<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> </head> <body text="#000000" bgcolor="#FFFFFF"> Hello everyone, I'm trying to make a(nother) C# binding for HarfBuzz, and having some troubles with hb_feature_from_string(). Here's how I called it in C#: ``` // <a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz/PlatformInvoke/Api.Shape.cs#L11"> platform invoke</a> [DllImport(HarfBuzzDll, CallingConvention = Cdecl)] public static extern bool hb_feature_from_string(byte[] str, int length, out Feature feature); // <a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz/HarfBuzz/Feature.cs"> definition of "Feature"</a> [StructLayout(LayoutKind.Sequential)] public struct Feature { private uint _tag; public uint Value; public uint Start; public uint End; } // calling hb_feature_to_string (<a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz.Test/ShapeTests/Tests.cs#L44">unit test</a> -> <a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz/HarfBuzz/Feature.cs#L23"> constructor</a>) var bytes = Encoding.ASCII.GetBytes("valt"); if (!Api.hb_feature_from_string(bytes, bytes.Length, out var feature)) throw new ArgumentException(); ``` then <a moz-do-not-send="true" href="https://ci.appveyor.com/project/TJYSunset/hardfuzz/build/0.1.3/tests"> the ArgumentException was thrown</a>, meaning hb_feature_from_string returned false. Also, calling hb_feature_to_string() on the returned `Feature` will result in a random string varying each run, as if read from a wild pointer. However, somehow the `_tag` can be successfully DETAGed as "valt". From my experience, <ul> <li>platform invoke definition is unlikely to blame; the `out` keyword and the usage of `byte[]` for marshaling `char *` proved to work in other API calls. </li><li>maybe the definition of `struct Feature` is incorrect; I had to define <a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz/HarfBuzz/Buffer/GlyphInfo.cs#L10"> hb_glyph_info_t</a> and <a moz-do-not-send="true" href="https://github.com/TJYSunset/HardFuzz/blob/d3fb178d69e8a88e616c7f3a778978b062b99c6d/HardFuzz/HarfBuzz/Buffer/GlyphPosition.cs#L10"> hb_glyph_position_t</a> as 20-byte-long struct for them to work, even if they only have three or four uint32s. But tried Size=20 with no luck. </li><li>the passed string is unlikely to be incorrect according to this <a href="https://github.com/ufyTeX/luaharfbuzz/wiki/Feature-Strings"> third-party documentation</a> and my glance at hb-common.cc. </li></ul> I'm wondering, what part of this process is wrong? Again, thank you in advance! Todd <pre class="moz-signature" cols="72">-- Todd J. York (pseudonym) zh-Hans-CN, en-US | UTC+08:00 Sent from Thunderbird</pre> </body> </html>