From 3dcb1c2e4b441768e3a0e7d34e6a4b1ef76762ca Mon Sep 17 00:00:00 2001
From: Stephen Gutekanst <stephen@hexops.com>
Date: Sun, 20 Feb 2022 15:52:57 -0700
Subject: [PATCH] gpu-dawn: use cross-platform process.getEnvVarOwned

Helps hexops/mach#86

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
---
 gpu-dawn/src/dawn/hello_triangle.zig |  2 +-
 gpu-dawn/src/dawn/sample_utils.zig   | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/gpu-dawn/src/dawn/hello_triangle.zig b/gpu-dawn/src/dawn/hello_triangle.zig
index 74b5237003..4a48886419 100644
--- a/gpu-dawn/src/dawn/hello_triangle.zig
+++ b/gpu-dawn/src/dawn/hello_triangle.zig
@@ -15,7 +15,7 @@ pub fn main() !void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     var allocator = gpa.allocator();
 
-    const setup = try sample_utils.setup();
+    const setup = try sample_utils.setup(allocator);
     const queue = c.wgpuDeviceGetQueue(setup.device);
 
     var descriptor = std.mem.zeroes(c.WGPUSwapChainDescriptor);
diff --git a/gpu-dawn/src/dawn/sample_utils.zig b/gpu-dawn/src/dawn/sample_utils.zig
index 73aad500f8..8cf58753af 100644
--- a/gpu-dawn/src/dawn/sample_utils.zig
+++ b/gpu-dawn/src/dawn/sample_utils.zig
@@ -51,8 +51,17 @@ const Setup = struct {
     window: glfw.Window,
 };
 
-fn detectBackendType() c.WGPUBackendType {
-    if (std.os.getenv("WGPU_BACKEND")) |backend| {
+fn getEnvVarOwned(allocator: std.mem.Allocator, key: []const u8) error{ OutOfMemory, InvalidUtf8 }!?[]u8 {
+    return std.process.getEnvVarOwned(allocator, key) catch |err| switch (err) {
+        error.EnvironmentVariableNotFound => @as(?[]u8, null),
+        else => |e| e,
+    };
+}
+
+fn detectBackendType(allocator: std.mem.Allocator) !c.WGPUBackendType {
+    const WGPU_BACKEND = try getEnvVarOwned(allocator, "WGPU_BACKEND");
+    if (WGPU_BACKEND) |backend| {
+        defer allocator.free(backend);
         if (std.ascii.eqlIgnoreCase(backend, "opengl")) return c.WGPUBackendType_OpenGL;
         if (std.ascii.eqlIgnoreCase(backend, "opengles")) return c.WGPUBackendType_OpenGLES;
         if (std.ascii.eqlIgnoreCase(backend, "d3d11")) return c.WGPUBackendType_D3D11;
@@ -82,8 +91,8 @@ fn backendTypeString(t: c.WGPUBackendType) []const u8 {
     };
 }
 
-pub fn setup() !Setup {
-    const backend_type = detectBackendType();
+pub fn setup(allocator: std.mem.Allocator) !Setup {
+    const backend_type = try detectBackendType(allocator);
     const cmd_buf_type = CmdBufType.none;
 
     try glfw.init(.{});