Export JPEG and Canvas Size take the app's colour picker; a panel opens over a modal sheet (13.4a)

src/Document/ColorPalette+Session.h

@@ -28,6 +28,11 @@ public:
     void openEffectColorPicker(LayerEffectKind kind);
     // The effect follows the picker's working colour.
     void previewEffectColor();
+    // The picker on a dialog's colour, which hears each change.
+    void openDialogColorPicker(const QString &title, const PaletteColor &color, std::function<void(const PaletteColor &)> change);
+    // A dialog covers the canvas: nothing to sample.
+    bool pickingForDialog() const;
+    void previewDialogColor() const;
     // The open text draft previews the picker's working colour.
     void previewTextColor();
     // Paints the open text's selected letters, or all of it.

src/Document/ColorPalette.cpp

@@ -109,6 +109,8 @@ QString ColorPickerTarget::title() const
         return QStringLiteral("Color Picker (Vignette Color)");
     if (kind == Kind::dither)
         return light ? QStringLiteral("Color Picker (Dither Light Color)") : QStringLiteral("Color Picker (Dither Dark Color)");
+    if (kind == Kind::dialog)
+        return QStringLiteral("Color Picker (%1)").arg(dialogTitle);
     return background ? QStringLiteral("Color Picker (Background Color)") : QStringLiteral("Color Picker (Foreground Color)");
 }
 
@@ -257,6 +259,8 @@ void EditorSession::closeColorPicker(bool commit)
         setVignetteColor(commit ? color : picker.original);
     } else if (picker.target.kind == ColorPickerTarget::Kind::dither) {
         setDitherColor(commit ? color : picker.original, picker.target.light);
+    } else if (picker.target.kind == ColorPickerTarget::Kind::dialog) {
+        picker.dialogChange(commit ? color : picker.original);
     } else if (picker.target.kind == ColorPickerTarget::Kind::effect) {
         const PaletteColor chosen = commit ? color : picker.original;
         changeEffects([&](LayerEffects &effects) { effects.setColor(chosen, picker.target.effect); });
@@ -440,3 +444,26 @@ std::optional<PaletteColor> EditorSession::sampleCompositeColor(QPointF point) c
         return std::nullopt;
     }
 }
+
+void EditorSession::openDialogColorPicker(const QString &title, const PaletteColor &color, std::function<void(const PaletteColor &)> change)
+{
+    if (m_colorPicker)
+        return;
+    ColorPickerTarget target{ColorPickerTarget::Kind::dialog};
+    target.dialogTitle = title;
+    m_colorPicker.emplace(target, color);
+    m_colorPicker->dialogChange = std::move(change);
+    notify();
+}
+
+bool EditorSession::pickingForDialog() const
+{
+    return m_colorPicker && m_colorPicker->target.kind == ColorPickerTarget::Kind::dialog;
+}
+
+// The dialog follows the working colour; the session keeps nothing.
+void EditorSession::previewDialogColor() const
+{
+    if (pickingForDialog())
+        m_colorPicker->dialogChange(m_colorPicker->color());
+}

src/Document/ColorPalette.h

@@ -3,6 +3,7 @@
 #include <QColor>
 #include <QString>
 #include <QUuid>
+#include <functional>
 #include <optional>
 
 // Swift's PaletteColor: an sRGB colour without alpha.
@@ -38,7 +39,7 @@ enum class LayerEffectKind;
 
 // The picker's targets: palette, text, effect, a filter's colour.
 struct ColorPickerTarget {
-    enum class Kind { palette, text, gradientMap, effect, vignette, dither };
+    enum class Kind { palette, text, gradientMap, effect, vignette, dither, dialog };
     Kind kind;
     bool background = false;
     std::optional<QUuid> draftID = std::nullopt;
@@ -48,6 +49,8 @@ struct ColorPickerTarget {
     LayerEffectKind effect{};
     // Dither's Two Colors: the light one, else the dark.
     bool light = false;
+    // A dialog's own colour, such as Export JPEG's background.
+    QString dialogTitle{};
     QString title() const;
     friend bool operator==(const ColorPickerTarget &, const ColorPickerTarget &) = default;
 };
@@ -66,5 +69,7 @@ struct ColorPickerState {
         LayerTextStyle style;
     };
     std::optional<EditedText> editedText;
+    // A dialog's colour: told as it moves, then on closing.
+    std::function<void(const PaletteColor &)> dialogChange;
     PaletteColor color() const { return hsb.rgb().quantized(); }
 };