[gtk+] Add an api to create intermediate textures

[Matthias Clasen <matthiasc src gnome org>]

commit ff188f6bf075d2fe3f6a4faa401a4a83c80af483
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Sep 26 19:12:20 2017 -0400

    Add an api to create intermediate textures
    
    The new function creates a vulkan image that is suitable for
    use as a framebuffer to render to and as a texture to read from.

 gsk/gskvulkanimage.c        |   29 ++++++++++++++++++++++++++---
 gsk/gskvulkanimageprivate.h |    3 +++
 2 files changed, 29 insertions(+), 3 deletions(-)
---
diff --git a/gsk/gskvulkanimage.c b/gsk/gskvulkanimage.c
index 1eb9c3a..f64a3ac 100644
--- a/gsk/gskvulkanimage.c
+++ b/gsk/gskvulkanimage.c
@@ -148,7 +148,7 @@ gsk_vulkan_uploader_upload (GskVulkanUploader *self)
 
       command_buffer = gsk_vulkan_command_pool_get_buffer (self->command_pool);
       vkCmdPipelineBarrier (command_buffer,
-                            VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT,
+                            VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT | 
VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT,
                             VK_PIPELINE_STAGE_HOST_BIT | VK_PIPELINE_STAGE_TRANSFER_BIT,
                             0,
                             0, NULL,
@@ -604,6 +604,29 @@ gsk_vulkan_image_new_for_atlas (GdkVulkanContext *context,
   return self;
 }
 
+GskVulkanImage *
+gsk_vulkan_image_new_for_texture (GdkVulkanContext *context,
+                                  gsize             width,
+                                  gsize             height)
+{
+  GskVulkanImage *self;
+
+  self = gsk_vulkan_image_new (context,
+                               width,
+                               height,
+                               VK_IMAGE_TILING_OPTIMAL,
+                               VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT |
+                               VK_IMAGE_USAGE_SAMPLED_BIT |
+                               VK_IMAGE_USAGE_TRANSFER_SRC_BIT,
+                               VK_IMAGE_LAYOUT_UNDEFINED,
+                               0,
+                               VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);
+
+  gsk_vulkan_image_ensure_view (self, VK_FORMAT_B8G8R8A8_UNORM);
+
+  return self;
+}
+
 GskTexture *
 gsk_vulkan_image_download (GskVulkanImage    *self,
                            GskVulkanUploader *uploader)
@@ -615,14 +638,14 @@ gsk_vulkan_image_download (GskVulkanImage    *self,
   gsk_vulkan_uploader_add_image_barrier (uploader,
                                          FALSE,
                                          self,
-                                         VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
+                                         VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
                                          VK_ACCESS_TRANSFER_READ_BIT);
 
   buffer = gsk_vulkan_buffer_new_download (self->vulkan, self->width * self->height * 4);
 
   vkCmdCopyImageToBuffer (gsk_vulkan_uploader_get_copy_buffer (uploader),
                           self->vk_image,
-                          VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
+                          VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
                           gsk_vulkan_buffer_get_buffer (buffer),
                           1,
                           (VkBufferImageCopy[1]) {
diff --git a/gsk/gskvulkanimageprivate.h b/gsk/gskvulkanimageprivate.h
index 8676062..f6223e9 100644
--- a/gsk/gskvulkanimageprivate.h
+++ b/gsk/gskvulkanimageprivate.h
@@ -51,6 +51,9 @@ GskVulkanImage *        gsk_vulkan_image_new_for_framebuffer            (GdkVulk
 GskVulkanImage *        gsk_vulkan_image_new_for_atlas                  (GdkVulkanContext       *context,
                                                                          gsize                   width,
                                                                          gsize                   height);
+GskVulkanImage *        gsk_vulkan_image_new_for_texture                (GdkVulkanContext       *context,
+                                                                         gsize                   width,
+                                                                         gsize                   height);
 
 GskTexture *            gsk_vulkan_image_download                       (GskVulkanImage         *self,
                                                                          GskVulkanUploader      *uploader);