Question

I’m creating a custom (layer-hosting) document view, which is contained within a scroll view. The root layer has two sub layers of the same size–one for the view’s content, and one for anything that needs to hover over the main content. I set the frame to 2500×2500 and added a number of cells to the content layer, which was fine. On adding a translucent clone of one of the cell’s layers to the overlay layer, the whole view clears briefly, and I get a log message ‘core animation: surface 2502×2502 is too large’. This happens between adding the new layer and the next cycle of the event loop, so I guess when core animation renders the new layer.

I knew that a layer’s content size is related to opengl texture size, but didn’t think its frame mattered. I’m not drawing anything to these layers, not setting any style properties, and remove offscreen sub layers. All I’m really using them for is to handle the geometry of the document view. Is this an appropriate use of CA layers? If not, are there better ways of handling a large core animation-based document view?

Edit:

I’ve had this problem again, caused by an implicit animation on adding sublayers to the large parent. So in addition to what is suggested below, that’s one to check if you run into this.

Answer 1

I would check to make sure that you’re not setting any properties on your 2500×2500 layers which could require offscreen rendering. (This causes the layer to try and create a full-size buffer off-screen and render its contents into that buffer, rather than just rendering the contents to the screen directly.)

For example, setting an opacity, masksToBounds, mask, shouldRasterize, etc, could cause offscreen-rendering. You can see if offscreen-rendering is happening with the Core Animation instrument. (There’s a checkbox to highlight offscreen-rendered areas.)