From a9e731ed5968f812fd7ecbaa37c7c89a1dcec744 Mon Sep 17 00:00:00 2001
From: Pietro Gagliardi <pietro10@mac.com>
Date: Tue, 24 May 2016 22:14:05 -0400
Subject: [PATCH] Added uiMainStep() and implemented it on Windows.

---
 ui.h             |  1 +
 windows/main.cpp | 82 ++++++++++++++++++++++++++++++++++++------------
 2 files changed, 63 insertions(+), 20 deletions(-)

diff --git a/ui.h b/ui.h
index c1d7bb31..adc0b327 100644
--- a/ui.h
+++ b/ui.h
@@ -36,6 +36,7 @@ _UI_EXTERN void uiUninit(void);
 _UI_EXTERN void uiFreeInitError(const char *err);
 
 _UI_EXTERN void uiMain(void);
+_UI_EXTERN int uiMainStep(int wait);
 _UI_EXTERN void uiQuit(void);
 
 _UI_EXTERN void uiQueueMain(void (*f)(void *data), void *data);
diff --git a/windows/main.cpp b/windows/main.cpp
index 2480cd46..3edd8635 100644
--- a/windows/main.cpp
+++ b/windows/main.cpp
@@ -41,31 +41,73 @@ void unregisterMessageFilter(void)
 		logLastError(L"error unregistering libui message filter");
 }
 
-// TODO http://blogs.msdn.com/b/oldnewthing/archive/2005/04/08/406509.aspx when adding accelerators, TranslateAccelerators() before IsDialogMessage()
+// LONGTERM http://blogs.msdn.com/b/oldnewthing/archive/2005/04/08/406509.aspx when adding accelerators, TranslateAccelerators() before IsDialogMessage()
+
+static void processMessage(MSG *msg)
+{
+	HWND active;
+
+	// TODO really active? or parentToplevel(msg->hwnd)?
+	active = GetActiveWindow();
+	if (active != NULL)
+		// TODO find documentation that says IsDialogMessage() calls CallMsgFilter() for us, because that's what's happening
+		if (IsDialogMessage(active, msg) != 0)
+			return;
+	TranslateMessage(msg);
+	DispatchMessageW(msg);
+}
+
+static int waitMessage(MSG *msg)
+{
+	int res;
+
+	res = GetMessageW(msg, NULL, 0, 0);
+	if (res < 0) {
+		logLastError(L"error calling GetMessage()");
+		return 0;		// bail out on error
+	}
+	return res != 0;		// returns false on WM_QUIT
+}
 
 void uiMain(void)
 {
-	MSG msg;
-	int res;
-	HWND active;
+	while (uiMainStep(1))
+		;
+}
 
-	for (;;) {
-		res = GetMessageW(&msg, NULL, 0, 0);
-		if (res < 0) {
-			logLastError(L"error calling GetMessage()");
-			break;		// bail out on error
-		}
-		if (res == 0)		// WM_QUIT
-			break;
-		// TODO really active? or parentToplevel(msg->hwnd)?
-		active = GetActiveWindow();
-		if (active != NULL)
-			// TODO find documentation that says IsDialogMessage() calls CallMsgFilter() for us, because that's what's happening
-			if (IsDialogMessage(active, &msg) != 0)
-				continue;
-		TranslateMessage(&msg);
-		DispatchMessageW(&msg);
+static int peekMessage(MSG *msg)
+{
+	BOOL res;
+
+	res = PeekMessageW(msg, NULL, 0, 0, PM_REMOVE);
+	if (res == 0)
+		return 2;		// no message available
+	if (msg->message != WM_QUIT)
+		return 1;		// a message
+	return 0;			// WM_QUIT
+}
+
+int uiMainStep(int wait)
+{
+	MSG msg;
+
+	if (wait) {
+		if (!waitMessage(&msg))
+			return 0;
+		processMessage(&msg);
+		return 1;
 	}
+
+	// don't wait for a message
+	switch (peekMessage(&msg)) {
+	case 0:		// quit
+		// TODO PostQuitMessage() again?
+		return 0;
+	case 1:		// process a message
+		processMessage(&msg);
+		// fall out to the case for no message
+	}
+	return 1;		// no message
 }
 
 void uiQuit(void)