Add a switch to invert web contents (non-accel only).

The switch will just be used during development of this feature.
The idea is for this to be turned automatically for Windows users
who enable an inverted (white-on-black) color scheme - see bug
for detail.

This first patch only handles the non-accelerated graphics path;
a subsequent change will handle the accelerated path.

BUG=112944
TEST=manually test with --invert-web-contents switch


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=120928

Review URL: http://codereview.chromium.org/9353012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@121541 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 70 insertions, 1 deletions

diff --git a/content/browser/renderer_host/render_view_host.cc b/content/browser/renderer_host/render_view_host.cc
index 24e09f5..6d610b0 100644
--- a/content/browser/renderer_host/render_view_host.cc
+++ b/content/browser/renderer_host/render_view_host.cc
@@ -45,6 +45,7 @@
 #include "content/public/browser/user_metrics.h"
 #include "content/public/common/bindings_policy.h"
 #include "content/public/common/content_constants.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/result_codes.h"
 #include "content/public/common/url_constants.h"
 #include "net/base/net_util.h"
@@ -209,6 +210,10 @@ bool RenderViewHost::CreateRenderView(const string16& frame_name,
   // Let our delegate know that we created a RenderView.
   delegate_->RenderViewCreated(this);
 
+  // Invert the color scheme if a flag was set.
+  if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kInvertWebContent))
+    Send(new ViewMsg_InvertWebContent(routing_id(), true));
+
   FOR_EACH_OBSERVER(
       content::RenderViewHostObserver, observers_, RenderViewHostInitialized());
 
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 9d90eb1..d247651 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -2016,3 +2016,8 @@ IPC_MESSAGE_ROUTED0(ViewHostMsg_UnlockMouse)
 IPC_MESSAGE_ROUTED2(ViewHostMsg_DomOperationResponse,
                     std::string  /* json_string */,
                     int  /* automation_id */)
+
+// Enable or disable inverting of web content pixels, for users who prefer
+// white-on-black.
+IPC_MESSAGE_ROUTED1(ViewMsg_InvertWebContent,
+                    bool /* invert */)
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 6baf3c7..0bec7fa 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -373,6 +373,10 @@ const char kInProcessPlugins[]              = "in-process-plugins";
 // Runs WebGL inside the renderer process.
 const char kInProcessWebGL[]                = "in-process-webgl";
 
+// Invert web content pixels, for users who prefer white-on-black.
+// (Temporary, just during development and testing of this feature.)
+const char kInvertWebContent[]              = "invert-web-content";
+
 // Specifies the flags passed to JS engine
 const char kJavaScriptFlags[]               = "js-flags";
 
diff --git a/content/public/common/content_switches.h b/content/public/common/content_switches.h
index 6802555..f271ebd 100644
--- a/content/public/common/content_switches.h
+++ b/content/public/common/content_switches.h
@@ -117,6 +117,7 @@ CONTENT_EXPORT extern const char kIgnoreGpuBlacklist[];
 extern const char kInProcessGPU[];
 extern const char kInProcessPlugins[];
 CONTENT_EXPORT extern const char kInProcessWebGL[];
+CONTENT_EXPORT extern const char kInvertWebContent[];
 CONTENT_EXPORT extern const char kJavaScriptFlags[];
 extern const char kLoadPlugin[];
 CONTENT_EXPORT extern const char kLoggingLevel[];
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index bbc4ecc..99b3731 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -24,6 +24,7 @@
 #include "ipc/ipc_sync_message.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkShader.h"
+#include "third_party/skia/include/effects/SkTableColorFilter.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebCursorInfo.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebPoint.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPopupMenu.h"
@@ -98,7 +99,8 @@ RenderWidget::RenderWidget(WebKit::WebPopupType popup_type)
       is_accelerated_compositing_active_(false),
       animation_update_pending_(false),
       animation_task_posted_(false),
-      invalidation_task_posted_(false) {
+      invalidation_task_posted_(false),
+      invert_(false) {
   RenderProcess::current()->AddRefProcess();
   DCHECK(RenderThread::Get());
   has_disable_gpu_vsync_switch_ = CommandLine::ForCurrentProcess()->HasSwitch(
@@ -217,6 +219,7 @@ bool RenderWidget::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ViewMsg_Repaint, OnMsgRepaint)
     IPC_MESSAGE_HANDLER(ViewMsg_SetTextDirection, OnSetTextDirection)
     IPC_MESSAGE_HANDLER(ViewMsg_Move_ACK, OnRequestMoveAck)
+    IPC_MESSAGE_HANDLER(ViewMsg_InvertWebContent, OnInvertWebContent)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -587,6 +590,16 @@ void RenderWidget::PaintRect(const gfx::Rect& rect,
   canvas->translate(static_cast<SkScalar>(-canvas_origin.x()),
                     static_cast<SkScalar>(-canvas_origin.y()));
 
