Fix settings persistence, streaming stability, and UI polish

- Fix device settings partial update using model_fields_set for true merge
- Add missing interpolation_mode and smoothing to all API responses
- Fix send_pixels race condition when wled_client is None during stop
- Allow LED segments to exceed edge pixel count (float stepping)
- Fix modal scroll lock using position:fixed to prevent layout shift
- Show loading state for brightness slider until real value is fetched
- Remove stream description from stream selector dialog

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/api/routes.py

@@ -304,6 +304,7 @@ async def create_device(
                 border_width=device.settings.border_width,
                 interpolation_mode=device.settings.interpolation_mode,
                 brightness=device.settings.brightness,
+                smoothing=device.settings.smoothing,
                 state_check_interval=device.settings.state_check_interval,
             ),
             calibration=CalibrationSchema(**calibration_to_dict(device.calibration)),
@@ -339,7 +340,9 @@ async def list_devices(
                     display_index=device.settings.display_index,
                     fps=device.settings.fps,
                     border_width=device.settings.border_width,
+                    interpolation_mode=device.settings.interpolation_mode,
                     brightness=device.settings.brightness,
+                    smoothing=device.settings.smoothing,
                     state_check_interval=device.settings.state_check_interval,
                 ),
                 calibration=CalibrationSchema(**calibration_to_dict(device.calibration)),
@@ -384,7 +387,9 @@ async def get_device(
             display_index=device.settings.display_index,
             fps=device.settings.fps,
             border_width=device.settings.border_width,
+            interpolation_mode=device.settings.interpolation_mode,
             brightness=device.settings.brightness,
+            smoothing=device.settings.smoothing,
             state_check_interval=device.settings.state_check_interval,
         ),
         calibration=CalibrationSchema(**calibration_to_dict(device.calibration)),
@@ -474,6 +479,7 @@ async def update_device(
                 border_width=device.settings.border_width,
                 interpolation_mode=device.settings.interpolation_mode,
                 brightness=device.settings.brightness,
+                smoothing=device.settings.smoothing,
                 state_check_interval=device.settings.state_check_interval,
             ),
             calibration=CalibrationSchema(**calibration_to_dict(device.calibration)),
@@ -619,6 +625,7 @@ async def update_settings(
     """Update processing settings for a device.
 
     Merges with existing settings so callers can send partial updates.
+    Only fields explicitly included in the request body are applied.
     """
     try:
         # Get existing device to merge settings
@@ -627,20 +634,31 @@ async def update_settings(
             raise HTTPException(status_code=404, detail=f"Device {device_id} not found")
 
         existing = device.settings
+        sent = settings.model_fields_set  # fields the client actually sent
 
-        # Merge: use new values where provided, keep existing otherwise
+        # Merge: only override fields the client explicitly provided
         new_settings = ProcessingSettings(
-            display_index=settings.display_index,
+            display_index=settings.display_index if 'display_index' in sent else existing.display_index,
-            fps=settings.fps,
+            fps=settings.fps if 'fps' in sent else existing.fps,
-            border_width=settings.border_width,
+            border_width=settings.border_width if 'border_width' in sent else existing.border_width,
-            interpolation_mode=settings.interpolation_mode,
+            interpolation_mode=settings.interpolation_mode if 'interpolation_mode' in sent else existing.interpolation_mode,
-            brightness=settings.color_correction.brightness if settings.color_correction else existing.brightness,
+            brightness=settings.brightness if 'brightness' in sent else existing.brightness,
-            gamma=settings.color_correction.gamma if settings.color_correction else existing.gamma,
+            gamma=existing.gamma,
-            saturation=settings.color_correction.saturation if settings.color_correction else existing.saturation,
+            saturation=existing.saturation,
-            smoothing=settings.smoothing,
+            smoothing=settings.smoothing if 'smoothing' in sent else existing.smoothing,
-            state_check_interval=settings.state_check_interval,
+            state_check_interval=settings.state_check_interval if 'state_check_interval' in sent else existing.state_check_interval,
         )
 
+        # Apply color_correction fields if explicitly sent
+        if 'color_correction' in sent and settings.color_correction:
+            cc_sent = settings.color_correction.model_fields_set
+            if 'brightness' in cc_sent:
+                new_settings.brightness = settings.color_correction.brightness
+            if 'gamma' in cc_sent:
+                new_settings.gamma = settings.color_correction.gamma
+            if 'saturation' in cc_sent:
+                new_settings.saturation = settings.color_correction.saturation
+
         # Update in storage
         device = store.update_device(device_id, settings=new_settings)
 
@@ -657,6 +675,7 @@ async def update_settings(
             border_width=device.settings.border_width,
             interpolation_mode=device.settings.interpolation_mode,
             brightness=device.settings.brightness,
+            smoothing=device.settings.smoothing,
             state_check_interval=device.settings.state_check_interval,
         )
 

server/src/wled_controller/core/processor_manager.py

@@ -613,6 +613,8 @@ class ProcessorManager:
                         )
 
