Some changes in RENDERMODE_CONTINUOUS mode when max_fps has been set.

	
	If Renderer::max_fps has been set, rendering is driven by incoming new
	textures. We draw on each new texture as long as not exceeding max_fps.

	If we are in RENDERMODE_ON_DEMAND mode, Client::Render() can still set dirty
	specifically.

	If we are in ENDERMODE_CONTINUOUS mode, we do NOT set dirty on each tick any
	more (since it is already driven by new textures.).
	There is one problem here: what if new texture don't come in for some reason?
	If that happened, no rendering callback will be invoked and this can cause
	problem sometimes. For example, some UI may depend on the rendering callback
	to work correctly.
	So, in RENDERMODE_CONTINUOUS mode, if we have set max_fps but haven't
	received any new texture for a while, we draw anyway to trigger the rendering
	callback.
	
	
Review URL: http://codereview.chromium.org/2899008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@51982 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 43 insertions, 0 deletions

diff --git a/o3d/core/cross/client.cc b/o3d/core/cross/client.cc
index 271df8e42..f534ef3 100644
--- a/o3d/core/cross/client.cc
+++ b/o3d/core/cross/client.cc
@@ -65,6 +65,25 @@ using std::vector;
 using std::make_pair;
 
 namespace o3d {
+// If Renderer::max_fps has been set, rendering is driven by incoming new
+// textures. We draw on each new texture as long as not exceeding max_fps.
+//
+// If we are in RENDERMODE_ON_DEMAND mode, Client::Render() can still set dirty
+// specifically.
+//
+// If we are in RENDERMODE_CONTINUOUS mode, we do NOT set dirty on each tick any
+// more (since it is already driven by new textures.).
+// There is one problem here: what if new texture don't come in for some reason?
+// If that happened, no rendering callback will be invoked and this can cause
+// problem sometimes. For example, some UI may depend on the rendering callback
+// to work correctly.
+// So, in RENDERMODE_CONTINUOUS mode, if we have set max_fps but haven't
+// received any new texture for a while, we draw anyway to trigger the rendering
+// callback.
+// This value defines the minimum number of draws per seconds in
+// RENDERMODE_CONTINUOUS mode.
+static const float kContinuousModeMinDrawPerSecond = 15;
+// TODO(zhurunz) Tuning this value.
 
 // Client constructor.  Creates the default root node for the scenegraph
 Client::Client(ServiceLocator* service_locator)
@@ -356,6 +375,30 @@ bool Client::IsRendering() {
   return (renderer_.IsAvailable() && renderer_->rendering());
 }
 
+bool Client::NeedsContinuousRender() {
+  // Sanity check
+  if (!renderer_.IsAvailable()) {
+    return false;
+  }
+
+  bool needRender = false;
+  // Only may happen in RENDERMODE_CONTINUOUS mode.
+  if (render_mode() == RENDERMODE_CONTINUOUS) {
+    // Always need a draw in normal RENDERMODE_CONTINUOUS mode.
+    needRender = true;
+
+    // If max_fps has been set, only need a draw when "long time no draw".
+    int max_fps = renderer_->max_fps();
+    if (max_fps > 0 &&
+        render_elapsed_time_timer_.GetElapsedTimeWithoutClearing() <
+        1.0/kContinuousModeMinDrawPerSecond)
+    {
+      needRender = false;
+    }
+  }
+  return needRender;
+}
+
 // Executes draw calls for all visible shapes in a subtree
 void Client::RenderTree(RenderNode *tree_root) {
   if (!renderer_.IsAvailable())