TheShovel/CanvasEffects: don't scale render size block by DPI (#2489)

Author: CST1229

extensions/TheShovel/CanvasEffects.js

@@ -503,7 +503,12 @@
       updateStyle();
     }
     renderscale({ X, Y }) {
-      Scratch.vm.renderer.resize(X, Y);
+      // The function normally expects a stage size and therefore scales by DPI.
+      // However, this block is meant for a fixed pixel size
+      // (usually used in conjunction with the pixelated resize rendering mode).
+      // Therefore, scale it back according to the devicePixelRatio.
+      const pixelRatio = window.devicePixelRatio || 1;
+      Scratch.vm.renderer.resize(X / pixelRatio, Y / pixelRatio);
     }
     setBorder(args) {
       borderWidth = Scratch.Cast.toNumber(args.WIDTH);