From e258a17b18ed7413863934fb56381a5e10965f82 Mon Sep 17 00:00:00 2001
From: narzoul <narzoul@users.noreply.github.com>
Date: Sat, 23 Jan 2016 23:01:01 +0100
Subject: [PATCH] Draw size box for windows with WS_SIZEBOX style

---
 DDrawCompat/CompatGdiWinProc.cpp | 47 ++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/DDrawCompat/CompatGdiWinProc.cpp b/DDrawCompat/CompatGdiWinProc.cpp
index 1cda7dd..025a1df 100644
--- a/DDrawCompat/CompatGdiWinProc.cpp
+++ b/DDrawCompat/CompatGdiWinProc.cpp
@@ -10,6 +10,7 @@
 namespace
 {
 	void eraseBackground(HWND hwnd, HDC dc);
+	bool isScrollBarVisible(HWND hwnd, LONG windowStyles, LONG sbStyle, LONG sbObjectId);
 	void ncPaint(HWND hwnd);
 	void updateScrolledWindow(HWND hwnd);
 
@@ -45,6 +46,36 @@ namespace
 		return CallNextHookEx(nullptr, nCode, wParam, lParam);
 	}
 
+	void drawSizeBox(HWND hwnd, HDC compatDc, const RECT& windowRect, const RECT& clientRect)
+	{
+		LONG style = GetWindowLongPtr(hwnd, GWL_STYLE);
+		if (!(style & WS_SIZEBOX))
+		{
+			return;
+		}
+
+		int width = GetSystemMetrics(SM_CXHSCROLL);
+		int height = GetSystemMetrics(SM_CXVSCROLL);
+		RECT sizeBoxRect = { 0, 0, width, height };
+
+		const bool isVisibleH = isScrollBarVisible(hwnd, style, WS_HSCROLL, OBJID_HSCROLL);
+		const bool isVisibleV = isScrollBarVisible(hwnd, style, WS_VSCROLL, OBJID_VSCROLL);
+
+		OffsetRect(&sizeBoxRect,
+			clientRect.right - (!isVisibleH ? width : 0),
+			clientRect.bottom - (!isVisibleV ? height : 0));
+
+		if (!isVisibleH || !isVisibleV)
+		{
+			HRGN sizeBoxRgn = CreateRectRgnIndirect(&sizeBoxRect);
+			OffsetRgn(sizeBoxRgn, windowRect.left, windowRect.top);
+			ExtSelectClipRgn(compatDc, sizeBoxRgn, RGN_OR);
+			DeleteObject(sizeBoxRgn);
+		}
+
+		CALL_ORIG_GDI(DrawFrameControl)(compatDc, &sizeBoxRect, DFC_SCROLL, DFCS_SCROLLSIZEGRIP);
+	}
+
 	void eraseBackground(HWND hwnd, HDC dc)
 	{
 		if (CompatGdi::beginGdiRendering())
@@ -59,6 +90,20 @@ namespace
 		}
 	}
 
+	bool isScrollBarVisible(HWND hwnd, LONG windowStyles, LONG sbStyle, LONG sbObjectId)
+	{
+		if (!(windowStyles & sbStyle))
+		{
+			return false;
+		}
+
+		SCROLLBARINFO sbi = {};
+		sbi.cbSize = sizeof(sbi);
+		GetScrollBarInfo(hwnd, sbObjectId, &sbi);
+
+		return !(sbi.rgstate[0] & (STATE_SYSTEM_INVISIBLE | STATE_SYSTEM_OFFSCREEN));
+	}
+
 	LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam)
 	{
 		if (HC_ACTION == nCode)
@@ -97,6 +142,8 @@ namespace
 			CALL_ORIG_GDI(BitBlt)(compatDc, 0, 0,
 				windowRect.right - windowRect.left, windowRect.bottom - windowRect.top, windowDc, 0, 0, SRCCOPY);
 
+			drawSizeBox(hwnd, compatDc, windowRect, clientRect);
+
 			CompatGdiDc::releaseDc(windowDc);
 		}