Bug 1516413 Part 1: Make EventStateManager zoom delta functions send chrome events instead of acting directly. r=mstange

This patch changes the zoom behavior to always be routed through the frontend
Zoom Actor. In the existing code, the ZoomChangeUsingMouseWheel event is sent
as an after-the-fact notification of the zoom being modified directly. This
part of the patch supplements the existing event with 2 new events that
trigger the frontend to do the +/- 10% math in ChangeFullZoom and
ChangeTextZoom. The next part of the patch supplies that logic in the frontend
Zoom Actor.

This also changes the handling of events from the zoom in/out keys. Before,
those keys would only change full zoom levels. Now, they will respect the
full zoom vs text zoom toggle.

Differential Revision: https://phabricator.services.mozilla.com/D59259

--HG--
extra : moz-landing-system : lando

dom/events/EventStateManager.cpp

@@ -26,7 +26,6 @@
 #include "mozilla/dom/FrameLoaderBinding.h"
 #include "mozilla/dom/MouseEventBinding.h"
 #include "mozilla/dom/BrowserChild.h"
-#include "mozilla/dom/BrowserParent.h"
 #include "mozilla/dom/UIEvent.h"
 #include "mozilla/dom/UIEventBinding.h"
 #include "mozilla/dom/UserActivation.h"
@@ -2223,44 +2222,18 @@ nsresult EventStateManager::GetContentViewer(nsIContentViewer** aCv) {
   return NS_OK;
 }
 
-nsresult EventStateManager::ChangeTextSize(int32_t change) {
-  nsCOMPtr<nsIContentViewer> cv;
-  nsresult rv = GetContentViewer(getter_AddRefs(cv));
-  NS_ENSURE_SUCCESS(rv, rv);
+nsresult EventStateManager::ChangeZoom(int32_t change) {
+  MOZ_ASSERT(change == 1 || change == -1, "Can only change by +/- 10%.");
 
-  if (cv) {
-    float textzoom;
-    float zoomMin = ((float)StaticPrefs::zoom_minPercent()) / 100;
-    float zoomMax = ((float)StaticPrefs::zoom_maxPercent()) / 100;
-    cv->GetTextZoom(&textzoom);
-    textzoom += ((float)change) / 10;
-    if (textzoom < zoomMin)
-      textzoom = zoomMin;
-    else if (textzoom > zoomMax)
-      textzoom = zoomMax;
-    cv->SetTextZoom(textzoom);
-  }
-
-  return NS_OK;
-}
-
-nsresult EventStateManager::ChangeFullZoom(int32_t change) {
-  nsCOMPtr<nsIContentViewer> cv;
-  nsresult rv = GetContentViewer(getter_AddRefs(cv));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (cv) {
-    float fullzoom;
-    float zoomMin = ((float)StaticPrefs::zoom_minPercent()) / 100;
-    float zoomMax = ((float)StaticPrefs::zoom_maxPercent()) / 100;
-    cv->GetFullZoom(&fullzoom);
-    fullzoom += ((float)change) / 10;
-    if (fullzoom < zoomMin)
-      fullzoom = zoomMin;
-    else if (fullzoom > zoomMax)
-      fullzoom = zoomMax;
-    cv->SetFullZoom(fullzoom);
-  }
+  // Send the zoom change as a chrome event so it will be handled
+  // by the front end actors in the same way as other zoom actions.
+  // This excludes documents hosted in non-browser containers, like
+  // in a WebExtension.
+  nsContentUtils::DispatchChromeEvent(
+      mDocument, ToSupports(mDocument),
+      (change == 1 ? NS_LITERAL_STRING("DoZoomEnlargeBy10")
+                   : NS_LITERAL_STRING("DoZoomReduceBy10")),
+      CanBubble::eYes, Cancelable::eYes);
 
   return NS_OK;
 }
@@ -2288,12 +2261,7 @@ void EventStateManager::DoScrollZoom(nsIFrame* aTargetFrame,
     int32_t change = (adjustment > 0) ? -1 : 1;
 
     EnsureDocument(mPresContext);
-    if (Preferences::GetBool("browser.zoom.full") ||
-        content->OwnerDoc()->IsSyntheticDocument()) {
-      ChangeFullZoom(change);
-    } else {
-      ChangeTextSize(change);
-    }
+    ChangeZoom(change);
     nsContentUtils::DispatchChromeEvent(
         mDocument, ToSupports(mDocument),
         NS_LITERAL_STRING("ZoomChangeUsingMouseWheel"), CanBubble::eYes,
@@ -3136,8 +3104,8 @@ void EventStateManager::PostHandleKeyboardEvent(
   switch (aKeyboardEvent->mKeyNameIndex) {
     case KEY_NAME_INDEX_ZoomIn:
     case KEY_NAME_INDEX_ZoomOut:
-      ChangeFullZoom(
-          aKeyboardEvent->mKeyNameIndex == KEY_NAME_INDEX_ZoomIn ? 1 : -1);
+      ChangeZoom(aKeyboardEvent->mKeyNameIndex == KEY_NAME_INDEX_ZoomIn ? 1
+                                                                        : -1);
       aStatus = nsEventStatus_eConsumeNoDefault;
       break;
     default:

dom/events/EventStateManager.h

@@ -926,8 +926,7 @@ class EventStateManager : public nsSupportsWeakReference, public nsIObserver {
   void DoScrollHistory(int32_t direction);
   void DoScrollZoom(nsIFrame* aTargetFrame, int32_t adjustment);
   nsresult GetContentViewer(nsIContentViewer** aCv);
-  nsresult ChangeTextSize(int32_t change);
-  nsresult ChangeFullZoom(int32_t change);
+  nsresult ChangeZoom(int32_t change);
 
   /**
    * DeltaAccumulator class manages delta values for dispatching DOMMouseScroll