ssd_part_type contains several node types that are not actually part of
server-side decorations (ROOT, MENU, OSD, etc.)
Rename it accordingly and move it to a common location, along with some
related conversion/comparison functions.
Our codebase for ssd scenes has grown with a lot of technical debts:
- We needed to call `ssd_get_part()` everywhere to get the scene node of a
ssd part. We then needed to cast it to `wlr_scene_rect` and
`wlr_scene_buffer`. This bloated our codebase and even blocked
duplicated button types in `<titlebar><layout>`.
- `ssd_get_part_type()` was a dirty hack. It compared parent, grandparent
and grandgrandparent of a node with each subtree in the ssd to get the
part type of the node.
To resolve this issues, this commit changes how ssd scenes are managed:
- Access scene rects and scene buffers just as a member of `struct ssd`.
- `ssd_part` is now a attachment to a scene node that can be accessed via
node_descriptor->data, with a new node-descriptor type
`LAB_NODE_DESC_SSD_PART`. `LAB_NODE_DESC_SSD_BUTTON` is unified into it.
Now the scene graph under ssd->tree looks like below. The parentheses
indicate the type of ssd_part attached to the node:
ssd->tree (LAB_SSD_NONE)
+--titlebar (LAB_SSD_PART_TITLEBAR)
| +--inactive
| | +--background bar
| | +--left corner
| | +--right corner
| | +--title (LAB_SSD_PART_TITLE)
| | +--iconify button (LAB_SSD_BUTTON_ICONIFY)
| | | +--normal close icon image
| | | +--hovered close icon image
| | | +--...
| | +--window icon (LAB_SSD_BUTTON_WINDOW_ICON)
| | | +--window icon image
| | +--...
| +--active
| +--...
+--border
| +--inactive
| | +--top
| | +--...
| +--active
| +--top
| +--...
+--shadow
| +--inactive
| | +--top
| | +--...
| +--active
| +--top
| +--...
+--extents
+--top
+--...
When hovering on SSD, `get_cursor_context()` traverses this scene node
from the leaf. If it finds a `ssd_part` attached to the node, it returns
`ssd_part_type` that represents the resizing direction, button types or
`Title`/`Titlebar`.
We always create a SSD for 0x0 window since decorations are usually
requested before a window is mapped. Thus the sizes of some buffers/rects
like edge shadows could be negative, which is asserted in wlroots 0.19.
For example, variables:
`theme->window_inactive_border_color`
`theme->window_active_border_color`
are converted to:
`theme->window[THEME_INACTIVE].border_color`
`theme->window[THEME_ACTIVE].border_color`
This fixes the ugly look of SSD for tiny windows (e.g. "xterm -geometry
1x1") due to the early return in `ssd_update_geometry()`. Now SSDs are
rendered correctly for those windows by hiding some buttons when the
window width is smaller than the total width of buttons. Additionally for
windows smaller than (button width)*2, the corners are un-rounded so a
small titlebar can be rendered with a scene-rect.
