perf(render): Shadow Baking + Glyph Blitting optimizado (v0.27.0-v0.27.1)

Shadow Baking:
- ShadowCache prerenderiza sombras blur (key: w,h,blur,radius,spread)
- initWithCache() habilita cache, deinit() lo libera
- 4.2x más rápido en Debug, 2.5x en ReleaseSafe

Glyph Blitting:
- Early exit si glifo fuera de clip
- Pre-cálculo región visible
- Acceso directo fb.pixels[]
- Aritmética u32 (sin structs Color)
- Fast path alpha=255

Correcciones:
- Integer overflow: saturating arithmetic (+|, -|, *|)
- u16→u32 en blitShadowCache

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -47,6 +47,8 @@
 | 2025-12-30 | v0.25.0 | ⭐ IdleCompanion widget: mascota animada que aparece tras inactividad |
 | 2025-12-31 | v0.26.0 | ⭐ Z-Design V5 Pixel Perfect: títulos legibles (contrastTextColor), botones centrados (+2px TTF), semáforo reubicado (texto + cuadrado derecha) |
 | 2025-12-31 | v0.26.1 | Fix: drawBeveledRect bisel ahora +1px inset (no solapa borde exterior) |
+| 2026-01-02 | v0.27.0 | ⭐ **PERF: Shadow Baking** - Cache de sombras prerenderizadas en SoftwareRenderer |
+| 2026-01-02 | v0.27.1 | ⭐ **PERF: Glyph Blitting Optimizado** - drawGlyphBitmap con acceso directo a píxeles |
 
 ---
 
@@ -116,3 +118,73 @@ Sistema de mascota animada reutilizable para cualquier aplicación:
   ```
 
 → Archivo: `widgets/idle_companion.zig`
+
+### v0.27.0-v0.27.1 - Optimizaciones de Rendimiento (2026-01-02)
+
+Optimizaciones profundas del motor de renderizado software para alcanzar 60fps.
+
+#### Shadow Baking (v0.27.0)
+
+Sistema de cache de sombras prerenderizadas que elimina el recálculo costoso de sombras blur cada frame.
+
+**Problema original:**
+- Las sombras con blur dibujaban N capas de rectángulos redondeados por frame
+- Cada capa ejecutaba `fillRoundedRect` que hace `@sqrt()` por cada píxel
+- Una sombra blur=8 sobre 200x100px = 8 × 20,000 × sqrt = 160,000 operaciones sqrt/frame
+
+**Solución:**
+- Nuevo `ShadowCache` struct con HashMap para sombras prerenderizadas
+- Key: (w, h, blur, radius, spread) - forma de la sombra
+- Value: Buffer de alpha (u8[]) con la sombra ya calculada
+- Primer frame: renderiza sombra a buffer, cachea
+- Frames siguientes: blit rápido del buffer con color aplicado
+
+**Resultados medidos:**
+| Modo | Sin Cache | Con Cache | Mejora |
+|------|-----------|-----------|--------|
+| Debug | ~180ms | ~43ms | **4.2x** |
+| ReleaseSafe | ~11ms | ~4.4ms | **2.5x** |
+
+**API:**
+```zig
+// Antes (sin cache)
+var renderer = SoftwareRenderer.init(&fb);
+
+// Ahora (con cache - recomendado)
+var renderer = SoftwareRenderer.initWithCache(&fb, allocator);
+defer renderer.deinit();
+```
+
+**Archivos modificados:**
+- `src/render/software.zig`: +200 LOC (ShadowCache, ShadowCacheKey, ShadowCacheEntry, fillAlphaRect, fillAlphaRectAdditive, blitShadowCache)
+
+#### Glyph Blitting Optimizado (v0.27.1)
+
+Optimización de `drawGlyphBitmap` en TTF rendering.
