Chams: per-colour alpha and a softer viewmodel additive base

- Colour picker gains an optional alpha bar (checkerboard preview, #RRGGBBAA
  readout); add_color_alpha is used for the chams colours. Chams colours are
  now r,g,b,a and chams_apply sets $alpha plus MATERIAL_VAR_TRANSLUCENT when
  alpha < 255. Config stores vis_a / inv_a / vm a.
- The additive viewmodel base is now a faint translucent tint (alpha/8)
  instead of an opaque fill, so additive/Fullbright stay see-through and the
  viewmodel no longer becomes a solid blob. Fullbright whitening reduced to
  25% so blue stays blue instead of turning lavender.

1 files changed, 100 insertions, 26 deletions

diff --git a/src/gui.cpp b/src/gui.cpp
index 3cbb40a..89888da 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -195,7 +195,8 @@ struct Ctrl {
   const char *desc;
   bool *bval; // CK_TOGGLE
   int *ival;  // CK_SLIDER
-  int *rgb;   // CK_COLOR: three ints, 0..255
+  int *rgb;   // CK_COLOR: three or four ints, 0..255 (see has_alpha)
+  bool has_alpha; // CK_COLOR: rgb[3] is an editable alpha channel
   const char *const *opts; // CK_DROPDOWN
   int nopts;               // CK_DROPDOWN
   int min, max;
@@ -256,6 +257,7 @@ static void add_ctrl(int card, int kind, const char *label, const char *desc,
   c.action = action;
   c.zero_unlimited = false;
   c.rgb = nullptr;
+  c.has_alpha = false;
   c.opts = nullptr;
   c.nopts = 0;
   c.hue = 0.0f;
@@ -287,6 +289,14 @@ static void add_color(int card, const char *label, const char *desc,
   add_ctrl(card, CK_COLOR, label, desc, 0, 255, nullptr, nullptr, ACT_NONE);
   g_ctrls[i].rgb = rgb;
 }
+// Same picker, plus an editable alpha bar; rgb must hold four ints.
+static void add_color_alpha(int card, const char *label, const char *desc,
+                            int *rgba) {
+  int i = g_nctrl;
+  add_ctrl(card, CK_COLOR, label, desc, 0, 255, nullptr, nullptr, ACT_NONE);
+  g_ctrls[i].rgb = rgba;
+  g_ctrls[i].has_alpha = true;
+}
 static void add_dropdown(int card, const char *label, const char *desc,
                          const char *const *opts, int nopts, int *value) {
   int i = g_nctrl;
@@ -456,15 +466,15 @@ static void build_cards() {
                &g.vis_on);
     add_dropdown(chams, "Visible material", "Material for the visible pass.",
                  chams_mat_names, 7, &g.vis_mat);
-    add_color(chams, "Visible colour", "Colour for the visible pass.",
-              g.vis_rgb);
+    add_color_alpha(chams, "Visible colour", "Colour and alpha for the visible pass.",
+                    g.vis_rgb);
     add_toggle(chams, "Through walls", "Draw a pass with the depth test off.",
                &g.inv_on);
     add_dropdown(chams, "Invisible material",
                  "Material for the through-wall pass.", chams_mat_names, 7,
                  &g.inv_mat);
-    add_color(chams, "Invisible colour",
-              "Colour for the through-wall pass.", g.inv_rgb);
+    add_color_alpha(chams, "Invisible colour",
+                    "Colour and alpha for the through-wall pass.", g.inv_rgb);
   };
   add_chams_group("Hostile", g_chams_hostile);
   add_chams_group("Neutral", g_chams_neutral);
@@ -475,8 +485,8 @@ static void build_cards() {
              &g_chams_viewmodel);
   add_dropdown(chams, "Viewmodel material", "Material for the viewmodel.",
                chams_mat_names, 7, &g_chams_vm_mat);
-  add_color(chams, "Viewmodel colour", "Colour for the viewmodel.",
-            g_chams_vm_rgb);
+  add_color_alpha(chams, "Viewmodel colour", "Colour and alpha for the viewmodel.",
+                  g_chams_vm_rgb);
   int view = add_card(2, nullptr, "Camera / display",
                       "Camera FOV, viewmodel FOV and HDR brightness.", true);
   add_slider(view, "Camera FOV",
@@ -970,7 +980,7 @@ static int button_w(const char *label) {
 
