Removing custom material variable inside of LineMesh (#16767)

LineMesh uses its own private variable to hold the material of the mesh.
The problem with this, is that Mesh has logic related to materials and
LineMesh while inheriting from Mesh, is missing all this logic.

I have removed the custom variable inside of LineMesh and adjusted the
code to use the Material of the Mesh class instead. I have maintained
the LineMesh interface where get/set material returns Material instead
of Nullable<Material> like Mesh does.

Author: VicenteCartas

packages/dev/core/src/Meshes/linesMesh.ts

@@ -45,9 +45,11 @@ export class LinesMesh extends Mesh {
      */
     public intersectionThreshold: number;
 
-    private _lineMaterial: Material;
+    private _isShaderMaterial(shader: Nullable<Material>): shader is ShaderMaterial {
+        if (!shader) {
+            return false;
+        }
 
-    private _isShaderMaterial(shader: Material): shader is ShaderMaterial {
         return shader.getClassName() === "ShaderMaterial";
     }
 
@@ -143,14 +145,6 @@ export class LinesMesh extends Mesh {
         }
     }
 
-    public override isReady() {
-        if (!this._lineMaterial.isReady(this, !!this._userInstancedBuffersStorage || this.hasThinInstances)) {
-            return false;
-        }
-
-        return super.isReady();
-    }
-
     /**
      * @returns the string "LineMesh"
      */
@@ -161,16 +155,18 @@ export class LinesMesh extends Mesh {
     /**
      * @internal
      */
-    public override get material(): Material {
-        return this._lineMaterial;
+    public override get material(): Nullable<Material> {
+        return this._internalAbstractMeshDataInfo._material as Material;
     }
 
     /**
      * @internal
      */
-    public override set material(value: Material) {
-        this._lineMaterial = value;
-        this._lineMaterial.fillMode = Material.LineListDrawMode;
+    public override set material(value: Nullable<Material>) {
+        this._setMaterial(value);
+        if (this.material) {
+            this.material.fillMode = Material.LineListDrawMode;
+        }
     }
 
     /**
@@ -201,10 +197,10 @@ export class LinesMesh extends Mesh {
         }
 
         // Color
-        if (!this.useVertexColor && this._isShaderMaterial(this._lineMaterial)) {
+        if (!this.useVertexColor && this._isShaderMaterial(this.material)) {
             const { r, g, b } = this.color;
             this._color4.set(r, g, b, this.alpha);
-            this._lineMaterial.setColor4("color", this._color4);
+            this.material.setColor4("color", this._color4);
         }
 
         return this;
@@ -230,20 +226,6 @@ export class LinesMesh extends Mesh {
         return this;
     }
 
-    /**
-     * Disposes of the line mesh
-     * @param doNotRecurse If children should be disposed
-     * @param disposeMaterialAndTextures This parameter is not used by the LineMesh class
-     * @param doNotDisposeMaterial If the material should not be disposed (default: false, meaning the material is disposed)
-     */
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    public override dispose(doNotRecurse?: boolean, disposeMaterialAndTextures = false, doNotDisposeMaterial?: boolean): void {
-        if (!doNotDisposeMaterial) {
-            this._lineMaterial.dispose(false, false, true);
-        }
-        super.dispose(doNotRecurse);
-    }
-
     /**
      * Returns a new LineMesh object cloned from the current one.
      * @param name defines the cloned mesh name