Block weight

The block weight set in a pattern is lost when the pattern runs. In fact, only weight -1, 0 and 1 are working, the rest is discarded.

This is because when a block is created, two forms are retrieved and executed: block_add_block_form, and block_admin_display_form. The first form creates or updates block properties, but the region and weight are set in the second form.

The second form (block_admin_display_form) generally displays all the blocks, and allows the user to change the order of the blocks (or change the weights if JS is not enabled). The problem is that, when generating the form, the range of allowed weight (the delta for the field type weight) is calculated from the number of blocks displayed in the form:

Now, when pattern, for each block, calls (block_admin_display_form), there is only one block in the form, which result in the delta for the field weight to be 1. As a consequence, the allowed weights for a block created/updated by a pattern are: -1, 0 or 1.

The fix has to be made in Drupal core... (unless I am mistaken). Basically, since we almost all the time have several blocks on the page, the only time where we have only one block is when we call the form programmatically, such as pattern does. So we can consider that if the number of blocks in the form is 1, it is because we are generating the form programmatically, and therefore we need to force the weight delta to be an arbitrary number, greater than the potential number of blocks in the system. If the number of blocks is already greater than 1, it is business as usual, we change nothing.

So the patch simply does this: if the number of blocks is 1, we assume that there may be more blocks existing, or to be created, and we set the weight delta to be 999:

This allows us to create blocks in a pattern, and set the weight precisely. Also, since the weight range does not rely on the number of blocks when generating the form programmatically, we can add dozens of blocks with patterns, setting their weight independently of the number of blocks.