runtime: present-time scanline post-process (host display enhancement)

recompiler/src/config_loader.cpp

@@ -635,6 +635,15 @@ static RuntimeConfig parse_runtime_block(const toml::value& cfg, const fs::path&
                 "[video] crt_filter must be \"raw\"|\"crt\"|\"composite\"|\"trinitron\": {}",
                 mode));
         }
+        if (video.contains("scanlines")) {
+            rt.video_scanlines = toml::find<bool>(video, "scanlines");
+        }
+        if (video.contains("scanline_strength")) {
+            double s = toml::find<double>(video, "scanline_strength");
+            if (s < 0.0) s = 0.0;
+            if (s > 1.0) s = 1.0;
+            rt.video_scanline_strength = s;
+        }
         if (video.contains("auto_skip_fmv")) {
             rt.video_auto_skip_fmv = toml::find<bool>(video, "auto_skip_fmv");
         }
@@ -2296,6 +2305,15 @@ UserSettings load_user_settings(const fs::path& path) {
             else if (m == "composite") { s.screen_kind = 2; s.has_screen_kind = true; }
             else if (m == "trinitron") { s.screen_kind = 3; s.has_screen_kind = true; }
         });
+        if (v.contains("scanlines")) try_get([&]{
+            s.scanlines = toml::find<bool>(v, "scanlines"); s.has_scanlines = true;
+        });
+        if (v.contains("scanline_strength")) try_get([&]{
+            double d = toml::find<double>(v, "scanline_strength");
+            if (d < 0.0) d = 0.0;
+            if (d > 1.0) d = 1.0;
+            s.scanline_strength = d; s.has_scanline_strength = true;
+        });
         if (v.contains("auto_skip_fmv")) try_get([&]{
             s.auto_skip_fmv = toml::find<bool>(v, "auto_skip_fmv"); s.has_auto_skip_fmv = true;
         });
@@ -2615,6 +2633,10 @@ bool save_user_settings(const fs::path& path, const UserSettings& s) {
                       : s.screen_kind == 3 ? "trinitron" : "raw";
         f << "crt_filter        = \"" << k << "\"\n";
     }
+    if (s.has_scanlines)
+        f << "scanlines         = " << (s.scanlines ? "true" : "false") << "\n";
+    if (s.has_scanline_strength)
+        f << "scanline_strength = " << s.scanline_strength << "\n";
     if (s.has_auto_skip_fmv)
         f << "auto_skip_fmv     = " << (s.auto_skip_fmv ? "true" : "false") << "\n";
     /* turbo_loads is deliberately NOT written back: it is deprecated and no

recompiler/src/config_loader.h

@@ -488,6 +488,13 @@ struct RuntimeConfig {
     // PSX_SCREEN env var overrides this at runtime (debug path).
     int                   video_screen_kind = 0;
 
+    // scanlines: present-time horizontal scanline darkening (host enhancement,
+    // orthogonal to crt_filter's colour LUT — the two compose). Off by default;
+    // scanline_strength 0..1 is the dark-gap depth. PSX_SCANLINES /
+    // PSX_SCANLINE_STRENGTH override at runtime (debug path).
+    bool                  video_scanlines = false;
+    double                video_scanline_strength = 0.5;
+
     // auto_skip_fmv: when true, full-motion videos (streaming XA audio + MDEC
     // video) are skipped the instant they're detected — presentation + pacing are
     // suppressed and audio muted for the duration, so an FMV ends in a fraction of
@@ -1196,6 +1203,10 @@ struct UserSettings {
     bool has_geometry_correction   = false; bool geometry_correction   = false;
     bool has_perspective_texturing = false; bool perspective_texturing = false;
     bool has_screen_kind    = false; int  screen_kind    = 0; // 0..3 (ScreenKind)
+    // Scanline post-process (see RuntimeConfig::video_scanlines). Strength stored
+    // 0..1; the launcher ABI carries it as an integer percent.
+    bool has_scanlines         = false; bool   scanlines         = false;
+    bool has_scanline_strength = false; double scanline_strength = 0.5;
     bool has_auto_skip_fmv  = false; bool auto_skip_fmv  = false; // skip FMVs
     // [video] turbo_loads: DEPRECATED AND IGNORED — the legacy home of the
     // generic Turbo loads switch, back when the launcher drew a row for it.

