Initially hide the window / add appWindowParams.hidden

(initially hidden so that initial positionning & resizing is invisible)

src/hello_imgui/app_window_params.h

@@ -152,9 +152,12 @@ for details.
    _Note: on a mobile device, the application will always be full screen._
 * `restorePreviousGeometry`: _bool, default=false_.
   If true, then save & restore windowGeometry from last run (the geometry will be written in imgui_app_window.ini)
-* `borderless`: _bool, default = false_.
-* `resizable`: _bool, default = false_.
-@@md
+* `borderless`: _bool, default = false_. Should the window have borders. This is taken into account at
+creation.
+* `resizable`: _bool, default = false_. Should the window have borders. This is taken into account at
+creation.
+* `hidden`: _bool, default = false_. Should the window be hidden. This is taken into account dynamically (you
+can show/hide the window with this). Full screen windows cannot be hidden.@@md
 **/
 struct AppWindowParams
 {
@@ -167,6 +170,7 @@ struct AppWindowParams
 
     bool borderless = false;
     bool resizable = true;
+    bool hidden = false;
 };
 
 }  // namespace HelloImGui

src/hello_imgui/internal/backend_impls/abstract_runner.cpp

@@ -12,6 +12,7 @@
 #include <chrono>
 #include <cassert>
 #include <fstream>
+#include <thread>
 
 #ifdef HELLOIMGUI_MACOS
 #import <AppKit/NSScreen.h>
@@ -406,7 +407,7 @@ void AbstractRunner::Setup()
         }
     }
 
-    void AbstractRunner::RenderGui()
+void AbstractRunner::RenderGui()
 {
     DockingDetails::ProvideWindowOrDock(params.imGuiWindowParams, params.dockingParams);
 
@@ -443,13 +444,14 @@ void AbstractRunner::Setup()
 
 
 void AbstractRunner::CreateFramesAndRender()
-{
-    // Note about the application window sizing 
-    // - On the first frame, we create a window, and use the user provided size (if provided)
-    // - On the second frame, we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
+{    
+    // Note about the application window initial placement and sizing 
+    // - On the first frame (mIdxFrame==0), we create a window, and use the user provided size (if provided). The window is initially hidden.
+    // - On the second frame (mIdxFrame == 1), we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
     // - At the end of the second frame, we measure the size of the widgets and use it as the application window size, if the user required auto size
-    // - At the begining of the third frame, we may apply the auto-size and recenter the window to the center of the monitor
-    // Argh...
+    // - At the beginning of the third frame (mIdxFrame==2 / mWasWindowAutoResizedOnPreviousFrame), we may apply the auto-size and recenter the window to the center of the monitor
+    // - At the 4th frame (mIdxFrame >= 3), we finally show the window
+    // Phew...
 
     //
     // Window size setup, etc:
@@ -461,6 +463,7 @@ void AbstractRunner::CreateFramesAndRender()
         HandleDpiOnSecondFrame();
     }
 
+
     if (mWasWindowAutoResizedOnPreviousFrame)
     {
         // The window was resized on last frame
@@ -477,6 +480,15 @@ void AbstractRunner::CreateFramesAndRender()
         params.appWindowParams.windowGeometry.resizeAppWindowAtNextFrame = false;
     }
 
+
+    if (mIdxFrame >= 3)
+    {
+        if (params.appWindowParams.hidden)
+            mBackendWindowHelper->HideWindow(mWindow);
+        else
+            mBackendWindowHelper->ShowWindow(mWindow);
+    }
+
 #ifndef __EMSCRIPTEN__
     // Idling for non emscripten, where HelloImGui is responsible for the main loop.
     // This form of idling will call WaitForEventTimeout(), which may call sleep():

src/hello_imgui/internal/backend_impls/backend_window_helper/glfw_window_helper.cpp

@@ -76,6 +76,7 @@ namespace HelloImGui { namespace BackendApi
         else
             glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
 
+        glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
 
         // GLFW_SCALE_TO_MONITOR is set to false: we set manually the window size in screen coordinates,
         // then AbstractRunner::MakeWindowSizeRelativeTo96Ppi_IfRequired() may resize the window at the second frame

src/hello_imgui/internal/backend_impls/backend_window_helper/sdl_window_helper.cpp

@@ -117,6 +117,8 @@ namespace HelloImGui { namespace BackendApi
         else if (appWindowParams.windowGeometry.windowSizeState == WindowSizeState::Maximized)
             window_flags |= SDL_WINDOW_MAXIMIZED;
 
+        window_flags |= SDL_WINDOW_HIDDEN;
+
         auto window = SDL_CreateWindow(appWindowParams.windowTitle.c_str(),
                                        window_pos_sdl[0], window_pos_sdl[1],
                                        windowSize[0], windowSize[1],
@@ -220,11 +222,11 @@ namespace HelloImGui { namespace BackendApi
 
     void SdlWindowHelper::HideWindow(WindowPointer window)
     {
-        SDL_ShowWindow((SDL_Window *) window);
+        SDL_HideWindow((SDL_Window *) window);
     }
     void SdlWindowHelper::ShowWindow(WindowPointer window)
     {
-        SDL_HideWindow((SDL_Window *) window);
+        SDL_ShowWindow((SDL_Window *) window);
     }
     bool SdlWindowHelper::IsWindowHidden(WindowPointer window)
     {