blendFunc and blendFuncSeparate constant validation is incorrect #323
Description
I think the validation for constant blend functions is currently too aggressive. All constant blends are blocked, but in the spec its only an error to use a combination of "alpha" and "color" constants for src and dst
https://registry.khronos.org/webgl/specs/1.0/
6.13 Blending With Constant Color
In the WebGL API, constant color and constant alpha cannot be used together as source
and destination factors in the blend function. A call to blendFunc will generate an
INVALID_OPERATION error if one of the two factors is set to CONSTANT_COLOR or ONE_MINUS_CONSTANT_COLOR
and the other to CONSTANT_ALPHA or ONE_MINUS_CONSTANT_ALPHA. A call to blendFuncSeparate will generate an
INVALID_OPERATION error if srcRGB is set to CONSTANT_COLOR or ONE_MINUS_CONSTANT_COLOR and dstRGB is set to
CONSTANT_ALPHA or ONE_MINUS_CONSTANT_ALPHA or vice versa.
patch to fix:
diff --git a/src/javascript/webgl-rendering-context.js b/src/javascript/webgl-rendering-context.js
index de011e9..18aba98 100644
--- a/src/javascript/webgl-rendering-context.js
+++ b/src/javascript/webgl-rendering-context.js
@@ -293,12 +293,18 @@ class WebGLRenderingContextHelper extends NativeWebGLRenderingContext {
return null
}
- _isConstantBlendFunc (factor) {
+ _isConstantColorBlendFunc (factor) {
return (
factor === this.CONSTANT_COLOR ||
- factor === this.ONE_MINUS_CONSTANT_COLOR ||
+ factor === this.ONE_MINUS_CONSTANT_COLOR
+ )
+ }
+
+ _isConstantAlphaBlendFunc (factor) {
+ return (
factor === this.CONSTANT_ALPHA ||
- factor === this.ONE_MINUS_CONSTANT_ALPHA)
+ factor === this.ONE_MINUS_CONSTANT_ALPHA
+ )
}
_isObject (object, method, Wrapper) {
@@ -868,7 +874,8 @@ class WebGLRenderingContextHelper extends NativeWebGLRenderingContext {
this.setError(this.INVALID_ENUM)
return
}
- if (this._isConstantBlendFunc(sfactor) && this._isConstantBlendFunc(dfactor)) {
+ if (this._isConstantColorBlendFunc(sfactor) && this._isConstantAlphaBlendFunc(dfactor) ||
+ this._isConstantColorBlendFunc(dfactor) && this._isConstantAlphaBlendFunc(sfactor)) {
this.setError(this.INVALID_OPERATION)
return
}
@@ -893,8 +900,8 @@ class WebGLRenderingContextHelper extends NativeWebGLRenderingContext {
return
}
- if ((this._isConstantBlendFunc(srcRGB) && this._isConstantBlendFunc(dstRGB)) ||
- (this._isConstantBlendFunc(srcAlpha) && this._isConstantBlendFunc(dstAlpha))) {
+ if ((this._isConstantColorBlendFunc(srcRGB) && this._isConstantAlphaBlendFunc(dstRGB)) ||
+ (this._isConstantColorBlendFunc(dstRGB) && this._isConstantAlphaBlendFunc(srcRGB))) {
this.setError(this.INVALID_OPERATION)
return
}