Fix for a crash when deleting FileBrowserComponent under certain circumstances.

modules/juce_gui_basics/layout/juce_ScrollBar.cpp

@@ -60,6 +60,7 @@ ScrollBar::ScrollBar (const bool vertical_)
       thumbAreaSize (0),
       thumbStart (0),
       thumbSize (0),
+      minimumScrollBarThumbSize (0),
       initialDelayInMillisecs (100),
       repeatDelayInMillisecs (50),
       minimumDelayInMillisecs (10),
@@ -67,6 +68,8 @@ ScrollBar::ScrollBar (const bool vertical_)
       isDraggingThumb (false),
       autohides (true)
 {
+    minimumScrollBarThumbSize = getLookAndFeel().getMinimumScrollbarThumbSize (*this);
+
     setRepaintsOnMouseActivity (true);
     setFocusContainer (true);
 }
@@ -190,10 +193,8 @@ void ScrollBar::updateThumbPosition()
     int newThumbSize = roundToInt (totalRange.getLength() > 0 ? (visibleRange.getLength() * thumbAreaSize) / totalRange.getLength()
                                                               : thumbAreaSize);
 
-    LookAndFeel& lf = getLookAndFeel();
-
-    if (newThumbSize < lf.getMinimumScrollbarThumbSize (*this))
-        newThumbSize = jmin (lf.getMinimumScrollbarThumbSize (*this), thumbAreaSize - 1);
+    if (newThumbSize < minimumScrollBarThumbSize)
+        newThumbSize = jmin (minimumScrollBarThumbSize, thumbAreaSize - 1);
 
     if (newThumbSize > thumbAreaSize)
         newThumbSize = thumbAreaSize;
@@ -280,6 +281,7 @@ void ScrollBar::resized()
     const int length = vertical ? getHeight() : getWidth();
 
     LookAndFeel& lf = getLookAndFeel();
+    minimumScrollBarThumbSize = lf.getMinimumScrollbarThumbSize (*this);
     const bool buttonsVisible = lf.areScrollbarButtonsVisible();
     int buttonSize = 0;
 

modules/juce_gui_basics/layout/juce_ScrollBar.h

@@ -382,6 +382,7 @@ private:
     Range <double> totalRange, visibleRange;
     double singleStepSize, dragStartRange;
     int thumbAreaStart, thumbAreaSize, thumbStart, thumbSize;
+    int minimumScrollBarThumbSize;
     int dragStartMousePos, lastMousePos;
     int initialDelayInMillisecs, repeatDelayInMillisecs, minimumDelayInMillisecs;
     bool vertical, isDraggingThumb, autohides;

modules/juce_gui_basics/layout/juce_Viewport.cpp

@@ -24,6 +24,7 @@
 
 Viewport::Viewport (const String& name)
   : Component (name),
+    customScrollBarThickness(false),
     scrollBarThickness (0),
     singleStepX (16),
     singleStepY (16),
@@ -39,6 +40,8 @@ Viewport::Viewport (const String& name)
     addAndMakeVisible (contentHolder);
     contentHolder.setInterceptsMouseClicks (false, true);
 
+    scrollBarThickness = getLookAndFeel().getDefaultScrollbarWidth();
+
     addChildComponent (verticalScrollBar);
     addChildComponent (horizontalScrollBar);
 
@@ -174,6 +177,14 @@ void Viewport::componentMovedOrResized (Component&, bool, bool)
     updateVisibleArea();
 }
 
+void Viewport::lookAndFeelChanged()
+{
+    if (customScrollBarThickness == false)
+    {
+        scrollBarThickness = getLookAndFeel().getDefaultScrollbarWidth();
+    }
+}
+
 void Viewport::resized()
 {
     updateVisibleArea();
@@ -314,17 +325,32 @@ void Viewport::setScrollBarsShown (const bool showVerticalScrollbarIfNeeded,
 
 void Viewport::setScrollBarThickness (const int thickness)
 {
-    if (scrollBarThickness != thickness)
+    int newThickness;
+
+    // To stay compatible with the previous code: use the
+    // default thickness if thickness parameter is zero
+    // or negative
+    if (thickness <= 0)
     {
-        scrollBarThickness = thickness;
+        customScrollBarThickness = false;
+        newThickness = getLookAndFeel().getDefaultScrollbarWidth();
+    }
+    else
+    {
+        customScrollBarThickness = true;
+        newThickness = thickness;
+    }
+
+    if (scrollBarThickness != newThickness)
+    {
+        scrollBarThickness = newThickness;
         updateVisibleArea();
     }
 }
 
 int Viewport::getScrollBarThickness() const
 {
-    return scrollBarThickness > 0 ? scrollBarThickness
-                                  : getLookAndFeel().getDefaultScrollbarWidth();
+    return scrollBarThickness;
 }
 
 void Viewport::scrollBarMoved (ScrollBar* scrollBarThatHasMoved, double newRangeStart)

modules/juce_gui_basics/layout/juce_Viewport.h

@@ -253,6 +253,8 @@ public:
     /** @internal */
     void componentMovedOrResized (Component&, bool wasMoved, bool wasResized) override;
     /** @internal */
+    void lookAndFeelChanged() override;
+    /** @internal */
     bool useMouseWheelMoveIfNeeded (const MouseEvent&, const MouseWheelDetails&);
     /** @internal */
     static bool respondsToKey (const KeyPress&);
@@ -261,6 +263,7 @@ private:
     //==============================================================================
     WeakReference<Component> contentComp;
     Rectangle<int> lastVisibleArea;
+    bool customScrollBarThickness;
     int scrollBarThickness;
     int singleStepX, singleStepY;
     bool showHScrollbar, showVScrollbar, deleteContent;