hot reload of color palette

src/lib.rs

@@ -82,8 +82,9 @@ pub struct Platform {
     bind_group:       wgpu::BindGroup,
     pipeline:         wgpu::RenderPipeline,
     index_tex:        wgpu::Texture,
-    #[allow(dead_code)]
     palette_tex:      wgpu::Texture,
+    palette:          [[u8; 3]; 256],
+    palette_dirty:    bool,
     params_buf:       wgpu::Buffer,
     params:           Params,
     surface:          wgpu::Surface<'static>,
@@ -215,7 +216,9 @@ impl Platform {
         });
 
         let mut platform = Self {
-            bind_group, pipeline, index_tex, palette_tex, params_buf, params,
+            bind_group, pipeline, index_tex, palette_tex,
+            palette: cfg.palette, palette_dirty: false,
+            params_buf, params,
             surface, config: surface_config, device, queue, instance,
             window, events, glfw,
             framebuffer:      vec![0u8; (src_w * src_h) as usize],
@@ -285,7 +288,35 @@ impl Platform {
     pub fn framebuffer_mut(&mut self) -> &mut [u8] { &mut self.framebuffer }
     pub fn framebuffer_size(&self) -> (u32, u32)  { self.framebuffer_size }
 
+    /// Liefert &mut auf die 256-Einträge-Palette. Setzt pessimistisch ein
+    /// Dirty-Flag — der nächste `present()` lädt die Palette neu hoch.
+    pub fn palette_mut(&mut self) -> &mut [[u8; 3]; 256] {
+        self.palette_dirty = true;
+        &mut self.palette
+    }
+    pub fn palette(&self) -> &[[u8; 3]; 256] { &self.palette }
+
     pub fn present(&mut self) {
+        if self.palette_dirty {
+            let rgba: [u8; 256 * 4] = {
+                let mut buf = [0u8; 256 * 4];
+                for (i, [r, g, b]) in self.palette.iter().enumerate() {
+                    buf[i * 4]     = *r;
+                    buf[i * 4 + 1] = *g;
+                    buf[i * 4 + 2] = *b;
+                    buf[i * 4 + 3] = 255;
+                }
+                buf
+            };
+            self.queue.write_texture(
+                wgpu::TexelCopyTextureInfoBase { texture: &self.palette_tex, mip_level: 0, origin: wgpu::Origin3d::ZERO, aspect: wgpu::TextureAspect::All },
+                &rgba,
+                wgpu::TexelCopyBufferLayout { offset: 0, bytes_per_row: Some(256 * 4), rows_per_image: None },
+                wgpu::Extent3d { width: 256, height: 1, depth_or_array_layers: 1 },
+            );
+            self.palette_dirty = false;
+        }
+
         let (w, h) = self.framebuffer_size;
         self.queue.write_texture(
             wgpu::TexelCopyTextureInfoBase { texture: &self.index_tex, mip_level: 0, origin: wgpu::Origin3d::ZERO, aspect: wgpu::TextureAspect::All },