Add smart tick labels and move direction arrows inside screen

- Add intermediate tick labels at nice intervals (5, 10, 25, 50, 100, 250, 500)
  with max 5 labels per edge and pixel-based overlap prevention
- Move direction chevrons from outside edge bars to inside the screen area
- Make chevrons filled with green fill and white outline for better contrast

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

server/src/wled_controller/static/app.js

@@ -1219,12 +1219,13 @@ function renderCalibrationCanvas() {
         right:  ox + cW + 3,     // labels right of right edge
     };
 
-    // Arrow positions (further out than tick labels)
+    // Arrow positions (inside the screen area, near each edge bar)
+    const arrowInset = 12;
     const arrowPos = {
-        top:    oy - 10,
+        top:    oy + ch + arrowInset,
-        bottom: oy + cH + 10,
+        bottom: oy + cH - ch - arrowInset,
-        left:   ox - 10,
+        left:   ox + cw + arrowInset,
-        right:  ox + cW + 10,
+        right:  ox + cW - cw - arrowInset,
     };
 
     // Draw ticks and direction arrows for each segment
@@ -1235,17 +1236,55 @@ function renderCalibrationCanvas() {
         const count = seg.led_count;
         if (count === 0) return;
 
-        // Show only first and last LED index per edge, plus LED 0 if offset > 0
+        // Mandatory ticks: first and last LED index per edge, plus LED 0 if offset > 0
         const labelsToShow = new Set();
         labelsToShow.add(0);
         if (count > 1) labelsToShow.add(count - 1);
 
-        // Add LED 0 tick on the edge where it wraps
         if (offset > 0 && totalLeds > 0) {
             const zeroPos = (totalLeds - seg.led_start % totalLeds) % totalLeds;
             if (zeroPos < count) labelsToShow.add(zeroPos);
         }
 
+        // Add intermediate ticks at "nice" intervals (max 5 labels per edge)
+        if (count > 2) {
+            const edgeLen = geo.horizontal ? (geo.x2 - geo.x1) : (geo.y2 - geo.y1);
+            const maxDigits = String(totalLeds > 0 ? totalLeds - 1 : count - 1).length;
+            const minSpacing = geo.horizontal ? maxDigits * 7 + 8 : 22;
+
+            const maxIntermediate = Math.max(0, 5 - labelsToShow.size);
+            const niceSteps = [5, 10, 25, 50, 100, 250, 500];
+            let step = niceSteps[niceSteps.length - 1];
+            for (const s of niceSteps) {
+                if (Math.floor(count / s) <= maxIntermediate) {
+                    step = s;
+                    break;
+                }
+            }
+
+            // Pixel position helper (0..edgeLen along the edge)
+            const tickPx = i => {
+                const f = i / (count - 1);
+                return (seg.reverse ? (1 - f) : f) * edgeLen;
+            };
+
+            // Collect pixel positions of mandatory ticks
+            const placed = [];
+            labelsToShow.forEach(i => placed.push(tickPx(i)));
+
+            // Add ticks at LED indices divisible by step
+            for (let i = 1; i < count - 1; i++) {
+                const idx = totalLeds > 0 ? (seg.led_start + i) % totalLeds : seg.led_start + i;
+                if (idx % step === 0) {
+                    const px = tickPx(i);
+                    if (!placed.some(p => Math.abs(px - p) < minSpacing)) {
+                        labelsToShow.add(i);
+                        placed.push(px);
+                    }
+                }
+            }
+        }
+
         // Tick styling
         const tickLen = 5;
         ctx.strokeStyle = 'rgba(255, 255, 255, 0.4)';
@@ -1291,8 +1330,8 @@ function renderCalibrationCanvas() {
             }
         });
 
-        // Draw direction chevron at midpoint, outside the edge bar
+        // Draw direction chevron at midpoint, inside the screen area
-        const s = 5;
+        const s = 7;
         let mx, my, angle;
         if (geo.horizontal) {
             mx = (geo.x1 + geo.x2) / 2;
@@ -1307,14 +1346,17 @@ function renderCalibrationCanvas() {
         ctx.save();
         ctx.translate(mx, my);
         ctx.rotate(angle);
-        ctx.strokeStyle = '#4CAF50';
+        ctx.fillStyle = 'rgba(76, 175, 80, 0.85)';
-        ctx.lineWidth = 1.5;
+        ctx.strokeStyle = 'rgba(255, 255, 255, 0.6)';
+        ctx.lineWidth = 1;
         ctx.lineCap = 'round';
         ctx.lineJoin = 'round';
         ctx.beginPath();
-        ctx.moveTo(-s * 0.4, -s * 0.5);
+        ctx.moveTo(-s * 0.5, -s * 0.6);
-        ctx.lineTo(s * 0.4, 0);
+        ctx.lineTo(s * 0.5, 0);
-        ctx.lineTo(-s * 0.4, s * 0.5);
+        ctx.lineTo(-s * 0.5, s * 0.6);
+        ctx.closePath();
+        ctx.fill();
         ctx.stroke();
         ctx.restore();
     });