Add 'Arcs and curved wires' (Arc tool, PR #1202); drop the merged #1200 notice

New page drawing_arcs, linked from the sidebar, mouse modifiers, the
shapes file format, keyboard control and drawing faster. Every mention
of the Arc tool carries a pending notice for PR #1202. The wire-hops
notice on conductors comes out: PR #1200 merged today.

_Sidebar.md

@@ -46,6 +46,8 @@
 
 **[Pictures on a folio](pictures)** — labels, crop, transparency, what they cost in the file
 
+**[Arcs and curved wires](drawing_arcs)** — the Arc tool, pulling an arc in or out, dashed arcs for lighting layouts
+
 **[Grouping items](grouping_items)** — select, move and copy several items as one
 
 **[Finding your place on a folio](navigating_folios)** — go to a cell like B13 or 4-B7, keep the headers in sight, show the cell limits, zoom and pan

conductors.md

@@ -293,12 +293,6 @@ Both are per project, and both are toggles you can leave off.
 
 ## 9. Hops where wires cross
 
-> **Status: pending.** This section describes
-> [PR #1200](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1200),
-> not yet merged. Nothing here works until that lands — check the PR before
-> trying any of this against your own build. This notice will come out once
-> it merges.
-
 Where two wires cross without being connected, a project can draw a small
 arc — a **hop** — on one of them, so the crossing cannot be read as a
 connection. Until now the only way to show this was to insert a jump symbol

data_files/project_diagram_child_shapes.md

@@ -15,6 +15,12 @@ attribute : none
    * closed -- for polygons
    * z -- stacking order
    * is_movable -- `1` / `0`
+ * inside an `Ellipse` shape that is cut down to an arc, an `<arc>` child:
+   * startAngle -- where the arc starts, in degrees, anticlockwise from three o'clock
+   * spanAngle -- how far it runs; negative runs clockwise
+   * closure -- `chord` or `pie` when the arc is closed; absent when it is open
+
+   A whole ellipse has no `<arc>` child. See [Arcs and curved wires](drawing_arcs).
 
 These are diagram shapes and are **not** the same as the element drawing
 primitives documented under [description](elements_child_description), even

drawing_arcs.md

@@ -0,0 +1,126 @@
+# Arcs and curved wires
+
+Lighting and house-wiring layouts often draw the wire from a switch to a lamp
+as a curve rather than a straight line, so it stands apart from walls and
+furniture on the plan. QElectroTech draws these as **arcs**: free drawing on
+the folio, like lines and rectangles, not conductors. An arc is not connected
+to anything — it does not appear in the wiring list, the parts list or any
+export that follows wires.
+
+There are two ways to get one: the **Arc** tool, which draws a half arc in two
+clicks and gives it a handle to pull in or out, and the older way of cutting
+an ellipse down with its end handles.
+
+---
+
+## 1. The Arc tool
+
+> **Status: pending.** This section describes
+> [PR #1202](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1202),
+> not yet merged. Nothing here works until that lands — check the PR before
+> trying any of this against your own build. This notice will come out once
+> it merges.
+
+![The drawing toolbar: line, rectangle, ellipse, the new arc button, polyline](https://raw.githubusercontent.com/wiki/qelectrotech/qelectrotech-source-mirror/images/drawing-arc-toolbar.png)
+
+The **Ajouter un arc** (*add an arc*) button sits on the drawing toolbar
+between the ellipse and the polyline. It is also in **Édition → Ajouter**, and
+in the command search (`Ctrl+Shift+M`, type `arc`).
+
+1. Click where one end of the arc should be.
+2. Move to the other end, and up or down to the height the arc should reach.
+   The arc follows the cursor.
+3. Click again. Right-click instead to cancel.
+
+The result is always a **half arc**: its two ends sit on one horizontal line,
+and it bulges up if you finished above the first click, down if you finished
+below it.
+
+| Hold | Result |
+|---|---|
+| *nothing* | both clicks snapped to the grid |
+| **Shift** | a true half circle — the height is half the distance between the ends |
+| **Ctrl** | off the grid |
+
+A new arc takes the line colour, thickness and style of the last shape you
+drew, but **never its fill**: a filled arc would close into a half disc. The
+tool stays active, so you can draw the next arc straight away; clicking the
+selection arrow, or the Arc button again, ends it, and Enter starts it again
+later
+(see [Drawing faster](drawing_faster)).
+
+### Pulling an arc in or out
+
+![Left: a half arc as drawn, with its middle handle at the top. Centre: the handle pulled in, the arc flatter. Right: the handle pulled past the ends, the arc now bulging downwards. The two end handles do not move in any of the three.](https://raw.githubusercontent.com/wiki/qelectrotech/qelectrotech-source-mirror/images/drawing-arc-handle.png)
+
+Select a half arc and it shows a turquoise handle in the **middle of the
+curve**, as well as one at each end.
+
+- Drag the middle handle **away from the ends** to make the arc deeper.
+- Drag it **towards the ends** to make it flatter.
+- Drag it **past the line between the ends** and the arc turns over to the
+  other side.
+
+The two ends do not move while you do this, so an arc drawn between a switch
+and a lamp stays connected to both by eye. Ctrl frees the handle from the
+grid. One drag is one undo step.
+
+The middle handle is only there on a **half arc** — every arc the Arc tool
+draws, also after you rotate it, and an ellipse cut down to exactly a half
+along its width or height (section 2, with Shift). Drag one of the end handles and the arc stops being a half arc:
+the middle handle disappears, and the end handles work as in section 2. Drag
+the end back to make a half arc again and the middle handle returns.
+
+---
+
+## 2. Cutting an ellipse down to an arc
+
+Any ellipse can be turned into an arc. Select it, and drag one of the two
+turquoise handles on its outline: that end of the curve follows the cursor
+round the ellipse. Hold **Shift** to move in 15° steps. Drag one end all the
+way round onto the other and the ellipse closes again.
+
+This gives arcs of any length, not only halves, but each end moves round the
+ellipse rather than staying where you put it, which makes it slow to fit an
+arc between two fixed points. For that, use the Arc tool.
+
+---
+
+## 3. A dashed arc
+
+Select the arc, open **Propriétés de la sélection** (*selection properties*),
+and under **Trait** (*line*) set **Type** to **Tiret** (*dash*) or
+**Pointillé** (*dotted*). The thickness and colour are on the same panel.
+
+Because a new arc copies the last shape's line style, the next arcs you draw
+come out dashed too, until you change it back.
+
+---
+
+## 4. In the file
+
+An arc is saved as an ordinary `Ellipse` shape with an `<arc>` child giving
+its start angle and span in degrees, measured anticlockwise from three
+o'clock. A half arc bulging upwards is `startAngle="0" spanAngle="180"`; the
+same arc pulled past its ends is `spanAngle="-180"`. The Arc tool adds nothing
+new to the file, so a project with arcs in it opens in any version that reads
+ellipse arcs. See [shapes](project_diagram_child_shapes).
+
+---
+
+## Limitations
+
+- The Arc tool only draws half arcs. A shallower or longer curve is a half arc
+  pulled in or out, or an ellipse cut down by hand.
+- The middle handle works only on half arcs.
+- Ctrl does not draw the arc out from its centre, as it does for an ellipse;
+  it only takes the clicks off the grid.
+- The start and end angles cannot be typed in the properties panel.
+- An arc is drawing, not a wire. For a curve that is part of the circuit,
+  use a conductor.
+
+## See also
+
+- [Mouse modifiers](mouse_modifiers) — every Shift, Ctrl and Alt while drawing and reshaping
+- [Drawing faster](drawing_faster) — command search, repeating the last tool
+- [Conductors](conductors) — real wires, and hops where they cross

