ability to fetch memory usage by the graphics server

fyrox-graphics/src/gpu_texture.rs

@@ -497,14 +497,15 @@ define_as_any_trait!(GpuTextureAsAny => GpuTextureTrait);
 /// ```
 pub trait GpuTextureTrait: GpuTextureAsAny {
     /// Sets the new data of the texture. This method is also able to change the kind of the texture
-    /// and its pixel kind.
+    /// and its pixel kind. Returns the number of bytes occupied by the texture in the video memory.
+    /// If there's no data specified, the texture will still take the space defined by its metrics.
     fn set_data(
         &self,
         kind: GpuTextureKind,
         pixel_kind: PixelKind,
         mip_count: usize,
         data: Option<&[u8]>,
-    ) -> Result<(), FrameworkError>;
+    ) -> Result<usize, FrameworkError>;
 
     /// Returns kind of the texture.
     fn kind(&self) -> GpuTextureKind;

fyrox-graphics/src/server.rs

@@ -51,6 +51,18 @@ pub struct ServerCapabilities {
     pub max_lod_bias: f32,
 }
 
+/// Contains information about used memory per each category of GPU resource. This is not precise
+/// data; it only calculates total requested memory by the user of a graphics server and does not
+/// include additional memory overhead in the video driver. Yet this information could still be
+/// useful.
+#[derive(Default, Debug, Clone)]
+pub struct ServerMemoryUsage {
+    /// Total number of bytes used by all textures (including render targets).
+    pub textures: usize,
+    /// Total number of bytes used by all buffers (vertex, index, uniform, etc.)
+    pub buffers: usize,
+}
+
 /// A shared reference to a graphics server.
 pub type SharedGraphicsServer = Rc<dyn GraphicsServer>;
 
@@ -168,6 +180,9 @@ pub trait GraphicsServer: GraphicsServerAsAny {
     /// way of mipmaps generation, depending on the underlying GAPI capabilities.
     fn generate_mipmap(&self, texture: &GpuTexture);
 
+    /// Fetches the total amount of memory used by the graphics server.
+    fn memory_usage(&self) -> ServerMemoryUsage;
+
     /// A shortcut for [`Self::create_texture`], that creates a rectangular texture with the given
     /// size and pixel kind.
     fn create_2d_render_target(