From f864f31f8ef206a363d0dac43558d42c5db46baa Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sat, 10 Dec 2016 12:42:20 +0100
Subject: Enable offset world drawing; center in viewport

---
 life.cc     | 32 ++++++++++++++++++++------------
 src/world.h | 14 ++++++++++++--
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/life.cc b/life.cc
index 6d98a08..d76055b 100644
--- a/life.cc
+++ b/life.cc
@@ -19,21 +19,25 @@ template<
 	std::size_t WIDTH,
 	std::size_t HEIGHT
 >
-void draw(life::World<WIDTH, HEIGHT>& world) {
+void draw(
+	std::size_t x,
+	std::size_t y,
+	life::World<WIDTH, HEIGHT>& world
+) {
 	tb_clear();
 
 	for ( std::size_t i = 0; i < HEIGHT; i++ ) {
 		for ( std::size_t j = 0; j < WIDTH; j++ ) {
 			if ( world.isLifeAt(i,j) ) {
-				tb_change_cell(i, j, 0x2588, TB_BLACK, TB_GREEN);
+				tb_change_cell(x+i, y+j, 0x2588, TB_BLACK, TB_GREEN);
 			} else {
-				tb_change_cell(i, j, 0x2591, TB_BLACK, TB_BLUE);
+				tb_change_cell(x+i, y+j, 0x2591, TB_BLACK, TB_BLUE);
 			}
 		}
 	}
 
-	print_tb(1, 21, TB_WHITE, TB_DEFAULT, "Age:");
-	print_tb(6, 21, TB_WHITE, TB_DEFAULT, std::to_string(world.getAge()));
+	print_tb(x+1, y+21, TB_WHITE, TB_DEFAULT, "Age:");
+	print_tb(x+6, y+21, TB_WHITE, TB_DEFAULT, std::to_string(world.getAge()));
 
 	tb_present();
 }
@@ -42,11 +46,14 @@ int main(int, char*[]) {
 	tb_init();
 
 	tb_select_output_mode(TB_OUTPUT_NORMAL);
-	tb_select_input_mode(TB_INPUT_ESC | TB_INPUT_MOUSE);	
+	tb_select_input_mode(TB_INPUT_ESC | TB_INPUT_MOUSE);
 
 	life::World<20,20> world;
 
-	draw(world);
+	std::size_t worldOffsetX = tb_width()  / 2 - 10;
+	std::size_t worldOffsetY = tb_height() / 2 - 10;
+
+	draw(worldOffsetX, worldOffsetY, world);
 
 	while ( true ) {
 		struct tb_event ev;
@@ -57,7 +64,7 @@ int main(int, char*[]) {
 			return -1;
 		}
 
-		switch (t) {
+		switch ( t ) {
 			case TB_EVENT_KEY:
 				switch ( ev.key ) {
 					case TB_KEY_ESC:
@@ -69,16 +76,17 @@ int main(int, char*[]) {
 				}
 				break;
 			case TB_EVENT_MOUSE:
-				if (ev.key == TB_KEY_MOUSE_LEFT) {
-					world.summonLifeAt(ev.x, ev.y);
+				if ( ev.key == TB_KEY_MOUSE_LEFT ) {
+					world.summonLifeAt(ev.x - worldOffsetX, ev.y - worldOffsetY);
 				}
-
 				break;
 			case TB_EVENT_RESIZE:
+				worldOffsetX = ev.w / 2 - 10;
+				worldOffsetY = ev.h / 2 - 10;
 				break;
 		}
 
-		draw(world);
+		draw(worldOffsetX, worldOffsetY, world);
 	}
 
 	return 0;
diff --git a/src/world.h b/src/world.h
index d951cf5..72cc32f 100644
--- a/src/world.h
+++ b/src/world.h
@@ -69,11 +69,21 @@ class World {
 		}
 
 		void summonLifeAt(std::size_t x, std::size_t y) {
-			this->matrix_[y][x] = true;
+			if ( x >= 0      &&
+			     x <  WIDTH  &&
+			     y >= 0      &&
+			     y <  HEIGHT ) {
+				this->matrix_[y][x] = true;
+			}
 		}
 
 		void extinguishLifeAt(std::size_t x, std::size_t y) {
-			this->matrix_[y][x] = false;
+			if ( x >= 0      &&
+			     x <  WIDTH  &&
+			     y >= 0      &&
+			     y <  HEIGHT ) {
+				this->matrix_[y][x] = false;
+			}
 		}
 
 		void tick() {
-- 
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