+
+**Problema original:**
+- 6 checks de bounds por cada píxel del glifo
+- Llamadas a `getPixel()`/`setPixel()` (con más bounds checks)
+- Creación de struct `Color` por cada píxel semi-transparente
+- Sin early exit para glifos fuera del clip
+
+**Optimizaciones aplicadas:**
+1. **Early exit**: Si glifo entero está fuera de clip/framebuffer, return inmediato
+2. **Pre-cálculo de región visible**: Intersección glifo ∩ clip ∩ framebuffer calculada una vez
+3. **Acceso directo a `fb.pixels[]`**: Sin getPixel/setPixel
+4. **Aritmética u32**: Sin crear structs Color por cada píxel
+5. **Fast path opaco**: Si alpha=255, escritura directa sin blending
+
+**Archivos modificados:**
+- `src/render/ttf.zig`: drawGlyphBitmap() reescrito (~80 LOC)
+
+#### Correcciones de Estabilidad
+
+Durante la implementación se detectaron y corrigieron varios integer overflows:
+
+- **fillAlphaRect/fillAlphaRectAdditive**: Aritmética saturante (`+|`, `-|`, `*|`) y bounds checks
+- **blitShadowCache**: Color math con u32 en lugar de u16 para evitar overflow en multiplicación
+- **renderShadow**: Límite de tamaño máximo (2048x2048) para evitar allocaciones enormes
+
+→ Archivos: `src/render/software.zig`, `src/render/ttf.zig`
+→ Telemetría: Añadida en `zsimifactu/src/main.zig` para medir Exec time

src/render/software.zig

@@ -23,6 +23,7 @@
 //! ```
 
 const std = @import("std");
+const Allocator = std.mem.Allocator;
 
 const Command = @import("../core/command.zig");
 const Style = @import("../core/style.zig");
@@ -35,6 +36,279 @@ const Color = Style.Color;
 const Rect = Layout.Rect;
 const DrawCommand = Command.DrawCommand;
 
+// =============================================================================
+// Shadow Cache - Pre-rendered shadows for instant blitting
+// =============================================================================
+
+/// Key for shadow cache lookup (shape only, not position/color)
+const ShadowCacheKey = struct {
+    w: u32,
+    h: u32,
+    blur: u8,
+    radius: u8,
+    spread: i8,
+};
+
+/// Cached pre-rendered shadow (alpha channel only)
+const ShadowCacheEntry = struct {
+    /// Alpha values (0-255) for each pixel
+    alpha: []u8,
+    /// Total width including blur expansion
+    width: u32,
+    /// Total height including blur expansion
+    height: u32,
+    /// How much the shadow extends beyond the original rect (left/top)
+    padding: u32,
+};
+
+/// Shadow cache with LRU eviction
+const ShadowCache = struct {
+    entries: std.AutoHashMap(ShadowCacheKey, ShadowCacheEntry),
+    allocator: Allocator,
+    /// Maximum cached shadows (LRU eviction when exceeded)
+    max_entries: usize = 64,
+
+    pub fn init(allocator: Allocator) ShadowCache {
+        return .{
+            .entries = std.AutoHashMap(ShadowCacheKey, ShadowCacheEntry).init(allocator),
+            .allocator = allocator,
+        };
+    }
+
+    pub fn deinit(self: *ShadowCache) void {
+        var it = self.entries.iterator();
+        while (it.next()) |entry| {
+            self.allocator.free(entry.value_ptr.alpha);
+        }
+        self.entries.deinit();
+    }
+
+    /// Get cached shadow or create new one
+    pub fn getOrCreate(self: *ShadowCache, key: ShadowCacheKey) ?ShadowCacheEntry {
+        // Check cache first
+        if (self.entries.get(key)) |entry| {
+            return entry;
+        }
+
+        // Evict if cache is full
+        if (self.entries.count() >= self.max_entries) {
+            // Simple eviction: remove first entry (not true LRU, but fast)
+            var it = self.entries.iterator();
+            if (it.next()) |first| {
+                self.allocator.free(first.value_ptr.alpha);
+                self.entries.removeByPtr(first.key_ptr);
+            }
+        }
+
+        // Render new shadow
+        const entry = self.renderShadow(key) orelse return null;
+        self.entries.put(key, entry) catch return null;
+        return entry;
+    }
+
+    /// Render shadow to alpha buffer
+    fn renderShadow(self: *ShadowCache, key: ShadowCacheKey) ?ShadowCacheEntry {
+        const blur: u32 = key.blur;
+        const spread_abs: u32 = @intCast(@abs(key.spread));
+        const padding = blur +| spread_abs; // Saturating add
