Write down the develop gestures, since only their author knew them

FR-UI-4 says a gesture with no visible counterpart is a feature only its
author knows about, and the vocabulary the application actually publishes had
two sections in it — the library grid and people. Develop had none. Every one
of its gestures was documented in the comment beside the `TouchArea` that
implements it, which is where the previous sixteen were before this scanner
existed, and unreachable to anybody not reading the source.

Thirteen now carry tags: magnify by pinch or wheel, pan a magnified frame,
fit and 1:1, hold to see the original, sample a neutral, undo and redo, step
through the folder, reset one control, show or hide a mask layer, choose a
group of adjustments, and copy and paste the settings. Each has a pointer and
a touch route, so none of them is keyboard-only.

Three bindings were genuinely missing and are added here rather than merely
described. Ctrl+C and Ctrl+V for the settings clipboard, which the Settings
panel's own comment has claimed existed for as long as the panel has and
nothing bound; and [ and ] to step through the adjustment groups. The groups
are whatever the operation set declares itself to be about, so there are as
many as the pipeline has and no key can name one of them — stepping is the
binding that survives a node being added, and "everything" is part of the
cycle rather than a way out of it.

Two are described and not bound. Resetting a control from the keyboard and
toggling a mask layer from the keyboard both need a notion of which control
or layer has focus, and the generated panel has none — the rows are a model
the repeater rebuilds, and inventing a focus ring for them is a larger change
than a keyboard shortcut. Both are reachable by pointer and by finger, and
the tags say so rather than promising a key that is not there.

ui/dr-ui/src/gesture_book.rs

@@ -22,6 +22,97 @@ pub struct Gesture {
 
 /// Every gesture, in the order the sections were first seen in the source.
 pub const GESTURES: &[Gesture] = &[
+    Gesture {
+        title: "Set the white balance from the photograph",
+        section: "Develop",
+        touch: "Press \"pick\" in the group's heading, then tap something neutral in the picture",
+        pointer: "Press \"pick\", then click something neutral",
+        keys: "",
+    },
+    Gesture {
+        title: "Magnify the photograph by any amount",
+        section: "Develop",
+        touch: "Pinch it with two fingers",
+        pointer: "The scroll wheel over it",
+        keys: "",
+    },
+    Gesture {
+        title: "Move a magnified photograph about",
+        section: "Develop",
+        touch: "Drag it",
+        pointer: "Drag it",
+        keys: "",
+    },
+    Gesture {
+        title: "Take back the last change",
+        section: "Develop",
+        touch: "Tap the step above the current one in the History list",
+        pointer: "Click it, or press Undo in the History header",
+        keys: "Ctrl+Z",
+    },
+    Gesture {
+        title: "Do it again after taking it back",
+        section: "Develop",
+        touch: "Tap the step below the current one in the History list",
+        pointer: "Click it, or press Redo in the History header",
+        keys: "Ctrl+Shift+Z",
+    },
+    Gesture {
+        title: "Copy the settings from this photograph",
+        section: "Develop",
+        touch: "Press Copy in the Settings panel",
+        pointer: "Press Copy in the Settings panel",
+        keys: "Ctrl+C",
+    },
+    Gesture {
+        title: "Paste the settings onto this photograph",
+        section: "Develop",
+        touch: "Press Paste in the Settings panel",
+        pointer: "Press Paste in the Settings panel",
+        keys: "Ctrl+V",
+    },
+    Gesture {
+        title: "Change which group of adjustments is on screen",
+        section: "Develop",
+        touch: "Tap a group in the rail down the left",
+        pointer: "Click a group in the strip above the develop column",
+        keys: "[ and ] step through them, wrapping round through \"everything\"",
+    },
+    Gesture {
+        title: "Look at the photograph at 1:1",
+        section: "Develop",
+        touch: "Double-tap the photograph",
+        pointer: "Double-click it, or press the zoom readout floating over the canvas",
+        keys: "Z",
+    },
+    Gesture {
+        title: "Move to the next or previous photograph",
+        section: "Develop",
+        touch: "Tap a frame in the roll along the foot of the canvas",
+        pointer: "Click a frame in the roll",
+        keys: "Right arrow or space for the next, left arrow for the one before",
+    },
+    Gesture {
+        title: "See the photograph before you edited it",
+        section: "Develop",
+        touch: "Press and hold \"Before\"",
+        pointer: "Press and hold \"Before\"",
+        keys: "Hold \\",
+    },
+    Gesture {
+        title: "Put one control back to its default",
+        section: "Develop",
+        touch: "Double-tap its track",
+        pointer: "Double-click its track, or right-click it",
+        keys: "",
+    },
+    Gesture {
+        title: "Show or hide one mask layer",
+        section: "Develop",
+        touch: "Tap the ring at the head of its row",
+        pointer: "Click the ring at the head of its row",
+        keys: "",
+    },
     Gesture {
         title: "Pull a face out of the wrong person",
         section: "People",