 static int label_row_h(const Ctrl &c);
 static bool picker_open_for(const Ctrl &c);
-static int picker_panel_h();
+static int picker_panel_h(bool with_alpha);
 static bool card_in_category(int i);
 static Rect card_rect(int index, int y);
 static int card_h(const Card &c);
@@ -978,7 +988,7 @@ 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();
+    h += picker_panel_h(c.has_alpha);
   return h;
 }
 
@@ -989,6 +999,7 @@ static int row_h(const Ctrl &c) {
 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_ALPHA_H = 12;
 static constexpr int PICKER_GAP = 8;
 
 static bool picker_open_for(const Ctrl &c) {
@@ -996,9 +1007,11 @@ static bool picker_open_for(const Ctrl &c) {
          &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 picker_panel_h(bool with_alpha) {
+  int h = PICKER_GAP + PICKER_SV_H + PICKER_GAP + PICKER_HUE_H + PICKER_GAP;
+  if (with_alpha)
+    h += PICKER_ALPHA_H + PICKER_GAP;
+  return S((float)h);
 }
 
 static int label_row_h(const Ctrl &c) {
@@ -1069,16 +1082,17 @@ static void rgb_to_hsv(int r, int g, int b, float &h, float &s, float &v) {
 }
 
 struct PickerRects {
-  Rect panel, sv, hue, preview;
+  Rect panel, sv, hue, alpha, preview;
 };
 
-static PickerRects picker_rects(const Rect &cr, int row_y, int base_h) {
+static PickerRects picker_rects(const Rect &cr, int row_y, int base_h,
+                                bool with_alpha) {
   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()};
+  p.panel = Rect{px, py, pw, picker_panel_h(with_alpha)};
   int preview_w = S(84.0f);
   int svw = S((float)PICKER_SV_W);
   if (svw + preview_w + S(16.0f) > pw)
@@ -1089,6 +1103,8 @@ static PickerRects picker_rects(const Rect &cr, int row_y, int base_h) {
               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.alpha = Rect{p.hue.x, p.hue.y + p.hue.h + S(PICKER_GAP), svw,
+                 S((float)PICKER_ALPHA_H)};
   p.preview = Rect{p.sv.x + p.sv.w + S(12.0f), p.sv.y, preview_w, S(52.0f)};
   return p;
 }
@@ -1175,7 +1191,7 @@ static bool picker_rects_for(int ctrl_index, PickerRects &out) {
   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));
+  out = picker_rects(card, row.y, label_row_h(ct), ct.has_alpha);
   return true;
 }
 
@@ -1191,18 +1207,47 @@ static void picker_apply(Ctrl &ct, const PickerRects &p) {
     if (v > 1.0f) v = 1.0f;
     ct.sat = s;
     ct.val = v;
+    hsv_to_rgb(ct.hue, ct.sat, ct.val, ct.rgb[0], ct.rgb[1], ct.rgb[2]);
   } 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]);
+  } else if (g_picker_drag == 3 && ct.has_alpha) {
+    if (p.alpha.w <= 0)
+      return;
+    int a = (int)(255.0f * (float)(g_mouse_x - p.alpha.x) /
+                      (float)p.alpha.w +
+                  0.5f);
+    if (a < 0) a = 0;
+    if (a > 255) a = 255;
+    ct.rgb[3] = a;
+  }
+}
+
+static void draw_checker(const Rect &r, const Rect *clip) {
+  int sq = S(6.0f);
+  if (sq < 4)
+    sq = 4;
+  for (int yy = 0; yy < r.h; yy += sq) {
+    for (int xx = 0; xx < r.w; xx += sq) {
+      int w = sq < r.w - xx ? sq : r.w - xx;
+      int h = sq < r.h - yy ? sq : r.h - yy;
+      bool odd = ((xx / sq) + (yy / sq)) & 1;
+      fill(Rect{r.x + xx, r.y + yy, w, h},
+           odd ? Col{62, 66, 74, 255} : Col{38, 41, 47, 255}, clip);
+    }
   }
-  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));
+  PickerRects p = picker_rects(cr, row_y, label_row_h(ct), ct.has_alpha);
+  int pr = ct.rgb ? ct.rgb[0] : 255;
+  int pg = ct.rgb ? ct.rgb[1] : 255;
+  int pb = ct.rgb ? ct.rgb[2] : 255;
+  int pa = (ct.has_alpha && ct.rgb) ? ct.rgb[3] : 255;
   fill(p.panel, Col{20, 23, 29, 250}, &clip);
   outline(p.panel, C_BORDER, &clip);
 
