Implement keyPreviewMagnification actual functionality

Author: yawnoc

app/src/main/java/io/github/yawnoc/strokeinput/KeyPreview.java

@@ -62,13 +62,13 @@ public void update(final Key key, final int shiftMode) {
       return;
     }
 
-    width = key.width;
-    height = key.height;
+    width = (int) (key.previewMagnification * key.width);
+    height = (int) (key.previewMagnification * key.height);
     displayText = key.shiftAwareDisplayText(shiftMode);
-    textOffsetX = key.textOffsetX;
-    textOffsetY = key.textOffsetY;
+    textOffsetX = (int) (key.previewMagnification * key.textOffsetX);
+    textOffsetY = (int) (key.previewMagnification * key.textOffsetY);
 
-    rectangle.set(0, 0, key.width, key.height);
+    rectangle.set(0, 0, width, height);
 
     fillPaint.setColor(InputContainer.toPressedColour(key.fillColour));
     borderPaint.setColor(key.borderColour);