+
+        const total_w = key.w +| (padding *| 2); // Saturating
+        const total_h = key.h +| (padding *| 2);
+
+        // Safety: limit buffer size to prevent huge allocations
+        if (total_w > 2048 or total_h > 2048) return null;
+        if (total_w == 0 or total_h == 0) return null;
+
+        const alpha = self.allocator.alloc(u8, total_w * total_h) catch return null;
+        @memset(alpha, 0);
+
+        if (blur == 0) {
+            // Hard shadow - solid rect
+            const base_x = padding -| spread_abs;
+            const base_y = padding -| spread_abs;
+            const base_w = key.w +| (spread_abs *| 2);
+            const base_h = key.h +| (spread_abs *| 2);
+
+            fillAlphaRect(alpha, total_w, base_x, base_y, @min(base_w, total_w), @min(base_h, total_h), key.radius, 255);
+        } else {
+            // Soft shadow - multiple layers with decreasing alpha
+            const layers: u32 = blur;
+
+            // Draw from outermost to innermost
+            var layer: u32 = layers;
+            while (layer > 0) {
+                layer -= 1;
+
+                const t = @as(f32, @floatFromInt(layer)) / @as(f32, @floatFromInt(layers));
+                const alpha_factor = (1.0 - t) * (1.0 - t) * 0.5;
+                const layer_alpha: u8 = @intFromFloat(255.0 * alpha_factor);
+                if (layer_alpha == 0) continue;
+
+                const expand = layers - layer;
+                // Use saturating subtraction to prevent underflow
+                const layer_x = (padding -| expand) -| spread_abs;
+                const layer_y = (padding -| expand) -| spread_abs;
+                const layer_w = key.w +| ((expand +| spread_abs) *| 2);
+                const layer_h = key.h +| ((expand +| spread_abs) *| 2);
+                const layer_radius: u8 = if (key.radius > 0)
+                    key.radius +| @as(u8, @intCast(@min(255 - key.radius, expand)))
+                else
+                    0;
+
+                fillAlphaRectAdditive(alpha, total_w, layer_x, layer_y, @min(layer_w, total_w), @min(layer_h, total_h), layer_radius, layer_alpha);
+            }
+
+            // Core shadow
+            const core_x = padding -| spread_abs;
+            const core_y = padding -| spread_abs;
+            const core_w = key.w +| (spread_abs *| 2);
+            const core_h = key.h +| (spread_abs *| 2);
+            fillAlphaRectAdditive(alpha, total_w, core_x, core_y, @min(core_w, total_w), @min(core_h, total_h), key.radius, 178);
+        }
+
+        return ShadowCacheEntry{
+            .alpha = alpha,
+            .width = total_w,
+            .height = total_h,
+            .padding = padding,
+        };
+    }
+};
+
+/// Fill alpha rect (simple, for hard shadows)
+fn fillAlphaRect(alpha: []u8, stride: u32, x: u32, y: u32, w: u32, h: u32, radius: u8, value: u8) void {
+    if (w == 0 or h == 0) return;
+
+    if (radius == 0) {
+        // Fast path: no corners
+        var py: u32 = 0;
+        while (py < h) : (py += 1) {
+            const row_start = (y +| py) *| stride +| x;
+            if (row_start >= alpha.len) continue;
+            const end = @min(row_start + w, alpha.len);
+            if (end > row_start) {
+                @memset(alpha[row_start..end], value);
+            }
+        }
+    } else {
+        // Rounded corners - use distance check
+        const r: f32 = @floatFromInt(radius);
+        const r_sq = r * r;
+        const r_u32: u32 = radius;
+
+        var py: u32 = 0;
+        while (py < h) : (py += 1) {
+            var px: u32 = 0;
+            while (px < w) : (px += 1) {
+                // Safe index calculation with bounds check
+                const row = (y +| py) *| stride;
+                const idx = row +| x +| px;
+                if (idx >= alpha.len) continue;
+
+                // Check corners
+                var dist_sq: f32 = 0;
+                var in_corner = false;
+
+                // Top-left
+                if (px < r_u32 and py < r_u32) {
+                    const dx: f32 = r - @as(f32, @floatFromInt(px)) - 0.5;
+                    const dy: f32 = r - @as(f32, @floatFromInt(py)) - 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                }
