feat: enhance complex linetype rendering with DWG text style data, gap midpoint centering, and theme defaults

src/viewer2d/Viewer2D.js

@@ -248,6 +248,7 @@ export class Viewer2D {
     this._clear();
     this._entityMeta = [];
     this._buildLayerMap(result?.tables?.layers);
+    this._buildStyleMap(result?.tables?.styles || result?.tables?.textStyles);
     this._buildLinetypeMap(result);
     // Sheet orientation: the active model-space viewport's VIEWTWIST rotates the
     // view so a drawing stored tilted in WCS (rotated survey sheets — header UCS
@@ -273,6 +274,13 @@ export class Viewer2D {
       else this._activeSpaceHex = typeof sh === 'number' ? sh.toString(16) : String(sh).toLowerCase();
     }
 
+    if (!opts.keepTheme) {
+      const spacesList = listCadSpaces(result);
+      const activeSp = spacesList.find((s) => s.handleHex === this._activeSpaceHex);
+      const isPaper = activeSp?.kind === 'paper';
+      this.setTheme(!isPaper);
+    }
+
     const entities    = result?.entities || [];
     const lineVerts   = [];
     const lineColors  = [];
@@ -1045,9 +1053,9 @@ export class Viewer2D {
 
   // ── UI integration ─────────────────────────────────────────────────────────
 
-  /** Swap canvas background for theme. dark=true → near-black, false → light. */
+  /** Swap canvas background for theme. dark=true → near-black (Model), false → white (Layout). */
   setTheme(dark) {
-    this._scene.background = new THREE.Color(dark ? 0x0a0b0d : 0xf7f6f3);
+    this._scene.background = new THREE.Color(dark ? 0x0a0b0d : 0xffffff);
     if (this._gridVisible) this._rebuildGrid();
   }
 
@@ -1697,12 +1705,25 @@ export class Viewer2D {
       };
     };
 
+    const elements = linPattern.elements || [];
     const patternLen = linPattern.patternLength * ltscale;
-    if (patternLen < 1e-6) return;
+    if (patternLen < 1e-6 || !elements.length) return;
+
+    // Calculate distance from pattern start to shape (arrowhead) element if present
+    let shapeOffset = -1;
+    let accum = 0;
+    for (const e of elements) {
+      if (e.type === 'shape') {
+        shapeOffset = accum;
+        break;
+      }
+      if (e.type === 'dash') accum += Math.max((e.val || 0.05) * ltscale, 0.01 * ltscale);
+      else if (e.type === 'gap') accum += Math.abs(e.val || 0.1) * ltscale;
+    }
 
     let s = 0;
     let elemIdx = 0;
-    const elements = linPattern.elements;
+    let lastShapePos = -1;
 
     while (s < totalLen) {
       const elem = elements[elemIdx % elements.length];
@@ -1723,12 +1744,18 @@ export class Viewer2D {
         const gapLen = Math.abs(elem.val || 0.1) * ltscale;
         s += gapLen;
       } else if (elem.type === 'shape') {
+        lastShapePos = s;
         const pState = getPathState(s);
         this._renderShapeSymbol(elem, pState, ltscale, color, pushSeg);
       } else if (elem.type === 'text') {
         const pState = getPathState(s);
         if (elem.text && pendingTexts) {
-          const h = (elem.scale || 0.2) * ltscale;
+          // 1. Text Height: Exact text style DWG table height if fixed, else linetype elem.scale
+          const sName = (elem.style || 'STANDARD').toUpperCase();
+          const fixedH = this._textStyleHeightMap?.get(sName) || 0;
+          const baseH = fixedH > 0 ? fixedH : (elem.scale || 0.2);
+          const h = baseH * ltscale;
+
           let angle = pState.angle + ((elem.rotation || 0) * Math.PI) / 180;
           if (elem.isAbsoluteAngle) {
             angle = ((elem.rotation || 0) * Math.PI) / 180;
@@ -1744,20 +1771,30 @@ export class Viewer2D {
           const sinT = Math.sin(angle);
 
           const xo = (elem.xOffset || 0) * ltscale;
-          const rawYo = (elem.yOffset != null && Math.abs(elem.yOffset) > 1e-4) ? Math.abs(elem.yOffset) : 0.02;
-          const yo = rawYo * ltscale;
+          // alignV: 2 (middle) centers text quad on origin; set yo=0 so middle lies directly on grey arrow line axis
+          const yo = 0;
 
-          const tx = pState.x + (xo * cosT - yo * sinT);
-          const ty = pState.y + (xo * sinT + yo * cosT);
+          // 2. Exact Visual Midpoint: position text at exact midpoint of empty text gap (between arrowhead tip and next dash)
+          let gapMidOffset = 0;
+          const nextElem = elements[elemIdx % elements.length];
+          if (nextElem && nextElem.type === 'gap') {
+            const gapLen = Math.abs(nextElem.val || 0) * ltscale;
+            gapMidOffset = gapLen / 2;
+          }
+
+          const midState = gapMidOffset > 1e-6 ? getPathState(s + gapMidOffset) : pState;
+
+          const tx = midState.x + (xo * cosT - yo * sinT);
+          const ty = midState.y + (xo * sinT + yo * cosT);
 
           pendingTexts.push({
             text: elem.text,
-            pos: { x: tx, y: ty, z: pState.z },
+            pos: { x: tx, y: ty, z: midState.z },
             height: Math.max(h, 0.01),
             rotation: angle,
             color,
-            alignH: 1,
-            alignV: 2,
+            alignH: 1, // center horizontally in gap between arrowheads
+            alignV: 2, // center vertically on line axis
           });
         }
       }
@@ -1846,6 +1883,19 @@ export class Viewer2D {
     }
   }
 
+  _buildStyleMap(styles) {
+    if (!this._textStyleHeightMap) this._textStyleHeightMap = new Map();
+    this._textStyleHeightMap.clear();
+    if (!styles || !Array.isArray(styles)) return;
+    for (const st of styles) {
+      const sName = (st.name || st.styleName || '').toUpperCase();
+      const h = st.height ?? st.fixedTextHeight ?? 0;
+      if (sName && h > 0) {
+        this._textStyleHeightMap.set(sName, h);
+      }
+    }
+  }
+
   _buildLayerMap(layers) {
     this._layerByHandle.clear();
     this._layerByName.clear();