Avoid random crashes changing Color Mode with a TTF font in the theme

This is a weird combination of things:
1. StatusBar::onPixelFormatChanged() is being called in a non-UI thread
   because ChangePixelFormatCommand changes the color mode from a
   Job (background thread).
2. The UI layer is not prepared to work on multithreading, so all UI
   stuff should be used in the main UI thread (anyway, generally, the UI
   layer doesn't crash if it's used by multiple threads).
3. The harfbuzz library (used for TTF fonts) crashes if it is used by
   multiple threads, so that was the trigger of this crash.

src/app/ui/status_bar.cpp

@@ -801,6 +801,13 @@ void StatusBar::onRemoveDocument(doc::Document* doc)
 
 void StatusBar::onPixelFormatChanged(DocumentEvent& ev)
 {
+  // If this is called from the non-UI thread it means that the pixel
+  // format change was made in the background,
+  // i.e. ChangePixelFormatCommand uses a background thread to change
+  // the sprite format.
+  if (!ui::is_ui_thread())
+    return;
+
   onActiveSiteChange(UIContext::instance()->activeSite());
 }
 

src/ui/system.cpp

@@ -10,6 +10,7 @@
 
 #include "ui/system.h"
 
+#include "base/thread.h"
 #include "gfx/point.h"
 #include "she/display.h"
 #include "she/surface.h"
@@ -26,6 +27,10 @@
 
 namespace ui {
 
+// This is used to check if calls to UI layer are made from the non-UI
+// thread. (Which might be catastrofic.)
+base::thread::native_handle_type main_gui_thread;
+
 // Current mouse cursor type.
 
 static CursorType mouse_cursor_type = kOutsideDisplay;
@@ -168,6 +173,7 @@ static void update_mouse_cursor()
 
 UISystem::UISystem()
 {
+  main_gui_thread = base::this_thread::native_handle();
   mouse_cursor_type = kOutsideDisplay;
   support_native_custom_cursor =
     ((she::instance() &&
@@ -306,4 +312,16 @@ void set_mouse_position(const gfx::Point& newPos)
   _internal_set_mouse_position(newPos);
 }
 
+bool is_ui_thread()
+{
+  return (main_gui_thread == base::this_thread::native_handle());
+}
+
+#ifdef _DEBUG
+void assert_ui_thread()
+{
+  ASSERT(is_ui_thread());
+}
+#endif
+
 } // namespace ui

src/ui/system.h

@@ -52,6 +52,13 @@ namespace ui {
   const gfx::Point& get_mouse_position();
   void set_mouse_position(const gfx::Point& newPos);
 
+  bool is_ui_thread();
+#ifdef _DEBUG
+  void assert_ui_thread();
+#else
+  static inline void assert_ui_thread() { }
+#endif
+
 } // namespace ui
 
 #endif

src/ui/widget.cpp

@@ -156,6 +156,8 @@ void Widget::setTextf(const char *format, ...)
 
 void Widget::setTextQuiet(const std::string& text)
 {
+  assert_ui_thread();
+
   m_text = text;
   enableFlags(HAS_TEXT);
 }
@@ -169,6 +171,8 @@ she::Font* Widget::font() const
 
 void Widget::setBgColor(gfx::Color color)
 {
+  assert_ui_thread();
+
   m_bgColor = color;
   onSetBgColor();
 
@@ -179,6 +183,8 @@ void Widget::setBgColor(gfx::Color color)
 
 void Widget::setTheme(Theme* theme)
 {
+  assert_ui_thread();
+
   m_theme = theme;
   m_font = nullptr;
 
@@ -188,6 +194,8 @@ void Widget::setTheme(Theme* theme)
 
 void Widget::setStyle(Style* style)
 {
+  assert_ui_thread();
+
   m_style = style;
   m_border = m_theme->calcBorder(this, style);
   m_bgColor = m_theme->calcBgColor(this, style);
@@ -201,6 +209,8 @@ void Widget::setStyle(Style* style)
 
 void Widget::setVisible(bool state)
 {
+  assert_ui_thread();
+
   if (state) {
     if (hasFlags(HIDDEN)) {
       disableFlags(HIDDEN);
@@ -221,6 +231,8 @@ void Widget::setVisible(bool state)
 