+                // Top-right
+                else if (px >= w -| r_u32 and py < r_u32) {
+                    const dx: f32 = @as(f32, @floatFromInt(px)) - @as(f32, @floatFromInt(w -| r_u32)) + 0.5;
+                    const dy: f32 = r - @as(f32, @floatFromInt(py)) - 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                }
+                // Bottom-left
+                else if (px < r_u32 and py >= h -| r_u32) {
+                    const dx: f32 = r - @as(f32, @floatFromInt(px)) - 0.5;
+                    const dy: f32 = @as(f32, @floatFromInt(py)) - @as(f32, @floatFromInt(h -| r_u32)) + 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                }
+                // Bottom-right
+                else if (px >= w -| r_u32 and py >= h -| r_u32) {
+                    const dx: f32 = @as(f32, @floatFromInt(px)) - @as(f32, @floatFromInt(w -| r_u32)) + 0.5;
+                    const dy: f32 = @as(f32, @floatFromInt(py)) - @as(f32, @floatFromInt(h -| r_u32)) + 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                }
+
+                if (in_corner and dist_sq > r_sq) {
+                    continue; // Outside corner
+                }
+
+                alpha[idx] = value;
+            }
+        }
+    }
+}
+
+/// Fill alpha rect with additive blending (for layered soft shadows)
+fn fillAlphaRectAdditive(alpha: []u8, stride: u32, x: u32, y: u32, w: u32, h: u32, radius: u8, value: u8) void {
+    if (w == 0 or h == 0) return;
+
+    if (radius == 0) {
+        var py: u32 = 0;
+        while (py < h) : (py += 1) {
+            const row_start = (y +| py) *| stride +| x;
+            var px: u32 = 0;
+            while (px < w) : (px += 1) {
+                const idx = row_start +| px;
+                if (idx >= alpha.len) continue;
+                alpha[idx] = alpha[idx] +| value; // Saturating add
+            }
+        }
+    } else {
+        const r: f32 = @floatFromInt(radius);
+        const r_sq = r * r;
+        const r_u32: u32 = radius;
+
+        var py: u32 = 0;
+        while (py < h) : (py += 1) {
+            var px: u32 = 0;
+            while (px < w) : (px += 1) {
+                const row = (y +| py) *| stride;
+                const idx = row +| x +| px;
+                if (idx >= alpha.len) continue;
+
+                var dist_sq: f32 = 0;
+                var in_corner = false;
+
+                if (px < r_u32 and py < r_u32) {
+                    const dx: f32 = r - @as(f32, @floatFromInt(px)) - 0.5;
+                    const dy: f32 = r - @as(f32, @floatFromInt(py)) - 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                } else if (px >= w -| r_u32 and py < r_u32) {
+                    const dx: f32 = @as(f32, @floatFromInt(px)) - @as(f32, @floatFromInt(w -| r_u32)) + 0.5;
+                    const dy: f32 = r - @as(f32, @floatFromInt(py)) - 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                } else if (px < r_u32 and py >= h -| r_u32) {
+                    const dx: f32 = r - @as(f32, @floatFromInt(px)) - 0.5;
+                    const dy: f32 = @as(f32, @floatFromInt(py)) - @as(f32, @floatFromInt(h -| r_u32)) + 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                } else if (px >= w -| r_u32 and py >= h -| r_u32) {
+                    const dx: f32 = @as(f32, @floatFromInt(px)) - @as(f32, @floatFromInt(w -| r_u32)) + 0.5;
+                    const dy: f32 = @as(f32, @floatFromInt(py)) - @as(f32, @floatFromInt(h -| r_u32)) + 0.5;
+                    dist_sq = dx * dx + dy * dy;
+                    in_corner = true;
+                }
+
+                if (in_corner and dist_sq > r_sq) continue;
+
+                alpha[idx] = alpha[idx] +| value;
+            }
+        }
+    }
+}
+
 /// Software renderer state
 pub const SoftwareRenderer = struct {
     framebuffer: *Framebuffer,
@@ -46,9 +320,12 @@ pub const SoftwareRenderer = struct {
     clip_stack: [16]Rect,
     clip_depth: usize,
 
+    /// Shadow cache for instant shadow blitting (optional, requires allocator)
+    shadow_cache: ?ShadowCache = null,
+
     const Self = @This();
 
