From 276875bf52d8d50ad66be3fa169c79a3f2135876 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jaakko=20Ker=C3=A4nen?= <jaakko.keranen@iki.fi>
Date: Sat, 16 Apr 2016 10:27:09 +0300
Subject: [PATCH] libappfw|ScrollAreaWidget: Scrolling to show a specific
 widget

---
 .../include/de/widgets/scrollareawidget.h     | 26 ++++++++++++++---
 .../sdk/libappfw/src/widgets/menuwidget.cpp   |  1 +
 .../libappfw/src/widgets/scrollareawidget.cpp | 28 +++++++++++++++++++
 3 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/doomsday/sdk/libappfw/include/de/widgets/scrollareawidget.h b/doomsday/sdk/libappfw/include/de/widgets/scrollareawidget.h
index 046b3373f3..a7c502f942 100644
--- a/doomsday/sdk/libappfw/include/de/widgets/scrollareawidget.h
+++ b/doomsday/sdk/libappfw/include/de/widgets/scrollareawidget.h
@@ -114,6 +114,8 @@ class LIBAPPFW_PUBLIC ScrollAreaWidget : public GuiWidget
     void scrollX(int to, TimeDelta span = 0);
     void scrollY(int to, TimeDelta span = 0);
 
+    bool isScrollable() const;
+
     /**
      * Determines if the history view is at the bottom, showing the latest entry.
      */
@@ -150,15 +152,31 @@ class LIBAPPFW_PUBLIC ScrollAreaWidget : public GuiWidget
     bool handleEvent(Event const &event) override;
 
 public slots:
-    void scrollToTop(TimeDelta span = .3f);
+    void scrollToTop(TimeDelta span = 0.3);
 
     /**
      * Moves the scroll offset of the widget to the bottom of the content.
      */
-    void scrollToBottom(TimeDelta span = .3f);
+    void scrollToBottom(TimeDelta span = 0.3);
+
+    void scrollToLeft(TimeDelta span = 0.3);
+    void scrollToRight(TimeDelta span = 0.3);
 
-    void scrollToLeft(TimeDelta span = .3f);
-    void scrollToRight(TimeDelta span = .3f);
+    /**
+     * Moves the scroll offset to center on the given widget.
+     *
+     * @param widget  Widget to center on.
+     * @param span    Animation duration.
+     */
+    void scrollToWidget(GuiWidget const &widget, TimeDelta span = 0.3);
+
+    /**
+     * Finds the topmost scroll area that can be scrolled. May return this widget
+     * if there are no scrollable ancestors.
+     *
+     * @return
+     */
+    ScrollAreaWidget &findTopmostScrollable();
 
 protected:
     void glInit() override;
diff --git a/doomsday/sdk/libappfw/src/widgets/menuwidget.cpp b/doomsday/sdk/libappfw/src/widgets/menuwidget.cpp
index c4f01f2687..b5844bed9e 100644
--- a/doomsday/sdk/libappfw/src/widgets/menuwidget.cpp
+++ b/doomsday/sdk/libappfw/src/widgets/menuwidget.cpp
@@ -546,6 +546,7 @@ bool MenuWidget::handleEvent(Event const &event)
                 if(child->isVisible() && child->behavior().testFlag(Focusable))
                 {
                     root().setFocus(child);
+                    findTopmostScrollable().scrollToWidget(child->as<GuiWidget>());
                     return true;
                 }
             }
diff --git a/doomsday/sdk/libappfw/src/widgets/scrollareawidget.cpp b/doomsday/sdk/libappfw/src/widgets/scrollareawidget.cpp
index 1af031b2b1..0de0556df6 100644
--- a/doomsday/sdk/libappfw/src/widgets/scrollareawidget.cpp
+++ b/doomsday/sdk/libappfw/src/widgets/scrollareawidget.cpp
@@ -354,6 +354,11 @@ void ScrollAreaWidget::scrollY(int to, TimeDelta span)
     d->restartScrollOpacityFade();
 }
 
+bool ScrollAreaWidget::isScrollable() const
+{
+    return d->scrollingEnabled && maximumScrollY().valuei() > 0;
+}
+
 bool ScrollAreaWidget::isAtBottom() const
 {
     return d->origin == Bottom && d->y->animation().target() == 0;
@@ -485,6 +490,29 @@ void ScrollAreaWidget::scrollToRight(TimeDelta span)
     scrollX(maximumScrollX().valuei(), span);
 }
 
+void ScrollAreaWidget::scrollToWidget(GuiWidget const &widget, TimeDelta span)
+{
+    int off = widget.rule().midY().valuei() - contentRule().top().valuei() -
+            rule().height().valuei()/2;
+    qDebug() << "scroll off:" << off;
+    scrollY(off, span);
+}
+
+ScrollAreaWidget &ScrollAreaWidget::findTopmostScrollable()
+{
+    for(Widget *parent = parentWidget(); parent; parent = parent->parent())
+    {
+        if(ScrollAreaWidget *scroll = parent->maybeAs<ScrollAreaWidget>())
+        {
+            if(scroll->isScrollable())
+            {
+                return *scroll;
+            }
+        }
+    }
+    return *this;
+}
+
 void ScrollAreaWidget::glInit()
 {
     d->glInit();