freetype builds in png support, uses our own zlib

build.zig

@@ -145,11 +145,12 @@ fn addDeps(
     step.addIncludeDir("vendor/glad/include/");
     step.addCSourceFile("vendor/glad/src/gl.c", &.{});
 
+    // Dependencies of other dependencies
     const zlib_step = try zlib.link(b, step);
     const libpng_step = try libpng.link(b, step, .{
         .zlib = .{
             .step = zlib_step,
-            .include = zlib.include_path,
+            .include = &zlib.include_paths,
         },
     });
 
@@ -157,7 +158,15 @@ fn addDeps(
     step.addPackage(freetype.pkg);
     _ = try freetype.link(b, step, .{
         .libpng = freetype.Options.Libpng{
+            .enabled = true,
             .step = libpng_step,
+            .include = &libpng.include_paths,
+        },
+
+        .zlib = .{
+            .enabled = true,
+            .step = zlib_step,
+            .include = &zlib.include_paths,
         },
     });
 

pkg/freetype/build.zig

@@ -16,11 +16,18 @@ fn thisDir() []const u8 {
 
 pub const Options = struct {
     libpng: Libpng = .{},
+    zlib: Zlib = .{},
 
     pub const Libpng = struct {
         enabled: bool = false,
         step: ?*std.build.LibExeObjStep = null,
-        include: ?[]const u8 = null,
+        include: ?[]const []const u8 = null,
+    };
+
+    pub const Zlib = struct {
+        enabled: bool = false,
+        step: ?*std.build.LibExeObjStep = null,
+        include: ?[]const []const u8 = null,
     };
 };
 
@@ -57,8 +64,17 @@ pub fn buildFreetype(
         else
             lib.linkSystemLibrary("libpng");
 
-        if (opt.libpng.include) |dir|
-            lib.addIncludePath(dir);
+        if (opt.libpng.include) |dirs|
+            for (dirs) |dir| lib.addIncludePath(dir);
+    }
+    if (opt.zlib.enabled) {
+        if (opt.zlib.step) |zlib|
+            lib.linkLibrary(zlib)
+        else
+            lib.linkSystemLibrary("z");
+
+        if (opt.zlib.include) |dirs|
+            for (dirs) |dir| lib.addIncludePath(dir);
     }
 
     // Compile
@@ -71,7 +87,8 @@ pub fn buildFreetype(
         "-DHAVE_UNISTD_H",
         "-DHAVE_FCNTL_H",
     });
-    if (opt.libpng.enabled) try flags.append("-DFT_CONFIG_OPTION_USE_PNG");
+    if (opt.libpng.enabled) try flags.append("-DFT_CONFIG_OPTION_USE_PNG=1");
+    if (opt.zlib.enabled) try flags.append("-DFT_CONFIG_OPTION_SYSTEM_ZLIB=1");
 
     // C files
     lib.addCSourceFiles(srcs, flags.items);

pkg/libpng/build.zig

@@ -5,6 +5,8 @@ const root = thisDir() ++ "../../../vendor/libpng/";
 const include_path = root;
 const include_path_pnglibconf = thisDir();
 
+pub const include_paths = .{ include_path, include_path_pnglibconf };
+
 pub const pkg = std.build.Pkg{
     .name = "libpng",
     .source = .{ .path = thisDir() ++ "/main.zig" },
@@ -19,7 +21,7 @@ pub const Options = struct {
 
     pub const Zlib = struct {
         step: ?*std.build.LibExeObjStep = null,
-        include: ?[]const u8 = null,
+        include: ?[]const []const u8 = null,
     };
 };
 
@@ -59,8 +61,8 @@ pub fn buildLib(
     else
         lib.linkSystemLibrary("z");
 
-    if (opt.zlib.include) |dir|
-        lib.addIncludePath(dir);
+    if (opt.zlib.include) |dirs|
+        for (dirs) |dir| lib.addIncludePath(dir);
 
     // Compile
     var flags = std.ArrayList([]const u8).init(b.allocator);

pkg/zlib/build.zig

@@ -2,7 +2,9 @@ const std = @import("std");
 
 /// Directories with our includes.
 const root = thisDir() ++ "../../../vendor/zlib/";
-pub const include_path = root;
+const include_path = root;
+
+pub const include_paths = .{include_path};
 
 pub const pkg = std.build.Pkg{
     .name = "zlib",