Docs: minor amends to ImTextureData comments.

imgui.h

@@ -3513,7 +3513,7 @@ enum ImTextureStatus
 // You may use ImTextureData::Updates[] for the list, or ImTextureData::UpdateBox for a single bounding box.
 struct ImTextureRect
 {
-    unsigned short      x, y;       // Upper-left coordinates of rectangle to update
+    unsigned short      x, y;       // Upper-left coordinates of rectangle to update, within the parent Pixels[] array.
     unsigned short      w, h;       // Size of rectangle to update (in pixels)
 };
 
@@ -3535,7 +3535,7 @@ struct ImTextureData
     int                 Width;                  // w    r   // Texture width
     int                 Height;                 // w    r   // Texture height
     int                 BytesPerPixel;          // w    r   // 4 or 1
-    unsigned char*      Pixels;                 // w    r   // Pointer to buffer holding 'Width*Height' pixels and 'Width*Height*BytesPerPixels' bytes.
+    unsigned char*      Pixels;                 // w    r   // Pointer to whole texture buffer holding 'Width*Height' pixels and 'Width*Height*BytesPerPixels' bytes.
     ImTextureRect       UsedRect;               // w    r   // Bounding box encompassing all past and queued Updates[].
     ImTextureRect       UpdateRect;             // w    r   // Bounding box encompassing all queued Updates[].
     ImVector<ImTextureRect> Updates;            // w    r   // Array of individual updates.