Vulkan: Fallback to XCB for Xlib surfaces

Chromium builds the Vulkan loader without support Xlib (because it
prefers XCB) which caused Xlib wgpu::SwapChain creation to fail on the
Vulkan backend.

This CL adds a fallback to use VK_KHR_xcb_surface if VK_KHR_xlib_surface
isn't present.

Bug: dawn:662
Change-Id: I0e0128ee6b5c75da03998dbae231d17e48bacc81
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/41180
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Auto-Submit: Corentin Wallez <cwallez@chromium.org>

src/common/vulkan_platform.h

@@ -162,6 +162,7 @@ namespace dawn_native { namespace vulkan {
 
 #if defined(DAWN_USE_X11)
 #    define VK_USE_PLATFORM_XLIB_KHR
+#    define VK_USE_PLATFORM_XCB_KHR
 #    include "common/xlib_with_undefs.h"
 #endif  // defined(DAWN_USE_X11)
 

src/common/xlib_with_undefs.h

@@ -24,6 +24,7 @@
 // This header includes <X11/Xlib.h> but removes all the extra defines that conflict with
 // identifiers in internal code. It should never be included in something that is part of the public
 // interface.
+#include <X11/Xlib-xcb.h>
 #include <X11/Xlib.h>
 
 #undef Success

src/dawn_native/BUILD.gn

@@ -295,7 +295,10 @@ source_set("dawn_native_sources") {
   ]
 
   if (dawn_use_x11) {
-    libs += [ "X11" ]
+    libs += [
+      "X11",
+      "X11-xcb",
+    ]
   }
 
   if (is_win) {

src/dawn_native/CMakeLists.txt

@@ -179,8 +179,17 @@ target_link_libraries(dawn_native
 )
 
 if (DAWN_USE_X11)
-    find_package(X11 REQUIRED)
+    find_package(X11 REQUIRED OPTIONAL_COMPONENTS X11_xcb)
     target_link_libraries(dawn_native PRIVATE ${X11_LIBRARIES})
+    target_include_directories(dawn_native PRIVATE ${X11_INCLUDE_DIR})
+
+    if (DAWN_ENABLE_VULKAN)
+        if (NOT X11_X11_xcb_FOUND)
+            message(FATAL_ERROR "X11::X11_xcb cannot be found, maybe because cmake < 3.18. Consider filing an issue for Dawn to bundle its own FindX11_XCB script")
+        endif()
+        target_link_libraries(dawn_native PRIVATE ${X11_X11_xcb_LIB})
+        target_include_directories(dawn_native PRIVATE ${X11_X11_xcb_INCLUDE_PATH})
+    endif()
 endif()
 
 if (WIN32)

src/dawn_native/vulkan/SwapChainVk.cpp

@@ -145,6 +145,26 @@ namespace dawn_native { namespace vulkan {
                             "CreateXlibSurface"));
                         return vkSurface;
                     }
+
+                    // Fall back to using XCB surfaces if the Xlib extension isn't available.
+                    // See https://xcb.freedesktop.org/MixingCalls/ for more information about
+                    // interoperability between Xlib and XCB
+                    if (info.HasExt(InstanceExt::XcbSurface)) {
+                        VkXcbSurfaceCreateInfoKHR createInfo;
+                        createInfo.sType = VK_STRUCTURE_TYPE_XCB_SURFACE_CREATE_INFO_KHR;
+                        createInfo.pNext = nullptr;
+                        createInfo.flags = 0;
+                        // The XCB connection lives as long as the X11 display.
+                        createInfo.connection =
+                            XGetXCBConnection(static_cast<Display*>(surface->GetXDisplay()));
+                        createInfo.window = surface->GetXWindow();
+
+                        VkSurfaceKHR vkSurface = VK_NULL_HANDLE;
+                        DAWN_TRY(CheckVkSuccess(
+                            fn.CreateXcbSurfaceKHR(instance, &createInfo, nullptr, &*vkSurface),
+                            "CreateXcbSurfaceKHR"));
+                        return vkSurface;
+                    }
                     break;
 #endif  // defined(DAWN_USE_X11)
 

src/dawn_native/vulkan/VulkanFunctions.cpp

@@ -152,6 +152,10 @@ namespace dawn_native { namespace vulkan {
             GET_INSTANCE_PROC(CreateXlibSurfaceKHR);
             GET_INSTANCE_PROC(GetPhysicalDeviceXlibPresentationSupportKHR);
         }
+        if (globalInfo.HasExt(InstanceExt::XcbSurface)) {
+            GET_INSTANCE_PROC(CreateXcbSurfaceKHR);
+            GET_INSTANCE_PROC(GetPhysicalDeviceXcbPresentationSupportKHR);
+        }
 #endif  // defined(DAWN_USE_X11)
         return {};
     }

src/dawn_native/vulkan/VulkanFunctions.h

@@ -137,6 +137,11 @@ namespace dawn_native { namespace vulkan {
         PFN_vkCreateXlibSurfaceKHR CreateXlibSurfaceKHR = nullptr;
         PFN_vkGetPhysicalDeviceXlibPresentationSupportKHR
             GetPhysicalDeviceXlibPresentationSupportKHR = nullptr;
+
+        // KHR_xcb_surface
+        PFN_vkCreateXcbSurfaceKHR CreateXcbSurfaceKHR = nullptr;
+        PFN_vkGetPhysicalDeviceXcbPresentationSupportKHR
+            GetPhysicalDeviceXcbPresentationSupportKHR = nullptr;
 #endif  // defined(DAWN_USE_X11)
 
         // ---------- Device procs