From e6c66a8e58f1dda071e6fc4abed39afe49d348f8 Mon Sep 17 00:00:00 2001
From: David Gow <david@ingeniumdigital.com>
Date: Wed, 9 Apr 2014 14:40:43 +0800
Subject: [PATCH] You can move around a document with Click+Drag!

Uses some scary C++11 features, so no idea if this will break the CS Lab machines
and their ancient version of gcc.
---
 src/main.h     | 25 +++++++++++++++++++++++++
 src/screen.cpp | 32 ++++++++++++++++++++++++++++++++
 src/screen.h   | 22 ++++++++++++++++++++++
 src/view.cpp   |  6 ++++++
 src/view.h     |  2 ++
 5 files changed, 87 insertions(+)

diff --git a/src/main.h b/src/main.h
index ee8076a..c7d5eca 100644
--- a/src/main.h
+++ b/src/main.h
@@ -12,6 +12,31 @@ inline void MainLoop(Document & doc)
 {
 	View view(doc);
 	Screen scr;
+	scr.SetMouseHandler([&](int x, int y, int buttons, int wheel)
+	{
+		static bool oldButtonDown = false;
+		static int oldx, oldy;
+		if (buttons && !oldButtonDown)
+		{
+			// We're beginning a drag.
+			oldButtonDown = true;
+			oldx = x;
+			oldy = y;
+			scr.SetMouseCursor(Screen::CursorMove);
+		}
+		if (buttons)
+		{
+			view.Translate(Real(oldx-x)/Real(scr.ViewportWidth()), Real(oldy-y)/Real(scr.ViewportHeight()));
+		}
+		else
+		{
+			oldButtonDown = false;
+			scr.SetMouseCursor(Screen::CursorArrow);
+		}
+		oldx = x;
+		oldy = y;
+	}
+	);
 	while (scr.PumpEvents())
 	{
 		view.Render();
diff --git a/src/screen.cpp b/src/screen.cpp
index 6909be2..d924c06 100644
--- a/src/screen.cpp
+++ b/src/screen.cpp
@@ -18,6 +18,8 @@ Screen::Screen()
 	}
 
 	m_gl_context = SDL_GL_CreateContext(m_window);
+	
+	ResizeViewport(800, 600);
 
 }
 
@@ -55,6 +57,19 @@ bool Screen::PumpEvents()
 				break;
 			}
 			break;
+		case SDL_MOUSEMOTION:
+			if (m_mouse_handler)
+			{
+				m_mouse_handler(evt.motion.x, evt.motion.y,evt.motion.state, 0);
+			}
+			break;
+		case SDL_MOUSEBUTTONDOWN:
+		case SDL_MOUSEBUTTONUP:
+			if (m_mouse_handler)
+			{
+				m_mouse_handler(evt.button.x, evt.button.y, evt.button.state, 0);
+			}
+			break;
 		default:
 			break;
 		}
@@ -62,6 +77,23 @@ bool Screen::PumpEvents()
 	return no_quit_requested;
 }
 
+void Screen::SetMouseCursor(Screen::MouseCursors cursor)
+{
+	SDL_SystemCursor system_cursor_id = SDL_SYSTEM_CURSOR_ARROW;
+	switch (cursor)
+	{
+	case CursorArrow: system_cursor_id = SDL_SYSTEM_CURSOR_ARROW; break;
+	case CursorWait: system_cursor_id = SDL_SYSTEM_CURSOR_WAIT; break;
+	case CursorWaitArrow: system_cursor_id = SDL_SYSTEM_CURSOR_WAITARROW; break;
+	case CursorMove: system_cursor_id = SDL_SYSTEM_CURSOR_SIZEALL; break;
+	case CursorHand: system_cursor_id = SDL_SYSTEM_CURSOR_HAND; break;
+	default: break;
+	}
+	SDL_Cursor *system_cursor = SDL_CreateSystemCursor(system_cursor_id);
+	SDL_SetCursor(system_cursor);
+	//TODO: Check if we need to free the system cursors.
+}
+
 void Screen::Present()
 {
 	SDL_GL_SwapWindow(m_window);
diff --git a/src/screen.h b/src/screen.h
index ebe9da2..8452efc 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -3,6 +3,8 @@
 
 #include <SDL.h>
 
+#include <functional>
+
 namespace IPDF
 {
 	/*
@@ -24,14 +26,34 @@ namespace IPDF
 		// Get the current width/height of the window's viewport.
 		int ViewportWidth() { return m_viewport_width; }
 		int ViewportHeight() { return m_viewport_height; }
+		
+		// Handle mouse input.
+		typedef std::function<void(int x, int y, int button, int wheel)> MouseHandler;
+		void SetMouseHandler(MouseHandler handler)
+		{
+			m_mouse_handler = handler;
+		}
+		
+		enum MouseCursors
+		{
+			CursorArrow,
+			CursorWait,
+			CursorWaitArrow,
+			CursorMove,
+			CursorHand
+		};
+		void SetMouseCursor(MouseCursors cursor);
 	private:
 		void ResizeViewport(int width, int height);
+		
+		MouseHandler m_mouse_handler;
 
 		int m_viewport_width;
 		int m_viewport_height;
 		SDL_Window *m_window;
 		SDL_GLContext m_gl_context;
 	};
+
 }
 
 #endif // _SCREEN_H
diff --git a/src/view.cpp b/src/view.cpp
index ed62704..f78ec40 100644
--- a/src/view.cpp
+++ b/src/view.cpp
@@ -5,6 +5,12 @@
 using namespace IPDF;
 using namespace std;
 
+void View::Translate(Real x, Real y)
+{
+	m_bounds.x += x;
+	m_bounds.y += y;
+}
+
 void View::Render()
 {
 	static bool debug_output_done = false;
diff --git a/src/view.h b/src/view.h
index 9a519b0..cc09a89 100644
--- a/src/view.h
+++ b/src/view.h
@@ -13,6 +13,8 @@ namespace IPDF
 			virtual ~View() {}
 
 			void Render();
+			
+			void Translate(Real x, Real y);
 		
 		private:
 			Document & m_document;
-- 
2.20.1