From a1e507ef1284812b6921110e4a635a8efb376a48 Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Mon, 24 Mar 2014 21:32:24 +0100
Subject: [PATCH] Clip texture before rendering.

---
 src/texture.cpp | 106 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 101 insertions(+), 5 deletions(-)

diff --git a/src/texture.cpp b/src/texture.cpp
index 43966c7..5d3379b 100644
--- a/src/texture.cpp
+++ b/src/texture.cpp
@@ -65,11 +65,48 @@ namespace cloonel {
 			GraphicFormat enumvalue;
 		};
 
+		struct RectFloat {
+			float2 from;
+			float2 to;
+
+			RectFloat ( void ) = default;
+			RectFloat ( const RectFloat& parOther ) :
+				from(parOther.from),
+				to(parOther.to)
+			{
+				assert(IsValid());
+			}
+
+			RectFloat ( const SDL_Rect& parRect ) :
+				from(static_cast<float>(parRect.x), static_cast<float>(parRect.y)),
+				to(static_cast<float>(parRect.x + parRect.w), static_cast<float>(parRect.y + parRect.h))
+			{
+				assert(IsValid());
+			}
+
+			RectFloat ( const float2& parFrom, const float2& parTo ) :
+				from(parFrom),
+				to(parTo)
+			{
+				assert(IsValid());
+			}
+
+			~RectFloat ( void ) noexcept = default;
+
+			operator SDL_Rect ( void ) const noexcept { return { static_cast<int>(from.x()), static_cast<int>(from.y()), static_cast<int>(Width()), static_cast<int>(Height()) }; }
+
+			float Width ( void ) const noexcept { return to.x() - from.x(); }
+			float Height ( void ) const noexcept { return to.y() - from.y(); }
+			float2 WidthHeight ( void ) const noexcept { return float2(Width(), Height()); }
+			bool IsValid ( void ) const noexcept { return from <= to; }
+		};
+
 		const GraphicFormatItem g_graphicFormatItems[] = {
 			{".png", 4, GraphicFormat_Png}
 		};
 
 		GraphicFormat GuessGraphicFormatFromName (const std::string& parPath) __attribute__((pure));
+		bool ClipRect ( RectFloat& parSrc, RectFloat& parDest, const RectFloat& parClip );
 
 		///----------------------------------------------------------------------
 		///----------------------------------------------------------------------
@@ -210,6 +247,47 @@ namespace cloonel {
 
 			return retSurf;
 		}
+
+		///----------------------------------------------------------------------
+		///Adjustes parSrc and parDest so that parDest will fit into parClip and
+		///parSrc to be the relevant part of the source texture to be drawn.
+		///Returns true if such operation was possible and parSrc and parDest
+		///got set to a valid value, otherwise false.
+		///----------------------------------------------------------------------
+		bool ClipRect (RectFloat& parSrc, RectFloat& parDest, const RectFloat& parClip) {
+			assert(parSrc.IsValid());
+			assert(parDest.IsValid());
+
+			//If the dest rect is completely out of the clipping region, there
+			//is nothing to do at all.
+			if (parDest.to <= parClip.from or parDest.from >= parClip.to)
+				return false;
+
+			{
+				const RectFloat clip(float2(0.0f), float2(1.0f));
+				const float2 srcWidthHeight(parSrc.WidthHeight());
+				const float2 scaledOffs((parDest.from - parClip.from) / parClip.WidthHeight());
+				parSrc.from -= float2(std::min(0.0f, scaledOffs.x() * srcWidthHeight.x()), std::min(0.0f, scaledOffs.y() * srcWidthHeight.y()));
+				const float2 scaledCrop((parClip.to - parDest.to) / parClip.WidthHeight());
+				parSrc.to += float2(std::min(0.0f, scaledCrop.x() * srcWidthHeight.x()), std::min(0.0f, scaledCrop.y() * srcWidthHeight.y()));
+				assert(parSrc.IsValid());
+			}
+
+			RectFloat dst(parDest.from - parClip.from, parDest.to - parClip.from);
+			dst.from.x() = std::max(dst.from.x(), parClip.from.x());
+			dst.from.y() = std::max(dst.from.y(), parClip.from.y());
+			dst.to.x() = std::min(dst.to.x(), parClip.to.x());
+			dst.to.y() = std::min(dst.to.y(), parClip.to.y());
+
+			if (not dst.IsValid())
+				return false;
+
+			parDest.from += parClip.from;
+			parDest.to += parClip.from;
+
+			assert(parDest.IsValid());
+			return true;
+		}
 	} //unnamed namespace
 
 	///--------------------------------------------------------------------------
@@ -271,10 +349,28 @@ namespace cloonel {
 	///--------------------------------------------------------------------------
 	void Texture::Render (const float2& parPos, const float2& parSize, const float2& parScaling) const {
 		assert(IsLoaded());
-		const ushort2 pos(static_cast<ushort2>(parPos * parScaling + 0.5f));
-		const ushort2 siz(static_cast<ushort2>(parSize * parScaling + 0.5f));
-		const int screenHeight = m_sdlmain->WidthHeight().y();
-		const SDL_Rect dest = { pos.x(), screenHeight - pos.y() - siz.y(), siz.x(), siz.y() };
-		SDL_RenderCopy(m_sdlmain->GetRenderer(), m_texture, nullptr, &dest);
+
+		const float2 pos(parPos * parScaling);
+		const float2 siz(parSize * parScaling);
+		RectFloat dest(pos, pos + siz);
+		RectFloat src(float2(0.0f), m_size);
+
+		const RectFloat clip(float2(0.0f), static_cast<float2>(m_sdlmain->WidthHeight()));
+		const bool visible = ClipRect(src, dest, clip);
+		if (not visible)
+			return;
+
+		const SDL_Rect sdlsrc(src);
+		//std::cout << "src = " << src.from << " - " << src.to << ", size is " << m_size << "\n";
+		SDL_Rect sdldst(dest);
+		sdldst.y = m_sdlmain->WidthHeight().y() - sdldst.y - sdldst.h;
+
+		//By here everything is nice and clean
+		assert(sdlsrc.x >= 0 and sdlsrc.y >= 0);
+		assert(sdlsrc.w >= 0 and sdlsrc.w <= static_cast<int>(m_size.x()));
+		assert(sdlsrc.h >= 0 and sdlsrc.h <= static_cast<int>(m_size.y()));
+		assert(sdlsrc.x + sdlsrc.w <= m_sdlmain->WidthHeight().x());
+		assert(sdlsrc.y + sdlsrc.h <= m_sdlmain->WidthHeight().y());
+		SDL_RenderCopy(m_sdlmain->GetRenderer(), m_texture, &sdlsrc, &sdldst);
 	}
 } //namespace cloonel