nixpkgs/pkgs/development/libraries/vulkan-loader/use-xdg-paths.patch

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 27ab6e5..e59256e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -256,17 +256,10 @@ if(NOT WIN32)
     include(GNUInstallDirs)
 
     add_definitions(-DSYSCONFDIR="${CMAKE_INSTALL_FULL_SYSCONFDIR}")
-    add_definitions(-DDATADIR="${CMAKE_INSTALL_FULL_DATADIR}")
-
     # Make sure /etc is searched by the loader
-    if (NOT (CMAKE_INSTALL_FULL_SYSCONFDIR STREQUAL "/etc"))
+    if(NOT (CMAKE_INSTALL_FULL_SYSCONFDIR STREQUAL "/etc"))
         add_definitions(-DEXTRASYSCONFDIR="/etc")
     endif()
-
-    # Make sure /usr/share is searched by the loader
-    if (NOT (CMAKE_INSTALL_FULL_DATADIR STREQUAL "/usr/share"))
-        add_definitions(-DEXTRADATADIR="/usr/share")
-    endif()
 endif()
 
 if(UNIX)
diff --git a/loader/loader.c b/loader/loader.c
index 24758f4..af7cc85 100644
--- a/loader/loader.c
+++ b/loader/loader.c
@@ -2909,7 +2909,7 @@ static VkResult
 loader_get_manifest_files(const struct loader_instance *inst,
                           const char *env_override, const char *source_override,
                           bool is_layer, bool warn_if_not_present,
-                          const char *location, const char *home_location,
+                          const char *location, const char *relative_location,
                           struct loader_manifest_files *out_files) {
     const char * override = NULL;
     char *override_getenv = NULL;
@@ -2941,9 +2941,9 @@ loader_get_manifest_files(const struct loader_instance *inst,
     }
 
