Gallery: Flash of white when image is uploaded #11650
Description
Describe the bug
After the Gallery block finishes uploading an image, it swaps the temporary blob: image with the real http:// image. This causes a flash of white on slow to medium connections while the new image loads.
To Reproduce
- Simulate a Fast 3G connection
- Insert a Gallery block
- Upload a few images
Expected behavior
I'd expect the images to appear with some indication that they are loading (seperate issue: #8810), and then for the temporary image to be seamlessly replaced with the real image.
Actual behaviour
There is a flash of white while the temporary image is swapped out with the real image.
Screenshots
Additional context
We can do this by loading the real image using new Image() before inserting it into the DOM.