fix point() origin bug and stale per-vertex color leak

src/webgl/p5.RendererGL.Retained.js

@@ -247,15 +247,26 @@ p5.RendererGL.prototype._drawElements = function(drawMode, gId) {
 p5.RendererGL.prototype._drawPoints = function(vertices, pointBuffers) {
   const gl = this.GL;
   const pointShader = this._getImmediatePointShader();
-  this._setPointUniforms(pointShader);
 
-  // Prepare position and optional per-vertex color buffers
   if (Array.isArray(pointBuffers)) {
+    const geom = this.immediateMode.geometry;
+
+    if (geom.vertices !== vertices) {
+      geom.vertices = vertices;
+      geom.dirtyFlags.vertices = true;
+      if (geom.vertexStrokeColors.length > 0) {
+        geom.vertexStrokeColors.length = 0;
+        geom.dirtyFlags.vertexStrokeColors = true;
+      }
+    }
+
+    this._setPointUniforms(pointShader);
+
     for (const buff of pointBuffers) {
-      buff._prepareBuffer(this.immediateMode.geometry, pointShader);
+      buff._prepareBuffer(geom, pointShader);
     }
   } else {
-    // Backward compatibility if a raw GL buffer is passed
+    this._setPointUniforms(pointShader);
     this._bindBuffer(
       pointBuffers,
       gl.ARRAY_BUFFER,

test/unit/visual/cases/webgl.js

@@ -140,5 +140,34 @@ visualSuite('WebGL', function() {
       p5.box(30);
       screenshot();
     });
+
+    visualTest(
+      'Per-vertex POINTS color does not leak into point()',
+      (p5, screenshot) => {
+        p5.createCanvas(100, 100, p5.WEBGL);
+        p5.background(0);
+        p5.strokeWeight(8);
+
+        p5.beginShape(p5.POINTS);
+        p5.stroke(255, 0, 0);
+        p5.vertex(-30, -20, 0);
+        p5.stroke(0, 255, 0);
+        p5.vertex(-10, -20, 0);
+        p5.stroke(0, 0, 255);
+        p5.vertex(10, -20, 0);
+        p5.stroke(255, 255, 0);
+        p5.vertex(30, -20, 0);
+        p5.endShape();
+
+        p5.stroke(255, 0, 255);
+        p5.point(-20, 20, 0);
+        p5.stroke(0, 255, 255);
+        p5.point(0, 20, 0);
+        p5.stroke(255);
+        p5.point(20, 20, 0);
+
+        screenshot();
+      }
+    );
   });
 });

test/unit/visual/screenshots/WebGL/Strokes/Per-vertex POINTS color does not leak into point()/metadata.json

@@ -0,0 +1,3 @@
+{
+  "numScreenshots": 1
+}