From 23aee3322744aa3c65de28c3ebe1509e291b8702 Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Sat, 12 Mar 2022 16:11:02 -0500
Subject: [PATCH] Only redraw changed tiles when right clicking.

By changing the definition of game_check_goal to return a bit-mask
of mismatched positions, we can just pass that to the redraw mask to
reduce the amount of rendering needed.
---
 src/game.c     | 11 +++++++----
 src/game.h     |  5 +++--
 src/motif_ui.c |  4 ++--
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/game.c b/src/game.c
index c478eef..bdd8f2b 100644
--- a/src/game.c
+++ b/src/game.c
@@ -199,13 +199,16 @@ int game_do_move(struct board *board, int x, int y)
 	return 0;
 }
 
-int game_check_goal(struct board *board)
+uint_fast32_t game_check_goal(struct board *board)
 {
-	int i, ret = 1;
+	uint_least32_t *game = board->game;
+	uint_least16_t *goal = board->goal;
+	uint_least32_t mask = 0;
+	int i;
 
 	for (i = 0; i < 3; i++)
-		ret &= ((board->game[i] & GOAL_MASK) >> 6) == board->goal[i];
-	return ret;
+		mask |= goal[i] ^ (game[i] >> GOAL_SHIFT);
+	return (mask << GOAL_SHIFT) & GOAL_MASK;
 }
 
 void game_begin(struct board *board)
diff --git a/src/game.h b/src/game.h
index 99b5133..a734e22 100644
--- a/src/game.h
+++ b/src/game.h
@@ -166,9 +166,10 @@ static inline uint_fast32_t board_right(int x)
 int game_do_move(struct board *board, int x, int y);
 
 /*
- * Returns 1 if the game is in a winning position, or 0 otherwise.
+ * Returns the board bitmap setting game locations that differ from the goal.
+ * A return value of 0 therefore indicates a winning position.
  */
-int game_check_goal(struct board *board);
+uint_fast32_t game_check_goal(struct board *board);
 
 /*
  * Initialize the game RNG such that the next call to game_reset will produce a
diff --git a/src/motif_ui.c b/src/motif_ui.c
index c31d839..dfe4e82 100644
--- a/src/motif_ui.c
+++ b/src/motif_ui.c
@@ -223,7 +223,7 @@ static void do_input_move(struct app_state *state, int x, int y)
 	if (game_do_move(&state->board, x, y) == 0) {
 		uint_least32_t mask;
 
-		if (game_check_goal(&state->board)) {
+		if (game_check_goal(&state->board) == 0) {
 			int_fast32_t ms = game_finish(&state->board);
 			unsigned min, sec;
 
@@ -251,7 +251,7 @@ static void do_input_move(struct app_state *state, int x, int y)
 static void set_view_goal(struct app_state *state, int view_goal)
 {
 	state->view_goal_on_game = view_goal;
-	x11_redraw_game(state, GOAL_MASK);
+	x11_redraw_game(state, game_check_goal(&state->board));
 }
 
 static void game_input(Widget w, void *data, void *cb_data)
-- 
2.43.2