feat: Add GLSL renderer and implement FPS overlay across rendering backends

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

apps/wolf_3d_gui/lib/screens/game_screen.dart

@@ -7,6 +7,13 @@ import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 import 'package:wolf_3d_flutter/wolf_3d_flutter.dart';
 import 'package:wolf_3d_renderer/wolf_3d_ascii_renderer.dart';
 import 'package:wolf_3d_renderer/wolf_3d_flutter_renderer.dart';
+import 'package:wolf_3d_renderer/wolf_3d_glsl_renderer.dart';
+
+enum _RendererMode {
+  software,
+  ascii,
+  glsl,
+}
 
 /// Launches a [WolfEngine] via [Wolf3d] and exposes renderer/input integrations.
 class GameScreen extends StatefulWidget {
@@ -25,7 +32,7 @@ class GameScreen extends StatefulWidget {
 
 class _GameScreenState extends State<GameScreen> {
   late final WolfEngine _engine;
-  bool _useAsciiMode = false;
+  _RendererMode _rendererMode = _RendererMode.software;
 
   @override
   void initState() {
@@ -60,11 +67,7 @@ class _GameScreenState extends State<GameScreen> {
               onPointerHover: widget.wolf3d.input.onPointerMove,
               child: Stack(
                 children: [
-                  // Keep both renderers behind the same engine so mode switching does
-                  // not reset level state or audio playback.
-                  _useAsciiMode
-                      ? WolfAsciiRenderer(engine: _engine)
-                      : WolfFlutterRenderer(engine: _engine),
+                  _buildRenderer(),
 
                   if (!_engine.isInitialized)
                     Container(
@@ -93,7 +96,7 @@ class _GameScreenState extends State<GameScreen> {
                     onKeyEvent: (node, event) {
                       if (event is KeyDownEvent &&
                           event.logicalKey == LogicalKeyboardKey.tab) {
-                        setState(() => _useAsciiMode = !_useAsciiMode);
+                        setState(_cycleRendererMode);
                         return KeyEventResult.handled;
                       }
                       return KeyEventResult.ignored;
@@ -115,7 +118,7 @@ class _GameScreenState extends State<GameScreen> {
                     top: 16,
                     right: 16,
                     child: Text(
-                      'TAB: Swap Renderer',
+                      'TAB: ${_modeLabel(_rendererMode)}',
                       style: TextStyle(
                         color: Colors.white.withValues(alpha: 0.5),
                       ),
@@ -129,4 +132,54 @@ class _GameScreenState extends State<GameScreen> {
       ),
     );
   }
+
+  Widget _buildRenderer() {
+    // Keep all renderers behind the same engine so mode switching does not
+    // reset level state or audio playback.
+    switch (_rendererMode) {
+      case _RendererMode.software:
+        return WolfFlutterRenderer(engine: _engine);
+      case _RendererMode.ascii:
+        return WolfAsciiRenderer(engine: _engine);
+      case _RendererMode.glsl:
+        return WolfGlslRenderer(
+          engine: _engine,
+          onUnavailable: _onGlslUnavailable,
+        );
+    }
+  }
+
+  void _cycleRendererMode() {
+    switch (_rendererMode) {
+      case _RendererMode.software:
+        _rendererMode = _RendererMode.ascii;
+        break;
+      case _RendererMode.ascii:
+        _rendererMode = _RendererMode.glsl;
+        break;
+      case _RendererMode.glsl:
+        _rendererMode = _RendererMode.software;
+        break;
+    }
+  }
+
+  void _onGlslUnavailable() {
+    if (!mounted || _rendererMode != _RendererMode.glsl) {
+      return;
+    }
+    setState(() {
+      _rendererMode = _RendererMode.software;
+    });
+  }
+
+  String _modeLabel(_RendererMode mode) {
+    switch (mode) {
+      case _RendererMode.software:
+        return 'Software';
+      case _RendererMode.ascii:
+        return 'ASCII';
+      case _RendererMode.glsl:
+        return 'GLSL';
+    }
+  }
 }

packages/wolf_3d_dart/lib/src/engine/wolf_3d_engine_base.dart

@@ -74,6 +74,12 @@ class WolfEngine {
   /// Elapsed engine lifetime in milliseconds.
   int get timeAliveMs => _timeAliveMs;
 
