}
+
+	// return empty optional when not quitting app
+	return {};
+}
+
 LRESULT CALLBACK Window::HandleMsgSetup( HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam ) noexcept
 {
 	// use create parameter passed in from CreateWindow() to store window class pointer at WinAPI side

hw3d/Window.h

@@ -22,6 +22,7 @@
 #include "ChiliException.h"
 #include "Keyboard.h"
 #include "Mouse.h"
+#include <optional>
 
 
 class Window
@@ -61,6 +62,7 @@ public:
 	Window( const Window& ) = delete;
 	Window& operator=( const Window& ) = delete;
 	void SetTitle( const std::string& title );
+	static std::optional<int> ProcessMessages();
 private:
 	static LRESULT CALLBACK HandleMsgSetup( HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam ) noexcept;
 	static LRESULT CALLBACK HandleMsgThunk( HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam ) noexcept;