Customizer Custom Background does not set context

[kovshenin]

Steps to reproduce:

• Activate a theme with Custom Background support
• Fire up the Customizer and upload a new background image, save changes.
• Browse to the Media Library and find your new image

Expected context is "Background Image" but no context shows up. This bug also prevents background images uploaded through the Customizer to show up in its own Uploaded tab. It looks like the context is not being passed to ajax-actions.php by customize-controls.js.

[kovshenin]

Confirmed this has been broken since 3.4 for Custom Background. However, Custom Header did pass the context on upload in 3.4, but the Custom Header upload functionality was removed from the Customizer in 3.4.2.

[kovshenin]

Uses a control.uploader.params object to set the context and theme, which is then passed to the Uploader.

[kovshenin]

In ​22215.diff removing the use of this.uploader.supported which apparently is empty at that stage, and not using the control.uploader.param function, which is not defined when that code runs. Using a control.uploader.params object directly which is passed to the Uploader when it's created. Not entirely sure this is the right approach to solve this, feedback appreciated.

[koopersmith]

+1

Replying to kovshenin:

In ​22215.diff removing the use of this.uploader.supported which apparently is empty at that stage, and not using the control.uploader.param function, which is not defined when that code runs. Using a control.uploader.params object directly which is passed to the Uploader when it's created. Not entirely sure this is the right approach to solve this, feedback appreciated.

This is exactly the right approach to solve this. Since the wp.Uploader instance is created right after this code runs, we should use the params key (which you correctly did) instead of trying to use the wp.Uploader methods.

[nacin]

In 22484:

Properly set upload context when uploading a background image through the customizer. props kovshenin. fixes #22215.