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, 11 insertions, 11 deletions

diff --git a/undead.c b/undead.c
index b1f536e..2710223 100644
--- a/undead.c
+++ b/undead.c
@@ -1725,7 +1725,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
 
     if (button == 'a' || button == 'A') {
         ui->ascii = !ui->ascii;
-        return "";      
+        return UI_UPDATE;
     }
 
     if (button == 'm' || button == 'M') {
@@ -1771,12 +1771,12 @@ static char *interpret_move(const game_state *state, game_ui *ui,
               case CURSOR_LEFT:   ui->hx -= (ui->hx > 1)     ? 1 : 0; break;
             }
         ui->hshow = ui->hcursor = 1;
-        return "";
+        return UI_UPDATE;
     }
     if (ui->hshow && button == CURSOR_SELECT) {
         ui->hpencil = 1 - ui->hpencil;
         ui->hcursor = 1;
-        return "";
+        return UI_UPDATE;
     }
 
     if (ui->hshow == 1 && ui->hpencil == 1) {
@@ -1814,12 +1814,12 @@ static char *interpret_move(const game_state *state, game_ui *ui,
                 if (button == LEFT_BUTTON) {
                     ui->hshow = 1; ui->hpencil = 0; ui->hcursor = 0;
                     ui->hx = gx; ui->hy = gy;
-                    return "";
+                    return UI_UPDATE;
                 }
                 else if (button == RIGHT_BUTTON && g == 7) {
                     ui->hshow = 1; ui->hpencil = 1; ui->hcursor = 0;
                     ui->hx = gx; ui->hy = gy;
-                    return "";
+                    return UI_UPDATE;
                 }
             }
             else if (ui->hshow == 1) {
@@ -1828,36 +1828,36 @@ static char *interpret_move(const game_state *state, game_ui *ui,
                         if (gx == ui->hx && gy == ui->hy) {
                             ui->hshow = 0; ui->hpencil = 0; ui->hcursor = 0;
                             ui->hx = 0; ui->hy = 0;
-                            return "";
+                            return UI_UPDATE;
                         }
                         else {
                             ui->hshow = 1; ui->hpencil = 0; ui->hcursor = 0;
                             ui->hx = gx; ui->hy = gy;
-                            return "";
+                            return UI_UPDATE;
                         }
                     }
                     else {
                         ui->hshow = 1; ui->hpencil = 0; ui->hcursor = 0;
                         ui->hx = gx; ui->hy = gy;
-                        return "";
+                        return UI_UPDATE;
                     }
                 }
                 else if (button == RIGHT_BUTTON) {
                     if (ui->hpencil == 0 && g == 7) {
                         ui->hshow = 1; ui->hpencil = 1; ui->hcursor = 0;
                         ui->hx = gx; ui->hy = gy;
-                        return "";
+                        return UI_UPDATE;
                     }
                     else {
                         if (gx == ui->hx && gy == ui->hy) {
                             ui->hshow = 0; ui->hpencil = 0; ui->hcursor = 0;
                             ui->hx = 0; ui->hy = 0;
-                            return "";
+                            return UI_UPDATE;
                         }
                         else if (g == 7) {
                             ui->hshow = 1; ui->hpencil = 1; ui->hcursor = 0;
                             ui->hx = gx; ui->hy = gy;
-                            return "";
+                            return UI_UPDATE;
                         }
                     }
                 }