WebGLRenderingContext.isEnabled()

cap

GLenum 指定待检测的 WebGL 功能项。可能的值有：

Constant	Description
gl.BLEND	Blending of the computed fragment color values. See WebGLRenderingContext.blendFunc().
gl.CULL_FACE	Culling of polygons. See WebGLRenderingContext.cullFace().
gl.DEPTH_TEST	Depth comparisons and updates to the depth buffer. See WebGLRenderingContext.depthFunc().
gl.DITHER	Dithering of color components before they get written to the color buffer.
gl.POLYGON_OFFSET_FILL	Adding an offset to depth values of polygon's fragments. See WebGLRenderingContext.polygonOffset().
gl.SAMPLE_ALPHA_TO_COVERAGE	Computation of a temporary coverage value determined by the alpha value.
gl.SAMPLE_COVERAGE	ANDing the fragment's coverage with the temporary coverage value. See WebGLRenderingContext.sampleCoverage().
gl.SCISSOR_TEST	Scissor test that discards fragments that are outside of the scissor rectangle. See WebGLRenderingContext.scissor().
gl.STENCIL_TEST	Stencil testing and updates to the stencil buffer. See WebGLRenderingContext.stencilFunc().

当使用 WebGL 2 context 的时候，下列附加的值也是可选用的。

Constant	Description
gl.RASTERIZER_DISCARD	Primitives are discarded immediately before the rasterization stage, but after the optional transform feedback stage. gl.clear() commands are ignored.

GLboolean 指示能力项 cap 可用 (true)，不可用 (false)。

gl.isEnabled(gl.STENCIL_TEST);
// false

启用或停用给定的能力项，使用 WebGLRenderingContext.enable() 方法和 WebGLRenderingContext.disable() 方法：

gl.enable(gl.STENCIL_TEST);
gl.disable(gl.STENCIL_TEST);

• WebGLRenderingContext.enable()
• WebGLRenderingContext.disable()