 #if !defined(_WIN32)
-    if (location == NULL && home_location == NULL) {
+    if (location == NULL && relative_location == NULL) {
 #else
-    home_location = NULL;
+    relative_location = NULL;
     if (location == NULL) {
 #endif
         loader_log(inst, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
@@ -2962,16 +2962,89 @@ loader_get_manifest_files(const struct loader_instance *inst,
     // Make a copy of the input we are using so it is not modified
     // Also handle getting the location(s) from registry on Windows
     if (override == NULL) {
-        loc = loader_stack_alloc(strlen(location) + 1);
+        size_t loc_size = strlen(location) + 1;
+#if !defined(_WIN32)
+        const char *xdgconfdirs = secure_getenv("XDG_CONFIG_DIRS");
+        const char *xdgdatadirs = secure_getenv("XDG_DATA_DIRS");
+        if (xdgconfdirs == NULL || xdgconfdirs[0] == '\0')
+            xdgconfdirs = "/etc/xdg";
+        if (xdgdatadirs == NULL || xdgdatadirs[0] == '\0')
+            xdgdatadirs = "/usr/local/share:/usr/share";
+        const size_t rel_size = strlen(relative_location);
+        // Leave space for trailing separators
+        loc_size += strlen(xdgconfdirs) + strlen(xdgdatadirs) + 2*rel_size + 2;
+        for (const char *x = xdgconfdirs; *x; ++x)
+            if (*x == PATH_SEPARATOR) loc_size += rel_size;
+        for (const char *x = xdgdatadirs; *x; ++x)
+            if (*x == PATH_SEPARATOR) loc_size += rel_size;
+        loc_size += strlen(SYSCONFDIR) + rel_size + 1;
+#ifdef EXTRASYSCONFDIR
+        loc_size += strlen(EXTRASYSCONFDIR) + rel_size + 1;
+#endif
+#endif
+        loc = loader_stack_alloc(loc_size);
         if (loc == NULL) {
             loader_log(inst, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
                        "loader_get_manifest_files: Failed to allocate "
                        "%d bytes for manifest file location.",
-                       strlen(location));
+                       loc_size);
             res = VK_ERROR_OUT_OF_HOST_MEMORY;
             goto out;
         }
-        strcpy(loc, location);
+        char *loc_write = loc;
+#if !defined(_WIN32)
+        const char *loc_read;
+
+        loc_read = &xdgconfdirs[0];
+        for (const char *x = loc_read;; ++x) {
+            if (*x == PATH_SEPARATOR || *x == '\0') {
+                const size_t s = x - loc_read;
+                memcpy(loc_write, loc_read, s);
+                loc_write += s;
+                memcpy(loc_write, relative_location, rel_size);
+                loc_write += rel_size;
+                *loc_write++ = PATH_SEPARATOR;
+                if (*x == 0)
+                    break;
+                loc_read = ++x;
+            }
+        }
+
+        memcpy(loc_write, SYSCONFDIR, strlen(SYSCONFDIR));
+        loc_write += strlen(SYSCONFDIR);
+        memcpy(loc_write, relative_location, rel_size);
+        loc_write += rel_size;
+        *loc_write++ = PATH_SEPARATOR;
+
+#ifdef EXTRASYSCONFDIR
+        memcpy(loc_write, EXTRASYSCONFDIR, strlen(EXTRASYSCONFDIR));
+        loc_write += strlen(EXTRASYSCONFDIR);
+        memcpy(loc_write, relative_location, rel_size);
+        loc_write += rel_size;
+        *loc_write++ = PATH_SEPARATOR;
+#endif
+
+        loc_read = &xdgdatadirs[0];
+        for (const char *x = loc_read;; ++x) {
+            if (*x == PATH_SEPARATOR || *x == '\0') {
+                const size_t s = x - loc_read;
+                memcpy(loc_write, loc_read, s);
+                loc_write += s;
+                memcpy(loc_write, relative_location, rel_size);
+                loc_write += rel_size;
+                *loc_write++ = PATH_SEPARATOR;
+                if (*x == 0)
+                    break;
+                loc_read = ++x;
+            }
+        }
+        --loc_write;
+        *loc_write = '\0';
+#else
+        memcpy(loc_write, location, loc_size);
+        loc[loc_size-1] = '\0';
+#endif
+
 #if defined(_WIN32)
         VkResult reg_result = loaderGetRegistryFiles(inst, loc, &reg);
         if (VK_SUCCESS != reg_result || NULL == reg) {
@@ -3122,14 +3195,14 @@ loader_get_manifest_files(const struct loader_instance *inst,
         }
         file = next_file;
 #if !defined(_WIN32)
-        if (home_location != NULL &&
+        if (relative_location != NULL &&
             (next_file == NULL || *next_file == '\0') && override == NULL) {
             char *xdgdatahome = secure_getenv("XDG_DATA_HOME");
             size_t len;
             if (xdgdatahome != NULL) {
 
                 char *home_loc = loader_stack_alloc(strlen(xdgdatahome) + 2 +
-                                                    strlen(home_location));
+                                                    strlen(relative_location));
                 if (home_loc == NULL) {
                     loader_log(inst, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
                                "loader_get_manifest_files: Failed to allocate "
@@ -3139,15 +3212,15 @@ loader_get_manifest_files(const struct loader_instance *inst,
                 }
                 strcpy(home_loc, xdgdatahome);
                 // Add directory separator if needed
-                if (home_location[0] != DIRECTORY_SYMBOL) {
+                if (relative_location[0] != DIRECTORY_SYMBOL) {
                     len = strlen(home_loc);
                     home_loc[len] = DIRECTORY_SYMBOL;
                     home_loc[len + 1] = '\0';
                 }
-                strcat(home_loc, home_location);
+                strcat(home_loc, relative_location);
                 file = home_loc;
                 next_file = loader_get_next_path(file);
-                home_location = NULL;
+                relative_location = NULL;
 
                 loader_log(
                     inst, VK_DEBUG_REPORT_DEBUG_BIT_EXT, 0,
@@ -3160,7 +3233,7 @@ loader_get_manifest_files(const struct loader_instance *inst,
                 char *home = secure_getenv("HOME");
                 if (home != NULL) {
                     char *home_loc = loader_stack_alloc(strlen(home) + 16 +
-                                                        strlen(home_location));
+                                                        strlen(relative_location));
                     if (home_loc == NULL) {
                         loader_log(
                             inst, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
@@ -3178,15 +3251,15 @@ loader_get_manifest_files(const struct loader_instance *inst,
                     }
                     strcat(home_loc, ".local/share");
 
