New name UI_UPDATE for interpret_move's return "".

Now midend.c directly tests the returned pointer for equality to this
value, instead of checking whether it's the empty string.

A minor effect of this is that games may now return a dynamically
allocated empty string from interpret_move() and treat it as just
another legal move description. But I don't expect anyone to be
perverse enough to actually do that! The main purpose is that it
avoids returning a string literal from a function whose return type is
a pointer to _non-const_ char, i.e. we are now one step closer to
being able to make this code base clean under -Wwrite-strings.

1 files changed, 8 insertions, 8 deletions

diff --git a/galaxies.c b/galaxies.c
index f4f75c6..03bed9c 100644
--- a/galaxies.c
+++ b/galaxies.c
@@ -2553,13 +2553,13 @@ static char *interpret_move(const game_state *state, game_ui *ui,
             ui->dy = y;
             ui->dotx = dot->x;
             ui->doty = dot->y;
-            return "";
+            return UI_UPDATE;
         }
     } else if (button == RIGHT_DRAG && ui->dragging) {
         /* just move the drag coords. */
         ui->dx = x;
         ui->dy = y;
-        return "";
+        return UI_UPDATE;
     } else if (button == RIGHT_RELEASE && ui->dragging) {
         ui->dragging = FALSE;
 
@@ -2574,7 +2574,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
 	 * is a null move; just update the ui and finish.
 	 */
 	if (px == ui->srcx && py == ui->srcy)
-	    return "";
+	    return UI_UPDATE;
 
 	/*
 	 * Otherwise, we remove the arrow from its starting
@@ -2601,7 +2601,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
 	if (buf[0])
 	    return dupstr(buf);
 	else
-	    return "";
+	    return UI_UPDATE;
     } else if (IS_CURSOR_MOVE(button)) {
         move_cursor(button, &ui->cur_x, &ui->cur_y, state->sx-1, state->sy-1, 0);
         if (ui->cur_x < 1) ui->cur_x = 1;
@@ -2611,11 +2611,11 @@ static char *interpret_move(const game_state *state, game_ui *ui,
             ui->dx = SCOORD(ui->cur_x);
             ui->dy = SCOORD(ui->cur_y);
         }
-        return "";
+        return UI_UPDATE;
     } else if (IS_CURSOR_SELECT(button)) {
         if (!ui->cur_visible) {
             ui->cur_visible = 1;
-            return "";
+            return UI_UPDATE;
         }
         sp = &SPACE(state, ui->cur_x, ui->cur_y);
         if (ui->dragging) {
@@ -2637,7 +2637,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
             ui->dy = SCOORD(ui->cur_y);
             ui->dotx = ui->srcx = ui->cur_x;
             ui->doty = ui->srcy = ui->cur_y;
-            return "";
+            return UI_UPDATE;
         } else if (sp->flags & F_TILE_ASSOC) {
             assert(sp->type == s_tile);
             ui->dragging = TRUE;
@@ -2647,7 +2647,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
             ui->doty = sp->doty;
             ui->srcx = ui->cur_x;
             ui->srcy = ui->cur_y;
-            return "";
+            return UI_UPDATE;
         } else if (sp->type == s_edge) {
             sprintf(buf, "E%d,%d", ui->cur_x, ui->cur_y);
             return dupstr(buf);