From 304e345a79e117477fa13117156a889795eeadc9 Mon Sep 17 00:00:00 2001
From: Henrik Hautakoski <henrik.hautakoski@gmail.com>
Date: Sat, 5 Dec 2020 18:19:52 +0100
Subject: [PATCH] Platform/Win32/Win32Display: Implementing true fullscreen
 with enterFullscreen() and exitFullscreen()

---
 source/Platform/Win32/Win32Display.cpp | 88 +++++++++++++++++++++++++-
 source/Platform/Win32/Win32Display.h   |  7 ++
 2 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/source/Platform/Win32/Win32Display.cpp b/source/Platform/Win32/Win32Display.cpp
index c38004c..18e50e6 100644
--- a/source/Platform/Win32/Win32Display.cpp
+++ b/source/Platform/Win32/Win32Display.cpp
@@ -36,7 +36,7 @@ Win32Display::~Win32Display()
 
 bool Win32Display::create(DisplayDescription description)
 {
-	DWORD flags = getWin32Flags(description.decoration);
+	DWORD flags;
 	Vector2i pos;
 
 	if (firstTime) {
@@ -44,7 +44,18 @@ bool Win32Display::create(DisplayDescription description)
 		firstTime = false;
 	}
 
-	pos = centerWindow(description.mode.width, description.mode.height);
+	if (description.decoration & DisplayDecorate::Fullscreen) {
+		m_fs_mode = description.mode;
+	}
+
+	if (m_fs_mode.empty() == false) {
+		// Only set these flags for fullscreen (borderless)
+		flags = WS_VISIBLE | WS_POPUP;
+	} else {
+		// Set window to center and set decorator flags for windowed displays.
+		pos = centerWindow(description.mode.width, description.mode.height);
+		flags = getWin32Flags(description.decoration);
+	}
 
 	// Create window.
 	m_handle = CreateWindowExA(0, WND_CLASSNAME, "", flags,
@@ -56,7 +67,11 @@ bool Win32Display::create(DisplayDescription description)
 		return false;
 	}
 
-	setSize(description.mode.width, description.mode.height);
+	if (m_fs_mode.empty() == false) {
+		enterFullscreen(m_fs_mode);
+	} else {
+		setSize(description.mode.width, description.mode.height);
+	}
 
 	// Store the size for use later.
 	m_size = getSize();
@@ -277,6 +292,60 @@ Vector2i Win32Display::centerWindow(int width, int height)
 	return v;
 }
 
+void Win32Display::enterFullscreen(DisplayMode mode)
+{
+	LONG rc;
+	::DEVMODEW dev;
+	dev.dmSize       = sizeof(dev);
+	dev.dmPelsWidth  = mode.width;
+	dev.dmPelsHeight = mode.height;
+	dev.dmBitsPerPel = mode.bpp;
+	dev.dmFields     = DM_PELSWIDTH | DM_PELSHEIGHT | DM_BITSPERPEL;
+
+	rc = ::ChangeDisplaySettingsW(&dev, CDS_FULLSCREEN);
+	if (rc != DISP_CHANGE_SUCCESSFUL) {
+		const char *msg;
+
+		switch(rc) {
+		case DISP_CHANGE_BADDUALVIEW :
+			msg = "The system is DualView capable"; break;
+		case DISP_CHANGE_BADFLAGS :
+			msg = "Invalid flags given"; break;
+		case DISP_CHANGE_BADPARAM :
+			msg = "Invalid parameter"; break;
+		case DISP_CHANGE_BADMODE :
+			msg = "Resolution not supported"; break;
+		case DISP_CHANGE_FAILED :
+			msg = "Display driver failed to set mode"; break;
+		case DISP_CHANGE_NOTUPDATED :
+			msg = "Unable to write settings to the registry"; break;
+		case DISP_CHANGE_RESTART :
+			msg = "System restart required"; break;
+		default :
+			msg = "Unkown error";
+		}
+
+		sp::Log::error("Win32: Failed to switch to fullscreen mode: %s.", msg);
+		return;
+	}
+
+	::SetWindowLong(m_handle, GWL_STYLE, WS_VISIBLE | WS_POPUP);
+	::SetWindowPos(m_handle, HWND_TOP, 0, 0, mode.width, mode.height, SWP_FRAMECHANGED | SWP_SHOWWINDOW);
+
+	grabCursor(true);
+
+	m_fs_mode = mode;
+}
+
+void Win32Display::exitFullscreen()
+{
+	if (!m_fs_mode.empty()) {
+		// Restore to previous mode.
+		::ChangeDisplaySettingsW(NULL, 0);
+		m_fs_mode = DisplayMode();
+	}
+}
+
 void Win32Display::processResizeMessage(const Vector2u& new_size)
 {
 	// Check if the size has actually changed.
@@ -301,9 +370,22 @@ void Win32Display::processMessage(UINT message, WPARAM wParam, LPARAM lParam)
 		break;
 	case WM_SETFOCUS :
 		Log::debug("WM_SETFOCUS");
+		if (m_fs_mode.empty() == false) {
+			enterFullscreen(m_fs_mode);
+		}
 		break;
 	case WM_KILLFOCUS :
 		Log::debug("WM_KILLFOCUS");
+		// If in fullscreen mode.
+		if (m_fs_mode.empty() == false) {
+			// Switch to window mode.
+			::ChangeDisplaySettingsW(NULL, 0);
+
+			// also minimize the window to get it out of the way.
+			minimize();
+		}
+
+		grabCursor(false);
 		break;
 	case WM_SIZE :
 
diff --git a/source/Platform/Win32/Win32Display.h b/source/Platform/Win32/Win32Display.h
index ccdaecc..510c275 100644
--- a/source/Platform/Win32/Win32Display.h
+++ b/source/Platform/Win32/Win32Display.h
@@ -35,6 +35,10 @@ public :
 
 	virtual void 	setDecoration(unsigned decoration);
 
+	virtual void 	enterFullscreen(DisplayMode mode);
+
+	virtual void 	exitFullscreen();
+
 	virtual void 	minimize();
 
 	virtual void 	maximize();
@@ -76,6 +80,9 @@ protected :
 	Vector2u	m_size;
 
 	Vector2u	m_minSize;
+
+	// Fullscreen mode.
+	DisplayMode m_fs_mode;
 };
 
 } // namespace sp