wb: keep CCT / illuminant / color swatch updated for DT_ILLUMINANT_FROM_WB is wb_coeffs are adjusted by user in _white balance_

Author: kofa73

src/iop/channelmixerrgb.c

@@ -3076,6 +3076,38 @@ static void _preview_pipe_finished_callback(gpointer instance, dt_iop_module_t *
 
   dt_iop_gui_enter_critical_section(self);
   gtk_label_set_markup(GTK_LABEL(g->label_delta_E), g->delta_E_label_text);
+
+  dt_iop_channelmixer_rgb_params_t *p = self->params;
+  if(p->illuminant == DT_ILLUMINANT_FROM_WB)
+  {
+    // The WB coefficients might have changed in the temperature module.
+    // We need to re-calculate the chromaticity (x, y) to update the GUI feedback.
+    float x = p->x;
+    float y = p->y;
+
+    if(find_temperature_from_wb_coeffs(&(self->dev->image_storage), self->dev->chroma.wb_coeffs, &x, &y))
+    {
+      p->x = x;
+      p->y = y;
+
+      darktable.gui->reset++;
+      // Update derived GUI widgets (CCT label, color patch)
+      _update_approx_cct(self);
+      _update_illuminant_color(self);
+
+      // Update Hue/Chroma sliders to match the new coordinates
+      dt_aligned_pixel_t xyY = { p->x, p->y, 1.f };
+      dt_aligned_pixel_t Lch;
+      dt_xyY_to_Lch(xyY, Lch);
+
+      if(Lch[1] > 0)
+        dt_bauhaus_slider_set(g->illum_x, rad2degf(Lch[2]));
+      dt_bauhaus_slider_set(g->illum_y, Lch[1]);
+
+      darktable.gui->reset--;
+    }
+  }
+
   dt_iop_gui_leave_critical_section(self);
   _set_trouble_messages(self);
 }