implement drag and drop colours from palette to template section

frontend/src/lib/components/editor/AppColorOverrides.svelte

@@ -6,8 +6,13 @@
         getAppOverrides,
         clearAppOverridesForApp,
         removeAppOverride,
+        setAppOverride,
     } from '$lib/stores/theme.svelte';
-    import {openOverrideColorPicker} from '$lib/stores/ui.svelte';
+    import {
+        openOverrideColorPicker,
+        getColorDrag,
+        setColorDrag,
+    } from '$lib/stores/ui.svelte';
     import {isLightColor, copyColor} from '$lib/utils/color';
     import ContextMenu from '$lib/components/shared/ContextMenu.svelte';
     import ExpandableSection from '$lib/components/shared/ExpandableSection.svelte';
@@ -113,6 +118,24 @@
         return SHORT_LABELS[role] || role.replace(/_/g, ' ');
     }
 
+    let dragOverRole = $state('');
+
+    $effect(() => {
+        if (!getColorDrag()) dragOverRole = '';
+    });
+
+    function onButtonMouseEnter(role: string) {
+        if (getColorDrag()) dragOverRole = role;
+    }
+
+    function onButtonMouseUp(e: MouseEvent, role: string) {
+        const drag = getColorDrag();
+        if (!drag || e.button !== 0) return;
+        setColorDrag(null);
+        setAppOverride(selectedApp, role, drag.color, true);
+        dragOverRole = '';
+    }
+
     let menu = $state({open: false, x: 0, y: 0, role: ''});
 
     function openMenu(e: MouseEvent, role: string) {
@@ -207,14 +230,19 @@
                             class="group relative flex h-9 cursor-pointer items-end justify-center overflow-hidden border px-1 transition-all duration-100
                             {isOverridden
                                 ? 'border-accent border-2'
-                                : 'border-border hover:border-border-focus'}"
+                                : dragOverRole === role
+                                  ? 'border-accent scale-[1.06] border-2 shadow-md'
+                                  : 'border-border hover:border-border-focus'}"
                             style:background-color={display}
                             onclick={() =>
                                 openOverrideColorPicker(selectedApp, role)}
                             oncontextmenu={e => openMenu(e, role)}
+                            onmouseenter={() => onButtonMouseEnter(role)}
+                            onmouseleave={() => (dragOverRole = '')}
+                            onmouseup={e => onButtonMouseUp(e, role)}
                             title="{role}{isOverridden
                                 ? ` · override ${appOverrides[role]}`
-                                : ` · computed ${display}`}\nClick edit · Right-click for menu"
+                                : ` · computed ${display}`}\nClick edit · Right-click for menu · Drag palette color to override"
                         >
                             <span
                                 class="block w-full select-none truncate pb-0.5 text-center text-[8px] leading-none opacity-80 transition-opacity group-hover:opacity-100

frontend/src/lib/components/editor/ColorDragGhost.svelte

@@ -0,0 +1,25 @@
+<script lang="ts">
+    import {getColorDrag} from '$lib/stores/ui.svelte';
+
+    let drag = $derived(getColorDrag());
+    let active = $derived(!!drag);
+
+    $effect(() => {
+        if (!active) return;
+        const previous = document.body.style.cursor;
+        document.body.style.cursor = 'copy';
+        return () => {
+            if (document.body.style.cursor === 'copy')
+                document.body.style.cursor = previous;
+        };
+    });
+</script>
+
+{#if drag}
+    <div
+        class="pointer-events-none fixed z-[9999] h-7 w-7 border-2 border-white shadow-lg"
+        style:background-color={drag.color}
+        style:left="{drag.x + 12}px"
+        style:top="{drag.y + 12}px"
+    ></div>
+{/if}

frontend/src/lib/components/editor/ColorSwatch.svelte

@@ -9,7 +9,7 @@
         contrastRatio,
         contrastLevel,
     } from '$lib/utils/color';
-    import {setEyedropperActive} from '$lib/stores/ui.svelte';
+    import {setEyedropperActive, setColorDrag} from '$lib/stores/ui.svelte';
     import {onActivate} from '$lib/utils/keyboard';
     import LockIcon from '$lib/components/shared/LockIcon.svelte';
     import ContextMenu from '$lib/components/shared/ContextMenu.svelte';
@@ -99,6 +99,10 @@
     }
 
