Make it possible to declare and define common preprocessor variables, functions, and global variables for multiple shader passes

[agyild]

As of now, if a shader's multiple passes use the same global variables, functions or preprocessor variables, they need to be (re)defined for both shader passes which is redundant and prone to cause bugs. Instead I propose a more elegant and bug-resistant method such as this:

//!SHARED BEGIN
// Anything here is visible to all passes that use shared variables
// Declare and define once, and use it multiple times
#define FOO 1
const float bar = 42.0;
uint baz() {
   return 42;
}
//!SHARED END
...
//!HOOK MAIN
//!BIND HOOKED
//!DESC Pass1
...
//!SHARED VARS // Insert shared variable definitions
vec4 hook() {
return vec4(bar + FOO + baz());
}
//!HOOK MAIN
//!BIND HOOKED
//!DESC Pass2
...
//!SHARED VARS // Insert shared variable definitions
vec4 hook() {
return vec4(bar + FOO + baz());
}

Could it work? Maybe by detecting the text block and injecting them into every shader pass pre-compilation? Or do you have a better idea?

[haasn]

It's a good idea. Probably just //!SHARED because there's no need to detect the block-end. (it's done implicitly by the start of the next block)

When/if we ever add support for custom runtime parameters we could also put them into the same //!SHARED block.