speed control: frame skipping to decouple terminal draw from emulation

Emulation always runs at native rate (correct game speed); --frameskip N draws
only 1 of every N+1 frames so a slow terminal no longer bottlenecks the loop.
Adds --fps cap, --uncapped/--turbo, live [ ] and f keys, HUD readout, and an
exit summary of emulated-vs-drawn fps. Replaces the confusing --render-fps.

1 files changed, 27 insertions, 2 deletions

diff --git a/src/render.c b/src/render.c
index f659da3..df39c99 100644
--- a/src/render.c
+++ b/src/render.c
@@ -51,8 +51,19 @@ static char outbuf[SCREEN_W * (SCREEN_H/2) * 40 + 4096];
 static u8 prev_fb[SCREEN_H][SCREEN_W][3];
 static bool need_full = true;              // force a complete repaint
 static volatile sig_atomic_t resized = 0;  // set by SIGWINCH
+static int  hud_frameskip = 0;
+static bool hud_turbo = false;
 
 void render_force_full(void) { need_full = true; }
+
+// Update the on-screen HUD values; forces a status-line repaint on change.
+void render_set_hud(int frameskip, bool turbo) {
+    if (frameskip != hud_frameskip || turbo != hud_turbo) {
+        hud_frameskip = frameskip;
+        hud_turbo = turbo;
+        need_full = true;
+    }
+}
 static void on_winch(int s) { (void)s; resized = 1; }
 
 void render_frame(GB *gb) {
@@ -99,8 +110,9 @@ void render_frame(GB *gb) {
     // status line: static text, only (re)draw on a full repaint
     if (need_full) {
         o += sprintf(o, "\x1b[0m\x1b[%d;1H\x1b[38;2;150;150;150m %.*s  "
-                        "[wasd/arrows] z:A x:B space:sel enter:start q:quit",
-                        SCREEN_H/2 + 1, 15, gb->cart.title);
+                        "skip:%d%s  [f]ast [ ][ ] q:quit\x1b[K",
+                        SCREEN_H/2 + 1, 12, gb->cart.title,
+                        hud_frameskip, hud_turbo ? " TURBO" : "");
     }
 
     memcpy(prev_fb, p->fb, sizeof(prev_fb));
@@ -119,8 +131,18 @@ void render_frame(GB *gb) {
 //   decay[] : momentary presses (keyboard, or FIFO taps), count down per frame
 static int  decay[8];       // frames remaining for each BTN bit position
 static u8   held;           // explicitly-held buttons (FIFO)
+static int  turbo_toggles;  // pending fast-forward toggles (consumed by main)
+static int  frameskip_delta;// pending frameskip adjustment (consumed by main)
 #define HOLD_FRAMES 4
 
+bool input_take_turbo(void) {
+    if (turbo_toggles > 0) { turbo_toggles--; return true; }
+    return false;
+}
+int input_take_frameskip_delta(void) {
+    int d = frameskip_delta; frameskip_delta = 0; return d;
+}
+
 static int mask_index(int mask) {
     for (int i = 0; i < 8; i++) if ((1 << i) == mask) return i;
     return -1;
@@ -226,6 +248,9 @@ bool input_poll(GB *gb) {
             case 'x': case 'k': tap(BTN_B, HOLD_FRAMES); break;
             case '\r': case '\n': tap(BTN_START, HOLD_FRAMES); break;
             case ' ': tap(BTN_SELECT, HOLD_FRAMES); break;
+            case 'f': turbo_toggles++; break;   // toggle fast-forward
+            case '[': frameskip_delta--; break; // fewer skipped frames
+            case ']': frameskip_delta++; break; // more skipped frames
             case 'q': case 3: quit = true; break;
         }
     }