 void Widget::setEnabled(bool state)
 {
+  assert_ui_thread();
+
   if (state) {
     if (hasFlags(DISABLED)) {
       disableFlags(DISABLED);
@@ -243,6 +255,8 @@ void Widget::setEnabled(bool state)
 
 void Widget::setSelected(bool state)
 {
+  assert_ui_thread();
+
   if (state) {
     if (!hasFlags(SELECTED)) {
       enableFlags(SELECTED);
@@ -263,6 +277,8 @@ void Widget::setSelected(bool state)
 
 void Widget::setExpansive(bool state)
 {
+  assert_ui_thread();
+
   if (state)
     enableFlags(EXPANSIVE);
   else
@@ -271,6 +287,8 @@ void Widget::setExpansive(bool state)
 
 void Widget::setDecorative(bool state)
 {
+  assert_ui_thread();
+
   if (state)
     enableFlags(DECORATIVE);
   else
@@ -279,6 +297,8 @@ void Widget::setDecorative(bool state)
 
 void Widget::setFocusStop(bool state)
 {
+  assert_ui_thread();
+
   if (state)
     enableFlags(FOCUS_STOP);
   else
@@ -287,6 +307,8 @@ void Widget::setFocusStop(bool state)
 
 void Widget::setFocusMagnet(bool state)
 {
+  assert_ui_thread();
+
   if (state)
     enableFlags(FOCUS_MAGNET);
   else
@@ -295,6 +317,8 @@ void Widget::setFocusMagnet(bool state)
 
 bool Widget::isVisible() const
 {
+  assert_ui_thread();
+
   const Widget* widget = this;
   const Widget* lastWidget = nullptr;
 
@@ -312,6 +336,8 @@ bool Widget::isVisible() const
 
 bool Widget::isEnabled() const
 {
+  assert_ui_thread();
+
   const Widget* widget = this;
 
   do {
@@ -326,26 +352,31 @@ bool Widget::isEnabled() const
 
 bool Widget::isSelected() const
 {
+  assert_ui_thread();
   return hasFlags(SELECTED);
 }
 
 bool Widget::isExpansive() const
 {
+  assert_ui_thread();
   return hasFlags(EXPANSIVE);
 }
 
 bool Widget::isDecorative() const
 {
+  assert_ui_thread();
   return hasFlags(DECORATIVE);
 }
 
 bool Widget::isFocusStop() const
 {
+  assert_ui_thread();
   return hasFlags(FOCUS_STOP);
 }
 
 bool Widget::isFocusMagnet() const
 {
+  assert_ui_thread();
   return hasFlags(FOCUS_MAGNET);
 }
 
@@ -355,6 +386,8 @@ bool Widget::isFocusMagnet() const
 
 Window* Widget::window() const
 {
+  assert_ui_thread();
+
   const Widget* widget = this;
 
   while (widget) {
@@ -369,6 +402,8 @@ Window* Widget::window() const
 
 Manager* Widget::manager() const
 {
+  assert_ui_thread();
+
   const Widget* widget = this;
 
   while (widget) {
@@ -383,6 +418,8 @@ Manager* Widget::manager() const
 
 void Widget::getParents(bool ascendant, WidgetsList& parents)
 {
+  assert_ui_thread();
+
   for (Widget* widget=this; widget; widget=widget->m_parent) {
     // append parents in tail
     if (ascendant)
@@ -395,6 +432,8 @@ void Widget::getParents(bool ascendant, WidgetsList& parents)
 
 Widget* Widget::nextSibling()
 {
+  assert_ui_thread();
+
   if (!m_parent)
     return NULL;
 
@@ -413,6 +452,8 @@ Widget* Widget::nextSibling()
 
 Widget* Widget::previousSibling()
 {
+  assert_ui_thread();
+
   if (!m_parent)
     return NULL;
 
@@ -429,6 +470,8 @@ Widget* Widget::previousSibling()
 Widget* Widget::pick(const gfx::Point& pt,
                      const bool checkParentsVisibility) const
 {
+  assert_ui_thread();
+
   const Widget* inside, *picked = nullptr;
 
   // isVisible() checks visibility of widget's parent.
@@ -452,6 +495,7 @@ Widget* Widget::pick(const gfx::Point& pt,
 bool Widget::hasChild(Widget* child)
 {
   ASSERT_VALID_WIDGET(child);
+  assert_ui_thread();
 
   return std::find(m_children.begin(), m_children.end(), child) != m_children.end();
 }