+  /// Exponential moving average of rendered frames per second.
+  double _smoothedFps = 0.0;
+
+  /// Current smoothed FPS, suitable for lightweight on-screen diagnostics.
+  double get fps => _smoothedFps;
+
   /// The episode index where the game session begins.
   final int? startingEpisode;
 
@@ -203,6 +209,14 @@ class WolfEngine {
 
     // Trust the incoming delta time natively
     _timeAliveMs += delta.inMilliseconds;
+    if (delta.inMicroseconds > 0) {
+      final double instantaneousFps = 1000000.0 / delta.inMicroseconds;
+      if (_smoothedFps <= 0.0) {
+        _smoothedFps = instantaneousFps;
+      } else {
+        _smoothedFps = (_smoothedFps * 0.88) + (instantaneousFps * 0.12);
+      }
+    }
 
     // 1. Process User Input
     input.update();

packages/wolf_3d_dart/lib/src/rendering/ascii_renderer.dart

@@ -351,6 +351,13 @@ class AsciiRenderer extends CliRendererBackend<dynamic> {
     }
   }
 
+  @override
+  void drawFpsOverlay(WolfEngine engine) {
+    const int textColor = 0xFFFFFFFF;
+    const int bgColor = 0xFF000000;
+    _writeString(1, 0, ' ${fpsLabel(engine)} ', textColor, bgColor);
+  }
+
   @override
   void drawMenu(WolfEngine engine) {
     final int bgColor = _rgbToPaletteColor(engine.menuBackgroundRgb);

packages/wolf_3d_dart/lib/src/rendering/renderer_backend.dart

@@ -79,6 +79,7 @@ abstract class RendererBackend<T>
 
     if (engine.difficulty == null) {
       drawMenu(engine);
+      drawFpsOverlay(engine);
       return finalizeFrame();
     }
 
@@ -88,6 +89,7 @@ abstract class RendererBackend<T>
     // 3. Draw 2D overlays.
     drawWeapon(engine);
     drawHud(engine);
+    drawFpsOverlay(engine);
 
     // 4. Finalize and return the frame data (Buffer or String/List).
     return finalizeFrame();
@@ -139,6 +141,14 @@ abstract class RendererBackend<T>
   /// Default implementation is a no-op for backends that don't support menus.
   void drawMenu(WolfEngine engine) {}
 
+  /// Draws a small FPS diagnostic in the top-left corner.
+  ///
+  /// Backends can override this to render text in their native format.
+  void drawFpsOverlay(WolfEngine engine) {}
+
+  /// Returns a compact FPS label used by renderer-specific overlays.
+  String fpsLabel(WolfEngine engine) => 'FPS ${engine.fps.round()}';
+
   /// Plots a VGA image into this backend's HUD coordinate space.
   ///
   /// Coordinates are in the original 320x200 HUD space. Backends that support

packages/wolf_3d_dart/lib/src/rendering/sixel_renderer.dart

@@ -333,6 +333,18 @@ class SixelRenderer extends CliRendererBackend<String> {
     drawStandardVgaHud(engine);
   }
 
+  @override
+  void drawFpsOverlay(WolfEngine engine) {
+    const int panelColor = 0;
+    const int textColor = 15;
+    final String label = fpsLabel(engine);
+    final int textWidth = WolfMenuFont.measureTextWidth(label, 1);
+    final int panelWidth = (textWidth + 8).clamp(16, 96);
+
+    _fillRect320(2, 2, panelWidth, 10, panelColor);
+    _drawMenuText(label, 4, 3, textColor, scale: 1);
+  }
+
   @override
   /// Blits a VGA image into the Sixel index buffer HUD space (320x200).
   void blitHudVgaImage(VgaImage image, int startX320, int startY200) {

packages/wolf_3d_dart/lib/src/rendering/software_renderer.dart

@@ -121,6 +121,19 @@ class SoftwareRenderer extends RendererBackend<FrameBuffer> {
     drawStandardVgaHud(engine);
   }
 