+  if (invert_) {
+    // Draw everything to a temporary bitmap and then apply an
+    // inverting color map to the result. This is balanced by an extra
+    // call to canvas->restore(), below.
+    DCHECK(invert_paint_.get());
+    SkRect bounds;
+    bounds.set(rect.x(), rect.y(), rect.right(), rect.bottom());
+    canvas->saveLayer(&bounds, invert_paint_.get());
+  }
+
   // If there is a custom background, tile it.
   if (!background_.empty()) {
     SkPaint paint;
@@ -647,6 +660,9 @@ void RenderWidget::PaintRect(const gfx::Rect& rect,
     skia::GetTopDevice(*canvas)->accessBitmap(false);
   }
 
+  if (invert_)
+    canvas->restore();
+
   PaintDebugBorder(rect, canvas);
   canvas->restore();
 }
@@ -1389,6 +1405,37 @@ void RenderWidget::OnSetTextDirection(WebTextDirection direction) {
   webwidget_->setTextDirection(direction);
 }
 
+void RenderWidget::OnInvertWebContent(bool invert) {
+  if (invert_ == invert)
+    return;
+
+  invert_ = invert;
+
+  if (invert_ && !invert_paint_.get()) {
+    // Gamma-aware color inversion: each source pixel value x is normally
+    // displayed on a computer monitor with a gamma correction x^gamma,
+    // where gamma is typically in the range 1.8...2.2. By approximating
+    // gamma as exactly 2, the formula to invert one value is sqrt(1 - x^2).
+    uint8_t table[256];
+    for (unsigned int i = 0; i < 256; i++) {
+      double value = i / 255.0;
+      value = sqrt(1 - (value * value));
+      table[i] = static_cast<uint8_t>(255 * value);
+    }
+
+    // Create a Skia Paint with this inverting color map.
+    invert_paint_.reset(new SkPaint());
+    invert_paint_->setStyle(SkPaint::kFill_Style);
+    invert_paint_->setColor(SK_ColorBLACK);
+    SkColorFilter* filter = SkTableColorFilter::CreateARGB(
+        NULL, table, table, table);
+    invert_paint_->setColorFilter(filter);
+    filter->unref();
+  }
+
+  OnMsgRepaint(size_);
+}
+
 webkit::ppapi::PluginInstance* RenderWidget::GetBitmapForOptimizedPluginPaint(
     const gfx::Rect& paint_bounds,
     TransportDIB** dib,
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index c1f53cd..d1968e0 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -233,6 +233,7 @@ class CONTENT_EXPORT RenderWidget
   void OnMsgRepaint(const gfx::Size& size_to_paint);
   void OnSetTextDirection(WebKit::WebTextDirection direction);
   void OnGetFPS();
+  void OnInvertWebContent(bool invert);
 
   // Override points to notify derived classes that a paint has happened.
   // WillInitiatePaint happens when we're about to generate a new bitmap and
@@ -495,6 +496,12 @@ class CONTENT_EXPORT RenderWidget
   // case NULL is added to the queue.
   std::deque<ViewHostMsg_UpdateRect*> updates_pending_swap_;
 
+  // Set to true if we should invert all pixels.
+  bool invert_;
+
+  // The Skia paint object for inverting.
+  scoped_ptr<SkPaint> invert_paint_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };