docs for quantity picking

Author: nmwsharp

cpp/source/basics/interactive_UIs_and_animation.md

@@ -270,9 +270,11 @@ A pick query returns a combined struct with info such as what structure was clic
 struct PickResult {
   bool isHit = false;                    // did we hit anything?
   Structure* structure = nullptr;        // pointer to the structure under the cursor
+  Quantity* quantity = nullptr;          // pointer to the quantity under the cursor (most quantities cannot be picked, you pick the structure instead)
   WeakHandle<Structure> structureHandle; // same as .structure, but with lifetime tracking
   std::string structureType = "";        // structure type which was hit, like "Point Cloud"
   std::string structureName = "";        // name of structure which was hit, like "my_points"
+  std::string quantityName = "";         // name of quantity which was hit (most quantities cannot be picked, you pick the structure instead)
   glm::vec2 screenCoords;                // coordinates of the query location
   glm::ivec2 bufferInds;                 // render buffer indices of the query location
   glm::vec3 position;                    // 3d position which was hit, in world space

py/source/basics/interactive_UIs_and_animation.md

@@ -413,15 +413,16 @@ A pick query returns a combined struct with info such as what structure was clic
 
 ```python
 class PickResult:
-    self.is_hit =               # did we hit anything?
-    self.structure_type_name =  # structure type which was hit, like "Point Cloud"
-    self.structure_name =       # name of structure which was hit, like "my_points"
-    self.screen_coords =        # coordinates of the query location
-    self.buffer_inds =          # render buffer indices of the query location
-    self.position =             # 3d position which was hit, in world space
-    self.depth =                # depth to the hit, in world units
-    self.local_index =          # structure-specific index of the element which was hit
-    self.structure_data =       # a dictionary of additional fields for the clicked structure
+    self.is_hit = ...               # did we hit anything?
+    self.structure_type_name = ...  # structure type which was hit, like "Point Cloud"
+    self.structure_name = ...       # name of structure which was hit, like "my_points"
+    self.quantity_name = ...        # name of quantity which was hit (most quantities cannot be picked, you pick the structure instead)
+    self.screen_coords = ...        # coordinates of the query location
+    self.buffer_inds = ...          # render buffer indices of the query location
+    self.position = ...             # 3d position which was hit, in world space
+    self.depth = ...                # depth to the hit, in world units
+    self.local_index = ...          # structure-specific index of the element which was hit
+    self.structure_data = ...       # a dictionary of additional fields for the clicked structure
 ```
 
 Additionally, many structures will report additional information about the pick, in the `structure_data` field. For instance, a `SurfaceMesh` gives info on whether a vertex/face/edge/etc was clicked on, the index of that element, and barycentric coordinates of the click within a face.