vo_gpu_next: respect --blend-subtitles=<yes/no>

This brings vo_gpu_next's behavior more in line with vo_gpu. Currently,
the status quo was that `vo_gpu_next` generated subtitles with the full
resolution of the dst crop, even though practical limitations of
libplacebo meant that such subtitles inevitably got cut off at the video
boundaries. This was actually a worse status quo than `vo_gpu`, which
simply constrained subtitles to the video dimensions to prevent these
issues.

With this change, the behavior is the same as `vo_gpu`, which has the
exact same problem w.r.t interpolation. Users are back to choosing
between --blend-subtitles=yes and not having subtitles in margins,
and using --blend-subtitles=no and not having subtitle interpolation.

There are different pros and cons to each approach, and I still
ultimately plan on allowing libplacebo to interpolate subtitles even in
the black bars, to solve this issue once and for all. But for now, let's
not let perfect be the enemy of good.

No attempt is made to implement `--blend-subs=video`, which I consider
deprecated.

Fixes: https://github.com/mpv-player/mpv/issues/10272

1 files changed, 31 insertions, 11 deletions

diff --git a/video/out/vo_gpu_next.c b/video/out/vo_gpu_next.c
index e48ba4032f..22950e0b6e 100644
--- a/video/out/vo_gpu_next.c
+++ b/video/out/vo_gpu_next.c
@@ -225,8 +225,8 @@ static struct mp_image *get_image(struct vo *vo, int imgfmt, int w, int h,
 }
 
 static void update_overlays(struct vo *vo, struct mp_osd_res res, double pts,
-                            int flags, struct osd_state *state,
-                            struct pl_frame *frame)
+                            int flags, enum pl_overlay_coords coords,
+                            struct osd_state *state, struct pl_frame *frame)
 {
     struct priv *p = vo->priv;
     static const bool subfmt_all[SUBBITMAP_COUNT] = {
@@ -292,7 +292,7 @@ static void update_overlays(struct vo *vo, struct mp_osd_res res, double pts,
             .num_parts = entry->num_parts,
             .color.primaries = frame->color.primaries,
             .color.transfer = frame->color.transfer,
-            .coords = PL_OVERLAY_COORDS_DST_FRAME,
+            .coords = coords,
         };
 
         // Reject HDR/wide gamut subtitles out of the box, since these are
@@ -907,10 +907,11 @@ static void draw_frame(struct vo *vo, struct vo_frame *frame)
 
     // Calculate target
     struct pl_frame target;
-    int osd_flags = frame->current ? OSD_DRAW_OSD_ONLY : 0;
     pl_frame_from_swapchain(&target, &swframe);
     apply_target_options(p, &target);
-    update_overlays(vo, p->osd_res, 0, osd_flags, &p->osd_state, &target);
+    update_overlays(vo, p->osd_res, frame->current ? frame->current->pts : 0,
+                    (frame->current && opts->blend_subs) ? OSD_DRAW_OSD_ONLY : 0,
+                    PL_OVERLAY_COORDS_DST_FRAME, &p->osd_state, &target);
     apply_crop(&target, p->dst, swframe.fbo->params.w, swframe.fbo->params.h);
 
     struct pl_frame_mix mix = {0};
@@ -954,11 +955,29 @@ static void draw_frame(struct vo *vo, struct vo_frame *frame)
             struct frame_priv *fp = mpi->priv;
             apply_crop(image, p->src, vo->params->w, vo->params->h);
 
-            if (fp->osd_sync < p->osd_sync) {
-                // Only update the overlays if the state has changed
-                update_overlays(vo, p->osd_res, mpi->pts, OSD_DRAW_SUB_ONLY,
-                                &fp->subs, image);
-                fp->osd_sync = p->osd_sync;
+            if (opts->blend_subs) {
+                if (fp->osd_sync < p->osd_sync) {
+                    // Only update the overlays if the state has changed
+                    float rx = pl_rect_w(p->dst) / pl_rect_w(image->crop);
+                    float ry = pl_rect_h(p->dst) / pl_rect_h(image->crop);
+                    struct mp_osd_res res = {
+                        .w = pl_rect_w(p->dst),
+                        .h = pl_rect_h(p->dst),
+                        .ml = -image->crop.x0 * rx,
+                        .mr = (image->crop.x1 - vo->params->w) * rx,
+                        .mt = -image->crop.y0 * ry,
+                        .mb = (image->crop.y1 - vo->params->h) * ry,
+                        .display_par = 1.0,
+                    };
+                    update_overlays(vo, res, mpi->pts, OSD_DRAW_SUB_ONLY,
+                                    PL_OVERLAY_COORDS_DST_CROP,
+                                    &fp->subs, image);
+                    fp->osd_sync = p->osd_sync;
+                }
+            } else {
+                // Disable overlays when blend_subs is disabled
+                image->num_overlays = 0;
+                fp->osd_sync = 0;
             }
         }
     }
@@ -1180,7 +1199,8 @@ static void video_screenshot(struct vo *vo, struct voctrl_screenshot *args)
         osd_flags |= OSD_DRAW_OSD_ONLY;
     if (!args->osd)
         osd_flags |= OSD_DRAW_SUB_ONLY;
-    update_overlays(vo, osd, mpi->pts, osd_flags, &p->osd_state, &target);
+    update_overlays(vo, osd, mpi->pts, osd_flags, PL_OVERLAY_COORDS_DST_FRAME,
+                    &p->osd_state, &target);
     image.num_overlays = 0; // Disable on-screen overlays
 
     if (!pl_render_image(p->rr, &image, &target, &p->params)) {