fix: use bitmap stride

Author: MrBrN197

src/gfx/font/native/Font.zig

@@ -78,36 +78,46 @@ pub fn render(f: *Font, allocator: std.mem.Allocator, glyph_index: u32, opt: Ren
     const buffer = glyph_bitmap.buffer();
     const width = glyph_bitmap.width();
     const height = glyph_bitmap.rows();
+    const pitch = @as(u32, @intCast(glyph_bitmap.pitch())); // TODO handle negative could be negative
     const margin = 1;
 
+    const dst_width = width + (margin * 2);
+    const dst_height = height + (margin * 2);
+
     if (buffer == null) return RenderedGlyph{
         .bitmap = null,
-        .width = width + (margin * 2),
-        .height = height + (margin * 2),
+        .width = dst_width,
+        .height = dst_height,
     };
 
+    const num_pixels = dst_width * dst_height;
+
     // Add 1 pixel padding to texture to avoid bleeding over other textures. This is part of the
     // render() API contract.
     f.bitmap.clearRetainingCapacity();
-    const num_pixels = (width + (margin * 2)) * (height + (margin * 2));
     // TODO: handle OOM here
     f.bitmap.ensureTotalCapacity(allocator, num_pixels) catch return error.RenderError;
     f.bitmap.resize(allocator, num_pixels) catch return error.RenderError;
-    for (f.bitmap.items, 0..) |*data, i| {
-        const x = i % (width + (margin * 2));
-        const y = i / (width + (margin * 2));
-        if (x < margin or x > (width + margin) or y < margin or y > (height + margin)) {
-            data.* = RGBA32{ .r = 0, .g = 0, .b = 0, .a = 0 };
-        } else {
-            const alpha = buffer.?[((y - margin) * width + (x - margin)) % buffer.?.len];
-            data.* = RGBA32{ .r = 0, .g = 0, .b = 0, .a = alpha };
+
+    @memset(f.bitmap.items, RGBA32{ .r = 0, .g = 0, .b = 0, .a = 0 });
+
+    for (0..height) |y| {
+        const src_row = buffer.?[y * pitch ..][0..width];
+
+        const dst_y = y + margin;
+        const dst_row_start = (dst_y * dst_width) + margin;
+        const dst_row = f.bitmap.items[dst_row_start..][0..width];
+
+        for (0..width) |x| {
+            const alpha = src_row[x];
+            dst_row[x] = RGBA32{ .r = 255, .g = 255, .b = 255, .a = alpha };
         }
     }
 
     return RenderedGlyph{
         .bitmap = f.bitmap.items,
-        .width = width + (margin * 2),
-        .height = height + (margin * 2),
+        .width = dst_width,
+        .height = dst_height,
     };
 }