-                    if (home_location[0] != DIRECTORY_SYMBOL) {
+                    if (relative_location[0] != DIRECTORY_SYMBOL) {
                         len = strlen(home_loc);
                         home_loc[len] = DIRECTORY_SYMBOL;
                         home_loc[len + 1] = '\0';
                     }
-                    strcat(home_loc, home_location);
+                    strcat(home_loc, relative_location);
                     file = home_loc;
                     next_file = loader_get_next_path(file);
-                    home_location = NULL;
+                    relative_location = NULL;
 
                     loader_log(
                         inst, VK_DEBUG_REPORT_DEBUG_BIT_EXT, 0,
@@ -3263,7 +3336,7 @@ VkResult loader_icd_scan(const struct loader_instance *inst,
     // Get a list of manifest files for ICDs
     res = loader_get_manifest_files(inst, "VK_ICD_FILENAMES", NULL, false, true,
                                     DEFAULT_VK_DRIVERS_INFO,
-                                    HOME_VK_DRIVERS_INFO, &manifest_files);
+                                    RELATIVE_VK_DRIVERS_INFO, &manifest_files);
     if (VK_SUCCESS != res || manifest_files.count == 0) {
         goto out;
     }
@@ -3490,7 +3563,7 @@ void loader_layer_scan(const struct loader_instance *inst,
     if (VK_SUCCESS !=
         loader_get_manifest_files(inst, LAYERS_PATH_ENV, LAYERS_SOURCE_PATH,
                                   true, true, DEFAULT_VK_ELAYERS_INFO,
-                                  HOME_VK_ELAYERS_INFO, &manifest_files[0])) {
+                                  RELATIVE_VK_ELAYERS_INFO, &manifest_files[0])) {
         goto out;
     }
 
@@ -3499,7 +3572,7 @@ void loader_layer_scan(const struct loader_instance *inst,
     // overridden by LAYERS_PATH_ENV
     if (VK_SUCCESS != loader_get_manifest_files(inst, NULL, NULL, true, false,
                                                 DEFAULT_VK_ILAYERS_INFO,
-                                                HOME_VK_ILAYERS_INFO,
+                                                RELATIVE_VK_ILAYERS_INFO,
                                                 &manifest_files[1])) {
         goto out;
     }
@@ -3569,7 +3642,7 @@ void loader_implicit_layer_scan(const struct loader_instance *inst,
     // overridden by LAYERS_PATH_ENV
     VkResult res = loader_get_manifest_files(
         inst, NULL, NULL, true, false, DEFAULT_VK_ILAYERS_INFO,
-        HOME_VK_ILAYERS_INFO, &manifest_files);
+        RELATIVE_VK_ILAYERS_INFO, &manifest_files);
     if (VK_SUCCESS != res || manifest_files.count == 0) {
         return;
     }
diff --git a/loader/vk_loader_platform.h b/loader/vk_loader_platform.h
index dc4ac10..50a7966 100644
--- a/loader/vk_loader_platform.h
+++ b/loader/vk_loader_platform.h
@@ -57,47 +57,9 @@
 #define VULKAN_ILAYERCONF_DIR "implicit_layer.d"
 #define VULKAN_LAYER_DIR      "layer"
 
