added additional information about shader behavior

src/webgl/material.js

@@ -342,6 +342,14 @@ p5.prototype.createFilterShader = function (fragSrc) {
  * Use <a href="#/p5/resetShader">resetShader()</a> to
  * restore the default shaders.
  *
+ * **Additional Information:**
+   * The shader will be used for:
+   - Fills when a texture is enabled if it includes a uniform `sampler2D`.
+   - Fills when lights are enabled if it includes the attribute `aNormal`, or if it has any of the following uniforms: `uUseLighting`, `uAmbientLightCount`, `uDirectionalLightCount`, `uPointLightCount`, `uAmbientColor`, `uDirectionalDiffuseColors`, `uDirectionalSpecularColors`, `uPointLightLocation`, `uPointLightDiffuseColors`, `uPointLightSpecularColors`, `uLightingDirection`, or `uSpecular`.
+   - Fills whenever there are no lights or textures.
+   - Strokes if it includes the uniform `uStrokeWeight`.
+   * **Note:** This behavior is considered experimental, and changes are planned in future releases.
+ *
  * Note, shaders can only be used in WEBGL mode.
  *
  * @method shader