GUI: add inline colour picker control

Replace the six RGB sliders on the World tint card with a CK_COLOR control:
each row shows a live swatch and expands an inline picker with a
saturation/value square, a hue bar, and hex/RGB preview. The picker grows the
card in place so it scrolls/clips like any other row, keeps HSV state while
open (grey does not lose its hue), writes the shared 0-255 RGB triple used by
the config, and saves on mouse release.

Costs ~1.2k small rects per frame only while a picker is open; no texture
interface needed.

2 files changed, 319 insertions, 14 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index ce4a02e..b48100b 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -144,6 +144,13 @@ vocabulary / decisions.
   `x`, `y`, `category` and an `expanded` bitmask (card index order). Every
   feature now persists an `active` and `bind` pair, including movement, melee
   and spread.
+- **Colour control (`CK_COLOR`)**: row shows a live swatch; clicking the row
+  expands an inline picker (saturation/value square + hue bar + hex/RGB
+  preview) instead of three RGB sliders, growing the card in place so it
+  scrolls and clips like any other row. The picker keeps HSV state so grey
+  colours do not lose their hue; dragging writes the 0-255 RGB triple shared
+  with the config and saves on mouse release. Only one picker is open at a
+  time; closing the GUI or collapsing the card hides it.
 - Config writes are atomic: `config.tmp` is written and flushed, then
   `rename()`d over the real file. A failed write raises an error toast.
 
diff --git a/src/gui.cpp b/src/gui.cpp
index 9d27a09..9981f25 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -182,7 +182,8 @@ enum CtrlKind {
   CK_BIND,
   CK_SECTION,
   CK_INFO,
-  CK_BUTTON
+  CK_BUTTON,
+  CK_COLOR
 };
 
 enum CtrlAction { ACT_NONE = 0, ACT_RELOAD, ACT_RESET };
@@ -193,9 +194,13 @@ struct Ctrl {
   const char *desc;
   bool *bval; // CK_TOGGLE
   int *ival;  // CK_SLIDER
+  int *rgb;   // CK_COLOR: three ints, 0..255
   int min, max;
   int action; // CK_BUTTON
   bool zero_unlimited; // slider: value 0 displays as "All"
+  // CK_COLOR picker state, kept while the picker is open so grey colours do
+  // not lose their hue when the user drags value/saturation.
+  float hue, sat, val;
 };
 
 struct Card {
@@ -247,6 +252,10 @@ static void add_ctrl(int card, int kind, const char *label, const char *desc,
   c.max = max;
   c.action = action;
   c.zero_unlimited = false;
+  c.rgb = nullptr;
+  c.hue = 0.0f;
+  c.sat = 0.0f;
+  c.val = 1.0f;
   g_cards[card].n++;
 }
 static void add_toggle(int card, const char *label, const char *desc,
@@ -267,6 +276,12 @@ static void add_button(int card, const char *label, const char *desc,
                        int action) {
   add_ctrl(card, CK_BUTTON, label, desc, 0, 0, nullptr, nullptr, action);
 }
+static void add_color(int card, const char *label, const char *desc,
+                      int *rgb) {
+  int i = g_nctrl;
+  add_ctrl(card, CK_COLOR, label, desc, 0, 255, nullptr, nullptr, ACT_NONE);
+  g_ctrls[i].rgb = rgb;
+}
 
 static int ctrl_val(const Ctrl &c) {
   if (c.kind == CK_TOGGLE && c.bval)
@@ -381,19 +396,11 @@ static void build_cards() {
   add_toggle(tint, "World brushes",
              "Tint world textures (sky and water excluded from this part).",
              &g_tint_world_on);
-  add_slider(tint, "World red", "Red channel of the world tint (0-255).", 0,
-             255, &g_tint_world_rgb[0]);
-  add_slider(tint, "World green", "Green channel of the world tint (0-255).", 0,
-             255, &g_tint_world_rgb[1]);
-  add_slider(tint, "World blue", "Blue channel of the world tint (0-255).", 0,
-             255, &g_tint_world_rgb[2]);
+  add_color(tint, "World colour", "Click the swatch to open the picker.",
+            g_tint_world_rgb);
   add_toggle(tint, "Skybox", "Tint the skybox textures.", &g_tint_sky_on);
-  add_slider(tint, "Sky red", "Red channel of the sky tint (0-255).", 0, 255,
-             &g_tint_sky_rgb[0]);
-  add_slider(tint, "Sky green", "Green channel of the sky tint (0-255).", 0,
-             255, &g_tint_sky_rgb[1]);
-  add_slider(tint, "Sky blue", "Blue channel of the sky tint (0-255).", 0, 255,
-             &g_tint_sky_rgb[2]);
+  add_color(tint, "Sky colour", "Click the swatch to open the picker.",
+            g_tint_sky_rgb);
 
