Update scaling math to land on 100% consistently.

Author: hipsterusername

invokeai/frontend/web/src/features/controlLayers/konva/CanvasStageModule.ts

@@ -31,7 +31,7 @@ type CanvasStageModuleConfig = {
 const DEFAULT_CONFIG: CanvasStageModuleConfig = {
   MIN_SCALE: 0.1,
   MAX_SCALE: 20,
-  SCALE_FACTOR: 0.999,
+  SCALE_FACTOR: 0.9995,
   FIT_LAYERS_TO_STAGE_PADDING_PX: 48,
 };
 
@@ -230,7 +230,24 @@ export class CanvasStageModule extends CanvasModuleBase {
    * Constrains a scale to be within the valid range
    */
   constrainScale = (scale: number): number => {
-    return clamp(Math.round(scale * 100) / 100, this.config.MIN_SCALE, this.config.MAX_SCALE);
+    // Round to 2 decimal places to avoid floating point precision issues
+    const rounded = Math.round(scale * 100) / 100;
+    const clamped = clamp(rounded, this.config.MIN_SCALE, this.config.MAX_SCALE);
+
+    // Snap to 100% (scale = 1.0) with a more generous tolerance
+    if (Math.abs(clamped - 1) < 0.05) {
+      return 1;
+    }
+
+    // Snap to other common zoom levels for better UX
+    const commonScales = [0.25, 0.5, 0.75, 1.5, 2, 3, 4, 5];
+    for (const commonScale of commonScales) {
+      if (Math.abs(clamped - commonScale) < 0.03) {
+        return commonScale;
+      }
+    }
+
+    return clamped;
   };
 
   /**