+  @override
+  void drawFpsOverlay(WolfEngine engine) {
+    const int panelX = 2;
+    const int panelY = 2;
+    const int panelW = 72;
+    const int panelH = 10;
+    final int panelColor = ColorPalette.vga32Bit[0];
+    final int textColor = ColorPalette.vga32Bit[15];
+
+    _fillMenuPanel(panelX, panelY, panelW, panelH, panelColor);
+    _drawMenuText(fpsLabel(engine), panelX + 3, panelY + 1, textColor);
+  }
+
   @override
   /// Blits a VGA image into the software framebuffer HUD space (320x200).
   void blitHudVgaImage(VgaImage image, int startX320, int startY200) {

packages/wolf_3d_renderer/lib/wolf_3d_glsl_renderer.dart

@@ -0,0 +1,182 @@
+/// Flutter widget that applies a GLSL post-process over Wolf3D frames.
+library;
+
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
+import 'package:wolf_3d_dart/wolf_3d_renderer.dart';
+import 'package:wolf_3d_renderer/base_renderer.dart';
+import 'package:wolf_3d_renderer/wolf_3d_asset_painter.dart';
+
+/// Displays software-rendered frames through a GLSL post-processing pass.
+class WolfGlslRenderer extends BaseWolfRenderer {
+  /// Callback when shader loading fails and software fallback should be used.
+  final VoidCallback? onUnavailable;
+
+  /// Creates a GLSL renderer bound to [engine].
+  const WolfGlslRenderer({
+    required super.engine,
+    this.onUnavailable,
+    super.key,
+  });
+
+  @override
+  State<WolfGlslRenderer> createState() => _WolfGlslRendererState();
+}
+
+class _WolfGlslRendererState extends BaseWolfRendererState<WolfGlslRenderer> {
+  static const int _renderWidth = 320;
+  static const int _renderHeight = 200;
+
+  final SoftwareRenderer _renderer = SoftwareRenderer();
+
+  ui.Image? _renderedFrame;
+  ui.FragmentProgram? _shaderProgram;
+  ui.FragmentShader? _shader;
+  bool _isRendering = false;
+  bool _isShaderUnavailable = false;
+
+  @override
+  void initState() {
+    super.initState();
+    if (widget.engine.frameBuffer.width != _renderWidth ||
+        widget.engine.frameBuffer.height != _renderHeight) {
+      widget.engine.setFrameBuffer(_renderWidth, _renderHeight);
+    }
+    _loadShader();
+  }
+
+  @override
+  Color get scaffoldColor => widget.engine.difficulty == null
+      ? _colorFromRgb(widget.engine.menuBackgroundRgb)
+      : const Color.fromARGB(255, 4, 64, 64);
+
+  @override
+  void dispose() {
+    _renderedFrame?.dispose();
+    super.dispose();
+  }
+
+  @override
+  void performRender() {
+    if (_isRendering) {
+      return;
+    }
+    _isRendering = true;
+
+    final FrameBuffer frameBuffer = widget.engine.frameBuffer;
+    _renderer.render(widget.engine);
+
+    ui.decodeImageFromPixels(
+      frameBuffer.pixels.buffer.asUint8List(),
+      frameBuffer.width,
+      frameBuffer.height,
+      ui.PixelFormat.rgba8888,
+      (ui.Image image) {
+        if (mounted) {
+          setState(() {
+            _renderedFrame?.dispose();
+            _renderedFrame = image;
+          });
+        } else {
+          image.dispose();
+        }
+        _isRendering = false;
+      },
+    );
+  }
+
+  @override
+  Widget buildViewport(BuildContext context) {
+    if (_renderedFrame == null) {
+      return const CircularProgressIndicator(color: Colors.white24);
+    }
+
+    if (_isShaderUnavailable || _shader == null) {
+      // Keep frames visible even if GLSL initialization failed.
+      return Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: AspectRatio(
+          aspectRatio: 4 / 3,
+          child: WolfAssetPainter.frame(_renderedFrame),
+        ),
+      );
+    }
+
+    return Padding(
+      padding: const EdgeInsets.all(16.0),
+      child: AspectRatio(
+        aspectRatio: 4 / 3,
+        child: CustomPaint(
+          painter: _GlslFramePainter(
+            frame: _renderedFrame!,
+            shader: _shader!,
+          ),
+          child: const SizedBox.expand(),
+        ),
+      ),
+    );
+  }
+
+  Future<void> _loadShader() async {
+    try {
+      final ui.FragmentProgram program = await ui.FragmentProgram.fromAsset(
+        'packages/wolf_3d_renderer/shaders/wolf_world.frag',
+      );
+      if (!mounted) {
+        return;
+      }
+      setState(() {
+        _shaderProgram = program;
+        _shader = _shaderProgram!.fragmentShader();
+        _isShaderUnavailable = false;
+      });
+    } catch (_) {
+      if (!mounted) {
+        return;
+      }
+      setState(() {
+        _isShaderUnavailable = true;
+      });
+      widget.onUnavailable?.call();
+    }
+  }
+
+  Color _colorFromRgb(int rgb) {
+    return Color(0xFF000000 | (rgb & 0x00FFFFFF));
+  }
+}
+
+class _GlslFramePainter extends CustomPainter {
+  final ui.Image frame;
+  final ui.FragmentShader shader;
+
+  _GlslFramePainter({
+    required this.frame,
+    required this.shader,
+  });
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final double texelX = frame.width > 0 ? 1.0 / frame.width : 1.0;
+    final double texelY = frame.height > 0 ? 1.0 / frame.height : 1.0;
+    shader
+      ..setFloat(0, size.width)
+      ..setFloat(1, size.height)
+      ..setFloat(2, texelX)
+      ..setFloat(3, texelY)
+      ..setImageSampler(0, frame);
+
+    final Paint paint = Paint()
+      ..shader = shader
+      ..filterQuality = FilterQuality.none;
+
+    canvas.drawRect(Offset.zero & size, paint);
+  }
+
+  @override
+  bool shouldRepaint(covariant _GlslFramePainter oldDelegate) {
+    return oldDelegate.frame != frame || oldDelegate.shader != shader;
+  }
+}

