Merge branch 'histogram'

# Conflicts:
#	ui/dr-ui/src/lib.rs

ui/dr-ui/ui/app.slint

@@ -4,9 +4,10 @@ import { LaunchScreen } from "launch.slint";
 import { LibraryGrid, LibraryCell, TimelineBar } from "library.slint";
 import { Button, PanelHeading, Label, Value, Caption, Panel, EmptyState, ProgressBar, ActivityRow } from "widgets.slint";
 import { CollectionsPanel, CollectionRow } from "collections.slint";
+import { HistogramPanel, HistogramView } from "histogram.slint";
 import { SettingsPage } from "settings.slint";
 
-export { LibraryCell, TimelineBar, CollectionRow, ActivityRow }
+export { LibraryCell, TimelineBar, CollectionRow, ActivityRow, HistogramView }
 
 // Status strip — surfaces the GPU backend and adapter, which matters during
 // v0.1 because assumption A1 is exactly "does this compositing path work on
@@ -223,6 +224,11 @@ export component AppWindow inherits Window {
     in property <int> total: 0;
     in property <string> load-error: "";
 
+    /// TRACES: FR-DSP-7
+    /// The counted frame. Set only when the render has settled — a histogram
+    /// of a draft frame is a histogram of an image nobody is reading.
+    in property <HistogramView> histogram;
+
     // --- zoom, pan and crop (FR-DEV-4) ---
     //
     // Zoom is a *viewing* state, not an edit: it changes the resolution the
@@ -1500,6 +1506,21 @@ in property <bool> panel-visible: true;
                             background: Theme.rule;
                         }
 
+                        // Directly under the capture metadata and above every
+                        // control, because it is the thing the controls are
+                        // judged against: exposure, blacks and whites are all
+                        // set by watching this move (FR-DSP-7). An instrument
+                        // below the sliders it reports on would have the
+                        // photographer looking away from it to use it.
+                        HistogramPanel {
+                            data: root.histogram;
+                        }
+
+                        Rectangle {
+                            height: 1px;
+                            background: Theme.rule;
+                        }
+
                         // Framing above the colour work, matching how the edit is
                         // made rather than how it is applied: the frame is decided
                         // by eye first and the pipeline runs it last (see