-#if defined(EXTRASYSCONFDIR)
-#define EXTRA_DRIVERS_SYSCONFDIR_INFO ":"                                      \
-    EXTRASYSCONFDIR VULKAN_DIR VULKAN_ICDCONF_DIR
-#define EXTRA_ELAYERS_SYSCONFDIR_INFO ":"                                      \
-    EXTRASYSCONFDIR VULKAN_DIR VULKAN_ELAYERCONF_DIR
-#define EXTRA_ILAYERS_SYSCONFDIR_INFO ":"                                      \
-    EXTRASYSCONFDIR VULKAN_DIR VULKAN_ILAYERCONF_DIR
-#else
-#define EXTRA_DRIVERS_SYSCONFDIR_INFO
-#define EXTRA_ELAYERS_SYSCONFDIR_INFO
-#define EXTRA_ILAYERS_SYSCONFDIR_INFO
-#endif
-
-#if defined(EXTRADATADIR)
-#define EXTRA_DRIVERS_DATADIR_INFO ":"                                         \
-    EXTRADATADIR VULKAN_DIR VULKAN_ICDCONF_DIR
-#define EXTRA_ELAYERS_DATADIR_INFO ":"                                         \
-    EXTRADATADIR VULKAN_DIR VULKAN_ELAYERCONF_DIR
-#define EXTRA_ILAYERS_DATADIR_INFO ":"                                         \
-    EXTRADATADIR VULKAN_DIR VULKAN_ILAYERCONF_DIR
-#else
-#define EXTRA_DRIVERS_DATADIR_INFO
-#define EXTRA_ELAYERS_DATADIR_INFO
-#define EXTRA_ILAYERS_DATADIR_INFO
-#endif
-
-#define DEFAULT_VK_DRIVERS_INFO                                                \
-    SYSCONFDIR   VULKAN_DIR VULKAN_ICDCONF_DIR ":"                             \
-    DATADIR      VULKAN_DIR VULKAN_ICDCONF_DIR                                 \
-    EXTRA_DRIVERS_SYSCONFDIR_INFO                                              \
-    EXTRA_DRIVERS_DATADIR_INFO
-#define DEFAULT_VK_ELAYERS_INFO                                                \
-    SYSCONFDIR   VULKAN_DIR VULKAN_ELAYERCONF_DIR ":"                          \
-    DATADIR      VULKAN_DIR VULKAN_ELAYERCONF_DIR                              \
-    EXTRA_ELAYERS_SYSCONFDIR_INFO                                              \
-    EXTRA_ELAYERS_DATADIR_INFO
-#define DEFAULT_VK_ILAYERS_INFO                                                \
-    SYSCONFDIR   VULKAN_DIR VULKAN_ILAYERCONF_DIR ":"                          \
-    DATADIR      VULKAN_DIR VULKAN_ILAYERCONF_DIR                              \
-    EXTRA_ILAYERS_SYSCONFDIR_INFO                                              \
-    EXTRA_ILAYERS_DATADIR_INFO
+#define DEFAULT_VK_DRIVERS_INFO ""
+#define DEFAULT_VK_ELAYERS_INFO ""
+#define DEFAULT_VK_ILAYERS_INFO ""
 
 #define DEFAULT_VK_DRIVERS_PATH ""
 #if !defined(DEFAULT_VK_LAYERS_PATH)
@@ -109,9 +71,9 @@
 #endif
 #define LAYERS_PATH_ENV "VK_LAYER_PATH"
 
-#define HOME_VK_DRIVERS_INFO VULKAN_DIR VULKAN_ICDCONF_DIR
-#define HOME_VK_ELAYERS_INFO VULKAN_DIR VULKAN_ELAYERCONF_DIR
-#define HOME_VK_ILAYERS_INFO VULKAN_DIR VULKAN_ILAYERCONF_DIR
+#define RELATIVE_VK_DRIVERS_INFO VULKAN_DIR VULKAN_ICDCONF_DIR
+#define RELATIVE_VK_ELAYERS_INFO VULKAN_DIR VULKAN_ELAYERCONF_DIR
+#define RELATIVE_VK_ILAYERS_INFO VULKAN_DIR VULKAN_ILAYERCONF_DIR
 
 // C99:
 #define PRINTF_SIZE_T_SPECIFIER "%zu"
@@ -251,9 +213,9 @@ loader_platform_thread_cond_broadcast(loader_platform_thread_cond *pCond) {
 #define LAYERS_SOURCE_PATH NULL
 #endif
 #define LAYERS_PATH_ENV "VK_LAYER_PATH"
-#define HOME_VK_DRIVERS_INFO ""
-#define HOME_VK_ELAYERS_INFO ""
-#define HOME_VK_ILAYERS_INFO ""
+#define RELATIVE_VK_DRIVERS_INFO ""
+#define RELATIVE_VK_ELAYERS_INFO ""
+#define RELATIVE_VK_ILAYERS_INFO ""
 #define PRINTF_SIZE_T_SPECIFIER "%Iu"
 
 // File IO