fix bug with adding combining chars to a full-width char

the logic was incorrectly sending the combinin char to x-1, but that
assumed a wcwidth==1 char. save last printed x coord and use that
instead.

xterm's ansi output for this is a little strange. unlike other
`expected.ansi` files, cat-ing this one to stdout doesn't seem to
render the correct output, and if you peek at its contents you'll see
some "\xef\xbf\xbf" (U+FFFF) which is an invalid codepoint. in any
case, it still picks up the regression so i'm adding it.

termbox2.h

@@ -1869,7 +1869,7 @@ int tb_print(int x, int y, uintattr_t fg, uintattr_t bg, const char *str) {
 
 int tb_print_ex(int x, int y, uintattr_t fg, uintattr_t bg, size_t *out_w,
     const char *str) {
-    int rv, w, ix;
+    int rv, w, ix, x_prev;
     uint32_t uni;
 
     if_not_init_return();
@@ -1879,6 +1879,7 @@ int tb_print_ex(int x, int y, uintattr_t fg, uintattr_t bg, size_t *out_w,
     }
 
     ix = x;
+    x_prev = x;
     if (out_w) *out_w = 0;
 
     while (*str) {
@@ -1895,6 +1896,7 @@ int tb_print_ex(int x, int y, uintattr_t fg, uintattr_t bg, size_t *out_w,
 
         if (uni == '\n') { // TODO: \r, \t, \v, \f, etc?
             x = ix;
+            x_prev = x;
             y += 1;
             continue;
         } else if (!iswprint((wint_t)uni)) {
@@ -1905,17 +1907,17 @@ int tb_print_ex(int x, int y, uintattr_t fg, uintattr_t bg, size_t *out_w,
         if (w < 0) {
             return TB_ERR;   // shouldn't happen if iswprint
         } else if (w == 0) { // combining character
-            if (cellbuf_in_bounds(&global.back, x - 1, y)) {
-                if_err_return(rv, tb_extend_cell(x - 1, y, uni));
+            if (cellbuf_in_bounds(&global.back, x_prev, y)) {
+                if_err_return(rv, tb_extend_cell(x_prev, y, uni));
             }
         } else {
             if (cellbuf_in_bounds(&global.back, x, y)) {
                 if_err_return(rv, tb_set_cell(x, y, uni, fg, bg));
             }
+            x_prev = x;
+            x += w;
+            if (out_w) *out_w += w;
         }
-
-        x += w;
-        if (out_w) *out_w += w;
     }
 
     return TB_OK;

tests/test_egc/expected.ansi

@@ -1,7 +1,7 @@
 #5aёb
 #5cёd
-
-
+#5Ｉ￿̤ͯ
+#5Ｉ￿̤ͯ
 
 
 

tests/test_egc/test.php

@@ -18,12 +18,22 @@
 $test->ffi->tb_set_cell_ex(1, $y, $test->ffi->cast('uint32_t *', FFI::addr($ech)), 2, 0, 0);
 $test->ffi->tb_set_cell(2, $y, ord('b'), 0, 0);
 
-++$y;
 // Same effect with tb_extend_cell
+++$y;
 $test->ffi->tb_set_cell(0, $y, ord('c'), 0, 0);
 $test->ffi->tb_set_cell(1, $y, $ech[0], 0, 0);
 $test->ffi->tb_extend_cell(1, $y, $ech[1]);
 $test->ffi->tb_set_cell(2, $y, ord('d'), 0, 0);
 
+// Another example with 2 combining characters
+++$y;
+$test->ffi->tb_set_cell(0, $y, 0xff29, 0, 0); // fullwidth latin capital letter i
+$test->ffi->tb_extend_cell(0, $y, 0x0324); // combining diaeresis below
+$test->ffi->tb_extend_cell(0, $y, 0x036f); // combining latin small letter x
+
+// Same as above via tb_print (should be equivalent)
+++$y;
+$test->ffi->tb_print(0, $y, 0, 0, "\xef\xbc\xa9\xcc\xa4\xcd\xaf");
+
 $test->ffi->tb_present();
 $test->screencap();

tests/test_prepend.php

@@ -26,9 +26,7 @@ public function __construct($ffi, $test) {
                 $this->test = $test;
             }
             public function __call(string $name, array $args) {
-                if ($name !== 'tb_set_cell') {
-                    $this->test->log("ffi $name " . json_encode($args));
-                }
+                $this->test->log("ffi $name " . json_encode($args));
                 return $this->ffi->$name(...$args);
             }
         };