     function handleClick(event: MouseEvent) {
+        if (didDrag) {
+            didDrag = false;
+            return;
+        }
         if (event.ctrlKey || event.metaKey) {
             event.preventDefault();
             copyColor(color);
@@ -113,6 +117,82 @@
     }
 
     let light = $derived(isLightColor(color));
+
+    let isDragging = $state(false);
+    let didDrag = $state(false);
+    let pendingDrag: {startX: number; startY: number; color: string} | null =
+        null;
+
+    function onMouseDown(e: MouseEvent) {
+        if (e.button !== 0) return;
+        clearDrag();
+        didDrag = false;
+        if (e.ctrlKey || e.metaKey || e.shiftKey) return;
+        if (
+            (e.target as Element).closest('[role="button"]') !== e.currentTarget
+        )
+            return;
+        pendingDrag = {startX: e.clientX, startY: e.clientY, color};
+        window.addEventListener('mousemove', onDragMove);
+        window.addEventListener('mouseup', onDragUp);
+        window.addEventListener('blur', clearDrag);
+        window.addEventListener('keydown', onDragKeydown);
+    }
+
+    function onDragMove(e: MouseEvent) {
+        if (!(e.buttons & 1)) {
+            clearDrag();
+            return;
+        }
+        if (!pendingDrag) return;
+        if (isDragging) {
+            e.preventDefault();
+            setColorDrag({
+                color: pendingDrag.color,
+                x: e.clientX,
+                y: e.clientY,
+            });
+            return;
+        }
+        const dx = e.clientX - pendingDrag.startX;
+        const dy = e.clientY - pendingDrag.startY;
+        if (Math.hypot(dx, dy) >= 4) {
+            didDrag = true;
+            isDragging = true;
+            e.preventDefault();
+            setColorDrag({
+                color: pendingDrag.color,
+                x: e.clientX,
+                y: e.clientY,
+            });
+        }
+    }
+
+    function onDragKeydown(e: KeyboardEvent) {
+        if (e.key === 'Escape') {
+            e.preventDefault();
+            clearDrag();
+        }
+    }
+
+    function onDragUp(e: MouseEvent) {
+        if (e.button === 0) clearDrag();
+    }
+
+    function clearDrag() {
+        window.removeEventListener('mousemove', onDragMove);
+        window.removeEventListener('mouseup', onDragUp);
+        window.removeEventListener('blur', clearDrag);
+        window.removeEventListener('keydown', onDragKeydown);
+        if (pendingDrag || isDragging) setColorDrag(null);
+        pendingDrag = null;
+        isDragging = false;
+    }
+
+    $effect(() => {
+        const _ = color;
+        return clearDrag;
+    });
 </script>
 
 <!-- Keyboard handling lives on the parent ColorPaletteGrid (roving tabindex). -->
@@ -123,16 +203,18 @@
         ? 'border-border cursor-default'
         : selected
           ? 'border-accent cursor-pointer border-2'
-          : 'hover:border-accent border-border cursor-pointer hover:z-10 hover:scale-[1.04] hover:shadow-lg'}"
+          : 'hover:border-accent border-border cursor-pointer hover:z-10 hover:scale-[1.04] hover:shadow-lg'}
+    {isDragging ? 'opacity-60' : ''}"
     style:background-color={color}
     role="button"
     tabindex={focused ? 0 : -1}
     data-swatch-idx={index}
     onclick={handleClick}
+    onmousedown={onMouseDown}
     oncontextmenu={handleContextMenu}
     title={`${label}${role ? ` · ${role}` : ''}\n${color}${
         showBadge ? `\nContrast vs BG: ${ratio.toFixed(2)}:1 (${level})` : ''
-    }\nClick edit · Ctrl+click copy · Shift+click select · Right-click for menu\n← → ↑ ↓ navigate · Enter open · L lock · C copy`}
+    }\nClick edit · Ctrl+click copy · Shift+click select · Right-click for menu\nDrag to copy into a template override\n← → ↑ ↓ navigate · Enter open · L lock · C copy`}
 >
     {#if selected}
         <span

