added barebones ui rendering

UI/GuiBatcher.cs

@@ -0,0 +1,83 @@
+using OpenTK.Graphics.OpenGL4;
+using OpenTK.Mathematics;
+
+public class GuiBatcher
+{
+    private List<UiVertex> _vertices = new List<UiVertex>();
+    private int _vbo;
+    private int _vao;
+
+    public GuiBatcher()
+    {
+        _vao = GL.GenVertexArray();
+        _vbo = GL.GenBuffer();
+
+        GL.BindVertexArray(_vao);
+        GL.BindBuffer(BufferTarget.ArrayBuffer, _vbo);
+
+        // Position (2 floats)
+        GL.EnableVertexAttribArray(0);
+        GL.VertexAttribPointer(0, 2, VertexAttribPointerType.Float, false, 8 * sizeof(float), 0);
+        // TexCoord (2 floats)
+        GL.EnableVertexAttribArray(1);
+        GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, 8 * sizeof(float), 2 * sizeof(float));
+        // Color (4 floats)
+        GL.EnableVertexAttribArray(2);
+        GL.VertexAttribPointer(2, 4, VertexAttribPointerType.Float, false, 8 * sizeof(float), 4 * sizeof(float));
+    }
+
+    public void DrawQuad(float x, float y, float w, float h, Vector4 uv, Vector4 color)
+    {
+        // Two triangles (Standard Minecraft Blit)
+        _vertices.Add(new UiVertex(x, y, uv.X, uv.Y, color));         // TL
+        _vertices.Add(new UiVertex(x + w, y, uv.Z, uv.Y, color));     // TR
+        _vertices.Add(new UiVertex(x, y + h, uv.X, uv.W, color));     // BL
+
+        _vertices.Add(new UiVertex(x + w, y, uv.Z, uv.Y, color));     // TR
+        _vertices.Add(new UiVertex(x + w, y + h, uv.Z, uv.W, color)); // BR
+        _vertices.Add(new UiVertex(x, y + h, uv.X, uv.W, color));     // BL
+    }
+
+    public void Render()
+    {
+        if (_vertices.Count == 0) return;
+
+        GL.BindVertexArray(_vao);
+        GL.BindBuffer(BufferTarget.ArrayBuffer, _vbo);
+
+        var data = _vertices.ToArray();
+        GL.BufferData(BufferTarget.ArrayBuffer, data.Length * 8 * sizeof(float), data, BufferUsageHint.StreamDraw);
+
+        GL.DrawArrays(PrimitiveType.Triangles, 0, _vertices.Count);
+        _vertices.Clear(); // Reset for next frame
+    }
+
+    public void DrawString(string text, float x, float y, float size, Vector4 color)
+    {
+        float charStep = 1.0f / 16.0f;
+        float currentX = x;
+
+        foreach (char c in text)
+        {
+            int ascii = (int)c;
+            int row = ascii / 16;
+            int col = ascii % 16;
+
+            float uStart = col * charStep;
+            float uEnd = uStart + charStep;
+
+            float vStart = 1.0f - (row * charStep);
+            float vEnd = vStart - charStep;
+
+            Vector4 uv = new Vector4(
+                uStart,          // U start
+                vStart,          // V start
+                uEnd,    // U end
+                vEnd     // V end
+            );
+
+            DrawQuad(currentX, y, size, size, uv, color);
+            currentX += size * 0.8f; // Tighten horizontal spacing
+        }
+    }
+}