via and double-sided pad

diylc/docs/plans/bottom-side-components.md

@@ -57,6 +57,8 @@ projects; the open questions below remain.
 | Bottom-side text is mirrored centrally in the Gerber output | Parts draw their labels readable from the top, which is backwards on the bottom silkscreen once the board is turned over. While `GerberExporter.drawComponent` draws a bottom-side part, `GerberG2DWrapper.setMirrorText` mirrors each string about the centre of its layout box, so no component changes and the canvas keeps readable labels. |
 | A part without a side placed in the mirror is placed unchanged | A jumper, eyelet or wire has no side to set, so it is placed at the reflected point like any other part rather than refused. |
 | A `SolderPad` opens the solder mask on its own side | It used to write `SolderMaskBot` whatever its layer, which was wrong for top-layer pads. It now writes `SolderMaskTop` for a pad on `_2`. |
+| A `SolderPad` with a plated through hole is on both layers, and its Layer is ignored | A plated hole has a copper ring on each side joined by the barrel. The pad reports layer id `0`, which connects to copper on every layer, draws as both sides, and writes both copper and both mask layers. Projects where such a pad overlaps a trace on its other side now net differently; PTH is not the default and arrived with Gerber export, so few projects are affected. |
+| `Via` is its own component, not a `SolderPad` option | It takes no lead and no node name, is tented (no mask opening), and has its own Gerber functions, `ViaPad` and `ViaDrill`. Like the PTH pad it reports layer id `0`. It has no Board Side, like `DrillHole`. |
 
 ## 3. Design
 

diylc/docs/plans/copper-side-view.md

@@ -67,7 +67,8 @@ were regenerated for the faded copper. The open questions below remain.
 - `ProtoBoard` declares its underside traces and underside mini pads `_1`.
 - `CopperTrace` and `PCBText` declare their whole canvas `draw` on `getLayer()`. `CurvedTrace` and
   `GroundFill` declare their copper fill. `SolderPad` declares the pad on its layer and its
-  drilled hole as both sides.
+  drilled hole as both sides; a pad with a plated through hole declares its pad as both sides
+  too, because it has copper on both. `Via` declares its copper and hole as both sides.
 - `TraceCut` draws its cut and hole as both sides.
 
 ### diylc-swing

diylc/docs/plans/fill-clearance.md

@@ -116,7 +116,8 @@ the gap always matches the drawn copper.
 | --- | --- |
 | `CopperTrace` | Stroked line, current thickness and `LineEndingStyle` cap |
 | `CurvedTrace` | Stroked curve, same stroke as `draw()` |
-| `SolderPad` | Pad outline per `Type` (round, oval H/V, square); the drill hole is ignored |
+| `SolderPad` | Pad outline per `Type` (round, oval H/V, square); the drill hole is ignored. A pad with a plated through hole is on both layers, so it clears fills on both |
+| `Via` | Round copper outline, on both layers like a plated pad |
 | `PCBText` | Glyph outlines (confirm it is copper and not silkscreen before including) |
 
 `PCBTerminalBlock` tracks no continuity and is not layered today, so it waits for phase 2.