Split and correct grid_see_grid.

There's now cell_see_cell which tests for visibility correctly,
albeit slowly. That's only used for placing features in the abyss
currently, but needs to be improved if it gets used more.

The second function used in monster movement was left as is, but
renamed to can_go_straight. This remains unreliable but probably
serves its purpose.

The grid_see_grid test is adapted to cell_see_cell; the
grid_see_grid lua binding is now actually useful.

Also reduce the number of tests in los_csc and los_symm.

1 files changed, 60 insertions, 0 deletions

diff --git a/crawl-ref/source/test/los_csc.lua b/crawl-ref/source/test/los_csc.lua
new file mode 100644
index 0000000000..499511a6c2
--- /dev/null
+++ b/crawl-ref/source/test/los_csc.lua
@@ -0,0 +1,60 @@
+-- Vet LOS for symmetry.
+
+local FAILMAP = 'losfail.map'
+local checks = 0
+
+local function test_cellseecell_symmetry()
+  -- Clear messages to prevent them accumulating and forcing a --more--
+  crawl.mesclr()
+  -- Send the player to a random spot on the level.
+  you.random_teleport()
+  you.losight()
+  crawl.redraw_view()
+
+  checks = checks + 1
+  local you_x, you_y = you.pos()
+
+  for y = -9, 9 do
+    for x = -9, 9 do
+      local px, py = x + you_x, y + you_y
+      if (x ~= 0 or y ~= 0) and dgn.in_bounds(px, py) then
+        local foreward = dgn.cell_see_cell(you_x, you_y, px, py)
+        local backward = dgn.cell_see_cell(px, py, you_x, you_y)
+        this_p = dgn.point(you_x, you_y)
+        other_p = dgn.point(px, py)
+        if not forward then
+          you.moveto(px, py)
+          local temp = this_p
+          this_p = other_p
+          other_p = temp
+        end
+        if (forward and backward) or (not forward and not backward) then
+          dgn.grid(other_p.x, other_p.y, "floor_special")
+          dgn.dbg_dump_map(FAILMAP)
+          assert(false,
+                 "cell_see_cell asymmetry detected (iter #" .. checks .. "): "
+                   .. this_p .. " sees " .. other_p .. ", but not vice versa."
+                   .. " Map saved to " .. FAILMAP)
+        end
+      end
+    end
+  end
+end
+
+local function run_los_tests(depth, nlevels, tests_per_level)
+  local place = "D:" .. depth
+  crawl.mpr("Running LOS tests on " .. place)
+  dgn.dbg_goto_place(place)
+
+  for lev_i = 1, nlevels do
+    dgn.dbg_flush_map_memory()
+    dgn.dbg_generate_level()
+    for t_i = 1, tests_per_level do
+      test_cellseecell_symmetry()
+    end
+  end
+end
+
+for depth = 1, 27 do
+  run_los_tests(depth, 1, 1)
+end