Fixed drawPngUrl http client infinite loop

Fixed drawPngUrl http client infinite loop

Author: TinyuZhao

src/M5Display.cpp

@@ -573,6 +573,8 @@ void M5Display::drawPngUrl(const char *url, uint16_t x, uint16_t y,
         http.end();
         return;
     }
+    // get length of document (is -1 when Server sends no Content-Length header)
+    int len = http.getSize();
 
     WiFiClient *stream = http.getStreamPtr();
 
@@ -603,24 +605,28 @@ void M5Display::drawPngUrl(const char *url, uint16_t x, uint16_t y,
     // Feed data to pngle
     uint8_t buf[1024];
     int remain = 0;
-    int len;
-    while (http.connected()) {
+    int c;
+    while (http.connected() && (len > 0 || len == -1)) {
         size_t size = stream->available();
         if (!size) {
             delay(1);
             continue;
         }
 
         if (size > sizeof(buf) - remain) size = sizeof(buf) - remain;
-        if ((len = stream->readBytes(buf + remain, size)) > 0) {
-            int fed = pngle_feed(pngle, buf, remain + len);
+        if ((c = stream->readBytes(buf + remain, size)) > 0) {
+            int fed = pngle_feed(pngle, buf, remain + c);
             if (fed < 0) {
                 log_e("[pngle error] %s", pngle_error(pngle));
                 break;
             }
 
-            remain = remain + len - fed;
+            remain = remain + c - fed;
             if (remain > 0) memmove(buf, buf + fed, remain);
+
+            if (len > 0) {
+                len -= c;
+            }
         }
     }