DDrawCompat/DDrawCompat/CompatGdiDc.cpp

#include <algorithm>
#include <unordered_map>

#include "CompatGdiDc.h"
#include "CompatGdiDcCache.h"
#include "DDrawLog.h"

namespace
{
	using CompatGdiDcCache::CachedDc;

	struct CompatDc : CachedDc
	{
		CompatDc(const CachedDc& cachedDc = {}) : CachedDc(cachedDc) {}
		DWORD refCount;
		HDC origDc;
		HGDIOBJ origFont;
		HGDIOBJ origBrush;
		HGDIOBJ origPen;
	};

	typedef std::unordered_map<HDC, CompatDc> CompatDcMap;
	CompatDcMap g_origDcToCompatDc;

	struct ExcludeClipRectsData
	{
		HDC compatDc;
		POINT origin;
		HWND rootWnd;
	};

	void copyDcAttributes(CompatDc& compatDc, HDC origDc, POINT& origin)
	{
		compatDc.origFont = SelectObject(compatDc.dc, GetCurrentObject(origDc, OBJ_FONT));
		compatDc.origBrush = SelectObject(compatDc.dc, GetCurrentObject(origDc, OBJ_BRUSH));
		compatDc.origPen = SelectObject(compatDc.dc, GetCurrentObject(origDc, OBJ_PEN));

		SetArcDirection(compatDc.dc, GetArcDirection(origDc));
		SetBkColor(compatDc.dc, GetBkColor(origDc));
		SetBkMode(compatDc.dc, GetBkMode(origDc));
		SetDCBrushColor(compatDc.dc, GetDCBrushColor(origDc));
		SetDCPenColor(compatDc.dc, GetDCPenColor(origDc));
		SetPolyFillMode(compatDc.dc, GetPolyFillMode(origDc));
		SetROP2(compatDc.dc, GetROP2(origDc));
		SetStretchBltMode(compatDc.dc, GetStretchBltMode(origDc));
		SetTextAlign(compatDc.dc, GetTextAlign(origDc));
		SetTextCharacterExtra(compatDc.dc, GetTextCharacterExtra(origDc));
		SetTextColor(compatDc.dc, GetTextColor(origDc));
		SetWindowOrgEx(compatDc.dc, -origin.x, -origin.y, nullptr);

		POINT brushOrg = {};
		GetBrushOrgEx(origDc, &brushOrg);
		SetBrushOrgEx(compatDc.dc, brushOrg.x, brushOrg.y, nullptr);

		POINT currentPos = {};
		MoveToEx(origDc, 0, 0, &currentPos);
		MoveToEx(origDc, currentPos.x, currentPos.y, nullptr);
		MoveToEx(compatDc.dc, currentPos.x, currentPos.y, nullptr);
	}

	BOOL CALLBACK excludeClipRectsForOverlappingWindows(HWND hwnd, LPARAM lParam)
	{
		auto excludeClipRectsData = reinterpret_cast<ExcludeClipRectsData*>(lParam);
		if (hwnd == excludeClipRectsData->rootWnd)
		{
			return FALSE;
		}

		if (!IsWindowVisible(hwnd))
		{
			return TRUE;
		}

		RECT rect = {};
		GetWindowRect(hwnd, &rect);
		OffsetRect(&rect, -excludeClipRectsData->origin.x, -excludeClipRectsData->origin.y);
		ExcludeClipRect(excludeClipRectsData->compatDc, rect.left, rect.top, rect.right, rect.bottom);
		return TRUE;
	}

	void setClippingRegion(HDC compatDc, HDC origDc, POINT& origin)
	{
		HRGN clipRgn = CreateRectRgn(0, 0, 0, 0);
		const bool isEmptyClipRgn = 1 != GetRandomRgn(origDc, clipRgn, SYSRGN);
		SelectClipRgn(compatDc, isEmptyClipRgn ? nullptr : clipRgn);
		DeleteObject(clipRgn);

		HRGN origClipRgn = CreateRectRgn(0, 0, 0, 0);
		if (1 == GetClipRgn(origDc, origClipRgn))
		{
			OffsetRgn(origClipRgn, origin.x, origin.y);
			ExtSelectClipRgn(compatDc, origClipRgn, RGN_AND);
		}
		DeleteObject(origClipRgn);

		if (!isEmptyClipRgn)
		{
			HWND hwnd = WindowFromDC(origDc);
			if (hwnd)
			{
				ExcludeClipRectsData excludeClipRectsData = { compatDc, origin, GetAncestor(hwnd, GA_ROOT) };
				EnumWindows(&excludeClipRectsForOverlappingWindows,
					reinterpret_cast<LPARAM>(&excludeClipRectsData));
			}
		}
	}
}

namespace CompatGdiDc
{
	HDC getDc(HDC origDc)
	{
		if (!origDc || OBJ_DC != GetObjectType(origDc) || DT_RASDISPLAY != GetDeviceCaps(origDc, TECHNOLOGY) ||
			g_origDcToCompatDc.end() != std::find_if(g_origDcToCompatDc.begin(), g_origDcToCompatDc.end(),
				[=](const CompatDcMap::value_type& compatDc) { return compatDc.second.dc == origDc; }))
		{
			return nullptr;
		}

		auto it = g_origDcToCompatDc.find(origDc);
		if (it != g_origDcToCompatDc.end())
		{
			++it->second.refCount;
			return it->second.dc;
		}

		CompatDc compatDc(CompatGdiDcCache::getDc());
		if (!compatDc.dc)
		{
			return nullptr;
		}

		POINT origin = {};
		GetDCOrgEx(origDc, &origin);

		copyDcAttributes(compatDc, origDc, origin);
		setClippingRegion(compatDc.dc, origDc, origin);

		compatDc.refCount = 1;
		compatDc.origDc = origDc;
		g_origDcToCompatDc.insert(CompatDcMap::value_type(origDc, compatDc));

		return compatDc.dc;
	}

	void releaseDc(HDC origDc)
	{
		auto it = g_origDcToCompatDc.find(origDc);
		if (it == g_origDcToCompatDc.end())
		{
			return;
		}
		
		CompatDc& compatDc = it->second;
		--compatDc.refCount;
		if (0 == compatDc.refCount)
		{
			SelectObject(compatDc.dc, compatDc.origFont);
			SelectObject(compatDc.dc, compatDc.origBrush);
			SelectObject(compatDc.dc, compatDc.origPen);
			CompatGdiDcCache::releaseDc(compatDc);
			g_origDcToCompatDc.erase(origDc);
		}
	}
}