Runtime UI (WGUI)

entity@ CreateUI(string layout);          // "UI/PauseMenu" (path without extension) or an asset id; shows it
void    ShowUI(entity@ ui);   void HideUI(entity@ ui);   bool IsUIVisible(entity@ ui);
void    DestroyUI(entity@ ui);
bool    IsAnyUIShown();

int     BindWidgets(entity@ ui);          // bind the calling behaviour's fields and On*_ handlers (see below)

Widget@            FindWidget(entity@ ui, string name);       // any kind
TextWidget@        FindText(entity@ ui, string name);         // null when the widget isn't a Text
ImageWidget@       FindImage(entity@ ui, string name);
ButtonWidget@      FindButton(entity@ ui, string name);
ProgressBarWidget@ FindProgressBar(entity@ ui, string name);
CheckBoxWidget@    FindCheckBox(entity@ ui, string name);
SliderWidget@      FindSlider(entity@ ui, string name);

// One-liners for the common HUD calls (false when there is no such widget).
bool SetWidgetText(entity@ ui, string name, string text);
bool SetWidgetVisible(entity@ ui, string name, bool visible);
bool SetWidgetPercent(entity@ ui, string name, float percent);
bool SetWidgetColor(entity@ ui, string name, vec4 color);

class pause_menu
{
    // Fields named after widgets are filled when the UI is created. The type
    // must match the widget's kind (Widget@ takes any kind).
    TextWidget@ Title;
    SliderWidget@ Volume;
    CheckBoxWidget@ Invert_Look;      // binds to "InvertLook" too

    private entity@ m_menu;

    void Start()
    {
        @m_menu = CreateUI("UI/PauseMenu");   // fields and handlers below are bound right here
        HideUI(m_menu);
        Volume.SetValue(save_get_float("volume", 0.8f));
    }

    // Methods named On<Event>_<WidgetName> are bound as that widget's handlers.
    void OnClicked_Resume()                 { HideUI(m_menu); SetInputModeGameOnly(); }
    void OnClicked_Quit()                   { load_level("Levels/MainMenu.wmap"); }
    void OnValueChanged_Volume(float value) { save_set_float("volume", value); }
    void OnCheckStateChanged_InvertLook(bool checked) { invert = checked; }
    void OnHovered_Resume()                 { Title.SetText("Back to the game"); }

    void Update(float dt)
    {
        if (is_key_pressed(key::escape)) { ShowUI(m_menu); SetInputModeUIOnly(m_menu); }
    }
}

string GetName();   widget_kind GetKind();   entity@ GetOwner();
void SetVisible(bool);  bool GetVisible();
void SetVisibility(widget_visibility);  widget_visibility GetVisibility();   // visible, hidden, collapsed, hit_test_invisible, self_hit_test_invisible
void SetEnabled(bool);  bool GetEnabled();

// canvas slot
void SetPosition(float x, float y);  vec2 GetPosition();      // SetOffset / GetOffset are the same
void SetSize(float w, float h);      vec2 GetSize();
void SetAnchors(float min_x, float min_y, float max_x, float max_y);
void SetAlignment(float x, float y);
void SetZOrder(int);  int GetZOrder();
void SetPadding(float l, float t, float r, float b);           // box slot

// appearance
void SetColor(vec4);  vec4 GetColor();   void SetTint(vec4);    // the same colour and opacity
void SetTexture(string texture_asset_id);
void SetOpacity(float);  float GetOpacity();

// render transform
void SetRenderTranslation(float x, float y);  vec2 GetRenderTranslation();
void SetRenderScale(float x, float y);        vec2 GetRenderScale();
void SetRenderAngle(float degrees);           float GetRenderAngle();
void SetRenderPivot(float x, float y);

vec2 GetScreenPosition();  vec2 GetScreenSize();   // where it was laid out last frame
Widget@ GetParent();  int GetChildCount();  Widget@ GetChild(int);
bool IsHovered();  bool IsPressed();
void BindOnHovered(string);  void BindOnUnhovered(string);

// TextWidget
void SetText(string);  string GetText();
void SetFontSize(float px);  float GetFontSize();      // 0 = the font's baked size
void SetJustification(text_justify);                   // left, center, right
void SetWordWrap(bool);
void SetShadow(float offset_x, float offset_y, vec4 color);

// ButtonWidget
void BindOnClicked(string);  void BindOnPressed(string);  void BindOnReleased(string);
void SetHoveredColor(vec4);  void SetPressedColor(vec4);  // switches the button to its custom style

// ProgressBarWidget
void SetPercent(float);  float GetPercent();
void SetFillColor(vec4);  void SetFillDirection(fill_direction);   // left_to_right, right_to_left, bottom_to_top, top_to_bottom

// CheckBoxWidget
void SetChecked(bool);  bool IsChecked();               // SetChecked raises no event
void BindOnCheckStateChanged(string);                   // handler: void f(bool)

// SliderWidget
void SetValue(float);  float GetValue();                // clamped and stepped; no event
void SetRange(float min, float max);  float GetMinValue();  float GetMaxValue();
void SetStep(float);
void BindOnValueChanged(string);                        // handler: void f(float)