runtime/include/gpu_gl_renderer.h

@@ -122,6 +122,14 @@ int gl_renderer_present_wide_fbo(int disp_x, int disp_y, int disp_h, int linear)
  * for the widescreen field-of-view hack. */
 void gl_renderer_set_display_aspect(int num, int den);
 
+/* Scanline post-process (host display setting). on toggles the effect; strength
+ * (0..1) is the depth of the dark gap between PS1 scanlines. Applied at the
+ * native display-line pitch in the present/interpolation shaders, and faded in
+ * with output scale so it never shimmers on a sub-2x window. gl_renderer_get_
+ * scanlines returns the on flag and (via out-param) the current strength. */
+void gl_renderer_set_scanlines(int on, float strength);
+int  gl_renderer_get_scanlines(float *strength);
+
 /* Select full native-wide mirror rendering instead of the centre-splice fast
  * path. Textured edge expansion needs the complete mirror surface. */
 void gl_renderer_set_wide_fast(int on);

runtime/include/host_keymap.h

@@ -21,6 +21,7 @@ typedef enum HostKeymapAction {
     HOST_KEYMAP_DISPLAY_PERF,
     HOST_KEYMAP_REWIND,           /* default F8 */
     HOST_KEYMAP_SAVE_STATE_MENU,  /* default F7 */
+    HOST_KEYMAP_SCANLINES,        /* default F6 */
     HOST_KEYMAP_ACTION_COUNT
 } HostKeymapAction;
 

runtime/src/debug_server.c

@@ -7846,6 +7846,25 @@ static void handle_ws_nw(int id, const char *json)
              id, psx_ws_get_native_wide(), ws.mode, ws.nw_extra);
 }
 
+/* Live scanline post-process toggle (A/B): `scanline on=<0|1> pct=<0..100>`.
+ * Either field is optional — omit `on` to keep the current toggle, omit `pct`
+ * to keep the current strength. Reports the resulting state. */
+extern void psx_video_set_scanlines(int on, float strength);
+extern int  psx_video_get_scanlines(float *strength);
+static void handle_scanline(int id, const char *json)
+{
+    int on  = json_get_int(json, "on", -1);
+    int pct = json_get_int(json, "pct", -1);
+    float cur = 0.f;
+    int cur_on = psx_video_get_scanlines(&cur);
+    int new_on = (on >= 0) ? (on ? 1 : 0) : cur_on;
+    float new_s = (pct >= 0 && pct <= 100) ? (float)pct / 100.f : cur;
+    psx_video_set_scanlines(new_on, new_s);
+    cur_on = psx_video_get_scanlines(&cur);
+    send_fmt("{\"id\":%d,\"ok\":true,\"scanlines\":%d,\"strength_pct\":%d}",
+             id, cur_on, (int)(cur * 100.f + 0.5f));
+}
+
 /* ws_backdrop_ring: dump the always-on auto_backdrop rewrite ring (which windows
  * fire, live extent/camera/DL-count, orig vs final bound). Read-only; small
  * heap envelope so the per-byte stall of a giant read is never in play. */
@@ -13531,6 +13550,7 @@ static const CmdEntry s_commands[] = {
     { "kernel_bless",      handle_kernel_bless },
     { "ws_aspect",         handle_ws_aspect },
     { "ws_nw",             handle_ws_nw },
+    { "scanline",          handle_scanline },
     { "ws_backdrop_ring",  handle_ws_backdrop_ring },
     { "ws_ui_groups",      handle_ws_ui_groups },
     { "ws_backdrop_margin", handle_ws_backdrop_margin },