   int spread = add_card(3, &g_spread, "Spread control",
                         "Choose a server shot seed that tightens the cone.",
@@ -436,6 +443,8 @@ static int g_scroll_drag_dy = 0;
 static float g_scroll_drag_start = 0.0f;
 static int g_hover_slider = -1;
 static int g_slider_drag = -1;
+static int g_picker_ctrl = -1; // CK_COLOR control with its picker expanded
+static int g_picker_drag = 0;  // 1 = SV square, 2 = hue bar
 static int g_capture_card = -1;
 static QAngle g_frozen{0, 0, 0};
 static int g_mouse_x = 0, g_mouse_y = 0;
@@ -821,7 +830,40 @@ static int button_w(const char *label) {
   return bw;
 }
 
+static int label_row_h(const Ctrl &c);
+static bool picker_open_for(const Ctrl &c);
+static int picker_panel_h();
+static bool card_in_category(int i);
+static Rect card_rect(int index, int y);
+static int card_h(const Card &c);
+
 static int row_h(const Ctrl &c) {
+  int h = label_row_h(c);
+  if (picker_open_for(c))
+    h += picker_panel_h();
+  return h;
+}
+
+// ---------------------------------------------------------------------------
+// Colour picker (CK_COLOR)
+// ---------------------------------------------------------------------------
+
+static constexpr int PICKER_SV_W = 180;
+static constexpr int PICKER_SV_H = 110;
+static constexpr int PICKER_HUE_H = 12;
+static constexpr int PICKER_GAP = 8;
+
+static bool picker_open_for(const Ctrl &c) {
+  return c.kind == CK_COLOR && g_picker_ctrl >= 0 &&
+         &c == &g_ctrls[g_picker_ctrl];
+}
+
+static int picker_panel_h() {
+  return S((float)(PICKER_GAP + PICKER_SV_H + PICKER_GAP + PICKER_HUE_H +
+                   PICKER_GAP));
+}
+
+static int label_row_h(const Ctrl &c) {
   if (c.kind == CK_BUTTON)
     return S(32.0f);
   int maxw = (c.kind == CK_INFO || c.kind == CK_SECTION)
@@ -837,6 +879,207 @@ static int row_h(const Ctrl &c) {
   return h < minh ? minh : h;
 }
 
