| // Copyright 2014-2021 The Khronos Group, Inc. |
| // |
| // SPDX-License-Identifier: CC-BY-4.0 |
| |
| include::{generated}/meta/{refprefix}VK_KHR_incremental_present.txt[] |
| |
| === Other Extension Metadata |
| |
| *Last Modified Date*:: |
| 2016-11-02 |
| *IP Status*:: |
| No known IP claims. |
| *Contributors*:: |
| - Ian Elliott, Google |
| - Jesse Hall, Google |
| - Alon Or-bach, Samsung |
| - James Jones, NVIDIA |
| - Daniel Rakos, AMD |
| - Ray Smith, ARM |
| - Mika Isojarvi, Google |
| - Jeff Juliano, NVIDIA |
| - Jeff Bolz, NVIDIA |
| |
| === Description |
| |
| This device extension extends flink:vkQueuePresentKHR, from the |
| `apiext:VK_KHR_swapchain` extension, allowing an application to specify a |
| list of rectangular, modified regions of each image to present. |
| This should be used in situations where an application is only changing a |
| small portion of the presentable images within a swapchain, since it enables |
| the presentation engine to avoid wasting time presenting parts of the |
| surface that have not changed. |
| |
| This extension is leveraged from the `EGL_KHR_swap_buffers_with_damage` |
| extension. |
| |
| include::{generated}/interfaces/VK_KHR_incremental_present.txt[] |
| |
| === Issues |
| |
| 1) How should we handle steroescopic-3D swapchains? We need to add a layer |
| for each rectangle. |
| One approach is to create another struct containing the slink:VkRect2D plus |
| layer, and have slink:VkPresentRegionsKHR point to an array of that struct. |
| Another approach is to have two parallel arrays, ptext:pRectangles and |
| ptext:pLayers, where ptext:pRectangles[i] and ptext:pLayers[i] must be used |
| together. |
| Which approach should we use, and if the array of a new structure, what |
| should that be called? |
| |
| *RESOLVED*: Create a new structure, which is a slink:VkRect2D plus a layer, |
| and will be called slink:VkRectLayerKHR. |
| |
| 2) Where is the origin of the slink:VkRectLayerKHR? |
| |
| *RESOLVED*: The upper left corner of the presentable image(s) of the |
| swapchain, per the definition of framebuffer coordinates. |
| |
| 3) Does the rectangular region, slink:VkRectLayerKHR, specify pixels of the |
| swapchain's image(s), or of the surface? |
| |
| *RESOLVED*: Of the image(s). |
| Some presentation engines may scale the pixels of a swapchain's image(s) to |
| the size of the surface. |
| The size of the swapchain's image(s) will be consistent, where the size of |
| the surface may vary over time. |
| |
| 4) What if all of the rectangles for a given swapchain contain a width |
| and/or height of zero? |
| |
| *RESOLVED*: The application is indicating that no pixels changed since the |
| last present. |
| The presentation engine may use such a hint and not update any pixels for |
| the swapchain. |
| However, all other semantics of flink:vkQueuePresentKHR must still be |
| honored, including waiting for semaphores to signal. |
| |
| 5) When the swapchain is created with |
| sname:VkSwapchainCreateInfoKHR::pname:preTransform set to a value other than |
| ename:VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR, should the rectangular region, |
| slink:VkRectLayerKHR, be transformed to align with the pname:preTransform? |
| |
| *RESOLVED*: No. |
| The rectangular region in slink:VkRectLayerKHR should not be tranformed. |
| As such, it may not align with the extents of the swapchain's image(s). |
| It is the responsibility of the presentation engine to transform the |
| rectangular region. |
| This matches the behavior of the Android presentation engine, which set the |
| precedent. |
| |
| === Version History |
| |
| * Revision 1, 2016-11-02 (Ian Elliott) |
| - Internal revisions |
| * Revision 2, 2021-03-18 (Ian Elliott) |
| - Clarified alignment of rectangles for presentation engines that support |
| transformed swapchains. |