[Android WebView] Update and extend the description of AwDrawGLInfo.

BUG=161409

Review URL: https://chromiumcodereview.appspot.com/11411010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@174234 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 23 insertions, 5 deletions

diff --git a/android_webview/public/browser/draw_gl.h b/android_webview/public/browser/draw_gl.h
index 8bea559..441793e 100644
--- a/android_webview/public/browser/draw_gl.h
+++ b/android_webview/public/browser/draw_gl.h
@@ -11,13 +11,15 @@ extern "C" {
 
 // Holds the information required to trigger an OpenGL drawing operation.
 struct AwDrawGLInfo {
-  // Input: Tells the Draw function what action to perform.
+  // Input: tells the draw function what action to perform.
   enum Mode {
     kModeDraw,
     kModeProcess,
   } mode;
 
-  // Input: current clip rect.
+  // Input: current clip rect in surface coordinates. Reflects the current state
+  // of the OpenGL scissor rect. Both the OpenGL scissor rect and viewport are
+  // set by the caller of the draw function and updated during View animations.
   int clip_left;
   int clip_top;
   int clip_right;
@@ -27,10 +29,26 @@ struct AwDrawGLInfo {
   int width;
   int height;
 
-  // Input: is the render target an FBO.
+  // Input: is the View rendered into an independent layer.
+  // If false, the surface is likely to hold to the full screen contents, with
+  // the scissor box set by the caller to the actual View location and size.
+  // Also the transformation matrix will contain at least a translation to the
+  // position of the View to render, plus any other transformations required as
+  // part of any ongoing View animation. View translucency (alpha) is ignored,
+  // although the framework will set is_layer to true for non-opaque cases.
+  // Can be requested via the View.setLayerType(View.LAYER_TYPE_NONE, ...)
+  // Android API method.
+  //
+  // If true, the surface is dedicated to the View and should have its size.
+  // The viewport and scissor box are set by the caller to the whole surface.
+  // Animation transformations are handled by the caller and not reflected in
+  // the provided transformation matrix. Translucency works normally.
+  // Can be requested via the View.setLayerType(View.LAYER_TYPE_HARDWARE, ...)
+  // Android API method.
   bool is_layer;
 
-  // Input: current transform matrix, in OpenGL format.
+  // Input: current transformation matrix in surface pixels.
+  // Uses the column-based OpenGL matrix format.
   float transform[16];
 
   // Output: tells the caller what to do next.
@@ -43,7 +61,7 @@ struct AwDrawGLInfo {
   // Output: mask indicating the status after calling the functor.
   unsigned int status_mask;
 
-  // Output: dirty region to redraw.
+  // Output: dirty region to redraw in surface coordinates.
   float dirty_left;
   float dirty_top;
   float dirty_right;