A rewrite of losight() to allow future generalization.

Parameters relevant to the LOS calculation are now passed as
an object los_param that takes care of coordinate translation,
bounds checking, opacity of cells and what is written to the
output array.

A check for in_bounds was changed to map_bounds for simlicity;
this should not have any effect.

Special casing for arena was removed from losight; instead
calc_show_los now calls the new losight_permissive.

1 files changed, 76 insertions, 0 deletions

diff --git a/crawl-ref/source/losparam.h b/crawl-ref/source/losparam.h
new file mode 100644
index 0000000000..a31fbb46f5
--- /dev/null
+++ b/crawl-ref/source/losparam.h
@@ -0,0 +1,76 @@
+/*
+ *  File:       losparam.h
+ *  Summary:    Parameters for the LOS algorithm
+ */
+
+#ifndef LOSPARAM_H
+#define LOSPARAM_H
+
+enum opacity_type
+{
+    OPC_CLEAR,
+    OPC_HALF,    // for opaque clouds; two or more block
+    OPC_OPAQUE,
+     
+    NUM_OPACITIES
+};
+
+// Subclasses of this are passed to losight() to modify the
+// LOS calculation. Implementations will have to translate between
+// relative coordinates (-8,-8)..(8,8) and real coordinates,
+// specify how opaque the cells are and determine what values
+// are written to the visible cells.
+struct los_param
+{
+    virtual ~los_param() {}
+
+    // Whether the translated coordinate lies in the map (including boundary)
+    virtual bool map_bounds(const coord_def& p) const = 0;
+
+    // appearance(p) will be copied to show(p) for visible p.
+    virtual unsigned appearance(const coord_def& p) const = 0;
+
+    virtual opacity_type opacity(const coord_def& p) const = 0;
+};
+
+// Provides translation to given center and bounds checking.
+struct los_param_trans : los_param
+{
+    coord_def center;
+
+    los_param_trans(const coord_def& c);
+
+    coord_def trans(const coord_def& p) const;
+
+    bool map_bounds(const coord_def& p) const;
+};
+
+// A complete base implementation that does standard visibility
+// based on env.grid.
+struct los_param_base : los_param_trans
+{
+    los_param_base(const coord_def& c);
+
+    dungeon_feature_type feature(const coord_def& p) const;
+    unsigned appearance(const coord_def& p) const;
+    unsigned short cloud_idx(const coord_def& p) const;
+    opacity_type opacity(const coord_def& p) const;
+};
+
+// Provides a compatible set of parameters for use with the
+// legacy losight() function.
+struct los_param_compat : los_param_base
+{
+    feature_grid grid;
+    bool solid_blocks;
+    bool ignore_clouds;
+
+    los_param_compat(const feature_grid& gr, const coord_def& c,
+                     bool sb, bool ic);
+
+    dungeon_feature_type feature(const coord_def& p) const;
+    unsigned appearance(const coord_def& p) const;
+    opacity_type opacity(const coord_def& p) const;
+};
+
+#endif