Add setting to isolate zoom changes by default.

components/zoom/zoom_controller.cc

Index: components/zoom/zoom_controller.cc
diff --git a/components/zoom/zoom_controller.cc b/components/zoom/zoom_controller.cc
index 8d258a5d7adb3ddaf7c36df2848d1be6af680252..3a61df0627b2ca86ef8942176bb7bdac597480d1 100644
--- a/components/zoom/zoom_controller.cc
+++ b/components/zoom/zoom_controller.cc
@@ -6,12 +6,15 @@
 
 #include "components/zoom/zoom_event_manager.h"
 #include "components/zoom/zoom_observer.h"
+#include "content/public/browser/browser_context.h"
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/navigation_handle.h"
+#include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/storage_partition.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_type.h"
 #include "content/public/common/page_zoom.h"
@@ -36,12 +39,40 @@ double ZoomController::GetZoomLevelForWebContents(
 ZoomController::ZoomController(content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
       can_show_bubble_(true),
-      zoom_mode_(ZOOM_MODE_DEFAULT),
+      default_scope_is_per_origin_(ZoomPrefsDelegate::kZoomScopeSettingDefault),
       zoom_level_(1.0),
       browser_context_(web_contents->GetBrowserContext()) {
   host_zoom_map_ = content::HostZoomMap::GetForWebContents(web_contents);
   zoom_level_ = host_zoom_map_->GetDefaultZoomLevel();
 
+  ZoomPrefsDelegate* zoom_prefs_delegate = static_cast<ZoomPrefsDelegate*>(
+      content::BrowserContext::GetStoragePartition(
+          browser_context_, web_contents->GetSiteInstance())
+              ->GetZoomLevelDelegate());
+  if (zoom_prefs_delegate) {
+    default_scope_is_per_origin_ =
+        zoom_prefs_delegate->GetZoomScopeIsPerOriginPref();
+    default_zoom_scope_subscription_ =
+        zoom_prefs_delegate->RegisterDefaultZoomScopeCallback(
+            base::Bind(&ZoomController::OnDefaultZoomScopeChanged,
+                       base::Unretained(this)));
+  }
+  zoom_mode_ =
+      default_scope_is_per_origin_ ? ZOOM_MODE_DEFAULT : ZOOM_MODE_ISOLATED;
+
+  // When in isolated zoom, a temporary zoom level needs to be set to override
+  // any existing per-host zoom levels.
+  // If this WebContents is a clone of another, don't overwrite the temporary
+  // level we've inherited.
+  int render_process_id = web_contents->GetRenderProcessHost()->GetID();
+  int render_view_id = web_contents->GetRenderViewHost()->GetRoutingID();
+  if (zoom_mode_ == ZOOM_MODE_ISOLATED &&
+      !host_zoom_map_->UsesTemporaryZoomLevel(render_process_id,
+                                              render_view_id)) {
+    host_zoom_map_->SetTemporaryZoomLevel(render_process_id, render_view_id,
+                                          zoom_level_);
+  }
+
   zoom_subscription_ = host_zoom_map_->AddZoomLevelChangedCallback(
       base::Bind(&ZoomController::OnZoomLevelChanged, base::Unretained(this)));
 
@@ -180,7 +211,9 @@ void ZoomController::SetZoomMode(ZoomMode new_mode) {
   DCHECK(!event_data_);
   event_data_.reset(new ZoomChangedEventData(
       web_contents(), original_zoom_level, original_zoom_level, new_mode,
-      new_mode != ZOOM_MODE_DEFAULT));
+      new_mode !=
+          (default_scope_is_per_origin_
+              ? ZOOM_MODE_DEFAULT : ZOOM_MODE_ISOLATED)));
 
   switch (new_mode) {
     case ZOOM_MODE_DEFAULT: {
@@ -261,28 +294,58 @@ void ZoomController::SetZoomMode(ZoomMode new_mode) {
 }
 
 void ZoomController::ResetZoomModeOnNavigationIfNeeded(const GURL& url) {
-  if (zoom_mode_ != ZOOM_MODE_ISOLATED && zoom_mode_ != ZOOM_MODE_MANUAL)
+  if ((!default_scope_is_per_origin_ || zoom_mode_ != ZOOM_MODE_ISOLATED) &&
+      zoom_mode_ != ZOOM_MODE_MANUAL)
     return;
 
