[Public WebGL] Buffer size and viewport

[Alan Chaney <alan@mechnicality.com>]

Hi

Desktop GL programming frequently requires that the user sets the window 
size as part of the game/application setup. This means that normally the 
viewport can be set to (0, 0, displaybufferwidth, displaybufferheight). 
However, in a WebGL application it is likely to be very common that the 
window size will change due to use input.

The default with WebGL is to set the buffer size to that of the canvas 
element and the viewport to that as well. This means that if the window 
is resized to greater dimensions than the original canvas size the 
display buffer must be discarded and a new buffer initialized - this 
takes time. One option that I can see is to make the display buffer 
considerably bigger than the canvas element - perhaps by doing some 
calculation based upon my UI layout and the underlying screen size and 
setting this value when creating the context.
Then as the canvas is resized  I simply set the viewport size to match 
the size of the canvas element, until, of course, it exceeds the 
underlying buffer size.

Does anyone have any feel to the relationship between viewport size and 
buffer size and performance? In other words, if I allocate a larger 
buffer than I actually display in the view port, is this likely to cause 
a significant performance issue?

Thanks in advance,

Alan

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