Add hidden window flag, to be in line with how imgui's sdl backend works

engine/core/src/imgui_backend.cpp

@@ -109,14 +109,16 @@ imgui_backend::imgui_backend() {
     platform_io.Monitors.push_back(monitor);
 
     platform_io.Platform_CreateWindow = [](ImGuiViewport* viewport) {
-        viewport->PlatformHandle = platform::open_window("", {viewport->Pos, viewport->Size}, WindowFlags::Borderless);
+        viewport->PlatformHandle = platform::open_window("", {viewport->Pos, viewport->Size}, WindowFlags::Borderless | WindowFlags::Hidden);
     };
     
     platform_io.Platform_DestroyWindow = [](ImGuiViewport* viewport) {
         platform::close_window(viewport->PlatformHandle);
     };
     
-    platform_io.Platform_ShowWindow = [](ImGuiViewport*) {};
+    platform_io.Platform_ShowWindow = [](ImGuiViewport* viewport) {
+        platform::show_window(viewport->PlatformHandle);
+    };
 
     platform_io.Platform_SetWindowPos = [](ImGuiViewport* viewport, const ImVec2 pos) {
         platform::set_window_position(viewport->PlatformHandle, pos);

engine/platform/include/platform.hpp

@@ -8,11 +8,20 @@
 
 /// Requestable window flags, which may or may not be respected by the platform.
 enum class WindowFlags {
-    None,
+    None = 0,
-    Resizable,
+    Resizable = 2,
-    Borderless
+    Borderless = 4,
+    Hidden = 8
 };
 
+inline WindowFlags operator|(const WindowFlags a, const WindowFlags b) {
+    return static_cast<WindowFlags>(static_cast<int>(a) | static_cast<int>(b));
+}
+
+inline bool operator&(const WindowFlags a, const WindowFlags b) {
+    return static_cast<int>(a) & static_cast<int>(b);
+}
+
 /// Represents a button. This includes keyboard, gamepad and mouse buttons.
 enum class InputButton {
     Invalid,
@@ -134,6 +143,9 @@ namespace platform {
     /// Sets the window title.
     void set_window_title(window_ptr window, std::string_view title);
 
+    /// Show window
+    void show_window(window_ptr window);
+
     /// Queries whether or not the button is currently pressed.
     bool get_key_down(InputButton key);
 

platforms/sdl/main.cpp.in

@@ -81,11 +81,15 @@ platform::window_ptr platform::open_window(const std::string_view title, const p
     auto& win = windows.emplace_back();
 
     int sdl_flags = SDL_WINDOW_VULKAN | SDL_WINDOW_ALLOW_HIGHDPI;
-    if(flags == WindowFlags::Borderless)
+    if(flags & WindowFlags::Borderless)
         sdl_flags |= SDL_WINDOW_BORDERLESS;
-    if(flags == WindowFlags::Resizable)
+
+    if(flags & WindowFlags::Resizable)
         sdl_flags |= SDL_WINDOW_RESIZABLE;
 
+    if(flags & WindowFlags::Hidden)
+        sdl_flags |= SDL_WINDOW_HIDDEN;
+
     auto resolution = platform::get_monitor_resolution();
 
     int real_x = rect.offset.x;
@@ -212,6 +216,12 @@ void platform::set_window_title(const platform::window_ptr index, const std::str
     SDL_SetWindowTitle(window, title.data());
 }
 
+void platform::show_window(const platform::window_ptr index) {
+    auto window = get_window(index);
+
+    SDL_ShowWindow(window);
+}
+
 bool platform::get_key_down(const InputButton key) {
     const Uint8 *state = SDL_GetKeyboardState(NULL);