Docs: update docs/comments about ImTextureRef, ImTextureID. (#8783)

imgui.h

@@ -317,7 +317,7 @@ IM_MSVC_RUNTIME_CHECKS_RESTORE
 // - When a Rendered Backend creates a texture, it store its native identifier into a ImTextureID value.
 //   (e.g. Used by DX11 backend to a `ID3D11ShaderResourceView*`; Used by OpenGL backends to store `GLuint`;
 //         Used by SDLGPU backend to store a `SDL_GPUTextureSamplerBinding*`, etc.).
-// - User may submit their own textures to e.g. ImGui::Image() function by passing the same type.
+// - User may submit their own textures to e.g. ImGui::Image() function by passing this value.
 // - During the rendering loop, the Renderer Backend retrieve the ImTextureID, which stored inside a
 //   ImTextureRef, which is stored inside a ImDrawCmd.
 // - Compile-time type configuration:
@@ -337,11 +337,12 @@ typedef ImU64 ImTextureID;      // Default: store up to 64-bits (any pointer or
 #define ImTextureID_Invalid     ((ImTextureID)0)
 #endif
 
-// ImTextureRef = higher-level identifier for a texture.
+// ImTextureRef = higher-level identifier for a texture. Store a ImTextureID _or_ a ImTextureData*.
 // The identifier is valid even before the texture has been uploaded to the GPU/graphics system.
 // This is what gets passed to functions such as `ImGui::Image()`, `ImDrawList::AddImage()`.
 // This is what gets stored in draw commands (`ImDrawCmd`) to identify a texture during rendering.
 // - When a texture is created by user code (e.g. custom images), we directly stores the low-level ImTextureID.
+//   Because of this, when displaying your own texture you are likely to ever only manage ImTextureID values on your side.
 // - When a texture is created by the backend, we stores a ImTextureData* which becomes an indirection
 //   to extract the ImTextureID value during rendering, after texture upload has happened.
 // - There is no constructor to create a ImTextureID from a ImTextureData* as we don't expect this