"DPAD" expression operation

Adds a "DPAD" expression operation that takes four input states and
produces a 0-8 value that can be used as a d-pad (hat switch) output
on a gamepad.

Example use:

0x00070050 input_state_binary
0x0007004f input_state_binary
0x00070052 input_state_binary
0x00070051 input_state_binary
dpad

EXPRESSIONS.md

@@ -142,3 +142,4 @@ Here's a list of all operations that can be used in an expression. Each operatio
 | `tap_state` | _usage_ | _tap\_state(usage)_ | 1 if input is in tap state, 0 otherwise. |
 | `hold_state` | _usage_ | _hold\_state(usage)_ | 1 if input is in hold state, 0 otherwise. |
 | `port` | _port number_ | | Sets the value of the port register that determines which input state is fetched by `input_state` etc. Defaults to 0 at the beginning of each mapping engine iteration, which means "all ports". |
+| `dpad` | _left_state_, _right_state_, _up_state_, _down_state_ | d-pad output state | Takes four input states and produces a 0-8 value that can be used as a d-pad (hat switch) output on a gamepad. |

config-tool-web/code.js

@@ -87,6 +87,7 @@ const ops = {
     "ATAN2": 32,
     "ROUND": 33,
     "PORT": 34,
+    "DPAD": 35,
 }
 
 const opcodes = Object.fromEntries(Object.entries(ops).map(([key, value]) => [value, key]));

config-tool/common.py

@@ -93,6 +93,7 @@
     "ATAN2": 32,
     "ROUND": 33,
     "PORT": 34,
+    "DPAD": 35,
 }
 
 opcodes = {v: k for k, v in ops.items()}

firmware/src/remapper.cc

@@ -252,6 +252,12 @@ bool is_expr_valid(uint8_t expr) {
                 }
                 on_stack--;
                 break;
+            case Op::DPAD:
+                if (on_stack < 4) {
+                    return false;
+                }
+                on_stack -= 3;
+                break;
             default:
                 printf("unknown op in is_expr_valid()\n");
                 return false;
@@ -580,6 +586,13 @@ void aggregate_relative(uint8_t* prev_report, const uint8_t* report, uint8_t rep
     }
 }
 
+static uint8_t dpad_table[16] = { 8, 6, 2, 8, 0, 7, 1, 0, 4, 5, 3, 4, 8, 6, 2, 8 };
+
+static inline uint8_t dpad(bool left, bool right, bool up, bool down) {
+    uint8_t index = left | (right << 1) | (up << 2) | (down << 3);
+    return dpad_table[index];
+}
+
 int32_t eval_expr(uint8_t expr, uint64_t now, bool auto_repeat) {
     static int32_t stack[STACK_SIZE];
     bool debug = false;
@@ -749,6 +762,10 @@ int32_t eval_expr(uint8_t expr, uint64_t now, bool auto_repeat) {
                 }
                 ptr--;
                 break;
+            case Op::DPAD:
+                stack[ptr - 3] = 1000 * dpad(stack[ptr - 3], stack[ptr - 2], stack[ptr - 1], stack[ptr]);
+                ptr -= 3;
+                break;
             default:
                 printf("unknown op!\n");
                 return 0;

firmware/src/types.h

@@ -86,6 +86,7 @@ enum class Op : int8_t {
     ATAN2 = 32,
     ROUND = 33,
     PORT = 34,
+    DPAD = 35,
 };
 
 struct expr_elem_t {