Avoid using previously bound texture if view texture isn't ready (#317)

* Revert "Initialize ViewRenderable with transparent texture and set it in material right away (#273)"

This reverts commit 6a15adc

* Avoid using previously bound texture if view texture isn't ready

core/assets-sources/materials/sceneform_view_material.mat

@@ -8,6 +8,10 @@ material {
            "type" : "samplerExternal",
            "name" : "viewTexture"
         },
+        {
+            "type" : "bool",
+            "name" : "viewTextureReady"
+        },
         {
             "type" : "float2",
             "name" : "offsetUv"
@@ -37,7 +41,11 @@ fragment {
         uv.x = uv.x + materialParams.offsetUv.x * (1.0 - 2.0 * uv.x);
         uv.y = uv.y + materialParams.offsetUv.y * (1.0 - 2.0 * uv.y);
 
-        material.baseColor = texture(materialParams_viewTexture, uv);
-        material.baseColor.rgb = inverseTonemapSRGB(material.baseColor.rgb);
+        if (materialParams.viewTextureReady) {
+            material.baseColor = texture(materialParams_viewTexture, uv);
+            material.baseColor.rgb = inverseTonemapSRGB(material.baseColor.rgb);
+        } else {
+            material.baseColor = vec4(0.0);
+        }
     }
 }

core/src/main/java/com/google/ar/sceneform/rendering/RenderViewToExternalTexture.java

@@ -53,26 +53,10 @@ public interface OnViewSizeChangedListener {
 
     externalTexture = new ExternalTexture();
 
-    initializeWithTransparentTexture();
-
     this.view = view;
     addView(view);
   }
 
-  private void initializeWithTransparentTexture() {
-    externalTexture.getSurfaceTexture().setDefaultBufferSize(1, 1);
-
-    // Sanity that the surface is valid.
-    Surface targetSurface = externalTexture.getSurface();
-    if (!targetSurface.isValid()) {
-      return;
-    }
-
-    Canvas surfaceCanvas = targetSurface.lockCanvas(null);
-    surfaceCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
-    targetSurface.unlockCanvasAndPost(surfaceCanvas);
-  }
-
   /**
    * Register a callback to be invoked when the size of the view changes.
    *
@@ -97,6 +81,10 @@ ExternalTexture getExternalTexture() {
     return externalTexture;
   }
 
+  public boolean isViewTextureReady() {
+    return externalTexture.getFilamentStream().getTimestamp() > 0;
+  }
+
   boolean hasDrawnToSurfaceTexture() {
     return hasDrawnToSurfaceTexture;
   }

core/src/main/java/com/google/ar/sceneform/rendering/ViewRenderable.java

@@ -233,15 +233,24 @@ void prepareForDraw() {
     ViewRenderableInternalData data = Preconditions.checkNotNull(viewRenderableData);
     RenderViewToExternalTexture renderViewToExternalTexture = data.getRenderView();
 
-    getMaterial().setExternalTexture("viewTexture", renderViewToExternalTexture.getExternalTexture());
+    getMaterial().setBoolean("viewTextureReady", renderViewToExternalTexture.isViewTextureReady());
 
     if (!renderViewToExternalTexture.isAttachedToWindow()
         || !renderViewToExternalTexture.isLaidOut()) {
       // Wait for the view to finish attachment.
       return;
     }
 
+    // Wait until one frame after the surface texture has been drawn to for the first time.
+    // Fixes an issue where the ViewRenderable would render black for a frame before displaying.
+    boolean hasDrawnToSurfaceTexture = renderViewToExternalTexture.hasDrawnToSurfaceTexture();
+    if (!hasDrawnToSurfaceTexture) {
+      return;
+    }
+
     if (!isInitialized) {
+      getMaterial()
+          .setExternalTexture("viewTexture", renderViewToExternalTexture.getExternalTexture());
       updateSuggestedCollisionShape();
 
       isInitialized = true;