Runtime fix for image scale with mesh

This resolves an issue found by @lancesnider where replacing an image at runtime that is a different size that the image used at design time would not work properly when the image has a mesh applied. This does not fix a similar issue experienced when images have n-slicing applied.

Image 1 at runtime:
<img width="798" alt="Screenshot 2025-01-08 at 2 47 28 PM" src="https://github.com/user-attachments/assets/aae66c2d-40ef-42ef-9509-4a092277bc15" />

Image 2 at runtime:
<img width="797" alt="Screenshot 2025-01-08 at 2 47 43 PM" src="https://github.com/user-attachments/assets/861713de-2d8d-4bd7-b497-c84c85ac4cf4" />

Diffs=
eca00184b8 Runtime fix for image scale with mesh (#8840)

Co-authored-by: Philip Chung <philterdesign@gmail.com>
Co-authored-by: Susan Wang <susan@rive.app>

.rive_head

@@ -1 +1 @@
-7c018ff174dc69f841e6b5011d995d8b0653ca01
+eca00184b8fb096243a60594f94f91f39607a15e

include/rive/shapes/mesh_drawable.hpp

@@ -7,6 +7,11 @@
 namespace rive
 {
 class RenderImage;
+enum class MeshType : uint8_t
+{
+    vertex = 0,
+    nslice = 1,
+};
 class MeshDrawable
 {
 protected:
@@ -17,6 +22,7 @@ protected:
     rcp<RenderBuffer> m_UVRenderBuffer;
 
 public:
+    MeshType type = MeshType::vertex;
     virtual ~MeshDrawable() = default;
     virtual void onAssetLoaded(RenderImage* image) = 0;
     virtual void draw(Renderer* renderer,

include/rive/shapes/slice_mesh.hpp

@@ -54,6 +54,7 @@ private:
 protected:
 public:
     SliceMesh(NSlicer* nslicer);
+    MeshType type = MeshType::nslice;
     void draw(Renderer* renderer,
               const RenderImage* image,
               BlendMode blendMode,

src/shapes/image.cpp

@@ -4,6 +4,7 @@
 #include "rive/importers/backboard_importer.hpp"
 #include "rive/assets/file_asset.hpp"
 #include "rive/assets/image_asset.hpp"
+#include "rive/layout/n_slicer.hpp"
 #include "rive/shapes/mesh_drawable.hpp"
 #include "rive/artboard.hpp"
 #include "rive/clip_result.hpp"
@@ -211,6 +212,11 @@ void Image::controlSize(Vec2D size,
 
 void Image::updateImageScale()
 {
+    // User-created meshes are not affected by scale
+    if (m_Mesh != nullptr && m_Mesh->type == MeshType::vertex)
+    {
+        return;
+    }
     if (imageAsset() != nullptr && imageAsset()->renderImage() != nullptr &&
         !std::isnan(m_layoutWidth) && !std::isnan(m_layoutHeight))
     {