Bug 982275 - Part 2: Add a pref for drawing layer-info inside layers. r=jrmuizel

gfx/layers/Layers.h

@@ -1308,6 +1308,13 @@ public:
    */
   void LogSelf(const char* aPrefix="");
 
+  // Print interesting information about this into aTo.  Internally
+  // used to implement Dump*() and Log*().  If subclasses have
+  // additional interesting properties, they should override this with
+  // an implementation that first calls the base implementation then
+  // appends additional info to aTo.
+  virtual nsACString& PrintInfo(nsACString& aTo, const char* aPrefix);
+
   static bool IsLogEnabled() { return LayerManager::IsLogEnabled(); }
 
   /**
@@ -1351,13 +1358,6 @@ public:
 protected:
   Layer(LayerManager* aManager, void* aImplData);
 
-  // Print interesting information about this into aTo.  Internally
-  // used to implement Dump*() and Log*().  If subclasses have
-  // additional interesting properties, they should override this with
-  // an implementation that first calls the base implementation then
-  // appends additional info to aTo.
-  virtual nsACString& PrintInfo(nsACString& aTo, const char* aPrefix);
-
   /**
    * We can snap layer transforms for two reasons:
    * 1) To avoid unnecessary resampling when a transform is a translation

gfx/layers/composite/ContainerLayerComposite.cpp

@@ -31,6 +31,7 @@
 #include "nsRect.h"                     // for nsIntRect
 #include "nsRegion.h"                   // for nsIntRegion
 #include "nsTArray.h"                   // for nsAutoTArray
+#include "TextRenderer.h"               // for TextRenderer
 #include <vector>
 
 namespace mozilla {
@@ -120,6 +121,32 @@ static gfx::Point GetScrollData(Layer* aLayer) {
   return origin;
 }
 
+static void DrawLayerInfo(const nsIntRect& aClipRect,
+                          LayerManagerComposite* aManager,
+                          Layer* aLayer)
+{
+
+  if (aLayer->GetType() == Layer::LayerType::TYPE_CONTAINER) {
+    // XXX - should figure out a way to render this, but for now this
+    // is hard to do, since it will often get superimposed over the first
+    // child of the layer, which is bad.
+    return;
+  }
+
+  nsAutoCString layerInfo;
+  aLayer->PrintInfo(layerInfo, "");
+
+  nsIntRegion visibleRegion = aLayer->GetVisibleRegion();
+
+  uint32_t maxWidth = visibleRegion.GetBounds().width < 500 ? visibleRegion.GetBounds().width : 500;
+
+  nsIntPoint topLeft = visibleRegion.GetBounds().TopLeft();
+  aManager->GetTextRenderer()->RenderText(layerInfo.get(), gfx::IntPoint(topLeft.x, topLeft.y),
+                                          aLayer->GetEffectiveTransform(), 16,
+                                          maxWidth);
+
+}
+
 static LayerVelocityUserData* GetVelocityData(Layer* aLayer) {
   static char sLayerVelocityUserDataKey;
   void* key = reinterpret_cast<void*>(&sLayerVelocityUserDataKey);
@@ -361,6 +388,10 @@ ContainerRender(ContainerT* aContainer,
     if (gfxPrefs::LayersScrollGraph()) {
       DrawVelGraph(clipRect, aManager, layerToRender->GetLayer());
     }
+
+    if (gfxPrefs::DrawLayerInfo()) {
+      DrawLayerInfo(clipRect, aManager, layerToRender->GetLayer());
+    }
     // invariant: our GL context should be current here, I don't think we can
     // assert it though
   }

gfx/layers/composite/LayerManagerComposite.cpp

@@ -51,7 +51,7 @@
 #include <android/log.h>
 #endif
 #include "GeckoProfiler.h"
-#include "TextRenderer.h"
+#include "TextRenderer.h"               // for TextRenderer
 
 class gfxASurface;
 class gfxContext;

gfx/thebes/gfxPrefs.h

@@ -154,6 +154,7 @@ private:
   DECL_GFX_PREF(Live, "layers.draw-bigimage-borders",          DrawBigImageBorders, bool, false);
   DECL_GFX_PREF(Live, "layers.draw-borders",                   DrawLayerBorders, bool, false);
   DECL_GFX_PREF(Live, "layers.draw-tile-borders",              DrawTileBorders, bool, false);
+  DECL_GFX_PREF(Live, "layers.draw-layer-info",                DrawLayerInfo, bool, false);
   DECL_GFX_PREF(Once, "layers.dump",                           LayersDump, bool, false);
   DECL_GFX_PREF(Once, "layers.enable-tiles",                   LayersTilesEnabled, bool, false);
   DECL_GFX_PREF(Once, "layers.simple-tiles",                   LayersUseSimpleTiles, bool, false);