make vertex by midpoint double-clicking

modules/behavior/select.js

@@ -27,7 +27,9 @@ export function behaviorSelect(context) {
             lasso = d3.select('#surface .lasso').node(),
             mode = context.mode();
 
-        if (!(datum instanceof osmEntity)) {
+        if (datum.type === 'midpoint') {
+            // do nothing
+        } else if (!(datum instanceof osmEntity)) {
             if (!d3.event.shiftKey && !lasso && mode.id !== 'browse')
                 context.enter(modeBrowse(context));
 

modules/modes/select.js

@@ -245,6 +245,15 @@ export function modeSelect(context, selectedIDs) {
                     t('operations.add.annotation.vertex')
                 );
 
+                d3.event.preventDefault();
+                d3.event.stopPropagation();
+            } else if (datum.type === 'midpoint') {
+                var node = osmNode();
+
+                context.perform(
+                    actionAddMidpoint({loc: datum.loc, edge: datum.edge}, node),
+                    t('operations.add.annotation.vertex'));
+
                 d3.event.preventDefault();
                 d3.event.stopPropagation();
             }