vo_gpu_next: retrieve the preferred PRIM and TRF from the swapchain

This patch allows vo_gpu_next to automatically switch to the preferred
primaries and transfer function of the current output without the user
having to specify them on the command line.

Without this patch, libplacebo will always pick an HDR color space that
will require the compositor to perform tone and gamut mapping on SDR
outputs.  This will likely be of lower quality than what libplacebo can
achieve when it instead picks an SDR color space.

Author: mahkoh

video/out/d3d11/context.c

@@ -189,7 +189,8 @@ static int d3d11_color_depth(struct ra_swapchain *sw)
     return MPMIN(ra_fmt->component_depth[0], desc1.BitsPerColor);
 }
 
-static struct pl_color_space d3d11_target_color_space(struct ra_swapchain *sw)
+static struct pl_color_space d3d11_target_color_space(struct ra_swapchain *sw,
+                                                      bool *target_is_preferred)
 {
     struct priv *p = sw->priv;
 

video/out/gpu/context.h

@@ -115,7 +115,7 @@ struct ra_swapchain_fns {
     int (*color_depth)(struct ra_swapchain *sw);
 
     // Target device color space. Optional.
-    pl_color_space_t (*target_csp)(struct ra_swapchain *sw);
+    pl_color_space_t (*target_csp)(struct ra_swapchain *sw, bool *target_is_preferred);
 
     // Called when rendering starts. Returns NULL on failure. This must be
     // followed by submit_frame, to submit the rendered frame. This function

video/out/opengl/context.c

@@ -305,11 +305,14 @@ static void ra_gl_ctx_get_vsync(struct ra_swapchain *sw,
         p->params.get_vsync(sw->ctx, info);
 }
 
-static pl_color_space_t ra_gl_ctx_target_csp(struct ra_swapchain *sw)
+static pl_color_space_t ra_gl_ctx_target_csp(struct ra_swapchain *sw,
+                                             bool *target_is_preferred)
 {
     struct priv *p = sw->priv;
-    if (p->params.preferred_csp)
+    if (p->params.preferred_csp) {
+        *target_is_preferred = true;
         return p->params.preferred_csp(sw->ctx);
+    }
     return DEFAULT_TARGET_CSP;
 }
 

video/out/vo_gpu_next.c

@@ -984,11 +984,12 @@ static bool draw_frame(struct vo *vo, struct vo_frame *frame)
     struct ra_swapchain *sw = p->ra_ctx->swapchain;
 
     bool pass_colorspace = false;
+    bool target_csp_is_preferred = false;
     struct pl_color_space target_csp;
     // Assume HDR is supported, if query is not available
     // TODO: Implement this for all backends
     target_csp = sw->fns->target_csp
-                     ? sw->fns->target_csp(sw)
+                     ? sw->fns->target_csp(sw, &target_csp_is_preferred)
                      : DEFAULT_TARGET_CSP;
     if (!pl_color_transfer_is_hdr(target_csp.transfer)) {
         target_csp.hdr.max_luma = 0;
@@ -1001,13 +1002,21 @@ static bool draw_frame(struct vo *vo, struct vo_frame *frame)
                        (p->next_opts->target_hint == -1 &&
                         pl_color_transfer_is_hdr(target_csp.transfer));
     if (target_hint && frame->current) {
+        enum pl_color_primaries primaries = opts->target_prim;
+        enum pl_color_transfer transfer = opts->target_trc;
+        if (target_csp_is_preferred) {
+            if (!primaries)
+                primaries = target_csp.primaries;
+            if (!transfer)
+                transfer = target_csp.transfer;
+        }
         hint = frame->current->params.color;
         if (p->ra_ctx->fns->pass_colorspace && p->ra_ctx->fns->pass_colorspace(p->ra_ctx))
             pass_colorspace = true;
-        if (opts->target_prim)
-            hint.primaries = opts->target_prim;
-        if (opts->target_trc)
-            hint.transfer = opts->target_trc;
+        if (primaries)
+            hint.primaries = primaries;
+        if (transfer)
+            hint.transfer = transfer;
         if (target_peak)
             hint.hdr.max_luma = target_peak;
         apply_target_contrast(p, &hint, target_csp.hdr.min_luma);

video/out/vulkan/context.c

@@ -375,11 +375,13 @@ static void get_vsync(struct ra_swapchain *sw,
         p->params.get_vsync(sw->ctx, info);
 }
 
-static pl_color_space_t target_csp(struct ra_swapchain *sw)
+static pl_color_space_t target_csp(struct ra_swapchain *sw, bool *target_is_preferred)
 {
     struct priv *p = sw->priv;
-    if (p->params.preferred_csp)
+    if (p->params.preferred_csp) {
+        *target_is_preferred = true;
         return p->params.preferred_csp(sw->ctx);
+    }
     return DEFAULT_TARGET_CSP;
 }