libappfw|LabelWidget: Optionally animate label size when ready for dr…

…awing

doomsday/libappfw/include/de/widgets/labelwidget.h

@@ -170,6 +170,28 @@ class LIBAPPFW_PUBLIC LabelWidget : public GuiWidget
     void setWidthPolicy(ui::SizePolicy policy);
     void setHeightPolicy(ui::SizePolicy policy);
 
+    enum AppearanceAnimation {
+        AppearInstantly,
+        AppearGrowHorizontally,
+        AppearGrowVertically
+    };
+
+    /**
+     * Sets the way the label's content affects its size.
+     *
+     * @param method  Method of appearance:
+     * - AppearInstantly: The size is unaffected by the content's state.
+     *                    This is the default.
+     * - AppearGrowHorizontally: The widget's width is initially zero, but when the
+     *                    content is ready for drawing, the width will animate
+     *                    to the appropriate width in the specified time span.
+     * - AppearGrowVertically: The widget's height is initially zero, but when the
+     *                    content is ready for drawing, the height will animate
+     *                    to the appropriate height in the specified time span.
+     * @param span  Animation time span for the appearance.
+     */
+    void setAppearanceAnimation(AppearanceAnimation method, TimeDelta const &span = 0.0);
+
     // Events.
     void viewResized();
     void update();

doomsday/libappfw/src/widgets/labelwidget.cpp

@@ -49,6 +49,9 @@ public Font::RichFormat::IStyle
 
     ConstantRule *width;
     ConstantRule *height;
+    ScalarRule *appearSize;
+    LabelWidget::AppearanceAnimation appearType;
+    TimeDelta appearSpan;
 
     // Style.
     Vector4i margin;
@@ -83,6 +86,9 @@ public Font::RichFormat::IStyle
         , imageColor  (1, 1, 1, 1)
         , textGLColor (1, 1, 1, 1)
         , maxTextWidth(0)
+        , appearSize  (new ScalarRule(0))
+        , appearType  (AppearInstantly)
+        , appearSpan  (0.0)
         , gapId       ("label.gap")
         , richStyle   (0)
         , uMvpMatrix  ("uMvpMatrix", GLUniform::Mat4)
@@ -99,6 +105,7 @@ public Font::RichFormat::IStyle
     {
         releaseRef(width);
         releaseRef(height);
+        releaseRef(appearSize);
     }
 
     void updateStyle()
@@ -432,6 +439,18 @@ public Font::RichFormat::IStyle
         height->set(combined.height() + margin.y + margin.w);
     }
 
+    void updateAppearanceAnimation()
+    {
+        if(appearType != AppearInstantly)
+        {
+            float const target = (appearType == AppearGrowHorizontally? width->value() : height->value());
+            if(!fequal(appearSize->animation().target(), target))
+            {
+                appearSize->set(target, appearSpan);
+            }
+        }
+    }
+
     void updateGeometry()
     {
         // Update the image on the atlas.
@@ -591,6 +610,7 @@ void LabelWidget::update()
     GuiWidget::update();
 
     d->updateSize();
+    d->updateAppearanceAnimation();
 }
 
 void LabelWidget::drawContent()
@@ -678,6 +698,30 @@ void LabelWidget::setHeightPolicy(SizePolicy policy)
     }
 }
 
+void LabelWidget::setAppearanceAnimation(AppearanceAnimation method, TimeDelta const &span)
+{
+    d->appearType = method;
+    d->appearSpan = span;
+
+    switch(d->appearType)
+    {
+    case AppearInstantly:
+        if(d->horizPolicy == Expand) rule().setInput(Rule::Width,  *d->width);
+        if(d->vertPolicy  == Expand) rule().setInput(Rule::Height, *d->height);
+        break;
+
+    case AppearGrowHorizontally:
+        if(d->horizPolicy == Expand) rule().setInput(Rule::Width,  *d->appearSize);
+        if(d->vertPolicy  == Expand) rule().setInput(Rule::Height, *d->height);
+        break;
+
+    case AppearGrowVertically:
+        if(d->horizPolicy == Expand) rule().setInput(Rule::Width,  *d->width);
+        if(d->vertPolicy  == Expand) rule().setInput(Rule::Height, *d->appearSize);
+        break;
+    }
+}
+
 LabelWidget *LabelWidget::newWithText(String const &label, GuiWidget *parent)
 {
     LabelWidget *w = new LabelWidget;