Use C++17 [[fallthrough]] if needed

docs/CODING_STYLE.md

@@ -148,5 +148,6 @@ We are using C++17 standard. You can safely use:
 * Use `static constexpr T v = ...;`
 * You can use `<atomic>`, `<thread>`, `<mutex>`, and `<condition_variable>`
 * Prefer `using T = ...;` instead of `typedef ... T`
+* Use `[[fallthrough]]` if needed
 * We use gcc 9.2 or clang 9.0 on Linux, so check the features available in
   https://en.cppreference.com/w/cpp/compiler_support

src/CMakeLists.txt

@@ -1,5 +1,5 @@
 # Aseprite
-# Copyright (C) 2019-2020  Igara Studio S.A.
+# Copyright (C) 2019-2022  Igara Studio S.A.
 # Copyright (C) 2001-2018  David Capello
 
 ######################################################################
@@ -8,6 +8,9 @@
 if(UNIX)
   # All warnings except for switch cases with missing enum items
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wno-switch")
+
+  # Prefer C++17 [[fallthrough]] attribute
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wimplicit-fallthrough")
 endif()
 
 if(MSVC)

src/app/commands/cmd_undo_history.cpp

@@ -110,6 +110,7 @@ public:
 
         case ui::kMouseDownMessage:
           captureMouse();
+          [[fallthrough]];
 
         case ui::kMouseMoveMessage:
           if (hasCapture()) {

src/app/commands/filters/color_curve_editor.cpp

@@ -120,7 +120,8 @@ bool ColorCurveEditor::onProcessMessage(Message* msg)
 
       captureMouse();
 
-      // continue in motion message...
+      // Continue in motion message...
+      [[fallthrough]];
     }
 
     case kMouseMoveMessage: {

src/app/file/png_format.cpp

@@ -255,12 +255,14 @@ bool PngFormat::onLoad(FileOp* fop)
 
     case PNG_COLOR_TYPE_RGB_ALPHA:
       fop->sequenceSetHasAlpha(true);
+      [[fallthrough]];
     case PNG_COLOR_TYPE_RGB:
       pixelFormat = IMAGE_RGB;
       break;
 
     case PNG_COLOR_TYPE_GRAY_ALPHA:
       fop->sequenceSetHasAlpha(true);
+      [[fallthrough]];
     case PNG_COLOR_TYPE_GRAY:
       pixelFormat = IMAGE_GRAYSCALE;
       break;
@@ -799,6 +801,7 @@ void PngFormat::saveColorSpace(png_structp png_ptr, png_infop info_ptr,
       }
 
       // Continue to RGB case...
+      [[fallthrough]];
 
     case gfx::ColorSpace::RGB: {
       if (colorSpace->hasPrimaries()) {

src/app/ui/browser_view.cpp

@@ -417,6 +417,7 @@ private:
             inImage = true;
           else if (ev_type == CMARK_EVENT_EXIT)
             inImage = false;
+          break;
         }
 
         case CMARK_NODE_LINK: {
@@ -434,6 +435,7 @@ private:
             }
             inLink = nullptr;
           }
+          break;
         }
 
       }

src/app/ui/color_selector.cpp

@@ -316,8 +316,7 @@ bool ColorSelector::onProcessMessage(ui::Message* msg)
         break;
 
       captureMouse();
-
-      // Continue...
+      [[fallthrough]];
 
     case kMouseMoveMessage: {
       MouseMessage* mouseMsg = static_cast<MouseMessage*>(msg);

src/app/ui/file_list.cpp

@@ -178,6 +178,7 @@ bool FileList::onProcessMessage(Message* msg)
 
     case kMouseDownMessage:
       captureMouse();
+      [[fallthrough]];
 
     case kMouseMoveMessage:
       if (hasCapture()) {

src/app/ui/palette_view.cpp

@@ -339,8 +339,7 @@ bool PaletteView::onProcessMessage(Message* msg)
       }
 
       captureMouse();
-
-      // Continue...
+      [[fallthrough]];
 
     case kMouseMoveMessage: {
       MouseMessage* mouseMsg = static_cast<MouseMessage*>(msg);

src/app/ui/toolbar.cpp

@@ -245,7 +245,7 @@ bool ToolBar::onProcessMessage(Message* msg)
       m_openedRecently = false;
 
       releaseMouse();
-      // fallthrough
+      [[fallthrough]];
 
     case kMouseLeaveMessage:
       if (hasCapture())
@@ -609,7 +609,7 @@ bool ToolBar::ToolStrip::onProcessMessage(Message* msg)
 
     case kMouseDownMessage:
       captureMouse();
-      // fallthrough
+      [[fallthrough]];
 
     case kMouseMoveMessage: {
       MouseMessage* mouseMsg = static_cast<MouseMessage*>(msg);

src/doc/handle_anidir.cpp

@@ -50,6 +50,7 @@ frame_t calculate_next_frame(
 
     case AniDir::REVERSE:
       frameDelta = -frameDelta;
+      [[fallthrough]];
 
     case AniDir::FORWARD:
       frame += frameDelta;

src/ui/entry.cpp

@@ -395,6 +395,8 @@ bool Entry::onProcessMessage(Message* msg)
       if (!m_selecting_words.isEmpty())
         m_selecting_words.reset();
 
+      [[fallthrough]];
+
     case kMouseMoveMessage:
       if (hasCapture()) {
         bool is_dirty = false;

src/ui/listbox.cpp

@@ -206,6 +206,7 @@ bool ListBox::onProcessMessage(Message* msg)
 
     case kMouseDownMessage:
       captureMouse();
+      [[fallthrough]];
 
     case kMouseMoveMessage:
       if (hasCapture()) {

src/ui/manager.cpp

@@ -1858,11 +1858,10 @@ bool Manager::processFocusMovementMessage(Message* msg)
         break;
 
       // Arrow keys
-      case kKeyLeft:  if (!cmp) cmp = cmp_left;
-      case kKeyRight: if (!cmp) cmp = cmp_right;
-      case kKeyUp:    if (!cmp) cmp = cmp_up;
+      case kKeyLeft:  if (!cmp) cmp = cmp_left;  [[fallthrough]];
+      case kKeyRight: if (!cmp) cmp = cmp_right; [[fallthrough]];
+      case kKeyUp:    if (!cmp) cmp = cmp_up;    [[fallthrough]];
       case kKeyDown:  if (!cmp) cmp = cmp_down;
-
         // More than one widget
         if (count > 1) {
           // Position where the focus come

src/ui/menu.cpp

@@ -443,7 +443,7 @@ bool MenuBox::onProcessMessage(Message* msg)
       if (!base->was_clicked)
         break;
 
-      //[[fallthrough]];
+      [[fallthrough]];
     }
 
     case kMouseDownMessage:

src/ui/scroll_bar.cpp

@@ -132,7 +132,8 @@ bool ScrollBar::onProcessMessage(Message* msg)
       setSelected(true);
       captureMouse();
 
-      // continue to kMouseMoveMessage handler...
+      // Continue to kMouseMoveMessage handler...
+      [[fallthrough]];
     }
 
     case kMouseMoveMessage:

src/ui/slider.cpp

@@ -115,7 +115,7 @@ bool Slider::onProcessMessage(Message* msg)
 
       setupSliderCursor();
 
-      // Fall through
+      [[fallthrough]];
 
     case kMouseMoveMessage:
       if (hasCapture()) {

src/ui/splitter.cpp

@@ -100,6 +100,7 @@ bool Splitter::onProcessMessage(Message* msg)
         captureMouse();
 
         // Continue with motion message...
+        [[fallthrough]];
       }
       else
         break;