Dim the histogram while the canvas shows a draft

The histogram is measured on settled frames only, so during a drag it
describes the frame from before the gesture while the canvas shows
something newer, and nothing said so. The draft flag stopped at the
render closure.

It now reaches the interface: `canvas-draft` on the window and
`Levels.provisional` for the readouts, both set on every canvas render
from the flag that chose the frame's resolution, and cleared when a
render fails. The histogram panel dims its display reading to half
while a draft is up and brings it back when the frame settles. Dimmed
rather than captioned, because a caption appearing on every drag would
move the column; the raw reading has no frame to lag and is left alone.

docs/gestures.md

@@ -25,7 +25,11 @@ Sampling a neutral is the first move of the tonal pass — every colour judgemen
 
 Anchored on the fingers' midpoint, and on the pointer, so the gesture reads as magnifying the picture rather than sliding it about. Double-tap is the way to an exact 1:1; this is the way to everything in between. Past 1:1 the pixels are shown as they are, square and unsmoothed; below it, filtered.
 
+<<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:1715`</sub>
+=======
+<sub>`ui/dr-ui/ui/app.slint:1710`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Move a magnified photograph about
 
@@ -34,7 +38,11 @@ Anchored on the fingers' midpoint, and on the pointer, so the gesture reads as m
 
 Only once there is something outside the viewport to reach, which is why the cursor becomes a hand exactly then. The view is clamped to the frame: panning past the edge would show undefined area beside the photograph, and that reads as a rendering fault rather than as the end of the picture.
 
+<<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:1808`</sub>
+=======
+<sub>`ui/dr-ui/ui/app.slint:1801`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Paint a mask by hand
 
@@ -43,7 +51,11 @@ Only once there is something outside the viewport to reach, which is why the cur
 
 A model's mask stops inside a shoulder and leaks into the hair, and no single edge control fixes two errors that go opposite ways. The whole stroke is one step in the history, so taking a mark back costs one press however long it took to make.
 
+<<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:1895`</sub>
+=======
+<sub>`ui/dr-ui/ui/app.slint:1888`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Take back the last change
 
@@ -53,11 +65,15 @@ A model's mask stops inside a shoulder and leaks into the hair, and no single ed
 
 A whole drag is one step, so undo takes back a decision rather than a frame of a gesture. The list is there because arriving six steps back costs what arriving from one does.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2123`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2116`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2116`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Do it again after taking it back
 
@@ -65,11 +81,15 @@ A whole drag is one step, so undo takes back a decision rather than a frame of a
 - **Pointer** — Click it, or press Redo in the History header
 - **Keyboard** — Ctrl+Shift+Z
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2136`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2129`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2129`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Copy the settings from this photograph
 
@@ -79,11 +99,15 @@ A whole drag is one step, so undo takes back a decision rather than a frame of a
 
 The button is the copy that has to work: a tablet has no modifier key to hold and no menu bar to hang the action from. The shortcut is an accelerator for a control that is on screen either way.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2169`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2162`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2162`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Paste the settings onto this photograph
 
@@ -93,11 +117,15 @@ The button is the copy that has to work: a tablet has no modifier key to hold an
 
 The button names what would be pasted — "3 adjustments", and whether the crop is coming with it — which the shortcut cannot say. Both paste the same scope.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2181`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2174`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2174`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Choose which kinds of edit a copy carries
 
@@ -107,11 +135,15 @@ The button names what would be pasted — "3 adjustments", and whether the crop
 
 Lightroom's Copy Settings. Pasting a look across a shoot usually means leaving each frame's crop and rotation alone, and that is a choice to make at the moment of copying.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2198`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2191`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2191`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Export this photograph as the last one was
 
@@ -121,11 +153,15 @@ Lightroom's Copy Settings. Pasting a look across a shoot usually means leaving e
 
 Every export runs on the defaults in Settings, so "as the last one was" is what the button already does. The chord is Lightroom's and darktable's, kept so hands that learned it there need not learn it again.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2227`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2220`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2220`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Choose how to export, then export
 
@@ -135,11 +171,15 @@ Every export runs on the defaults in Settings, so "as the last one was" is what
 
 The export sheet is the export defaults alone with an Export button. What is chosen there is kept, so it is also what the next Ctrl+Shift+E uses.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2239`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2232`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2232`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Change which group of adjustments is on screen
 
@@ -149,11 +189,15 @@ The export sheet is the export defaults alone with an Export button. What is cho
 
 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 be assigned to one of them by name. Stepping is the binding that survives a node being added.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2264`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2257`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2257`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Look at the photograph at 1:1
 
@@ -163,11 +207,15 @@ The groups are whatever the operation set declares itself to be about, so there
 
 Noise reduction and capture sharpening are judgements about single pixels, and a fitted view averages several of the file's into each one on screen — so the frame looks softer than it is and the correction goes too far. The point and the magnification survive opening the next photograph, which is what makes checking the same eye across forty portraits forty keystrokes rather than forty pans. From 1:1 on the photograph is drawn as its own pixels, each a hard-edged square, rather than smoothed into a blur.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2299`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2292`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2292`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Move to the next or previous photograph
 
@@ -177,11 +225,15 @@ Noise reduction and capture sharpening are judgements about single pixels, and a
 
 The edit on screen is saved on the way out, so stepping through a folder is as much a departure as going back to the grid and loses nothing. A and D as well as the arrows, so the left hand steps along the roll while the right stays on the mouse. Unmodified only: Ctrl+D and Ctrl+A are not this.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2354`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2344`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2344`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### See the photograph before you edited it
 
@@ -191,11 +243,15 @@ The edit on screen is saved on the way out, so stepping through a folder is as m
 
 Held rather than toggled, and no split screen: a split halves the working image on the tablet the column was sized for, and the comparison photographers describe making is a flick back and forth. It takes no history step, so checking whether a frame is overcooked costs nothing to undo afterwards.
 
+<<<<<<< HEAD
 <<<<<<< HEAD
 <sub>`ui/dr-ui/ui/app.slint:2487`</sub>
 =======
 <sub>`ui/dr-ui/ui/app.slint:2477`</sub>
 >>>>>>> 5b5164f (Say so when a crop leaves a mask outside the frame)
+=======
+<sub>`ui/dr-ui/ui/app.slint:2477`</sub>
+>>>>>>> d11c8aa (Dim the histogram while the canvas shows a draft)
 
 ### Put one control back to its default