vulkan: add pl_vulkan_swapchain_params.disable_10bit_sdr

To mirror the D3D11 option, and to work around driver-related dithering
bugs.

See-Also: mpv-player/mpv#11862
Supersedes: https://code.videolan.org/videolan/libplacebo/-/merge_requests/494

meson.build

@@ -12,6 +12,7 @@ project('libplacebo', ['c', 'cpp'],
     6,
     # API version
     {
+      '294': 'add pl_vulkan_swapchain_params.disable_10bit_sdr',
       '293': 'add pl_test_pixfmt_caps',
       '292': 'add pl_peak_detect_high_quality_params and pl_color_map_high_quality_params',
       '291': 'add PL_COLOR_HDR_BLACK, PL_COLOR_SDR_CONTRAST and PL_COLOR_HLG_PEAK',

src/include/libplacebo/vulkan.h

@@ -347,6 +347,11 @@ struct pl_vulkan_swapchain_params {
     // calling `pl_swapchain_resize` as appropriate. libplacebo will tolerate
     // the "suboptimal" status indefinitely.
     bool allow_suboptimal;
+
+    // Disable high-bit (10 or more) SDR formats. May help work around buggy
+    // drivers which don't dither properly when outputting high bit depth
+    // SDR backbuffers to 8-bit screens.
+    bool disable_10bit_sdr;
 };
 
 #define pl_vulkan_swapchain_params(...) (&(struct pl_vulkan_swapchain_params) { __VA_ARGS__ })

src/vulkan/swapchain.c

@@ -163,6 +163,9 @@ static bool pick_surf_format(pl_swapchain sw, const struct pl_color_space *hint)
         if (!map_color_space(p->formats.elem[i].colorSpace, &space))
             continue;
 
+        bool disable10 = !pl_color_transfer_is_hdr(space.transfer) &&
+                         p->params.disable_10bit_sdr;
+
         switch (p->formats.elem[i].format) {
         // Only accept floating point formats for linear curves
         case VK_FORMAT_R16G16B16_SFLOAT:
@@ -188,14 +191,16 @@ static bool pick_surf_format(pl_swapchain sw, const struct pl_color_space *hint)
         // Only accept 10 bit formats for non-linear curves
         case VK_FORMAT_A2R10G10B10_UNORM_PACK32:
         case VK_FORMAT_A2B10G10R10_UNORM_PACK32:
-            if (space.transfer != PL_COLOR_TRC_LINEAR)
+            if (space.transfer != PL_COLOR_TRC_LINEAR && !disable10)
                 break; // accept
             continue;
 
         // Accept 16-bit formats for everything
         case VK_FORMAT_R16G16B16_UNORM:
         case VK_FORMAT_R16G16B16A16_UNORM:
-             break; // accept
+            if (!disable10)
+                break; // accept
+            continue;
 
         default: continue;
         }