Exposed exaggeration factor when rendering heightmap.

Added checkbox to select whether to run autoleveled program or not.
Heightmap can handle non integer from_x and to_x.

heightmap_test.cpp

@@ -23,4 +23,27 @@ TEST(heightmap, get_z_at) {
 
     z = grid.get_z_at(1, 0.5f);
     EXPECT_EQ(2, z);
+}
+
+TEST(heightmap, get_z_at_non_zero_origin) {
+    auto grid = grbl::heightmap::from_params(0 - 0.123, 0 + 0.234, 1 - 0.123, 1 + 0.234, 1);
+    grid.vertices[0].z = 0;
+    grid.vertices[1].z = 1;
+    grid.vertices[2].z = 2;
+    grid.vertices[3].z = 3;
+
+    auto z = grid.get_z_at(0.5f - 0.123f, 0.5f + 0.234f);
+    EXPECT_EQ(true, grbl::float_equal(1.5, z));
+
+    z = grid.get_z_at(0.5f - 0.123f, 0 + 0.234f);
+    EXPECT_EQ(true, grbl::float_equal(0.5, z));
+
+    z = grid.get_z_at(0.5f - 0.123f, 1 + 0.234f);
+    EXPECT_EQ(true, grbl::float_equal(2.5, z));
+
+    z = grid.get_z_at(0 - 0.123f, 0.5f + 0.234f);
+    EXPECT_EQ(true, grbl::float_equal(1, z));
+
+    z = grid.get_z_at(1 - 0.123f, 0.5f + 0.234f);
+    EXPECT_EQ(true, grbl::float_equal(2, z));
 }