From a269b3e29535918a390f448829a3459e4853425b Mon Sep 17 00:00:00 2001
From: David Gow <david@ingeniumdigital.com>
Date: Wed, 9 Apr 2014 16:01:54 +0800
Subject: [PATCH] Zoom in and out with the mouse wheel.

Note that zoom-out is totally broken with half-precision,
so single-precision is the default. You can still see some artefacts
in single precision mode if you zoom in enough.

Zoom into the corner of a rectangle and then click on the corner an try to drag it.
Eventually you'll notice the reduced precision, and the rectangle will jump around.
---
 src/main.h     |  5 +++++
 src/real.h     |  4 ++--
 src/screen.cpp | 10 ++++++++++
 src/screen.h   |  2 ++
 src/view.cpp   | 24 ++++++++++++++++++++++++
 src/view.h     |  1 +
 6 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/src/main.h b/src/main.h
index c7d5eca..2346119 100644
--- a/src/main.h
+++ b/src/main.h
@@ -35,6 +35,11 @@ inline void MainLoop(Document & doc)
 		}
 		oldx = x;
 		oldy = y;
+		
+		if (wheel)
+		{
+			view.ScaleAroundPoint(Real(x)/Real(scr.ViewportWidth()),Real(y)/Real(scr.ViewportHeight()), expf(-wheel/20.f));
+		}
 	}
 	);
 	while (scr.PumpEvents())
diff --git a/src/real.h b/src/real.h
index a7f56be..5703671 100644
--- a/src/real.h
+++ b/src/real.h
@@ -6,9 +6,9 @@
 namespace IPDF
 {
 
-//#define REAL_FLOAT
+#define REAL_SINGLE
 //#define REAL_DOUBLE
-#define REAL_HALF
+//#define REAL_HALF
 
 #ifdef REAL_SINGLE
 	typedef float Real;
diff --git a/src/screen.cpp b/src/screen.cpp
index d924c06..9ee15b4 100644
--- a/src/screen.cpp
+++ b/src/screen.cpp
@@ -58,6 +58,8 @@ bool Screen::PumpEvents()
 			}
 			break;
 		case SDL_MOUSEMOTION:
+			m_last_mouse_x = evt.motion.x;
+			m_last_mouse_y = evt.motion.y;
 			if (m_mouse_handler)
 			{
 				m_mouse_handler(evt.motion.x, evt.motion.y,evt.motion.state, 0);
@@ -65,11 +67,19 @@ bool Screen::PumpEvents()
 			break;
 		case SDL_MOUSEBUTTONDOWN:
 		case SDL_MOUSEBUTTONUP:
+			m_last_mouse_x = evt.button.x;
+			m_last_mouse_y = evt.button.y;
 			if (m_mouse_handler)
 			{
 				m_mouse_handler(evt.button.x, evt.button.y, evt.button.state, 0);
 			}
 			break;
+		case SDL_MOUSEWHEEL:
+			if (m_mouse_handler)
+			{
+				m_mouse_handler(m_last_mouse_x, m_last_mouse_y, 0, evt.wheel.y);
+			}
+			break;
 		default:
 			break;
 		}
diff --git a/src/screen.h b/src/screen.h
index 8452efc..4d92cb3 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -47,6 +47,8 @@ namespace IPDF
 		void ResizeViewport(int width, int height);
 		
 		MouseHandler m_mouse_handler;
+		int m_last_mouse_x;
+		int m_last_mouse_y;
 
 		int m_viewport_width;
 		int m_viewport_height;
diff --git a/src/view.cpp b/src/view.cpp
index f78ec40..80f4986 100644
--- a/src/view.cpp
+++ b/src/view.cpp
@@ -7,10 +7,34 @@ using namespace std;
 
 void View::Translate(Real x, Real y)
 {
+	x *= m_bounds.w;
+	y *= m_bounds.h;
 	m_bounds.x += x;
 	m_bounds.y += y;
 }
 
+void View::ScaleAroundPoint(Real x, Real y, Real scaleAmt)
+{
+	// Convert to local coords.
+	x *= m_bounds.w;
+	y *= m_bounds.h;
+	x += m_bounds.x;
+	y += m_bounds.y;
+	
+	Debug("Mouse wheel event %f %f %f\n", Float(x), Float(y), Float(scaleAmt));
+	
+	Real top = y - m_bounds.y;
+	Real left = x - m_bounds.x;
+	
+	top *= scaleAmt;
+	left *= scaleAmt;
+	
+	m_bounds.x = x - left;
+	m_bounds.y = y - top;
+	m_bounds.w *= scaleAmt;
+	m_bounds.h *= scaleAmt;
+}
+
 void View::Render()
 {
 	static bool debug_output_done = false;
diff --git a/src/view.h b/src/view.h
index cc09a89..6b63799 100644
--- a/src/view.h
+++ b/src/view.h
@@ -15,6 +15,7 @@ namespace IPDF
 			void Render();
 			
 			void Translate(Real x, Real y);
+			void ScaleAroundPoint(Real x, Real y, Real scaleAmt);
 		
 		private:
 			Document & m_document;
-- 
2.20.1