drawing_faster.md

@@ -75,7 +75,7 @@ Right-click an empty spot on a folio. The menu puts drawing first:
 |---|---|---|
 | **Renvoi de folio ▸** (*folio reference*) | places a folio report arrow where you right-clicked | [#1050](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1050) |
 | **Insérer le dernier élément** (*insert last element*) | starts placing the last symbol again, as **A** does; shown once something has been placed | [#1050](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1050) |
-| **Ajouter ▸** (*add*) | text, image, PDF, line, rectangle, ellipse, polyline, curve, terminal strip | merged ([#1041](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1041)) |
+| **Ajouter ▸** (*add*) | text, image, PDF, line, rectangle, ellipse, arc (pending: [PR #1202](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1202)), polyline, curve, terminal strip | merged ([#1041](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1041)) |
 | **Propriétés du folio** (*folio properties*) | the folio's properties dialog | merged |
 | **Lignes et colonnes ▸** (*rows and columns*) | add or remove a row or a column | merged — moved one level down by #1041 |
 

keyboard_control.md

@@ -115,7 +115,7 @@ asking whichever item has focus for its default one.
 
 **Édition → Ajouter** is a submenu holding every drawing tool that used to
 be toolbar-only: text field, image, PDF (where compiled in), line,
-rectangle, ellipse, polyline, curve, and terminal strip. Reach it with
+rectangle, ellipse, arc (pending: [PR #1202](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1202)), polyline, curve, and terminal strip. Reach it with
 `Alt+E` then `→` to open the submenu, arrow keys to pick a tool, `Enter` to
 activate it. The automatic-conductor-break toggle sits in **Projet**,
 beside the automatic-conductor setting it pairs with.

mouse_modifiers.md

@@ -90,6 +90,11 @@ While dragging out a rectangle or an ellipse:
 Shift has no effect on lines, polygons or paths — only on rectangles and
 ellipses.
 
+With the **Arc** tool (pending:
+[PR #1202](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1202)), **Shift** makes a true half circle and **Ctrl** only takes the
+clicks off the grid — there is no centre-anchored arc. See
+[Arcs and curved wires](drawing_arcs).
+
 Whether the shape is centre-anchored is decided **at the first click**, not
 re-checked while you drag. Letting go of Ctrl halfway through does not snap
 the shape back to corner-anchored; that is deliberate, so a tired hand does
@@ -109,6 +114,7 @@ Select a shape or an image and drag one of its handles.
 | Rotate | **Shift** | snap the angle to 15° steps |
 | Skew | **Shift** | snap the skew to 15° steps |
 | Arc start/end | **Shift** | snap the arc angle to 15° steps |
+| Arc middle (half arcs; pending: [PR #1202](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1202)) | **Ctrl** | off the grid; no other modifier. The ends stay put — see [Arcs and curved wires](drawing_arcs) |
 | Path node (node-edit mode) | **Alt** | give the node symmetric curve handles |
 | Curve handle | **Alt** | break the symmetry, making it a corner instead of mirroring the opposite handle |