vulkan: add vk_x11_strict_image_count option

This option strictly allocate the minImageCount given by the
application at swapchain creation.

This works around application that do not deal with the fact that the
implementation allocates more images than the minimum specified.

v2: Add values in default drirc (Bas)

v3: specify engine name/version (Lionel)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111522
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Cc: 19.2 <mesa-stable@lists.freedesktop.org>
diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
index 7a6af56..bdc38a5 100644
--- a/src/amd/vulkan/radv_device.c
+++ b/src/amd/vulkan/radv_device.c
@@ -559,6 +559,7 @@
 	DRI_CONF_SECTION_PERFORMANCE
 		DRI_CONF_ADAPTIVE_SYNC("true")
 		DRI_CONF_VK_X11_OVERRIDE_MIN_IMAGE_COUNT(0)
+		DRI_CONF_VK_X11_STRICT_IMAGE_COUNT("false")
 	DRI_CONF_SECTION_END
 DRI_CONF_END;
 
diff --git a/src/intel/vulkan/anv_device.c b/src/intel/vulkan/anv_device.c
index b458c15..50d9107 100644
--- a/src/intel/vulkan/anv_device.c
+++ b/src/intel/vulkan/anv_device.c
@@ -52,6 +52,7 @@
 DRI_CONF_BEGIN
    DRI_CONF_SECTION_PERFORMANCE
       DRI_CONF_VK_X11_OVERRIDE_MIN_IMAGE_COUNT(0)
+      DRI_CONF_VK_X11_STRICT_IMAGE_COUNT("false")
    DRI_CONF_SECTION_END
 DRI_CONF_END;
 
diff --git a/src/util/00-mesa-defaults.conf b/src/util/00-mesa-defaults.conf
index 3deb8ae..8f3e847 100644
--- a/src/util/00-mesa-defaults.conf
+++ b/src/util/00-mesa-defaults.conf
@@ -469,6 +469,15 @@
         <application name="Rayman Legends" executable="Rayman Legends.exe">
             <option name="dynamic_texture_workaround" value="true" />
         </application>
+
+        <!-- Vulkan workarounds: -->
+
+        <!-- Works around the game not starting (does not deal with
+             the implementation returning more images than the minimum
+             specified by the application. -->
+        <engine engine_name_match="UnrealEngine4.*" engine_versions="0:21">
+            <option name="vk_x11_strict_image_count" value="true" />
+        </engine>
     </device>
     <!-- vmwgfx doesn't like full buffer swaps and can't sync to vertical retraces.-->
     <device driver="vmwgfx">
diff --git a/src/util/xmlpool/t_options.h b/src/util/xmlpool/t_options.h
index 9f3dee4..e08ba1b 100644
--- a/src/util/xmlpool/t_options.h
+++ b/src/util/xmlpool/t_options.h
@@ -225,6 +225,11 @@
         DRI_CONF_DESC(en,gettext("Override the VkSurfaceCapabilitiesKHR::minImageCount (0 = no override)")) \
 DRI_CONF_OPT_END
 
+#define DRI_CONF_VK_X11_STRICT_IMAGE_COUNT(def) \
+DRI_CONF_OPT_BEGIN_B(vk_x11_strict_image_count, def) \
+        DRI_CONF_DESC(en,gettext("Force the X11 WSI to create exactly the number of image specified by the application in VkSwapchainCreateInfoKHR::minImageCount")) \
+DRI_CONF_OPT_END
+
 #define DRI_CONF_MESA_GLTHREAD(def) \
 DRI_CONF_OPT_BEGIN_B(mesa_glthread, def) \
         DRI_CONF_DESC(en,gettext("Enable offloading GL driver work to a separate thread")) \
diff --git a/src/vulkan/wsi/wsi_common.h b/src/vulkan/wsi/wsi_common.h
index b00fc3c..064b16a 100644
--- a/src/vulkan/wsi/wsi_common.h
+++ b/src/vulkan/wsi/wsi_common.h
@@ -113,6 +113,11 @@
       /* Override the minimum number of images on the swapchain.
        * 0 = no override */
       uint32_t override_minImageCount;
+
+      /* Forces strict number of image on the swapchain using application
+       * provided VkSwapchainCreateInfoKH::RminImageCount.
+       */
+      bool strict_imageCount;
    } x11;
 
    uint64_t (*image_get_modifier)(VkImage image);
diff --git a/src/vulkan/wsi/wsi_common_x11.c b/src/vulkan/wsi/wsi_common_x11.c
index af61bb9..491bd8a 100644
--- a/src/vulkan/wsi/wsi_common_x11.c
+++ b/src/vulkan/wsi/wsi_common_x11.c
@@ -1413,7 +1413,9 @@
    assert(pCreateInfo->sType == VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR);
 
    unsigned num_images = pCreateInfo->minImageCount;
-   if (present_mode == VK_PRESENT_MODE_MAILBOX_KHR)
+   if (wsi_device->x11.strict_imageCount)
+      num_images = pCreateInfo->minImageCount;
+   else if (present_mode == VK_PRESENT_MODE_MAILBOX_KHR)
       num_images = MAX2(num_images, 5);
 
    xcb_connection_t *conn = x11_surface_get_connection(icd_surface);
@@ -1630,6 +1632,10 @@
          wsi_device->x11.override_minImageCount =
             driQueryOptioni(dri_options, "vk_x11_override_min_image_count");
       }
+      if (driCheckOption(dri_options, "vk_x11_strict_image_count", DRI_BOOL)) {
+         wsi_device->x11.strict_imageCount =
+            driQueryOptionb(dri_options, "vk_x11_strict_image_count");
+      }
    }
 
    wsi->base.get_support = x11_surface_get_support;