+static void hsv_to_rgb(float h, float s, float v, int &r, int &g, int &b) {
+  if (h < 0.0f) h = 0.0f;
+  h = fmodf(h, 360.0f);
+  if (h < 0.0f) h += 360.0f;
+  if (s < 0.0f) s = 0.0f;
+  if (s > 1.0f) s = 1.0f;
+  if (v < 0.0f) v = 0.0f;
+  if (v > 1.0f) v = 1.0f;
+  float c = v * s;
+  float x = c * (1.0f - fabsf(fmodf(h / 60.0f, 2.0f) - 1.0f));
+  float m = v - c;
+  float rr = 0.0f, gg = 0.0f, bb = 0.0f;
+  if (h < 60.0f) {
+    rr = c; gg = x;
+  } else if (h < 120.0f) {
+    rr = x; gg = c;
+  } else if (h < 180.0f) {
+    gg = c; bb = x;
+  } else if (h < 240.0f) {
+    gg = x; bb = c;
+  } else if (h < 300.0f) {
+    rr = x; bb = c;
+  } else {
+    rr = c; bb = x;
+  }
+  r = (int)((rr + m) * 255.0f + 0.5f);
+  g = (int)((gg + m) * 255.0f + 0.5f);
+  b = (int)((bb + m) * 255.0f + 0.5f);
+}
+
+static void rgb_to_hsv(int r, int g, int b, float &h, float &s, float &v) {
+  float rf = r / 255.0f, gf = g / 255.0f, bf = b / 255.0f;
+  float mx = fmaxf(rf, fmaxf(gf, bf));
+  float mn = fminf(rf, fminf(gf, bf));
+  float d = mx - mn;
+  v = mx;
+  s = mx > 0.0f ? d / mx : 0.0f;
+  if (d <= 0.0f) {
+    h = 0.0f;
+    return;
+  }
+  if (mx == rf)
+    h = 60.0f * fmodf((gf - bf) / d, 6.0f);
+  else if (mx == gf)
+    h = 60.0f * ((bf - rf) / d + 2.0f);
+  else
+    h = 60.0f * ((rf - gf) / d + 4.0f);
+  if (h < 0.0f)
+    h += 360.0f;
+}
+
+struct PickerRects {
+  Rect panel, sv, hue, preview;
+};
+
+static PickerRects picker_rects(const Rect &cr, int row_y, int base_h) {
+  PickerRects p{};
+  int px = cr.x + S(16.0f);
+  int py = row_y + base_h;
+  int pw = card_content_w() - S(32.0f);
+  if (pw > S(340.0f)) pw = S(340.0f);
+  p.panel = Rect{px, py, pw, picker_panel_h()};
+  int preview_w = S(84.0f);
+  int svw = S((float)PICKER_SV_W);
+  if (svw + preview_w + S(16.0f) > pw)
+    svw = pw - preview_w - S(16.0f);
+  if (svw < S(60.0f))
+    svw = S(60.0f);
+  p.sv = Rect{px + S(PICKER_GAP), py + S(PICKER_GAP), svw,
+              S((float)PICKER_SV_H)};
+  p.hue = Rect{p.sv.x, p.sv.y + p.sv.h + S(PICKER_GAP), svw,
+               S((float)PICKER_HUE_H)};
+  p.preview = Rect{p.sv.x + p.sv.w + S(12.0f), p.sv.y, preview_w, S(52.0f)};
+  return p;
+}
+
+// Widget row/card used to map a control index back to screen space. Needed by
+// the drag handler, which runs outside click/layout context.
+static bool control_rect(int ctrl_index, Rect &out_card, Rect &out_row) {
+  Rect content{g_win_x + S(190.0f), g_win_y + S(38.0f),
+               g_win_w - S(190.0f), g_win_h - S(38.0f) - S(30.0f)};
+  int y = content.y - (int)g_scroll + S(8.0f);
+  for (int i = 0; i < g_ncards; i++) {
+    if (!card_in_category(i))
+      continue;
+    Card &c = g_cards[i];
+    Rect cr = card_rect(i, y);
+    if (c.expanded) {
+      int by = cr.y + header_h(c) + S(6.0f);
+      for (int j = 0; j < c.n; j++) {
+        Ctrl &ct = g_ctrls[c.c0 + j];
+        int rh = row_h(ct);
+        if (c.c0 + j == ctrl_index) {
+          out_card = cr;
+          out_row = Rect{cr.x, by, cr.w, rh};
+          return true;
+        }
+        by += rh;
+      }
+    }
+    y += card_h(c);
+  }
+  return false;
+}
+
+static bool picker_rects_for(int ctrl_index, PickerRects &out) {
+  if (ctrl_index < 0 || ctrl_index >= g_nctrl)
+    return false;
+  Rect card, row;
+  if (!control_rect(ctrl_index, card, row))
+    return false;
+  Ctrl &ct = g_ctrls[ctrl_index];
+  out = picker_rects(card, row.y, label_row_h(ct));
+  return true;
+}
+
+static void picker_apply(Ctrl &ct, const PickerRects &p) {
+  if (!ct.rgb || p.sv.w <= 0 || p.hue.w <= 0)
+    return;
+  if (g_picker_drag == 1) {
+    float s = (float)(g_mouse_x - p.sv.x) / (float)p.sv.w;
+    float v = 1.0f - (float)(g_mouse_y - p.sv.y) / (float)p.sv.h;
+    if (s < 0.0f) s = 0.0f;
+    if (s > 1.0f) s = 1.0f;
+    if (v < 0.0f) v = 0.0f;
+    if (v > 1.0f) v = 1.0f;
+    ct.sat = s;
+    ct.val = v;
+  } else if (g_picker_drag == 2) {
+    float h = 360.0f * (float)(g_mouse_x - p.hue.x) / (float)p.hue.w;
+    if (h < 0.0f) h = 0.0f;
+    if (h >= 360.0f) h = 359.9f;
+    ct.hue = h;
+  }
+  hsv_to_rgb(ct.hue, ct.sat, ct.val, ct.rgb[0], ct.rgb[1], ct.rgb[2]);
+}
+