-    /// Initialize the renderer
+    /// Initialize the renderer (without shadow cache)
     pub fn init(framebuffer: *Framebuffer) Self {
         return .{
             .framebuffer = framebuffer,
@@ -56,9 +333,30 @@ pub const SoftwareRenderer = struct {
             .ttf_font = null,
             .clip_stack = undefined,
             .clip_depth = 0,
+            .shadow_cache = null,
         };
     }
 
+    /// Initialize with shadow cache enabled (recommended for performance)
+    pub fn initWithCache(framebuffer: *Framebuffer, allocator: Allocator) Self {
+        return .{
+            .framebuffer = framebuffer,
+            .default_font = null,
+            .ttf_font = null,
+            .clip_stack = undefined,
+            .clip_depth = 0,
+            .shadow_cache = ShadowCache.init(allocator),
+        };
+    }
+
+    /// Deinitialize (frees shadow cache if present)
+    pub fn deinit(self: *Self) void {
+        if (self.shadow_cache) |*cache| {
+            cache.deinit();
+            self.shadow_cache = null;
+        }
+    }
+
     /// Set the default bitmap font
     pub fn setDefaultFont(self: *Self, font: *Font) void {
         self.default_font = font;
@@ -305,8 +603,91 @@ pub const SoftwareRenderer = struct {
     }
 
     /// Draw a multi-layer shadow to simulate blur effect
-    /// Draws expanding layers with decreasing alpha, creating soft edges
+    /// Uses cached pre-rendered shadows when available for maximum performance
     fn drawShadow(self: *Self, s: Command.ShadowCommand) void {
+        // Try to use cached shadow first (FAST PATH)
+        if (self.shadow_cache) |*cache| {
+            const key = ShadowCacheKey{
+                .w = s.w,
+                .h = s.h,
+                .blur = s.blur,
+                .radius = s.radius,
+                .spread = s.spread,
+            };
+
+            if (cache.getOrCreate(key)) |entry| {
+                // Blit cached shadow with color
+                self.blitShadowCache(s, entry);
+                return;
+            }
+        }
+
+        // Fallback: render shadow directly (SLOW PATH)
+        self.drawShadowDirect(s);
+    }
+
+    /// Blit a cached shadow to the framebuffer
+    fn blitShadowCache(self: *Self, s: Command.ShadowCommand, entry: ShadowCacheEntry) void {
+        // Safe cast: padding is at most blur(255) + spread(128) = 383, fits in i32
+        const padding_i32: i32 = @intCast(@min(entry.padding, std.math.maxInt(i32)));
+        const dest_x = s.x + @as(i32, s.offset_x) - padding_i32;
+        const dest_y = s.y + @as(i32, s.offset_y) - padding_i32;
+
+        const clip = self.getClip();
+        const fb = self.framebuffer;
+
+        // Use u32 for all color math to prevent overflow
+        const color_r: u32 = s.color.r;
+        const color_g: u32 = s.color.g;
+        const color_b: u32 = s.color.b;
+        const color_a: u32 = s.color.a;
+
+        var py: u32 = 0;
+        while (py < entry.height) : (py += 1) {
+            const screen_y = dest_y + @as(i32, @intCast(py));
+            if (screen_y < clip.y or screen_y >= clip.y + @as(i32, @intCast(clip.h))) continue;
+            if (screen_y < 0 or screen_y >= @as(i32, @intCast(fb.height))) continue;
+
+            const src_row = py *| entry.width; // Saturating
+            const dst_row = @as(u32, @intCast(screen_y)) * fb.width;
+
+            var px: u32 = 0;
+            while (px < entry.width) : (px += 1) {
+                const src_idx = src_row +| px;
+                if (src_idx >= entry.alpha.len) continue;
+
+                const cached_alpha = entry.alpha[src_idx];
+                if (cached_alpha == 0) continue;
+
+                const screen_x = dest_x + @as(i32, @intCast(px));
+                if (screen_x < clip.x or screen_x >= clip.x + @as(i32, @intCast(clip.w))) continue;
+                if (screen_x < 0 or screen_x >= @as(i32, @intCast(fb.width))) continue;
+
+                const dst_idx = dst_row + @as(u32, @intCast(screen_x));
+                if (dst_idx >= fb.pixels.len) continue;
+
+                // Modulate alpha with shadow color's alpha (u32 math)
+                const final_alpha: u32 = (@as(u32, cached_alpha) * color_a) / 255;