packages/wolf_3d_renderer/pubspec.yaml

@@ -25,6 +25,8 @@ dev_dependencies:
 
 # The following section is specific to Flutter packages.
 flutter:
+  shaders:
+    - shaders/wolf_world.frag
 
   # To add assets to your package, add an assets section, like this:
   # assets:

packages/wolf_3d_renderer/shaders/wolf_world.frag

@@ -0,0 +1,43 @@
+#include <flutter/runtime_effect.glsl>
+
+uniform vec2 uResolution;
+uniform vec2 uTexel;
+uniform sampler2D uTexture;
+
+out vec4 fragColor;
+
+float luma(vec3 color) {
+  return dot(color, vec3(0.299, 0.587, 0.114));
+}
+
+void main() {
+  vec2 uv = FlutterFragCoord().xy / uResolution;
+  vec4 centerSample = texture(uTexture, uv);
+
+  vec3 sampleN = texture(uTexture, uv + vec2(0.0, -uTexel.y)).rgb;
+  vec3 sampleS = texture(uTexture, uv + vec2(0.0, uTexel.y)).rgb;
+  vec3 sampleE = texture(uTexture, uv + vec2(uTexel.x, 0.0)).rgb;
+  vec3 sampleW = texture(uTexture, uv + vec2(-uTexel.x, 0.0)).rgb;
+
+  float lumaCenter = luma(centerSample.rgb);
+  float lumaMin = min(
+    lumaCenter,
+    min(min(luma(sampleN), luma(sampleS)), min(luma(sampleE), luma(sampleW)))
+  );
+  float lumaMax = max(
+    lumaCenter,
+    max(max(luma(sampleN), luma(sampleS)), max(luma(sampleE), luma(sampleW)))
+  );
+
+  float edgeSpan = max(lumaMax - lumaMin, 0.0001);
+  float edgeAmount = smoothstep(0.03, 0.18, edgeSpan);
+  vec3 neighborhoodAvg = (sampleN + sampleS + sampleE + sampleW) * 0.25;
+  vec3 aaColor = mix(centerSample.rgb, neighborhoodAvg, edgeAmount * 0.45);
+
+  vec2 centered = uv - 0.5;
+  float vignette = 1.0 - dot(centered, centered) * 0.35;
+  vignette = clamp(vignette, 0.75, 1.0);
+
+  vec3 color = aaColor * vignette;
+  fragColor = vec4(color, centerSample.a);
+}