1 files changed, 38 insertions, 0 deletions
diff --git a/source/rendering/StarWorldCamera.cpp b/source/rendering/StarWorldCamera.cpp
new file mode 100644
index 0000000..0344bd6
--- /dev/null
+++ b/source/rendering/StarWorldCamera.cpp
@@ -0,0 +1,38 @@
+#include "StarWorldCamera.hpp"
+
+namespace Star {
+
+void WorldCamera::setCenterWorldPosition(Vec2F const& position) {
+  // Only actually move the world center if a half pixel distance has been
+  // moved in any direction.  This is sort of arbitrary, but helps prevent
+  // judder if the camera is at a boundary and floating point inaccuracy is
+  // causing the focus to jitter back and forth across the boundary.
+  if (fabs(position[0] - m_worldCenter[0]) < 1.0f / (TilePixels * m_pixelRatio * 2) && fabs(position[1] - m_worldCenter[1]) < 1.0f / (TilePixels * m_pixelRatio * 2))
+    return;
+
+  // First, make sure the camera center position is inside the main x
+  // coordinate bounds, and that the top and bototm of the screen are not
+  // outside of the y coordinate bounds.
+  m_worldCenter = m_worldGeometry.xwrap(position);
+  m_worldCenter[1] = clamp(m_worldCenter[1],
+      (float)m_screenSize[1] / (TilePixels * m_pixelRatio * 2),
+      m_worldGeometry.height() - (float)m_screenSize[1] / (TilePixels * m_pixelRatio * 2));
+
+  // Then, position the camera center position so that the tile grid is as
+  // close as possible aligned to whole pixel boundaries.  This is incredibly
+  // important, because this means that even without any complicated rounding,
+  // elements drawn in world space that are aligned with TilePixels will
+  // eventually also be aligned to real screen pixels.
+
+  if (m_screenSize[0] % 2 == 0)
+    m_worldCenter[0] = round(m_worldCenter[0] * (TilePixels * m_pixelRatio)) / (TilePixels * m_pixelRatio);
+  else
+    m_worldCenter[0] = (round(m_worldCenter[0] * (TilePixels * m_pixelRatio) + 0.5f) - 0.5f) / (TilePixels * m_pixelRatio);
+
+  if (m_screenSize[1] % 2 == 0)
+    m_worldCenter[1] = round(m_worldCenter[1] * (TilePixels * m_pixelRatio)) / (TilePixels * m_pixelRatio);
+  else
+    m_worldCenter[1] = (round(m_worldCenter[1] * (TilePixels * m_pixelRatio) + 0.5f) - 0.5f) / (TilePixels * m_pixelRatio);
+}
+
+}