Add very basic X-Resource extension

This only supports XResQueryVersion and XResQueryClientIds but it is
enough to get steam running

xbanan/CMakeLists.txt

@@ -6,6 +6,7 @@ set(XBANAN_SOURCES
 	Extensions.cpp
 	ExtBigReg.cpp
 	ExtRANDR.cpp
+	ExtXRes.cpp
 	Font.cpp
 	Image.cpp
 	Keymap.cpp

xbanan/ExtXRes.cpp

@@ -0,0 +1,119 @@
+#include "Extensions.h"
+#include "Utils.h"
+
+#include <X11/X.h>
+#include <X11/extensions/XResproto.h>
+
+template<typename F>
+static BAN::ErrorOr<void> for_each_client(uint32_t target_spec, const F& callback)
+{
+	for (auto [fd, thingy] : g_epoll_thingies)
+	{
+		if (thingy.type != EpollThingy::Type::Client)
+			continue;
+
+		Client& client_info = thingy.value.get<Client>();
+		if (target_spec && (target_spec >> 20) != client_info.fd)
+			continue;
+
+		TRY(callback(client_info, target_spec ? target_spec : (client_info.fd << 20)));
+	}
+	return {};
+}
+
+BAN::ErrorOr<void> extension_xres(Client& client_info, BAN::ConstByteSpan packet)
+{
+	const uint8_t major_opcode = packet[0];
+	const uint8_t minor_opcode = packet[1];
+
+	switch (minor_opcode)
+	{
+		case X_XResQueryVersion:
+		{
+			auto request = decode<xXResQueryVersionReq>(packet).value();
+
+			dprintln("XResQueryVersion");
+			dprintln("  clientMajor: {}", reqType.client_major);
+			dprintln("  clientMinor: {}", reqType.client_minor);
+   
+			xXResQueryVersionReply reply {
+				.type = X_Reply,
+				.sequenceNumber = client_info.sequence,
+				.length = 0,
+				.server_major = 1,
+				.server_minor = 2,
+			};
+			TRY(encode(client_info.output_buffer, reply));
+
+			break;
+		}
+		case X_XResQueryClientIds:
+		{
+			auto request = decode<xXResQueryClientIdsReq>(packet).value();
+
+			dprintln("XResQueryClientIds");
+			dprintln("  numSpecs: {}", request.numSpecs);
+
+			uint32_t num_ids { 0 };
+			BAN::Vector<uint8_t> query_result;
+
+			for (size_t i = 0; i < request.numSpecs; i++)
+			{
+				auto spec = decode<xXResClientIdSpec>(packet).value();
+
+				TRY(for_each_client(spec.client, [&](Client& client_info, uint32_t client_spec) -> BAN::ErrorOr<void> {
+					if (spec.mask == None || (spec.mask & X_XResClientXIDMask))
+					{
+						xXResClientIdValue value {
+							.spec = {
+								.client = client_spec,
+								.mask = X_XResClientXIDMask,
+							},
+							.length = 0,
+						};
+						TRY(encode(query_result, value));
+						num_ids++;
+					}
+					if ((spec.mask == None || (spec.mask & X_XResLocalClientPIDMask)) && client_info.pid.has_value())
+					{
+						xXResClientIdValue value {
+							.spec = {
+								.client = client_spec,
+								.mask = X_XResLocalClientPIDMask,
+							},
+							.length = 4,
+						};
+						TRY(encode(query_result, value));
+						TRY(encode(query_result, client_info.pid.value()));
+						num_ids++;
+					}
+					return {};
+				}));	
+			}
+
+			xXResQueryClientIdsReply reply {
+				.type = X_Reply,
+				.sequenceNumber = client_info.sequence,
+				.length = static_cast<uint32_t>(query_result.size() / 4),
+				.numIds = num_ids,
+			};
+			TRY(encode(client_info.output_buffer, reply));
+			TRY(encode(client_info.output_buffer, query_result));
+
+			break;
+		}
+		default:
+			dwarnln("unsupported opcode XRes minor opcode {}", minor_opcode);
+			break;
+	}
+
+	return {};
+}
+
+static struct XResInstaller
+{
+	XResInstaller()
+	{
+		install_extension(XRES_NAME, 6, 0, extension_xres);
+	}
+} installer;