Gamma: clamp slider to the engine's 2.6 cap, defer readback

The engine clamps mat_monitorgamma at 2.6, so the 2.8..3.0 end of the slider
did nothing. Read the value back one tick later (ClientCmd is queued) and
interpose SDL_SetWindowGammaRamp to see whether the engine pushes a ramp at
all.

1 files changed, 25 insertions, 2 deletions

diff --git a/src/gui.cpp b/src/gui.cpp
index 88e5521..e8bcac7 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -419,8 +419,9 @@ static void build_cards() {
              "Weapon model field of view (20-120; stock 54).", 20, 120,
              &g_fov_viewmodel);
   add_slider(view, "Gamma x10",
-             "mat_monitorgamma x10: 16 = 1.6, 30 = 3.0, stock is 22.", 16, 30,
-             &g_gamma);
+             "mat_monitorgamma x10: 16 = 1.6, 26 = 2.6 (engine max), stock "
+             "is 22.",
+             16, 26, &g_gamma);
 
   add_card(2, &g_fullbright, "Fullbright",
            "Ignore world lighting so dark areas are visible.", true);
@@ -2240,6 +2241,28 @@ SDL_WarpMouseGlobal(int x, int y) {
     real_warp_global(x, y);
 }
 
+// Diagnostic: tell whether mat_monitorgamma reaches the SDL gamma ramp at all.
+static int (*real_set_gamma_ramp)(void *, const unsigned short *,
+                                  const unsigned short *,
+                                  const unsigned short *) = nullptr;
+
+extern "C" __attribute__((visibility("default"))) int
+SDL_SetWindowGammaRamp(void *window, const unsigned short *r,
+                       const unsigned short *g, const unsigned short *b) {
+  if (!real_set_gamma_ramp)
+    real_set_gamma_ramp = (int (*)(void *, const unsigned short *,
+                                   const unsigned short *,
+                                   const unsigned short *))dlsym(
+        RTLD_NEXT, "SDL_SetWindowGammaRamp");
+  static int logs = 0;
+  if (logs < 12) {
+    logs++;
+    logf("gamma: SDL_SetWindowGammaRamp mid=%u/%u/%u", r ? r[128] : 0,
+         g ? g[128] : 0, b ? b[128] : 0);
+  }
+  return real_set_gamma_ramp ? real_set_gamma_ramp(window, r, g, b) : -1;
+}
+
 static unsigned int (*real_get_rel_mouse)(int *, int *) = nullptr;
 static int (*real_poll_event)(void *) = nullptr;