@@ -1236,6 +1281,23 @@ static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
   }
   outline(p.hue, Col{0, 0, 0, 255}, &clip);
 
+  // Alpha bar: checkerboard behind a transparent->opaque colour gradient.
+  if (ct.has_alpha) {
+    draw_checker(p.alpha, &clip);
+    int ax = S(4.0f);
+    if (ax < 2) ax = 2;
+    for (int xx = 0; xx < p.alpha.w; xx += ax) {
+      int a = p.alpha.w > 1 ? 255 * xx / (p.alpha.w - 1) : 255;
+      int rw = ax < p.alpha.w - xx ? ax : p.alpha.w - xx;
+      fill(Rect{p.alpha.x + xx, p.alpha.y, rw, p.alpha.h},
+           Col{pr, pg, pb, a}, &clip);
+    }
+    outline(p.alpha, Col{0, 0, 0, 255}, &clip);
+    int amx = p.alpha.x + (int)((float)pa / 255.0f * (float)p.alpha.w);
+    line(amx, p.alpha.y - S(2.0f), amx, p.alpha.y + p.alpha.h + S(2.0f),
+         Col{255, 255, 255, 255});
+  }
+
   // 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);
@@ -1249,17 +1311,21 @@ static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
        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);
+  draw_checker(p.preview, &clip);
+  fill(p.preview, Col{pr, pg, pb, pa}, &clip);
   outline(p.preview, C_BORDER, &clip);
   char hex[16];
-  snprintf(hex, sizeof(hex), "#%02X%02X%02X", pr, pg, pb);
+  if (ct.has_alpha)
+    snprintf(hex, sizeof(hex), "#%02X%02X%02X%02X", pr, pg, pb, pa);
+  else
+    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);
+  if (ct.has_alpha)
+    snprintf(rgb, sizeof(rgb), "%d %d %d %d", pr, pg, pb, pa);
+  else
+    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);
 }
@@ -1581,7 +1647,7 @@ static void handle_mouse_click() {
           int base = label_row_h(ct);
           bool is_open = (g_picker_ctrl == idx);
           if (is_open) {
-            PickerRects p = picker_rects(cr, by, base);
+            PickerRects p = picker_rects(cr, by, base, ct.has_alpha);
             if (p.sv.has(mx, my)) {
               g_picker_drag = 1;
               picker_apply(g_ctrls[idx], p);
@@ -1592,6 +1658,11 @@ static void handle_mouse_click() {
               picker_apply(g_ctrls[idx], p);
               return;
             }
+            if (ct.has_alpha && p.alpha.has(mx, my)) {
+              g_picker_drag = 3;
+              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)};
@@ -2015,9 +2086,12 @@ static void draw_card(const Rect &clip, int index, int y) {
         int pr = ct.rgb ? ct.rgb[0] : 255;
         int pg = ct.rgb ? ct.rgb[1] : 255;
         int pb = ct.rgb ? ct.rgb[2] : 255;
+        int pa = (ct.has_alpha && ct.rgb) ? ct.rgb[3] : 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);
+        if (pa < 255)
+          draw_checker(sw, &clip);
+        fill(sw, Col{pr, pg, pb, pa}, &clip);
         outline(sw, picker_open_for(ct) ? C_ACCENT : C_BORDER, &clip);
         if (picker_open_for(ct))
           draw_picker(clip, cr, ct, by);