drawing_arcs: the fillet tool (PR #1212) and the middle-handle change (PR #1211), both pending

_Sidebar.md

@@ -46,7 +46,7 @@
 
 **[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
+**[Arcs and curved wires](drawing_arcs)** — the Arc tool, pulling an arc in or out, rounding a corner with a fillet, dashed arcs for lighting layouts
 
 **[Grouping items](grouping_items)** — select, move and copy several items as one
 

drawing_arcs.md

@@ -66,6 +66,17 @@ along its width or height (section 2, with Shift). Drag one of the end handles a
 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.
 
+> **Status: pending.** This paragraph describes
+> [PR #1211](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1211),
+> not yet merged. Until it lands, the middle handle shows in both handle
+> modes and covers the handle under it.
+
+The middle handle shows with the **size** handles only. Click the arc again
+to switch to the rotate and skew handles and it goes away, so the skew handle
+at the top of the arc can be grabbed. With the size handles, the resize handle
+that would sit under it is hidden: the middle handle already changes that
+height.
+
 ---
 
 ## 2. Cutting an ellipse down to an arc
@@ -103,6 +114,56 @@ ellipse arcs. See [shapes](project_diagram_child_shapes).
 
 ---
 
+## 5. Rounding a corner: the fillet tool
+
+> **Status: pending.** This section describes
+> [PR #1212](https://github.com/qelectrotech/qelectrotech-source-mirror/pull/1212),
+> 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 **fillet** tool rounds the corner between two drawn lines, like the sketch
+fillet in a CAD program. It turns a sharp corner into a curve of the radius
+you choose, which is the usual way to draw a cable or pipe run that bends.
+
+![Left: a corner, two crossing lines, and two lines with a gap between them. Right: the same after a fillet on each, with the radius dialog.](https://raw.githubusercontent.com/wiki/qelectrotech/qelectrotech-source-mirror/images/drawing-fillet-before-after.png)
+
+1. Choose **Ajouter un congé** (*add a fillet*): in **Édition → Ajouter**, on
+   the drawing toolbar (behind its » arrow when the window is narrow), or
+   from the command search (`Ctrl+Shift+M`, type `congé`).
+2. Click the two lines one after the other — **or** click once where they
+   meet or cross.
+3. A small dialog asks for the **radius**. Type it and press **Enter**.
+   Escape in the dialog cancels that fillet.
+
+The tool stays on, so you can go straight to the next corner. **Escape**, a
+right-click, or clicking the button again ends it. A right-click after
+picking only the first line drops that pick instead.
+
+What happens to the lines:
+
+| The two lines… | Result |
+|---|---|
+| meet at a corner | both are shortened to where the curve starts |
+| cross each other | each keeps the part **on the side you clicked**; the other part is cut off. A single click on the crossing keeps the longer part of each |
+| do not reach each other | both are **extended** to meet the curve |
+
+The radius is in the same units as the sizes in **Propriétés de la
+sélection**, and the dialog starts with the last radius you used. The curve
+takes the line style of the first line you clicked. One Ctrl+Z undoes the
+whole fillet: both lines go back and the curve goes away.
+
+Nothing is done, and the status bar says why, when:
+
+- the two lines are parallel, or so nearly in line that there is no corner;
+- the radius is too big for the lines — the message gives the largest radius
+  that fits.
+
+The result is two ordinary lines and an ordinary arc (section 4), not a new
+kind of shape. Moving one of them afterwards does not move the others.
+
+---
+
 ## Limitations
 
 - The Arc tool only draws half arcs. A shallower or longer curve is a half arc
@@ -111,6 +172,8 @@ ellipse arcs. See [shapes](project_diagram_child_shapes).
 - 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.
+- The fillet tool works on drawn lines only — not yet on a corner of a
+  polyline, not on wires, and not in the symbol editor.
 - An arc is drawing, not a wire. For a curve that is part of the circuit,
   use a conductor.