+static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
+                        int row_y) {
+  PickerRects p = picker_rects(cr, row_y, label_row_h(ct));
+  fill(p.panel, Col{20, 23, 29, 250}, &clip);
+  outline(p.panel, C_BORDER, &clip);
+
+  // Saturation/value field: solid rows of a white->hue gradient scaled by V.
+  int sx = S(4.0f);
+  int sy = S(4.0f);
+  if (sx < 2) sx = 2;
+  if (sy < 2) sy = 2;
+  for (int yy = 0; yy < p.sv.h; yy += sy) {
+    float v = 1.0f - ((float)yy + (float)sy * 0.5f) / (float)p.sv.h;
+    int rh = sy < p.sv.h - yy ? sy : p.sv.h - yy;
+    for (int xx = 0; xx < p.sv.w; xx += sx) {
+      float s = ((float)xx + (float)sx * 0.5f) / (float)p.sv.w;
+      int r, g, b;
+      hsv_to_rgb(ct.hue, s, v, r, g, b);
+      int rw = sx < p.sv.w - xx ? sx : p.sv.w - xx;
+      fill(Rect{p.sv.x + xx, p.sv.y + yy, rw, rh}, Col{r, g, b, 255}, &clip);
+    }
+  }
+  outline(p.sv, Col{0, 0, 0, 255}, &clip);
+
+  // Hue bar.
+  int hx = S(4.0f);
+  if (hx < 2) hx = 2;
+  for (int xx = 0; xx < p.hue.w; xx += hx) {
+    float h = 360.0f * ((float)xx + (float)hx * 0.5f) / (float)p.hue.w;
+    int r, g, b;
+    hsv_to_rgb(h, 1.0f, 1.0f, r, g, b);
+    int rw = hx < p.hue.w - xx ? hx : p.hue.w - xx;
+    fill(Rect{p.hue.x + xx, p.hue.y, rw, p.hue.h}, Col{r, g, b, 255}, &clip);
+  }
+  outline(p.hue, Col{0, 0, 0, 255}, &clip);
+
+  // Selection markers.
+  int mx = p.sv.x + (int)(ct.sat * (float)p.sv.w);
+  int my = p.sv.y + (int)((1.0f - ct.val) * (float)p.sv.h);
+  Rect svm{mx - S(4.0f), my - S(4.0f), S(8.0f), S(8.0f)};
+  outline(svm, Col{0, 0, 0, 255}, &clip);
+  Rect svm2{mx - S(3.0f), my - S(3.0f), S(6.0f), S(6.0f)};
+  outline(svm2, Col{255, 255, 255, 255}, &clip);
+
+  int hxm = p.hue.x + (int)((ct.hue / 360.0f) * (float)p.hue.w);
+  line(hxm, p.hue.y - S(2.0f), hxm, p.hue.y + p.hue.h + S(2.0f),
+       Col{255, 255, 255, 255});
+
+  // Preview swatch and hex value.
+  int pr = ct.rgb ? ct.rgb[0] : 255;
+  int pg = ct.rgb ? ct.rgb[1] : 255;
+  int pb = ct.rgb ? ct.rgb[2] : 255;
+  fill(p.preview, Col{pr, pg, pb, 255}, &clip);
+  outline(p.preview, C_BORDER, &clip);
+  char hex[16];
+  snprintf(hex, sizeof(hex), "#%02X%02X%02X", pr, pg, pb);
+  text_in(clip, p.preview.x, p.preview.y + p.preview.h + S(8.0f), hex,
+          g_font_body, g_body_h, p.preview.w, C_TEXT);
+  char rgb[48];
+  snprintf(rgb, sizeof(rgb), "%d %d %d", pr, pg, pb);
+  text_in(clip, p.preview.x, p.preview.y + p.preview.h + S(8.0f) + g_body_h,
+          rgb, g_font_body, g_body_h, p.preview.w, C_DIM);
+}
+
 static int body_h(const Card &c) {
   if (!c.expanded)
     return 0;
@@ -877,6 +1120,8 @@ static void close_gui() {
   g_dragging = false;
   g_scroll_drag = false;
   g_slider_drag = -1;
+  g_picker_ctrl = -1;
+  g_picker_drag = 0;
   g_reset_armed = false;
   input_clear_mouse_states();
   if (g_sdl_ready) {
@@ -1115,6 +1360,37 @@ static void handle_mouse_click() {
           }
           return;
         }
+        if (ct.kind == CK_COLOR) {
+          int idx = c.c0 + j;
+          int base = label_row_h(ct);
+          bool is_open = (g_picker_ctrl == idx);
+          if (is_open) {
+            PickerRects p = picker_rects(cr, by, base);
+            if (p.sv.has(mx, my)) {
+              g_picker_drag = 1;
+              picker_apply(g_ctrls[idx], p);
+              return;
+            }
+            if (p.hue.has(mx, my)) {
+              g_picker_drag = 2;
+              picker_apply(g_ctrls[idx], p);
+              return;
+            }
+          }
+          Rect sw{cr.x + cr.w - S(96.0f), by + (base - S(20.0f)) / 2,
+                  S(72.0f), S(20.0f)};
+          if (my < by + base || sw.has(mx, my)) {
+            if (is_open) {
+              g_picker_ctrl = -1;
+            } else {
+              g_picker_ctrl = idx;
+              if (ct.rgb)
+                rgb_to_hsv(ct.rgb[0], ct.rgb[1], ct.rgb[2], ct.hue, ct.sat,
+                           ct.val);
+            }
+          }
+          return;
+        }
         if (ct.kind == CK_BUTTON) {
           int bw = button_w(ct.label);
           Rect b{cr.x + cr.w - S(16.0f) - bw,
@@ -1291,6 +1567,17 @@ void gui_handle_input() {
     }
   }
 