                     # Send to WLED with device brightness
+                    if not state.is_running or state.wled_client is None:
+                        break
                     brightness_value = int(wled_brightness * 255)
                     await state.wled_client.send_pixels(led_colors, brightness=brightness_value)
 

server/src/wled_controller/core/screen_capture.py

@@ -229,18 +229,16 @@ def get_edge_segments(
         divide_axis = 0  # Height
         edge_length = edge_pixels.shape[0]
 
-    if segment_count > edge_length:
+    # Use float stepping so multiple LEDs can share pixels when
-        raise ValueError(
+    # segment_count > edge_length (e.g. after downscaling).
-            f"segment_count {segment_count} is larger than edge length {edge_length}"
+    step = edge_length / segment_count
-        )
-
-    # Calculate segment size
-    segment_size = edge_length // segment_count
 
     segments = []
     for i in range(segment_count):
-        start = i * segment_size
+        start = int(i * step)
-        end = start + segment_size if i < segment_count - 1 else edge_length
+        end = max(start + 1, int((i + 1) * step))
+        # Clamp to edge bounds
+        end = min(end, edge_length)
 
         if divide_axis == 1:
             segment = edge_pixels[:, start:end, :]

server/src/wled_controller/static/app.js

@@ -47,16 +47,18 @@ const EDGE_TEST_COLORS = {
     left: [255, 255, 0]
 };
 
-// Modal body lock helpers - prevent layout jump when scrollbar disappears
+// Modal body lock helpers — uses position:fixed to freeze scroll without removing scrollbar
 function lockBody() {
-    const scrollbarWidth = window.innerWidth - document.documentElement.clientWidth;
+    const scrollY = window.scrollY;
-    document.body.style.paddingRight = scrollbarWidth + 'px';
+    document.body.style.top = `-${scrollY}px`;
     document.body.classList.add('modal-open');
 }
 
 function unlockBody() {
+    const scrollY = parseInt(document.body.style.top || '0', 10) * -1;
     document.body.classList.remove('modal-open');
-    document.body.style.paddingRight = '';
+    document.body.style.top = '';
+    window.scrollTo(0, scrollY);
 }
 
 // Image lightbox
@@ -764,12 +766,13 @@ function createDeviceCard(device) {
                 </div>
                 ` : ''}
             </div>
-            <div class="brightness-control">
+            <div class="brightness-control${_deviceBrightnessCache[device.id] == null ? ' brightness-loading' : ''}" data-brightness-wrap="${device.id}">
                 <input type="range" class="brightness-slider" min="0" max="255"
-                       value="${_deviceBrightnessCache[device.id] ?? 128}" data-device-brightness="${device.id}"
+                       value="${_deviceBrightnessCache[device.id] ?? 0}" data-device-brightness="${device.id}"
                        oninput="updateBrightnessLabel('${device.id}', this.value)"
                        onchange="saveCardBrightness('${device.id}', this.value)"
-                       title="${_deviceBrightnessCache[device.id] != null ? Math.round(_deviceBrightnessCache[device.id] / 255 * 100) + '%' : '...'}">
+                       title="${_deviceBrightnessCache[device.id] != null ? Math.round(_deviceBrightnessCache[device.id] / 255 * 100) + '%' : '...'}"
+                       ${_deviceBrightnessCache[device.id] == null ? 'disabled' : ''}>
             </div>
             <div class="card-actions">
                 ${isProcessing ? `
@@ -1231,7 +1234,10 @@ async function fetchDeviceBrightness(deviceId) {
         if (slider) {
             slider.value = data.brightness;
             slider.title = Math.round(data.brightness / 255 * 100) + '%';
+            slider.disabled = false;
         }
+        const wrap = document.querySelector(`[data-brightness-wrap="${deviceId}"]`);
+        if (wrap) wrap.classList.remove('brightness-loading');
     } catch (err) {
         // Silently fail — device may be offline
     }
@@ -4279,7 +4285,6 @@ async function updateStreamSelectorInfo(streamId) {
                 <span class="stream-card-prop" title="${t('streams.type')}">${typeIcon} ${typeName}</span>
                 ${propsHtml}
             </div>
-            ${stream.description ? `<div class="template-config" style="opacity:0.7;">${escapeHtml(stream.description)}</div>` : ''}
         `;
         infoPanel.style.display = '';
     } catch {

server/src/wled_controller/static/style.css

@@ -48,7 +48,8 @@ body {
 }
 
 body.modal-open {
-    overflow: hidden;
+    position: fixed;
+    width: 100%;
 }
 
 .container {
@@ -595,6 +596,11 @@ section {
     width: 100%;
 }
 
+.brightness-loading .brightness-slider {
+    opacity: 0.3;
+    pointer-events: none;
+}
+
 .section-header {
     display: flex;
     align-items: center;