GUI: Introduce dynamic layouts

Prior to this change, a GUI layout was only affected by the screen size.
Now, a layout can additionally be influenced by the GUI dialog and widgets
that uses it. This capability is leveraged to implement the following
features:

* Layout elements that are not bound to a GUI widget do not take space.
   This means that dialogs where the widgets shown depend on for example
   a feature being enabled at configure time no longer have blank spaces.
* Widgets can define a minimal required size for their contents not to be
   cut. For now this is only used for buttons so their width is always
   sufficient for their caption not to be cut. This mechanism could be
   applied to other widget types in the future.

1 files changed, 27 insertions, 4 deletions

diff --git a/gui/widget.cpp b/gui/widget.cpp
index bbb8b06ee6..17098df6ea 100644
--- a/gui/widget.cpp
+++ b/gui/widget.cpp
@@ -45,6 +45,7 @@ Widget::Widget(GuiObject *boss, int x, int y, int w, int h, const char *tooltip)
 Widget::Widget(GuiObject *boss, const Common::String &name, const char *tooltip)
 	: GuiObject(name), _type(0), _boss(boss), _tooltip(tooltip),
 	  _id(0), _flags(0), _hasFocus(false), _state(ThemeEngine::kStateDisabled) {
+	reflowLayout();
 	init();
 }
 
@@ -341,6 +342,13 @@ ButtonWidget::ButtonWidget(GuiObject *boss, const Common::String &name, const Co
 	_type = kButtonWidget;
 }
 
+void ButtonWidget::getMinSize(int &minWidth, int &minHeight) {
+	const Graphics::Font &font = g_gui.getFont(_font);
+
+	minWidth  = font.getStringWidth(_label);
+	minHeight = font.getFontHeight();
+}
+
 void ButtonWidget::handleMouseUp(int x, int y, int button, int clickCount) {
 	if (isEnabled() && _duringPress && x >= 0 && x < _w && y >= 0 && y < _h) {
 		setUnpressedState();
@@ -476,6 +484,14 @@ void DropdownButtonWidget::reflowLayout() {
 	reset();
 }
 
+void DropdownButtonWidget::getMinSize(int &minWidth, int &minHeight) {
+	ButtonWidget::getMinSize(minWidth, minHeight);
+
+	if (minWidth >= 0) {
+		minWidth += _dropdownWidth * 2;
+	}
+}
+
 void DropdownButtonWidget::appendEntry(const Common::String &label, uint32 cmd) {
 	Entry e;
 	e.label = label;
@@ -838,12 +854,16 @@ void GraphicsWidget::drawWidget() {
 
 #pragma mark -
 
-ContainerWidget::ContainerWidget(GuiObject *boss, int x, int y, int w, int h) : Widget(boss, x, y, w, h) {
+ContainerWidget::ContainerWidget(GuiObject *boss, int x, int y, int w, int h) :
+		Widget(boss, x, y, w, h),
+		_backgroundType(ThemeEngine::kWidgetBackgroundBorder) {
 	setFlags(WIDGET_ENABLED | WIDGET_CLEARBG);
 	_type = kContainerWidget;
 }
 
-ContainerWidget::ContainerWidget(GuiObject *boss, const Common::String &name) : Widget(boss, name) {
+ContainerWidget::ContainerWidget(GuiObject *boss, const Common::String &name) :
+		Widget(boss, name),
+		_backgroundType(ThemeEngine::kWidgetBackgroundBorder) {
 	setFlags(WIDGET_ENABLED | WIDGET_CLEARBG);
 	_type = kContainerWidget;
 }
@@ -875,9 +895,12 @@ void ContainerWidget::removeWidget(Widget *widget) {
 	Widget::removeWidget(widget);
 }
 
+void ContainerWidget::setBackgroundType(ThemeEngine::WidgetBackground backgroundType) {
+	_backgroundType = backgroundType;
+}
+
 void ContainerWidget::drawWidget() {
-	g_gui.theme()->drawWidgetBackground(Common::Rect(_x, _y, _x + _w, _y + _h), 0,
-	                                    ThemeEngine::kWidgetBackgroundBorder);
+	g_gui.theme()->drawWidgetBackground(Common::Rect(_x, _y, _x + _w, _y + _h), 0, _backgroundType);
 }
 
 } // End of namespace GUI