+                if (final_alpha == 0) continue;
+
+                // Blend with framebuffer (all u32 to prevent overflow)
+                const existing = fb.pixels[dst_idx];
+                const bg_r: u32 = existing & 0xFF;
+                const bg_g: u32 = (existing >> 8) & 0xFF;
+                const bg_b: u32 = (existing >> 16) & 0xFF;
+
+                const inv_alpha: u32 = 255 -| final_alpha; // Saturating subtract
+                const out_r: u8 = @intCast((color_r * final_alpha + bg_r * inv_alpha) / 255);
+                const out_g: u8 = @intCast((color_g * final_alpha + bg_g * inv_alpha) / 255);
+                const out_b: u8 = @intCast((color_b * final_alpha + bg_b * inv_alpha) / 255);
+
+                fb.pixels[dst_idx] = @as(u32, out_r) | (@as(u32, out_g) << 8) | (@as(u32, out_b) << 16) | (0xFF << 24);
+            }
+        }
+    }
+
+    /// Render shadow directly (fallback when cache unavailable)
+    fn drawShadowDirect(self: *Self, s: Command.ShadowCommand) void {
         if (s.blur == 0) {
             // Hard shadow - single solid rect
             const shadow_x = s.x + @as(i32, s.offset_x) - @as(i32, s.spread);
@@ -323,29 +704,24 @@ pub const SoftwareRenderer = struct {
         }
 
         // Soft shadow - draw multiple expanding layers with decreasing alpha
-        // Each layer is larger and more transparent, creating a blur effect
         const layers: u8 = s.blur;
         const base_alpha = s.color.a;
 
-        // Calculate base shadow position
         const base_x = s.x + @as(i32, s.offset_x) - @as(i32, s.spread);
         const base_y = s.y + @as(i32, s.offset_y) - @as(i32, s.spread);
         const base_w = s.w +| @as(u32, @intCast(@abs(s.spread) * 2));
         const base_h = s.h +| @as(u32, @intCast(@abs(s.spread) * 2));
 
-        // Draw from outermost (most transparent) to innermost (most opaque)
         var layer: u8 = layers;
         while (layer > 0) {
             layer -= 1;
 
-            // Calculate alpha for this layer (quadratic falloff for softer edges)
             const t = @as(f32, @floatFromInt(layer)) / @as(f32, @floatFromInt(layers));
-            const alpha_factor = (1.0 - t) * (1.0 - t); // Quadratic falloff
+            const alpha_factor = (1.0 - t) * (1.0 - t);
             const layer_alpha = @as(u8, @intFromFloat(@as(f32, @floatFromInt(base_alpha)) * alpha_factor * 0.5));
 
             if (layer_alpha == 0) continue;
 
-            // Expand layer outward
             const expand = @as(i32, @intCast(layers - layer));
             const layer_x = base_x - expand;
             const layer_y = base_y - expand;
@@ -362,7 +738,7 @@ pub const SoftwareRenderer = struct {
             }
         }
 
-        // Draw core shadow (innermost, full opacity relative to input)
+        // Core shadow
         const core_alpha = @as(u8, @intFromFloat(@as(f32, @floatFromInt(base_alpha)) * 0.7));
         if (core_alpha > 0) {
             const core_color = Color.rgba(s.color.r, s.color.g, s.color.b, core_alpha);

src/render/ttf.zig

@@ -310,6 +310,7 @@ pub const TtfFont = struct {
     }
 
     /// Draw a cached glyph bitmap with alpha blending
+    /// Optimized: pre-calculate visible region, direct pixel access
     fn drawGlyphBitmap(
         self: Self,
         fb: *Framebuffer,
@@ -321,44 +322,73 @@ pub const TtfFont = struct {
     ) void {
         _ = self;
 
-        // Calculate position: bearing_y is distance from baseline to top of glyph
+        const width: u32 = glyph.metrics.width;
+        const height: u32 = glyph.metrics.height;
+        if (width == 0 or height == 0) return;
+
+        // Calculate glyph position
         const glyph_x = x + glyph.metrics.bearing_x;
         const glyph_y = baseline_y - glyph.metrics.bearing_y;
 
-        const width = glyph.metrics.width;
-        const height = glyph.metrics.height;
+        // Early exit: entire glyph outside clip or framebuffer
+        const glyph_right = glyph_x + @as(i32, @intCast(width));
+        const glyph_bottom = glyph_y + @as(i32, @intCast(height));
+        const clip_right = clip.x + @as(i32, @intCast(clip.w));
+        const clip_bottom = clip.y + @as(i32, @intCast(clip.h));
 
