Expose the NO_EFFECT/UNUSED distinction through midend_process_key()

This removed the "handled" pointer and instead extends the existing
boolean return value (quit or don't quit) into an enumeration.  One of
the values still quits the program, but now there are different values
for keys that had an effect, had no effect, and are not used by the
puzzle at all.  The mapping from interpret_move results to process_key
results is roughly:

move string    -> PKR_SOME_EFFECT
MOVE_UI_UPDATE -> PKR_SOME_EFFECT
MOVE_NO_EFFECT -> PKR_NO_EFFECT
MOVE_UNUSED    -> PKR_UNUSED

The mid-end can also generate results internally, and is the only place
that PKR_QUIT can arise.

For compatibility, PKR_QUIT is zero, so anything expecting a false
return value to mean quit will be unsurprised.  The other values are
ordered so that lower values indicate a greater amount of handling of
the key.

1 files changed, 16 insertions, 9 deletions

diff --git a/emcc.c b/emcc.c
index 60ef8c8..7d7a09b 100644
--- a/emcc.c
+++ b/emcc.c
@@ -295,7 +295,7 @@ bool mousedown(int x, int y, int button)
 
     button = (button == 0 ? LEFT_BUTTON :
               button == 1 ? MIDDLE_BUTTON : RIGHT_BUTTON);
-    midend_process_key(me, x, y, button, &handled);
+    handled = midend_process_key(me, x, y, button) != PKR_UNUSED;
     post_move();
     return handled;
 }
@@ -306,7 +306,7 @@ bool mouseup(int x, int y, int button)
 
     button = (button == 0 ? LEFT_RELEASE :
               button == 1 ? MIDDLE_RELEASE : RIGHT_RELEASE);
-    midend_process_key(me, x, y, button, &handled);
+    handled = midend_process_key(me, x, y, button) != PKR_UNUSED;
     post_move();
     return handled;
 }
@@ -317,7 +317,7 @@ bool mousemove(int x, int y, int buttons)
                   buttons & 4 ? RIGHT_DRAG : LEFT_DRAG);
     bool handled;
 
-    midend_process_key(me, x, y, button, &handled);
+    handled = midend_process_key(me, x, y, button) != PKR_UNUSED;
     post_move();
     return handled;
 }
@@ -335,7 +335,7 @@ bool key(int keycode, const char *key, const char *chr, int location,
     #define DOM_KEY_LOCATION_RIGHT    2
     #define DOM_KEY_LOCATION_NUMPAD   3
     int keyevent = -1;
-    bool handled;
+    int process_key_result;
 
     if (!strnullcmp(key, "Backspace") || !strnullcmp(key, "Delete") ||
         !strnullcmp(key, "Del"))
@@ -422,9 +422,16 @@ bool key(int keycode, const char *key, const char *chr, int location,
         if (ctrl) keyevent |= MOD_CTRL;
         if (location == DOM_KEY_LOCATION_NUMPAD) keyevent |= MOD_NUM_KEYPAD;
 
-        midend_process_key(me, 0, 0, keyevent, &handled);
+        process_key_result = midend_process_key(me, 0, 0, keyevent);
         post_move();
-        return handled;
+        /*
+         * Treat Backspace specially because that's expected on KaiOS.
+         * https://developer.kaiostech.com/docs/design-guide/key
+         */
+        if (process_key_result == PKR_NO_EFFECT &&
+            !strnullcmp(key, "Backspace"))
+            return false;
+        return process_key_result != PKR_UNUSED;
     }
     return false; /* Event not handled, because we don't even recognise it. */
 }
@@ -839,7 +846,7 @@ void command(int n)
         post_move();
         break;
       case 5:                          /* New Game */
-        midend_process_key(me, 0, 0, UI_NEWGAME, NULL);
+        midend_process_key(me, 0, 0, UI_NEWGAME);
         post_move();
         js_focus_canvas();
         break;
@@ -849,12 +856,12 @@ void command(int n)
         js_focus_canvas();
         break;
       case 7:                          /* Undo */
-        midend_process_key(me, 0, 0, UI_UNDO, NULL);
+        midend_process_key(me, 0, 0, UI_UNDO);
         post_move();
         js_focus_canvas();
         break;
       case 8:                          /* Redo */
-        midend_process_key(me, 0, 0, UI_REDO, NULL);
+        midend_process_key(me, 0, 0, UI_REDO);
         post_move();
         js_focus_canvas();
         break;