ColorTarget constructor

Implementation

const ColorTarget({
  required this.texture,
  this.resolveTexture,
  this.loadAction = LoadAction.clear,
  this.storeAction = StoreAction.store,
  this.clearValue,
  this.face = 0,
  this.mipLevel = 0,
}) : assert(face >= 0 && face < 6, 'a texture has at most six faces'),
     assert(mipLevel >= 0, 'a mip level counts down from the base'),
     // **Checked here rather than by each backend, because no backend was
     // checking.** The doc on [resolveTexture] said "the backend checks" and
     // named a promise nobody kept: Impeller forwards both fields to
     // flutter_gpu and asks nothing, WebGL2 reads the resolve target and
     // never looks at the store action, and the software rasteriser has no
     // multisampling to resolve. So a resolve target with `StoreAction.store`
     // beside it was three different silences — and the symptom is a
     // multisampled attachment that never reaches the texture the next pass
     // samples, which is a black or stale picture rather than an error.
     //
     // One assert in the constructor is the same shape as
     // `StencilState.narrowReference` and `readbackRegionOf`: a rule the
     // three would otherwise each have to keep, decided once above them.
     assert(
       resolveTexture == null ||
           storeAction == StoreAction.multisampleResolve ||
           storeAction == StoreAction.storeAndMultisampleResolve,
       'a ColorTarget with a resolveTexture must store through it: '
       'StoreAction.multisampleResolve, or storeAndMultisampleResolve when '
       'the multisampled texture is wanted afterwards too. With '
       'StoreAction.store the resolve never happens and whatever samples the '
       'resolve target reads what was in it before.',
     );