Remove bounding-box normalization — compare paths in original dp space

swipetype-core/src/IdealPathGenerator.cpp

@@ -69,31 +69,12 @@ struct IdealPathGenerator::Impl {
         return result;
     }
 
-    // Normalize to [0,1] bounding box
+    // Keep coordinates in original dp space
     static GesturePath normalizeBB(const std::vector<GesturePoint>& points, float arcLen) {
         GesturePath result;
         if (points.empty()) return result;
 
-        float minX = points[0].x, maxX = points[0].x;
-        float minY = points[0].y, maxY = points[0].y;
-        for (const auto& p : points) {
-            minX = std::min(minX, p.x);
-            maxX = std::max(maxX, p.x);
-            minY = std::min(minY, p.y);
-            maxY = std::max(maxY, p.y);
-        }
-        float width  = maxX - minX;
-        float height = maxY - minY;
-
-        if (width < 0.001f && height < 0.001f) {
-            result.points.assign(points.size(), NormalizedPoint(0.5f, 0.5f, 0.5f));
-            result.aspectRatio = 1.0f;
-            result.totalArcLength = arcLen;
-            return result;
-        }
-
-        float scale = std::max(width, height);
-        result.aspectRatio = (height > 0.001f) ? (width / height) : 1.0f;
+        result.aspectRatio = 1.0f;
         result.totalArcLength = arcLen;
 
         int64_t firstTs = points.front().timestamp;
@@ -102,12 +83,10 @@ struct IdealPathGenerator::Impl {
 
         result.points.reserve(points.size());
         for (const auto& p : points) {
-            float nx = (p.x - minX) / scale;
-            float ny = (p.y - minY) / scale;
             float nt = (tsRange > 0.0f)
                 ? static_cast<float>(p.timestamp - firstTs) / tsRange
                 : 0.5f;
-            result.points.emplace_back(nx, ny, nt);
+            result.points.emplace_back(p.x, p.y, nt);
         }
         return result;
     }

swipetype-core/src/PathProcessor.cpp

@@ -114,7 +114,10 @@ struct PathProcessor::Impl {
     }
 
     /**
-     * Normalize coordinates to [0,1] bounding box preserving aspect ratio.
+     * Keep coordinates in original dp space — no bounding-box normalization.
+     * The gesture and ideal paths naturally share the same coordinate space
+     * (both derived from the same KeyboardLayout), so DTW on absolute
+     * positions correctly measures spatial distance on the keyboard.
      */
     GesturePath normalizeBoundingBox(const std::vector<GesturePoint>& points,
                                      float totalArcLength) const {
@@ -122,28 +125,7 @@ struct PathProcessor::Impl {
 
         if (points.empty()) return result;
 
-        float minX = points[0].x, maxX = points[0].x;
-        float minY = points[0].y, maxY = points[0].y;
-        for (const auto& p : points) {
-            minX = std::min(minX, p.x);
-            maxX = std::max(maxX, p.x);
-            minY = std::min(minY, p.y);
-            maxY = std::max(maxY, p.y);
-        }
-
-        float width  = maxX - minX;
-        float height = maxY - minY;
-
-        // Degenerate: near-point path
-        if (width < 0.001f && height < 0.001f) {
-            result.points.resize(points.size(), NormalizedPoint(0.5f, 0.5f, 0.5f));
-            result.aspectRatio = 1.0f;
-            result.totalArcLength = totalArcLength;
-            return result;
-        }
-
-        float scale = std::max(width, height);
-        result.aspectRatio = (height > 0.001f) ? (width / height) : 1.0f;
+        result.aspectRatio = 1.0f;
         result.totalArcLength = totalArcLength;
 
         int64_t firstTs = points.front().timestamp;
@@ -152,12 +134,10 @@ struct PathProcessor::Impl {
 
         result.points.reserve(points.size());
         for (const auto& p : points) {
-            float nx = (p.x - minX) / scale;
-            float ny = (p.y - minY) / scale;
             float nt = (tsRange > 0.0f)
                 ? static_cast<float>(p.timestamp - firstTs) / tsRange
                 : 0.5f;
-            result.points.emplace_back(nx, ny, nt);
+            result.points.emplace_back(p.x, p.y, nt);
         }
 
         return result;