From 046612f8dad72bee5ca166206195510971634625 Mon Sep 17 00:00:00 2001
From: Aiosa <horakj7@gmail.com>
Date: Wed, 26 Jul 2023 23:55:46 +0200
Subject: [PATCH] Better drawer resolution, also supporting inline class spec.
 Fix minor review stuff.

---
 Gruntfile.js      |  2 +-
 src/drawerbase.js |  4 +---
 src/matrix.js     |  5 ++---
 src/viewer.js     | 56 +++++++++++++++++++++++------------------------
 4 files changed, 32 insertions(+), 35 deletions(-)

diff --git a/Gruntfile.js b/Gruntfile.js
index c96e2e79..979a602a 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -67,7 +67,7 @@ module.exports = function(grunt) {
             "src/tilecache.js",
             "src/world.js",
 
-            // Aoisa's webgl drawer - needs optimization, polishing, trimming
+            // Aiosa's webgl drawer - needs optimization, polishing, trimming
             // "src/webgl/webGLWrapper.js",
             // "src/webgl/visualisationLayer.js",
             // "src/webgl/dataLoader.js",
diff --git a/src/drawerbase.js b/src/drawerbase.js
index e4df9068..62cb1e04 100644
--- a/src/drawerbase.js
+++ b/src/drawerbase.js
@@ -108,9 +108,7 @@ $.DrawerBase = class DrawerBase{
 
         this._checkForAPIOverrides();
     }
-    get isOpenSeadragonDrawer(){
-        return true;
-    }
+
     get canvas(){
         if(!this._renderingTarget){
             this._renderingTarget = this.createDrawingElement();
diff --git a/src/matrix.js b/src/matrix.js
index b0b91ab0..1f580658 100644
--- a/src/matrix.js
+++ b/src/matrix.js
@@ -1,8 +1,8 @@
-
 /*
  * OpenSeadragon - Mat3
  *
- * Copyright (C) 2010-2023 OpenSeadragon contributors
+ * Modified from https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html
+ * Copyright (C) 2010-2023 webglfundamentals.org and OpenSeadragon contributors
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -36,7 +36,6 @@
 
 /**
  * Matrix left-to-right system representation
- * Modified from https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html
  */
 $.Mat3 = class Mat3 {
     constructor(values){
diff --git a/src/viewer.js b/src/viewer.js
index 3b98cd74..4e823743 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -445,44 +445,44 @@ $.Viewer = function( options ) {
 
         delete this.drawerOptions.useCanvas;
     }
-    let drawerPriority = Array.isArray(this.drawer) ? this.drawer : [this.drawer];
-    let drawersToTry = drawerPriority.filter(d => ['webgl', 'canvas', 'html'].includes(d) || (d.prototype && d.prototype.isOpenSeadragonDrawer) );
-    if(drawerPriority.length !== drawersToTry.length){
-        $.console.error('An invalid drawer was requested.');
-    }
-    if(drawersToTry.length === 0){
-        drawersToTry = [$.DEFAULT_SETTINGS.drawer].flat(); // ensure it is a list
+    let drawerCandidates = Array.isArray(this.drawer) ? this.drawer : [this.drawer];
+    if (drawerCandidates.length === 0){
+        drawerCandidates = [$.DEFAULT_SETTINGS.drawer].flat(); // ensure it is a list
         $.console.warn('No valid drawers were selected. Using the default value.');
     }
     // extend the drawerOptions object with additional properties to pass to the Drawer implementation
     // TODO: how to deal with the possibility that none of the requested drawers are supported?
     this.drawer = null;
-    for(let i = 0; i < drawersToTry.length; i++){
+    for (let i = 0; i < drawerCandidates.length; i++) {
 
-        //todo necessary? why not to use class names as drawer IDs
-        let optsKey = drawersToTry[i];
-        let Drawer = $.determineDrawer(optsKey);
-        if (!Drawer) {
-            optsKey = 'custom';
-            //todo will raise error anyway...
+        let drawerCandidate = drawerCandidates[i];
+        let Drawer = null;
+
+        //if inherits from a drawer base, use it
+        if (drawerCandidate && drawerCandidate.prototype instanceof $.DrawerBase) {
+            Drawer = drawerCandidate;
+            drawerCandidate = 'custom';
+        } else if (typeof drawerCandidate === "string") {
+            Drawer = $.determineDrawer(drawerCandidate);
         } else {
-            // if the drawer is supported, create it and break the loop
-            if (Drawer.isSupported()){
-                this.drawer = new Drawer({
-                    viewer:             this,
-                    viewport:           this.viewport,
-                    element:            this.canvas,
-                    debugGridColor:     this.debugGridColor,
-                    options:            this.drawerOptions[optsKey],
-                });
-                this.drawerOptions.constructor = Drawer;
-                break;
-            }
+            $.console.warn('Unsupported drawer! Drawer must be an existing string type, or a class that extends OpenSeadragon.DrawerBase.');
+            continue;
         }
 
-
+        // if the drawer is supported, create it and break the loop
+        if (Drawer.isSupported()) {
+            this.drawer = new Drawer({
+                viewer:             this,
+                viewport:           this.viewport,
+                element:            this.canvas,
+                debugGridColor:     this.debugGridColor,
+                options:            this.drawerOptions[drawerCandidate],
+            });
+            this.drawerOptions.constructor = Drawer;
+            break;
+        }
     }
-    if(this.drawer === null){
+    if (!this.drawer){
         $.console.error('No drawer could be created!');
         throw('Error with creating the selected drawer(s)');
     }