Revert "delete unused code for dummy platform and renderer backends"

This reverts commit d616a13047e0f138e92fa582202f06d7dc3d5397.

imgui/src/docking_utils.rs

@@ -188,11 +188,92 @@ pub(crate) extern "C" fn platform_create_vk_surface(
     })
 }
 
+/// The default [`PlatformViewportBackend`], does nothing.
+pub(crate) struct DummyPlatformViewportBackend {}
+impl PlatformViewportBackend for DummyPlatformViewportBackend {
+    fn create_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn destroy_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn show_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn set_window_pos(&mut self, _viewport: &mut Viewport, _pos: [f32; 2]) {
+        unimplemented!()
+    }
+
+    fn get_window_pos(&mut self, _viewport: &mut Viewport) -> [f32; 2] {
+        unimplemented!()
+    }
+
+    fn set_window_size(&mut self, _viewport: &mut Viewport, _size: [f32; 2]) {
+        unimplemented!()
+    }
+
+    fn get_window_size(&mut self, _viewport: &mut Viewport) -> [f32; 2] {
+        unimplemented!()
+    }
+
+    fn set_window_focus(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn get_window_focus(&mut self, _viewport: &mut Viewport) -> bool {
+        unimplemented!()
+    }
+
+    fn get_window_minimized(&mut self, _viewport: &mut Viewport) -> bool {
+        unimplemented!()
+    }
+
+    fn set_window_title(&mut self, _viewport: &mut Viewport, _title: &str) {
+        unimplemented!()
+    }
+
+    fn set_window_alpha(&mut self, _viewport: &mut Viewport, _alpha: f32) {
+        unimplemented!()
+    }
+
+    fn update_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn render_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn swap_buffers(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn create_vk_surface(
+        &mut self,
+        _viewport: &mut Viewport,
+        _instance: u64,
+        _out_surface: &mut u64,
+    ) -> i32 {
+        unimplemented!()
+    }
+}
+
 /// Just holds a [`PlatformViewportBackend`].
 pub(crate) struct PlatformViewportContext {
     pub(crate) backend: Box<dyn PlatformViewportBackend>,
 }
 
+impl PlatformViewportContext {
+    pub(crate) fn dummy() -> Self {
+        Self {
+            backend: Box::new(DummyPlatformViewportBackend {}),
+        }
+    }
+}
+
 /// Trait that holds optional functions for a rendering backend to support multiple viewports.
 ///
 /// It is completely fine to not use this Backend at all, as all functions are optional.
@@ -233,11 +314,45 @@ pub(crate) extern "C" fn renderer_swap_buffers(viewport: *mut Viewport, _arg: *m
     })
 }
 
+/// The default [`RendererViewportBackend`], does nothing.
+pub(crate) struct DummyRendererViewportBackend {}
+impl RendererViewportBackend for DummyRendererViewportBackend {
+    fn create_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn destroy_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn set_window_size(&mut self, _viewport: &mut Viewport, _size: [f32; 2]) {
+        unimplemented!()
+    }
+
+    fn render_window(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+
+    fn swap_buffers(&mut self, _viewport: &mut Viewport) {
+        unimplemented!()
+    }
+}
+
 /// Just holds a [`RendererViewportBackend`].
 pub(crate) struct RendererViewportContext {
     pub(crate) backend: Box<dyn RendererViewportBackend>,
 }
 
+impl RendererViewportContext {
+    pub(crate) fn dummy() -> Self {
+        Self {
+            backend: Box::new(DummyRendererViewportBackend {}),
+        }
+    }
+}
+
+unsafe impl Send for RendererViewportContext {}
+
 /// Describes a monitor that can be used by ImGui.
 #[repr(C)]
 pub struct PlatformMonitor {