Is. #879: add loading attribute for img, iframe (#902)

Closes #879

Author: sidvishnoi

include/tidyenum.h

@@ -1083,6 +1083,7 @@ typedef enum
   TidyAttr_LAST_VISIT,             /**< LAST_VISIT= */
   TidyAttr_LEFTMARGIN,             /**< LEFTMARGIN= */
   TidyAttr_LINK,                   /**< LINK= */
+  TidyAttr_LOADING,                /**< LOADING= */
   TidyAttr_LONGDESC,               /**< LONGDESC= */
   TidyAttr_LOWSRC,                 /**< LOWSRC= */
   TidyAttr_MARGINHEIGHT,           /**< MARGINHEIGHT= */

src/attrdict.c

@@ -1631,6 +1631,7 @@ const AttrVersion TY_(W3CAttrsFor_IFRAME)[] =
   { TidyAttr_FRAMEBORDER,           xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx },
   { TidyAttr_HEIGHT,                xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 },
   { TidyAttr_ID,                    xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 }, /* CORE override */
+  { TidyAttr_LOADING,               xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 },
   { TidyAttr_LONGDESC,              xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx },
   { TidyAttr_MARGINHEIGHT,          xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx },
   { TidyAttr_MARGINWIDTH,           xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx },
@@ -1664,6 +1665,7 @@ const AttrVersion TY_(W3CAttrsFor_IMG)[] =
   { TidyAttr_ID,                    xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|H40S|H41S|X10S|XH11|XB10|HT50|XH50 }, /* CORE override */
   { TidyAttr_ISMAP,                 HT20|HT32|H40T|H41T|X10T|H40F|H41F|X10F|H40S|H41S|X10S|XH11|xxxx|HT50|XH50 },
   { TidyAttr_LANG,                  xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|H40S|H41S|X10S|xxxx|xxxx|HT50|XH50 }, /* CORE override */
+  { TidyAttr_LOADING,               xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|xxxx|HT50|XH50 },
   { TidyAttr_LONGDESC,              xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|H40S|H41S|X10S|XH11|XB10|xxxx|xxxx },
   { TidyAttr_NAME,                  xxxx|xxxx|xxxx|H41T|X10T|xxxx|H41F|X10F|xxxx|H41S|xxxx|xxxx|xxxx|xxxx|xxxx },
   { TidyAttr_OnCLICK,               xxxx|xxxx|H40T|H41T|X10T|H40F|H41F|X10F|H40S|H41S|X10S|XH11|xxxx|HT50|XH50 }, /* CORE override */

src/attrs.c

@@ -47,6 +47,7 @@ static AttrCheck CheckVType;
 static AttrCheck CheckScroll;
 static AttrCheck CheckTextDir;
 static AttrCheck CheckLang;
+static AttrCheck CheckLoading;
 static AttrCheck CheckType;
 static AttrCheck CheckRDFaSafeCURIE;
 static AttrCheck CheckRDFaTerm;
@@ -66,6 +67,7 @@ static AttrCheck CheckRDFaPrefix;
 #define CH_CLEAR       CheckClear
 #define CH_BORDER      CheckBool     /* kludge */
 #define CH_LANG        CheckLang
+#define CH_LOADING     CheckLoading
 #define CH_BOOL        CheckBool
 #define CH_COLS        NULL
 #define CH_NUMBER      CheckNumber
@@ -177,6 +179,7 @@ static const Attribute attribute_defs [] =
   { TidyAttr_LAST_VISIT,              "last_visit",              CH_PCDATA    }, /* A */
   { TidyAttr_LEFTMARGIN,              "leftmargin",              CH_NUMBER    }, /* used on BODY */
   { TidyAttr_LINK,                    "link",                    CH_COLOR     }, /* BODY */
+  { TidyAttr_LOADING,                 "loading",                 CH_LOADING   }, /* IMG, IFRAME */
   { TidyAttr_LONGDESC,                "longdesc",                CH_URL       }, /* IMG */
   { TidyAttr_LOWSRC,                  "lowsrc",                  CH_URL       }, /* IMG */
   { TidyAttr_MARGINHEIGHT,            "marginheight",            CH_NUMBER    }, /* FRAME, IFRAME, BODY */
@@ -2046,6 +2049,13 @@ void CheckLang( TidyDocImpl* doc, Node *node, AttVal *attval)
     }
 }
 
+/* checks loading attribute */
+void CheckLoading( TidyDocImpl* doc, Node *node, AttVal *attval)
+{
+    ctmbstr const values[] = {"lazy", "eager", NULL};
+    CheckAttrValidity( doc, node, attval, values );
+}
+
 /* checks type attribute */
 void CheckType( TidyDocImpl* doc, Node *node, AttVal *attval)
 {