From 357acfb941a8b5b4a6fb36e2134707d46e028d88 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 12 Jan 2014 14:14:31 +0200
Subject: [PATCH] Add viewport support to Framebuffer

---
 source/framebuffer.cpp | 39 ++++++++++++++++++++++++++++++++-------
 source/framebuffer.h   | 14 ++++++++++++++
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/source/framebuffer.cpp b/source/framebuffer.cpp
index 67249518..8c618ce5 100644
--- a/source/framebuffer.cpp
+++ b/source/framebuffer.cpp
@@ -55,10 +55,9 @@ Framebuffer::Framebuffer(unsigned i):
 	if(id)
 		throw invalid_argument("System framebuffer must have id 0");
 
-	int viewport[4];
-	glGetIntegerv(GL_VIEWPORT, viewport);
-	width = viewport[2];
-	height = viewport[3];
+	glGetIntegerv(GL_VIEWPORT, &view.left);
+	width = view.width;
+	height = view.height;
 }
 
 Framebuffer::Framebuffer():
@@ -133,6 +132,7 @@ void Framebuffer::update_attachment(unsigned mask) const
 
 void Framebuffer::check_size()
 {
+	bool full_viewport = (view.left==0 && view.bottom==0 && view.width==width && view.height==height);
 	for(vector<Attachment>::iterator i=attachments.begin(); i!=attachments.end(); ++i)
 		if(i->type)
 		{
@@ -152,8 +152,8 @@ void Framebuffer::check_size()
 				width = static_cast<TextureCube *>(i->tex)->get_size();
 				height = width;
 			}
-			if(current()==this)
-				glViewport(0, 0, width, height);
+			if(full_viewport)
+				reset_viewport();
 			break;
 		}
 }
@@ -224,6 +224,22 @@ void Framebuffer::require_complete() const
 		throw framebuffer_incomplete(status);
 }
 
+void Framebuffer::viewport(int l, int b, unsigned w, unsigned h)
+{
+	view.left = l;
+	view.bottom = b;
+	view.width = w;
+	view.height = h;
+
+	if(current()==this)
+		glViewport(view.left, view.bottom, view.width, view.height);
+}
+
+void Framebuffer::reset_viewport()
+{
+	viewport(0, 0, width, height);
+}
+
 void Framebuffer::clear(BufferBits bits)
 {
 	BindRestore _bind(this);
@@ -273,8 +289,9 @@ void Framebuffer::bind() const
 			update_attachment(dirty);
 			dirty = 0;
 		}
+
 		if(width && height)
-			glViewport(0, 0, width, height);
+			glViewport(view.left, view.bottom, view.width, view.height);
 	}
 }
 
@@ -323,5 +340,13 @@ void Framebuffer::Attachment::clear()
 	type = 0;
 }
 
+
+Framebuffer::Viewport::Viewport():
+	left(0),
+	bottom(0),
+	width(0),
+	height(0)
+{ }
+
 } // namespace GL
 } // namespace Msp
diff --git a/source/framebuffer.h b/source/framebuffer.h
index 3bf439f9..f34ecf5c 100644
--- a/source/framebuffer.h
+++ b/source/framebuffer.h
@@ -98,10 +98,21 @@ private:
 		void clear();
 	};
 
+	struct Viewport
+	{
+		int left;
+		int bottom;
+		unsigned width;
+		unsigned height;
+
+		Viewport();
+	};
+
 	unsigned id;
 	std::vector<Attachment> attachments;
 	unsigned width;
 	unsigned height;
+	Viewport view;
 	mutable unsigned dirty;
 
 	Framebuffer(unsigned);
@@ -131,6 +142,9 @@ public:
 	isn't. */
 	void require_complete() const;
 
+	void viewport(int, int, unsigned, unsigned);
+	void reset_viewport();
+
 	void clear(BufferBits);
 
 	/** Blits a region from another framebuffer into this one.  If the source
-- 
2.43.0