   int render_process_id = web_contents()->GetRenderProcessHost()->GetID();
   int render_view_id = web_contents()->GetRenderViewHost()->GetRoutingID();
   content::HostZoomMap* zoom_map =
       content::HostZoomMap::GetForWebContents(web_contents());
+  double old_zoom_level = GetZoomLevel();
+  // Set |zoom_level_| after calling GetZoomLevel() so we get the correct old
+  // zoom level if we're resetting from manual.
   zoom_level_ = zoom_map->GetDefaultZoomLevel();
-  double old_zoom_level = zoom_map->GetZoomLevel(web_contents());
-  double new_zoom_level = zoom_map->GetZoomLevelForHostAndScheme(
-      url.scheme(), net::GetHostOrSpecFromURL(url));
+  ZoomMode new_mode;
+  double new_zoom_level;
+  if (default_scope_is_per_origin_) {
+    new_mode = ZOOM_MODE_DEFAULT;
+    new_zoom_level = zoom_map->GetZoomLevelForHostAndScheme(
+        url.scheme(), net::GetHostOrSpecFromURL(url));
+  } else {
+    new_mode = ZOOM_MODE_ISOLATED;
+    new_zoom_level = zoom_level_;
+  }
   event_data_.reset(new ZoomChangedEventData(web_contents(), old_zoom_level,
-                                             new_zoom_level, ZOOM_MODE_DEFAULT,
+                                             new_zoom_level, new_mode,
                                              false /* can_show_bubble */));
-  // The call to ClearTemporaryZoomLevel() doesn't generate any events from
-  // HostZoomMap, but the call to UpdateState() at the end of this function
-  // will notify our observers.
-  // Note: it's possible the render_process/view ids have disappeared (e.g.
-  // if we navigated to a new origin), but this won't cause a problem in the
-  // call below.
-  zoom_map->ClearTemporaryZoomLevel(render_process_id, render_view_id);
-  zoom_mode_ = ZOOM_MODE_DEFAULT;
+  if (default_scope_is_per_origin_) {
+    // The call to ClearTemporaryZoomLevel() doesn't generate any events from
+    // HostZoomMap, but the call to UpdateState() at the end of this function
+    // will notify our observers.
+    // Note: it's possible the render_process/view ids have disappeared (e.g.
+    // if we navigated to a new origin), but this won't cause a problem in the
+    // call below.
+    zoom_map->ClearTemporaryZoomLevel(render_process_id, render_view_id);
+  } else {
+    // If we're resetting to isolated zoom, a temporary zoom level needs to
+    // be set to override any existing per-host zoom levels.
+    zoom_map->SetTemporaryZoomLevel(render_process_id, render_view_id,
+                                    new_zoom_level);
+  }
+  zoom_mode_ = new_mode;
+}
+
+void ZoomController::UpdateZoomModeOnScopeChangeIfNeeded() {
+  if (zoom_mode_ != ZOOM_MODE_DEFAULT && zoom_mode_ != ZOOM_MODE_ISOLATED)
+    return;
+
+  // When going from per-tab to per-host, if there isn't an existing per-host
+  // zoom level set, the first ZoomController (that has set a non-default
+  // temporary zoom level) to be notified of the scope change will set the
+  // per-host zoom level.

[Kevin McNee, 2017/02/03 23:17:20]

Is this acceptable behaviour?

[wjmaclean, 2017/02/06 16:09:07]

I don't think I understand the comment. I would have thought if we're switching
away from per-tab mode that, on the next navigation, we would use the per-host
level, or the default if no per-host level exists. We could also do this
immediately though it might be a little jarring to the user if the current zoom
level suddenly changes.

[Kevin McNee, 2017/02/06 18:26:12]

The problem with deferring the change in zoom mode until the next navigation is
that the behaviour of a zoom change will be temporarily inconsistent with the
current setting. For example, if I enable per-origin zooming and then zoom a
tab, the zoom will not be propagated if I haven't yet navigated.

[wjmaclean, 2017/02/06 18:48:38]

Ok. In that case I'd clarify the comment, since it's not obvious (to me at
least) what the "first ZoomController" is going to be ...

