Add modals!

src/ui/ui_widgets.h

@@ -14,6 +14,27 @@
 
 #define UI_WIDGET_MAX_DROPDOWN_ITEMS 32
 #define UI_WIDGET_MAX_TEXT_INPUTS    16
+#define UI_WIDGET_MAX_WINDOWS       16
+
+struct UI_ModalState {
+    B32      active;
+    uint32_t id;       // Hash of the modal's string ID
+    S32      result;   // Button index pressed, -1 = pending
+};
+
+struct UI_WindowSlot {
+    uint32_t id;       // Hash of the window's string ID (0 = unused)
+    Vec2F32  position;
+    Vec2F32  size;
+    B32      open;
+    int16_t  z_order;
+};
+
+struct UI_DragState {
+    uint32_t dragging_id;  // Window ID currently being dragged (0 = none)
+    Vec2F32  drag_anchor;  // Mouse position when drag started
+    Vec2F32  pos_anchor;   // Window position when drag started
+};
 
 struct UI_WidgetState {
     // Text input focus
@@ -38,6 +59,15 @@ struct UI_WidgetState {
 
     // Click detection
     B32 mouse_clicked; // true on the frame mouse transitions from up->down
+
+    // Modal state
+    UI_ModalState modal;
+
+    // Window state
+    UI_WindowSlot windows[UI_WIDGET_MAX_WINDOWS];
+    S32           window_count;
+    int16_t       next_z;
+    UI_DragState  drag;
 };
 
 extern UI_WidgetState g_wstate;
@@ -76,3 +106,16 @@ B32 ui_text_input(const char *id, char *buf, S32 buf_size);
 // Dropdown / combo box. Sets *selected to chosen index. Returns true if changed.
 // options is an array of label strings, count is the number of options.
 B32 ui_dropdown(const char *id, const char **options, S32 count, S32 *selected);
+
+// Modal dialog. Returns button index pressed (0-based), -1 if pending, -2 if Escape dismissed.
+// Call every frame while active — it draws the overlay and dialog box.
+S32 ui_modal(const char *id, const char *title, const char *message,
+             const char **buttons, S32 button_count);
+B32 ui_modal_is_active();
+
+// Draggable floating window. content_fn is called inside the window body each frame.
+// *open is set to 0 when the close button is clicked. Returns true while window is open.
+typedef void (*UI_WindowContentFn)(void *user_data);
+B32 ui_window(const char *id, const char *title, B32 *open,
+              Vec2F32 initial_pos, Vec2F32 initial_size,
+              UI_WindowContentFn content_fn, void *user_data);