-        if (width == 0 or height == 0) return;
+        if (glyph_right <= clip.x or glyph_x >= clip_right) return;
+        if (glyph_bottom <= clip.y or glyph_y >= clip_bottom) return;
+        if (glyph_right <= 0 or glyph_x >= @as(i32, @intCast(fb.width))) return;
+        if (glyph_bottom <= 0 or glyph_y >= @as(i32, @intCast(fb.height))) return;
 
-        // Draw each pixel with alpha blending
-        for (0..height) |py| {
-            for (0..width) |px| {
-                const alpha = glyph.bitmap[py * width + px];
+        // Calculate visible region (intersection of glyph, clip, and framebuffer)
+        const vis_x0 = @max(0, @max(glyph_x, clip.x));
+        const vis_y0 = @max(0, @max(glyph_y, clip.y));
+        const vis_x1 = @min(@as(i32, @intCast(fb.width)), @min(glyph_right, clip_right));
+        const vis_y1 = @min(@as(i32, @intCast(fb.height)), @min(glyph_bottom, clip_bottom));
+
+        if (vis_x0 >= vis_x1 or vis_y0 >= vis_y1) return;
+
+        // Precompute color for blending (u32 to avoid per-pixel struct creation)
+        const color_r: u32 = color.r;
+        const color_g: u32 = color.g;
+        const color_b: u32 = color.b;
+        const color_packed = color.toABGR();
+
+        // Draw only visible region with direct pixel access
+        var screen_y = vis_y0;
+        while (screen_y < vis_y1) : (screen_y += 1) {
+            const glyph_py: u32 = @intCast(screen_y - glyph_y);
+            const dst_row: u32 = @intCast(screen_y);
+            const dst_row_start = dst_row * fb.width;
+            const src_row_start = glyph_py * width;
+
+            var screen_x = vis_x0;
+            while (screen_x < vis_x1) : (screen_x += 1) {
+                const glyph_px: u32 = @intCast(screen_x - glyph_x);
+                const alpha = glyph.bitmap[src_row_start + glyph_px];
                 if (alpha == 0) continue;
 
-                const screen_x = glyph_x + @as(i32, @intCast(px));
-                const screen_y = glyph_y + @as(i32, @intCast(py));
+                const dst_idx = dst_row_start + @as(u32, @intCast(screen_x));
 
-                // Clip check
-                if (screen_x < clip.x or screen_x >= clip.x + @as(i32, @intCast(clip.w))) continue;
-                if (screen_y < clip.y or screen_y >= clip.y + @as(i32, @intCast(clip.h))) continue;
-                if (screen_x < 0 or screen_y < 0) continue;
-                if (screen_x >= @as(i32, @intCast(fb.width)) or screen_y >= @as(i32, @intCast(fb.height))) continue;
-
-                // Alpha blend
                 if (alpha == 255) {
-                    fb.setPixel(@intCast(screen_x), @intCast(screen_y), color);
+                    // Fully opaque: direct write
+                    fb.pixels[dst_idx] = color_packed;
                 } else {
-                    // Get background pixel and convert u32 to Color (ABGR format)
-                    const bg_u32 = fb.getPixel(@intCast(screen_x), @intCast(screen_y)) orelse 0;
-                    const bg = Color{
-                        .r = @truncate(bg_u32),
-                        .g = @truncate(bg_u32 >> 8),
-                        .b = @truncate(bg_u32 >> 16),
-                        .a = @truncate(bg_u32 >> 24),
-                    };
-                    const blended = blendColors(color, bg, alpha);
-                    fb.setPixel(@intCast(screen_x), @intCast(screen_y), blended);
+                    // Alpha blend with direct u32 math
+                    const bg = fb.pixels[dst_idx];
+                    const bg_r: u32 = bg & 0xFF;
+                    const bg_g: u32 = (bg >> 8) & 0xFF;
+                    const bg_b: u32 = (bg >> 16) & 0xFF;
+
+                    const a: u32 = alpha;
+                    const inv_a: u32 = 255 - a;
+
+                    const out_r: u8 = @intCast((color_r * a + bg_r * inv_a) / 255);
+                    const out_g: u8 = @intCast((color_g * a + bg_g * inv_a) / 255);
+                    const out_b: u8 = @intCast((color_b * a + bg_b * inv_a) / 255);
+
+                    fb.pixels[dst_idx] = @as(u32, out_r) | (@as(u32, out_g) << 8) | (@as(u32, out_b) << 16) | (0xFF << 24);
                 }
             }
         }