Issue #2030 - Allow child nodes of button to participate in mouse hit tests

This is needed for web compatibility, even if standards compliance is debatable.

dom/html/HTMLButtonElement.cpp

@@ -221,11 +221,14 @@ HTMLButtonElement::GetEventTargetParent(EventChainPreVisitor& aVisitor)
   bool outerActivateEvent =
     ((mouseEvent && mouseEvent->IsLeftClickEvent()) ||
      (aVisitor.mEvent->mMessage == eLegacyDOMActivate &&
-      !mInInternalActivate));
+      !mInInternalActivate &&
+      aVisitor.mEvent->mOriginalTarget == this));
 
   if (outerActivateEvent) {
     aVisitor.mItemFlags |= NS_OUTER_ACTIVATE_EVENT;
-    if (mType == NS_FORM_BUTTON_SUBMIT && mForm) {
+    if (mType == NS_FORM_BUTTON_SUBMIT && mForm &&
+        !aVisitor.mEvent->mFlags.mMultiplePreActionsPrevented) {
+      aVisitor.mEvent->mFlags.mMultiplePreActionsPrevented = true;
       aVisitor.mItemFlags |= NS_IN_SUBMIT_CLICK;
       // tell the form that we are about to enter a click handler.
       // that means that if there are scripted submissions, the

dom/html/HTMLInputElement.cpp

@@ -143,11 +143,14 @@ namespace dom {
 #define NS_ORIGINAL_CHECKED_VALUE (1 << 10)
 #define NS_NO_CONTENT_DISPATCH    (1 << 11)
 #define NS_ORIGINAL_INDETERMINATE_VALUE (1 << 12)
-#define NS_CONTROL_TYPE(bits)  ((bits) & ~( \
-  NS_OUTER_ACTIVATE_EVENT | NS_ORIGINAL_CHECKED_VALUE | NS_NO_CONTENT_DISPATCH | \
-  NS_ORIGINAL_INDETERMINATE_VALUE))
 #define NS_PRE_HANDLE_BLUR_EVENT  (1 << 13)
 #define NS_PRE_HANDLE_INPUT_EVENT (1 << 14)
+#define NS_IN_SUBMIT_CLICK (1 << 15)
+#define NS_CONTROL_TYPE(bits)                                             \
+  ((bits) & ~(NS_OUTER_ACTIVATE_EVENT | NS_ORIGINAL_CHECKED_VALUE |       \
+              NS_NO_CONTENT_DISPATCH |  NS_ORIGINAL_INDETERMINATE_VALUE | \
+              NS_PRE_HANDLE_BLUR_EVENT | NS_PRE_HANDLE_INPUT_EVENT |      \
+              NS_IN_SUBMIT_CLICK))
 
 // whether textfields should be selected once focused:
 //  -1: no, 1: yes, 0: uninitialized
@@ -3800,7 +3803,10 @@ HTMLInputElement::GetEventTargetParent(EventChainPreVisitor& aVisitor)
 
       case NS_FORM_INPUT_SUBMIT:
       case NS_FORM_INPUT_IMAGE:
-        if (mForm) {
+        if (mForm && !aVisitor.mEvent->mFlags.mMultiplePreActionsPrevented) {
+          // Make sure other submit elements don't try to trigger submission.
+          aVisitor.mEvent->mFlags.mMultiplePreActionsPrevented = true;
+          aVisitor.mItemFlags |= NS_IN_SUBMIT_CLICK;
           // tell the form that we are about to enter a click handler.
           // that means that if there are scripted submissions, the
           // latest one will be deferred until after the exit point of the handler.
@@ -4394,17 +4400,15 @@ HTMLInputElement::PostHandleEvent(EventChainPostVisitor& aVisitor)
     }
   }
 
-  if (outerActivateEvent) {
+  if ((aVisitor.mItemFlags & NS_IN_SUBMIT_CLICK) && mForm) {
     switch(oldType) {
       case NS_FORM_INPUT_SUBMIT:
       case NS_FORM_INPUT_IMAGE:
-        if (mForm) {
         // tell the form that we are about to exit a click handler
         // so the form knows not to defer subsequent submissions
         // the pending ones that were created during the handler
         // will be flushed or forgoten.
         mForm->OnSubmitClickEnd();
-        }
         break;
       default:
         break;
@@ -4770,7 +4774,8 @@ HTMLInputElement::PostHandleEvent(EventChainPostVisitor& aVisitor)
       if (outerActivateEvent) {
         if (mForm && (oldType == NS_FORM_INPUT_SUBMIT ||
                       oldType == NS_FORM_INPUT_IMAGE)) {
-          if (mType != NS_FORM_INPUT_SUBMIT && mType != NS_FORM_INPUT_IMAGE) {
+          if (mType != NS_FORM_INPUT_SUBMIT && mType != NS_FORM_INPUT_IMAGE &&
+              aVisitor.mItemFlags & NS_IN_SUBMIT_CLICK) {
             // If the type has changed to a non-submit type, then we want to
             // flush the stored submission if there is one (as if the submit()
             // was allowed to succeed)
@@ -4809,7 +4814,7 @@ HTMLInputElement::PostHandleEvent(EventChainPostVisitor& aVisitor)
           break;
         } //switch
       } //click or outer activate event
-    } else if (outerActivateEvent &&
+    } else if ((aVisitor.mItemFlags & NS_IN_SUBMIT_CLICK) &&
                (oldType == NS_FORM_INPUT_SUBMIT ||
                 oldType == NS_FORM_INPUT_IMAGE) &&
                mForm) {

layout/forms/nsHTMLButtonControlFrame.cpp

@@ -118,8 +118,8 @@ nsHTMLButtonControlFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
 
   nsDisplayListCollection set(aBuilder);
 
-  // Do not allow the child subtree to receive events.
+  // HTMLInputElement buttons are opaque to hit tests, HTMLButtonElement buttons are not.
-  if (!isForEventDelivery) {
+  if (!(isForEventDelivery && this->IsInput())) {
     DisplayListClipState::AutoSaveRestore clipState(aBuilder);
 
     if (ShouldClipPaintingToBorderBox()) {

widget/BasicEvents.h

@@ -80,6 +80,8 @@ public:
   // the first <label> element is clicked, that one may set this true.
   // Then, the second <label> element won't handle the event.
   bool    mMultipleActionsPrevented : 1;
+  // Similar to above but expected to be used during PreHandleEvent phase.
+  bool    mMultiplePreActionsPrevented : 1;
   // If mIsBeingDispatched is true, the DOM event created from the event is
   // dispatching into the DOM tree and not completed.
   bool    mIsBeingDispatched : 1;