frontend/src/lib/components/editor/ThemeEditor.svelte

@@ -9,6 +9,7 @@
     import SettingsSidebar from '../sidebar/SettingsSidebar.svelte';
     import ColorPickerDialog from '../color-picker/ColorPickerDialog.svelte';
     import WallpaperEditor from '../wallpaper-editor/WallpaperEditor.svelte';
+    import ColorDragGhost from './ColorDragGhost.svelte';
     import {getWallpaperPath, getPalette} from '$lib/stores/theme.svelte';
     import {
         getSidebarVisible,
@@ -74,4 +75,5 @@
         open={getImageEditorOpen()}
         onclose={() => setImageEditorOpen(false)}
     />
+    <ColorDragGhost />
 </div>

frontend/src/lib/stores/history.svelte.ts

@@ -19,6 +19,7 @@ export interface Snapshot {
     basePalette: string[];
     extendedColors: Record<string, string>;
     baseExtendedColors: Record<string, string>;
+    appOverrides: Record<string, Record<string, string>>;
     adjustments: Adjustments;
     paletteCurvePoints: [number, number][];
     extractionMode: string;
@@ -50,6 +51,12 @@ export function copySnapshot(snapshot: Snapshot): Snapshot {
         basePalette: [...snapshot.basePalette],
         extendedColors: {...snapshot.extendedColors},
         baseExtendedColors: {...snapshot.baseExtendedColors},
+        appOverrides: Object.fromEntries(
+            Object.entries(snapshot.appOverrides).map(([app, colors]) => [
+                app,
+                {...colors},
+            ])
+        ),
         adjustments: {...snapshot.adjustments},
         paletteCurvePoints: snapshot.paletteCurvePoints.map(([x, y]) => [x, y]),
         extractionMode: snapshot.extractionMode,

frontend/src/lib/stores/theme.svelte.ts

@@ -180,6 +180,7 @@ export function getHistorySnapshot(): Snapshot {
         basePalette,
         extendedColors,
         baseExtendedColors,
+        appOverrides,
         adjustments,
         paletteCurvePoints,
         extractionMode,
@@ -195,6 +196,7 @@ export function restoreHistorySnapshot(snapshot: Snapshot): void {
     basePalette = restored.basePalette;
     extendedColors = restored.extendedColors;
     baseExtendedColors = restored.baseExtendedColors;
+    appOverrides = restored.appOverrides;
     adjustments = restored.adjustments;
     paletteCurvePoints = restored.paletteCurvePoints;
     extractionMode = restored.extractionMode;
@@ -379,8 +381,18 @@ export function setPaletteCurvePoints(pts: [number, number][]): void {
     invalidateThemeRequests();
     paletteCurvePoints = pts.map(([x, y]) => [x, y]);
 }
-export function setAppOverride(app: string, role: string, hex: string): void {
+export function setAppOverride(
+    app: string,
+    role: string,
+    hex: string,
+    recordHistory = false
+): void {
     const current = appOverrides[app] || {};
+    if (current[role] === hex) return;
+    if (recordHistory) {
+        endColorEditSessions();
+        pushState(getHistorySnapshot());
+    }
     appOverrides = {...appOverrides, [app]: {...current, [role]: hex}};
 }
 export function removeAppOverride(app: string, role: string): void {

frontend/src/lib/stores/ui.svelte.ts

@@ -45,6 +45,7 @@ function writeBoolPref(key: string, value: boolean): void {
     } catch {}
 }
 let colorPickerOpen = $state<boolean>(false);
+let colorDrag = $state<{color: string; x: number; y: number} | null>(null);
 let colorPickerIndex = $state<number>(-1);
 let colorPickerExtKey = $state<string>(''); // non-empty = editing an extended color
 let colorPickerOverrideApp = $state<string>(''); // non-empty = editing an app override
@@ -276,3 +277,12 @@ export function getApplySaveDialogOpen(): boolean {
 export function setApplySaveDialogOpen(v: boolean): void {
     applySaveDialogOpen = v;
 }
+
+export function getColorDrag(): {color: string; x: number; y: number} | null {
+    return colorDrag;
+}
+export function setColorDrag(
+    v: {color: string; x: number; y: number} | null
+): void {
+    colorDrag = v;
+}