add render callback example, put the core basic window back how it was

examples/core/core_render_callback.c

@@ -0,0 +1,72 @@
+/*******************************************************************************************
+*
+*   raylib [core] example - basic render callback
+*
+*   Example complexity rating: [★★☆☆] 2/4
+*
+*   Welcome to raylib!
+*
+*   To test examples, just press F6 and execute 'raylib_compile_execute' script
+*   Note that compiled executable is placed in the same folder as .c file
+*
+*   To test the examples on Web, press F6 and execute 'raylib_compile_execute_web' script
+*   Web version of the program is generated in the same folder as .c file
+*
+*   You can find all basic examples on C:\raylib\raylib\examples folder or
+*   raylib official webpage: www.raylib.com
+*
+*   Enjoy using raylib. :)
+*
+*   Example originally created with raylib 6.1, last time updated with raylib 6.1
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2013-2026 Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include <math.h>
+
+// called by raylib once per frame. On web will use emcscrpten callback
+bool RunFrame(void)
+{
+    // return false if you want to exit
+    if (WindowShouldClose())
+        return false;
+
+    ClearBackground(BLACK);
+
+    // animate the text so you can see it move while the window is resized or dragged
+    float offset = cosf((float)GetTime() * 2.0f) *60.0f;
+    DrawTextEx(GetFontDefault(), "Hello Render Callback, drag the window!", (Vector2) { 190, 200 + offset}, 20, 2, LIGHTGRAY);
+    return true;
+}
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    SetConfigFlags(FLAG_WINDOW_RESIZABLE | FLAG_WINDOW_HIGHDPI | FLAG_VSYNC_HINT);
+    InitWindow(screenWidth, screenHeight, "raylib [core] example - basic render callback");
+
+    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+
+    // Run a game loop using the provided callback function, which will be called every frame
+    RunGameLoop(RunFrame);
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}