--- a/svghmi/gen_index_xhtml.xslt	Wed Mar 04 16:46:35 2020 +0100
+++ b/svghmi/gen_index_xhtml.xslt	Wed Mar 04 20:02:15 2020 +0100
@@ -423,6 +423,7 @@
 </xsl:text>
     <xsl:for-each select="$hmi_elements">
       <xsl:variable name="widget" select="func:parselabel(@inkscape:label)/widget"/>
+      <xsl:variable name="eltid" select="@id"/>
       <xsl:text>  "</xsl:text>
       <xsl:value-of select="@id"/>
       <xsl:text>": {
@@ -453,7 +454,11 @@
         <xsl:choose>
           <xsl:when test="count($hmitree_match) = 0">
             <xsl:message terminate="no">
-              <xsl:text>No match for path "</xsl:text>
+              <xsl:text>Widget </xsl:text>
+              <xsl:value-of select="$widget/@type"/>
+              <xsl:text> id="</xsl:text>
+              <xsl:value-of select="$eltid"/>
+              <xsl:text>" : No match for path "</xsl:text>
               <xsl:value-of select="$hmipath"/>
               <xsl:text>" in HMI tree</xsl:text>
             </xsl:message>
@@ -1295,12 +1300,21 @@
     <xsl:call-template name="defs_by_labels">
       <xsl:with-param name="hmi_element" select="$hmi_element"/>
       <xsl:with-param name="labels">
-        <xsl:text>value min max needle range</xsl:text>
+        <xsl:text>needle range</xsl:text>
       </xsl:with-param>
     </xsl:call-template>
+    <xsl:call-template name="defs_by_labels">
+      <xsl:with-param name="hmi_element" select="$hmi_element"/>
+      <xsl:with-param name="labels">
+        <xsl:text>value min max</xsl:text>
+      </xsl:with-param>
+      <xsl:with-param name="mandatory" select="'no'"/>
+    </xsl:call-template>
     <xsl:text>    dispatch: function(value) {
 </xsl:text>
-    <xsl:text>        this.value_elt.textContent = String(value);
+    <xsl:text>        if(this.value_elt)
+</xsl:text>
+    <xsl:text>            this.value_elt.textContent = String(value);
 </xsl:text>
     <xsl:text>        let [min,max,totallength] = this.range;
 </xsl:text>
@@ -1318,7 +1332,11 @@
 </xsl:text>
     <xsl:text>    init: function() {
 </xsl:text>
-    <xsl:text>        this.range = [Number(this.min_elt.textContent), Number(this.max_elt.textContent), this.range_elt.getTotalLength()]
+    <xsl:text>        let min = this.min_elt ? Number(this.min_elt.textContent) : 0;
+</xsl:text>
+    <xsl:text>        let max = this.max_elt ? Number(this.max_elt.textContent) : 100;
+</xsl:text>
+    <xsl:text>        this.range = [min, max, this.range_elt.getTotalLength()]
 </xsl:text>
     <xsl:text>        this.origin = this.needle_elt.getPointAtLength(0);
 </xsl:text>

--- a/svghmi/gen_index_xhtml.ysl2	Wed Mar 04 16:46:35 2020 +0100
+++ b/svghmi/gen_index_xhtml.ysl2	Wed Mar 04 20:02:15 2020 +0100
@@ -535,6 +535,7 @@
         | var hmi_widgets = {
         foreach "$hmi_elements" {
             const "widget", "func:parselabel(@inkscape:label)/widget";
+            const "eltid","@id";
         |   "«@id»": {
         |     type: "«$widget/@type»",
         |     args: [
@@ -547,7 +548,7 @@
                 const "hmitree_match","$indexed_hmitree/*[@hmipath = $hmipath]";
                 choose {
                     when "count($hmitree_match) = 0" {
-                        warning > No match for path "«$hmipath»" in HMI tree
+                        warning > Widget «$widget/@type» id="«$eltid»" : No match for path "«$hmipath»" in HMI tree
                     }
                     otherwise {
         |             «$hmitree_match/@index»`if "position()!=last()" > ,`
@@ -706,9 +707,11 @@
     template "widget[@type='Meter']", mode="widget_defs" {
         param "hmi_element";
         |     frequency: 10,
-        labels("value min max needle range");
+        labels("needle range");
+        optional_labels("value min max");
         |     dispatch: function(value) {
-        |         this.value_elt.textContent = String(value);
+        |         if(this.value_elt)
+        |             this.value_elt.textContent = String(value);
         |         let [min,max,totallength] = this.range;
         |         let length = Math.max(0,Math.min(totallength,(Number(value)-min)*totallength/(max-min)));
         |         let tip = this.range_elt.getPointAtLength(length);
@@ -717,7 +720,9 @@
         |     origin: undefined,
         |     range: undefined,
         |     init: function() {
-        |         this.range = [Number(this.min_elt.textContent), Number(this.max_elt.textContent), this.range_elt.getTotalLength()]
+        |         let min = this.min_elt ? Number(this.min_elt.textContent) : 0;
+        |         let max = this.max_elt ? Number(this.max_elt.textContent) : 100;
+        |         this.range = [min, max, this.range_elt.getTotalLength()]
         |         this.origin = this.needle_elt.getPointAtLength(0);
         |     },
     }