+  if (g_picker_drag) {
+    if (!g_mouse_down) {
+      g_picker_drag = 0;
+      config_save();
+    } else if (g_picker_ctrl >= 0) {
+      PickerRects p;
+      if (picker_rects_for(g_picker_ctrl, p))
+        picker_apply(g_ctrls[g_picker_ctrl], p);
+    }
+  }
+
   if (g_scroll_drag) {
     if (!g_mouse_down) {
       g_scroll_drag = false;
@@ -1472,7 +1759,8 @@ static void draw_card(const Rect &clip, int index, int y) {
       wrap_text(ct.label, maxw, g_body_h, lines);
       int lh = g_body_h + S(2.0f);
       int text_h = (int)lines.size() * lh - S(2.0f);
-      int ly = by + (rh - text_h) / 2;
+      int base_h = label_row_h(ct);
+      int ly = by + (base_h - text_h) / 2;
       draw_wrapped(clip, cr.x + S(16.0f), ly, ct.label, g_font_body, g_body_h,
                    maxw, C_TEXT, S(2.0f));
       if (ct.kind == CK_TOGGLE) {
@@ -1483,6 +1771,16 @@ static void draw_card(const Rect &clip, int index, int y) {
                 on ? C_GOOD : C_DIM);
       } else if (ct.kind == CK_SLIDER) {
         draw_slider(clip, cr, by, rh, ct);
+      } else if (ct.kind == CK_COLOR) {
+        int pr = ct.rgb ? ct.rgb[0] : 255;
+        int pg = ct.rgb ? ct.rgb[1] : 255;
+        int pb = ct.rgb ? ct.rgb[2] : 255;
+        Rect sw{cr.x + cr.w - S(96.0f),
+                by + (base_h - S(20.0f)) / 2, S(72.0f), S(20.0f)};
+        fill(sw, Col{pr, pg, pb, 255}, &clip);
+        outline(sw, picker_open_for(ct) ? C_ACCENT : C_BORDER, &clip);
+        if (picker_open_for(ct))
+          draw_picker(clip, cr, ct, by);
       }
     }
     by += rh;