CODEWITHSUNDEEP
cvulkan
Gary Allen
Gary Allen

Reputation: 1370

Create Vulkan surface for only a portion of a window

We have an application which has a window with a horizontal toolbar at the top. The windows-level handle we pass to Vulkan to create the surface ends up including the area behind the toolbar i.e. Vulkan is completely unaware of the toolbar and the surface includes the space "behind" it.

My question is, can a surface represent only a portion of this window? We obviously need not process data for the pixels that lie behind the toolbar, and so want to avoid creating a frame buffer, depth buffer etc. bigger than necessary.

I fully understand that I can accomplish this visually using a viewport which e.g. has an origin offset and height compensation, however to my understanding the frame buffer actually still contains information for pixels the full size of the surface (e.g. 800x600 for an 800x600 client-area window) even if I am only rendering to a portion of that window. The frame buffer then gets "mapped" and therefore squished to the viewport area.

All of this has sort of left me wondering what the purpose of a viewport is. If it simply defines a mapping from your image buffer to an area in the surface, is that not highly inefficient if your framebuffer contains considerably more pixels than the area it is being mapped to? Would it not make sense to rather section of portions in your application using e.g. different windows HWNDs FIRST, and then create different surfaces from then onwards?

How can I avoid rendering to an area bigger than necessary?

Upvotes: 1

Views: 1106

Answers (1)

Nicol Bolas
Nicol Bolas

Reputation: 473352

The way this gets handled for pretty much every application is that the client area of a window (ie: the stuff that isn't toolbars and the like) is a child window of the main frame window. When the frame is resized, you resize the client window to match the new client area (taking into account the new sizes of the toolbars/etc).

It is this client window which should have a Vulkan surface created for it.

Upvotes: 2

Related Questions