+  SetZoomMode(
+      default_scope_is_per_origin_ ? ZOOM_MODE_DEFAULT : ZOOM_MODE_ISOLATED);
 }
 
 void ZoomController::DidFinishNavigation(
@@ -303,6 +366,9 @@ void ZoomController::DidFinishNavigation(
 }
 
 void ZoomController::WebContentsDestroyed() {
+  // Once our WebContents is destroyed, we can no longer respond to zoom scope
+  // changes.
+  default_zoom_scope_subscription_.reset();
   // At this point we should no longer be sending any zoom events with this
   // WebContents.
   observers_.Clear();
@@ -311,9 +377,19 @@ void ZoomController::WebContentsDestroyed() {
 void ZoomController::RenderFrameHostChanged(
     content::RenderFrameHost* old_host,
     content::RenderFrameHost* new_host) {
-  // If our associated HostZoomMap changes, update our event subscription.
   content::HostZoomMap* new_host_zoom_map =
       content::HostZoomMap::GetForWebContents(web_contents());
+
+  // The HostZoomMap records temporary zoom levels per RenderView. When zooming
+  // is per-tab and our RenderView changes, we need to copy the level for our
+  // new RenderView so that the tab's zoom level is preserved.
+  if (old_host && !default_scope_is_per_origin_ &&
+      zoom_mode_ == ZOOM_MODE_ISOLATED) {
+    PreserveTemporaryZoomLevel(
+        host_zoom_map_, new_host_zoom_map, old_host, new_host);
+  }
+
+  // If our associated HostZoomMap changes, update our event subscription.
   if (new_host_zoom_map == host_zoom_map_)
     return;
 
@@ -322,11 +398,67 @@ void ZoomController::RenderFrameHostChanged(
       base::Bind(&ZoomController::OnZoomLevelChanged, base::Unretained(this)));
 }
 
+void ZoomController::PreserveTemporaryZoomLevel(
+    const content::HostZoomMap* old_zoom_map,
+    content::HostZoomMap* new_zoom_map,
+    content::RenderFrameHost* old_host,
+    content::RenderFrameHost* new_host) const {
+  const content::RenderViewHost* old_view_host = old_host->GetRenderViewHost();
+  const content::RenderViewHost* new_view_host = new_host->GetRenderViewHost();
+
+  DCHECK(old_zoom_map->UsesTemporaryZoomLevel(
+      old_view_host->GetProcess()->GetID(), old_view_host->GetRoutingID()));
+
+  const double level = old_zoom_map->GetTemporaryZoomLevel(
+      old_view_host->GetProcess()->GetID(), old_view_host->GetRoutingID());
+  new_zoom_map->SetTemporaryZoomLevel(
+      new_view_host->GetProcess()->GetID(), new_view_host->GetRoutingID(),
+      level);
+}
+
+void ZoomController::PreserveTemporaryZoomLevel(
+    content::WebContents* old_web_contents,
+    content::WebContents* new_web_contents) const {
+  if (default_scope_is_per_origin_ || zoom_mode_ != ZOOM_MODE_ISOLATED)
+    return;
+
+  content::RenderFrameHost* old_host = old_web_contents->GetMainFrame();
+  content::RenderFrameHost* new_host = new_web_contents->GetMainFrame();
+  const content::HostZoomMap* old_host_zoom_map =
+      content::HostZoomMap::GetForWebContents(old_web_contents);
+  content::HostZoomMap* new_host_zoom_map =
+      content::HostZoomMap::GetForWebContents(new_web_contents);
+
+  PreserveTemporaryZoomLevel(
+      old_host_zoom_map, new_host_zoom_map, old_host, new_host);
+}
+
+void ZoomController::DidCloneToNewWebContents(
+    content::WebContents* old_web_contents,
+    content::WebContents* new_web_contents) {
+  // If a WebContents is cloned when zooming is per-tab, have the clone inherit
+  // the original's zoom level.
+  PreserveTemporaryZoomLevel(old_web_contents, new_web_contents);
+}
+
+void ZoomController::WebContentsReplaced(
+    content::WebContents* new_web_contents) {
+  // A tab may replace its WebContents with another, but from the user's
+  // perspective, this is still the same tab, so we need to preserve the
+  // per-tab zoom.
+  PreserveTemporaryZoomLevel(web_contents(), new_web_contents);
+}
+
 void ZoomController::OnZoomLevelChanged(
     const content::HostZoomMap::ZoomLevelChange& change) {
   UpdateState(change.host);
 }
 
+void ZoomController::OnDefaultZoomScopeChanged() {
+  default_scope_is_per_origin_ = !default_scope_is_per_origin_;
+  UpdateZoomModeOnScopeChangeIfNeeded();
+}
+
 void ZoomController::UpdateState(const std::string& host) {
   // If |host| is empty, all observers should be updated.
   if (!host.empty()) {