[Chromecast] Handle device scale factor correctly

chromecast/browser/cast_content_browser_client.cc

Index: chromecast/browser/cast_content_browser_client.cc
diff --git a/chromecast/browser/cast_content_browser_client.cc b/chromecast/browser/cast_content_browser_client.cc
index 39ffe59e106972dfaeda5bba64eb4660ccaef65a..731902baf32b5336e9ab6588961ff517ce5f7428 100644
--- a/chromecast/browser/cast_content_browser_client.cc
+++ b/chromecast/browser/cast_content_browser_client.cc
@@ -27,6 +27,7 @@
 #include "chromecast/browser/cast_network_delegate.h"
 #include "chromecast/browser/cast_quota_permission_context.h"
 #include "chromecast/browser/cast_resource_dispatcher_host_delegate.h"
+#include "chromecast/browser/cast_web_contents_user_data.h"
 #include "chromecast/browser/geolocation/cast_access_token_store.h"
 #include "chromecast/browser/media/cma_message_filter_host.h"
 #include "chromecast/browser/service/cast_service_simple.h"
@@ -50,6 +51,7 @@
 #include "content/public/common/web_preferences.h"
 #include "net/ssl/ssl_cert_request_info.h"
 #include "net/url_request/url_request_context_getter.h"
+#include "ui/gfx/screen.h"
 #include "ui/gl/gl_switches.h"
 
 #if defined(ENABLE_MOJO_MEDIA_IN_BROWSER_PROCESS)
@@ -276,13 +278,40 @@ void CastContentBrowserClient::OverrideWebkitPrefs(
   // Enable 5% margins for WebVTT cues to keep within title-safe area
   prefs->text_track_margin_percentage = 5;
 
+  // This block of logic allows us to force 720p resolution for apps which don't
+  // handle scaling to higher resolutions (i.e. were built assuming 720p and
+  // have layout or performance problems at anything else).
+  // We use the viewport tag approach and ViewportStyle::TELEVISION to force a
+  // 720p layout viewport in this case.
+  // TODO(halliwell): require apps to handle scaling to any resolution; then
+  // we can simply run at the platform's native resolution.
 #if defined(OS_ANDROID)
-  // Enable the television style for viewport so that all cast apps have a
-  // 1280px wide layout viewport by default.
+  // Android has viewport enabled by default.  Disable for consistency with
+  // Linux (only enable below for 720p app case).
   DCHECK(prefs->viewport_enabled);
   DCHECK(prefs->viewport_meta_enabled);
-  prefs->viewport_style = content::ViewportStyle::TELEVISION;
+  prefs->viewport_enabled = false;

[alokp, 2016/05/11 16:46:53]

This seems risky to me. I am not sure what else we might break by disabling
viewport on Android. You should ask blink folks for advice.

I was under the impression that we would attempt the opposite - enable viewport
on non-android platforms. That gives applications most freedom to either use the
default viewport or define their own.

+  prefs->viewport_meta_enabled = false;
 #endif  // defined(OS_ANDROID)
+
+  content::WebContents* web_contents =
+      content::WebContents::FromRenderViewHost(render_view_host);
+  if (web_contents) {
+    CastWebContentsUserData* user_data =
+        static_cast<CastWebContentsUserData*>(
+            web_contents->GetUserData(CastWebContentsUserData::UserDataKey()));
+    if (user_data->resolution_height() == 720) {
+      prefs->viewport_enabled = true;
+      prefs->viewport_meta_enabled = true;
+      prefs->viewport_style = content::ViewportStyle::TELEVISION;
+
+      gfx::Size display_size =
+          gfx::Screen::GetScreen()->GetPrimaryDisplay().size();
+      const float scale_factor = display_size.height() / 720.0f;
+      prefs->default_minimum_page_scale_factor = scale_factor;
+      prefs->default_maximum_page_scale_factor = scale_factor;
+    }
+  }
 }
 
 void CastContentBrowserClient::ResourceDispatcherHostCreated() {