GUI: Add DropdownButtonWidget and use it in the launcher for mass add

DropdownButtonWidget is a button split in two parts vertically. Clicking
the left part triggers a default action. Clicking the right part shows a
list of other actions the user can choose from.

Using this widget on the launcher lets 'Mass add' be a secondary action
of the 'Add' button, removing the necessity of pressing the shift key to
access the feature.

1 files changed, 10 insertions, 0 deletions

diff --git a/gui/ThemeEngine.h b/gui/ThemeEngine.h
index 1c35b1ea03..827ec197f9 100644
--- a/gui/ThemeEngine.h
+++ b/gui/ThemeEngine.h
@@ -80,6 +80,13 @@ enum DrawData {
 	kDDButtonDisabled,
 	kDDButtonPressed,
 
+	kDDDropDownButtonIdle,
+	kDDDropDownButtonHoverLeft,
+	kDDDropDownButtonHoverRight,
+	kDDDropDownButtonDisabled,
+	kDDDropDownButtonPressedLeft,
+	kDDDropDownButtonPressedRight,
+
 	kDDSliderFull,
 	kDDSliderHover,
 	kDDSliderDisabled,
@@ -400,6 +407,9 @@ public:
 	void drawButton(const Common::Rect &r, const Common::String &str, WidgetStateInfo state = kStateEnabled,
 	                uint16 hints = 0);
 
+	void drawDropDownButton(const Common::Rect &r, uint32 dropdownWidth, const Common::String &str,
+	                        WidgetStateInfo buttonState, bool inButton, bool inDropdown);
+
 	void drawSurface(const Common::Point &p, const Graphics::Surface &surface, bool themeTrans = false);
 
 	void drawSlider(const Common::Rect &r, int width, WidgetStateInfo state = kStateEnabled);