Fix GH-17373: imagefttext() ignores clipping rect for palette images

We apply the same fix that has been applied to external libgd at least
as of 2.0.29.

To avoid issues regarding minor FreeType rendering differences, the
test case does not compare against an image, but rather checks that all
pixels outside the clipping rect have the background color.

Closes GH-17374.

Author: cmb69

NEWS

@@ -8,6 +8,8 @@ PHP                                                                        NEWS
 - GD:
   . Fixed bug GH-17349 (Tiled truecolor filling looses single color
     transparency). (cmb)
+  . Fixed bug GH-17373 (imagefttext() ignores clipping rect for palette
+    images). (cmb)
 
 - Intl:
   . Fixed bug GH-11874 (intl causing segfault in docker images). (nielsdos)

ext/gd/libgd/gdft.c

@@ -720,7 +720,7 @@ static char * gdft_draw_bitmap (gdCache_head_t *tc_cache, gdImage * im, int fg,
 		y = pen_y + row;
 
 		/* clip if out of bounds */
-		if (y >= im->sy || y < 0) {
+		if (y > im->cy2 || y < im->cy1) {
 			continue;
 		}
 
@@ -743,7 +743,7 @@ static char * gdft_draw_bitmap (gdCache_head_t *tc_cache, gdImage * im, int fg,
 				x = pen_x + col;
 
 				/* clip if out of bounds */
-				if (x >= im->sx || x < 0) {
+				if (x > im->cx2 || x < im->cx1) {
 					continue;
 				}
 				/* get pixel location in gd buffer */

ext/gd/tests/gh17373.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Bug GH-17373 (imagefttext() ignores clipping rect for palette images)
+--EXTENSIONS--
+gd
+--FILE--
+<?php
+$im = imagecreate(64, 32);
+$bg = imagecolorallocate($im, 0, 0, 0);
+$fg = imagecolorallocate($im, 255, 255, 255);
+imagefilledrectangle($im, 0, 0, 63, 31, $bg);
+imagesetclip($im, 32, 0, 63, 31);
+imagefttext($im, 16, 0, 10, 23, $fg, __DIR__ . "/Tuffy.ttf", "hello");
+
+imagesetclip($im, 0, 0, 63, 31);
+$count = 0;
+for ($j = 0; $j < 31; $j++) {
+    for ($i = 0; $i < 31; $i++) {
+        if (imagecolorat($im, $i, $j) !== $bg) {
+            $count++;
+        }
+    }
+}
+var_dump($count);
+?>
+--EXPECT--
+int(0)