Edit Mode Guide Lines

By
geekoo

Guide lines for Edit Mode. Create as many guides as you like, in any color, and the game's own snapping pulls frames onto them, the same way it snaps to the grid.

EditModeGuideLines

Guide lines for Edit Mode, on retail WoW and WoW: Forever. Create as many vertical or horizontal guides as you like, in any color, and the game's own snapping pulls frames onto them, the same way it snaps to the grid.

A guide is centered: it marks a band of the screen a given percentage wide (or tall) and draws the two lines that bound it. A vertical 50% guide on a 1000 px wide screen draws lines at 250 px and 750 px; a 0% guide is one line through the middle, 100% the screen edges. That makes it easy to build multi-area layouts on ultrawide screens: one guide marks the band the HUD lives in, another the side areas, and every frame snaps to their edges.

Prototype. Built against the Forever beta, which uses the Mainline (12.1-era) addon API, not the Classic one; retail uses the same API. The Edit Mode internals it relies on are identical on both clients.

Using it

In the panel, pick Vertical or Horizontal, type the width of the band in percent, pick a color (click the swatch for the game's color picker, with opacity) and press Add. Each guide in the list can be recolored, flipped between vertical and horizontal, given a new percentage (type and press Enter), hidden with its tick box, or deleted.

Then drag any frame as usual: when one of its edges or its center comes within a few pixels of a guide, the red preview line appears and the frame snaps to it on release, exactly like the grid. Both vertical and horizontal guides can snap at once. Snapping anchors the frame to the screen, not to the guide, so layouts don't depend on this addon being loaded, and deleting a guide leaves every frame where it is.

Settings (in the panel and in Options > AddOns > EditModeGuideLines):

Enabled: draw the guides and let frames snap to them.
Show outside Edit Mode: keep the guides on screen all the time. By default they appear with the Edit Mode window and go away with it.
Draw above frames: draw the guides over the UI instead of behind it.
Thickness: line thickness in screen pixels (1 to 8).
Show the guide panel in Edit Mode (settings only): whether the panel opens with Edit Mode. /emg or /emg panel opens it on demand.

Guides are saved per account (EditModeGuideLinesDB) and apply to every Edit Mode layout.

Slash commands

/emg (or /guidelines) opens the panel in Edit Mode, the settings otherwise. Everything the panel does is also a command:

/emg add v 50 green        add a vertical guide: lines at 25% and 75%
/emg add h 33.3 #ff8800    add a horizontal guide, hex color
/emg list                  list the guides with their numbers
/emg del 2                 remove guide 2; /emg clear removes all
/emg percent 1 60          change guide 1's percentage
/emg flip 1                vertical <-> horizontal
/emg color 1 cyan          recolor guide 1
/emg toggle 1              hide or show guide 1
/emg on | off              enable or disable the addon
/emg show | hide           show the guides outside Edit Mode, or not
/emg above                 toggle drawing above the frames
/emg thickness 2           line thickness in pixels
/emg panel | editmode      open the panel, open Edit Mode

Colors: red, green, blue, yellow, cyan, magenta, orange, white, or hex like #ff8800 (#ff880080 with alpha).

How the snapping works

Edit Mode's snapping lives in Blizzard's EditModeMagnetismManager (Blizzard_EditMode/Shared/EditModeUtil.lua). While the grid is shown, each grid line is registered there as a coordinate in UIParent space; when a frame is dropped (and while it is dragged, for the red preview line) the manager finds the closest registered line within 8 screen pixels of the frame's left/right/center (or top/bottom/center), and anchors the frame to UIParent at that position.

This addon registers its guide lines in that same table, under keys of its own, and puts them back whenever the grid rebuilds or clears the table. The result behaves exactly like extra grid lines at the positions you chose: edges and centers snap, the preview line shows, and the saved layout never references the addon. The other extension point, registering frames as "magnetic frames", was deliberately not used: snapping to one of those anchors the frame to that frame, which would tie saved layouts to the addon's guide frames.

Positions are rounded to whole screen pixels before they are drawn and registered, so a snapped frame sits exactly on the drawn line.

Known limitations

Snapping needs Edit Mode's Snap to Frames option on, and happens within the game's 8 px magnetism range; the guides are not a magnet from across the screen.
The game only snaps on release and picks the single closest target: if a frame edge is nearer to another frame than to a guide, it snaps to the frame.
Guides are per account, not per layout.
Forever beta SavedVariables bug: the beta saves SavedVariables on logout but doesn't load them on startup, so guides won't survive a restart there until Blizzard fixes it (the Forever Data Protect addon works around it).
Not yet verified in game; the WoW API is mocked in the tests, and the panel is only checked for wiring, not layout.

License

MIT