Add ability to use mnemonic without modifiers in alerts

Requested in https://community.aseprite.org/t/16845

src/ui/alert.cpp

@@ -111,7 +111,12 @@ void Alert::addSeparator()
 void Alert::addButton(const std::string& text)
 {
   auto button = new Button(text);
-  button->processMnemonicFromText();
+
+  // Process the mnemonic next to & character and "false" means that
+  // the mnemonic letter can be used without Alt or Command key
+  // modifiers.
+  button->processMnemonicFromText('&', false);
+
   button->setMinSize(gfx::Size(60*guiscale(), 0));
   m_buttons.push_back(button);
 

src/ui/button.cpp

@@ -80,8 +80,11 @@ bool ButtonBase::onProcessMessage(Message* msg)
       KeyScancode scancode = keymsg->scancode();
 
       if (isEnabled() && isVisible()) {
-        bool mnemonicPressed =
-          ((msg->altPressed() || msg->cmdPressed()) &&
+        const bool mnemonicPressed =
+          (mnemonic() &&
+           (!mnemonicRequiresModifiers() ||
+            msg->altPressed() ||
+            msg->cmdPressed()) &&
            isMnemonicPressed(keymsg));
 
         // For kButtonWidget

src/ui/widget.cpp

@@ -1503,12 +1503,18 @@ gfx::Point Widget::mousePosInDisplay() const
   return display()->nativeWindow()->pointFromScreen(get_mouse_position());
 }
 
-void Widget::setMnemonic(int mnemonic)
+void Widget::setMnemonic(const int mnemonic,
+                         const bool requireModifiers)
 {
-  m_mnemonic = mnemonic;
+  static_assert((kMnemonicCharMask & kMnemonicModifiersMask) == 0);
+  ASSERT((mnemonic & kMnemonicModifiersMask) == 0);
+  m_mnemonic =
+    (mnemonic & kMnemonicCharMask) |
+    (requireModifiers ? kMnemonicModifiersMask: 0);
 }
 
-void Widget::processMnemonicFromText(int escapeChar)
+void Widget::processMnemonicFromText(const int escapeChar,
+                                     const bool requireModifiers)
 {
   // Avoid calling setText() when the widget doesn't have the HAS_TEXT flag
   if (!hasText())
@@ -1526,7 +1532,7 @@ void Widget::processMnemonicFromText(int escapeChar)
         break;    // Ill-formed string (it ends with escape character)
       }
       else if (chr != escapeChar) {
-        setMnemonic(chr);
+        setMnemonic(chr, requireModifiers);
       }
     }
     newText.push_back(chr);

src/ui/widget.h

@@ -372,14 +372,23 @@ namespace ui {
 
     // Returns lower-case letter that represet the mnemonic of the widget
     // (the underscored character, i.e. the letter after & symbol).
-    int mnemonic() const { return m_mnemonic; }
-    void setMnemonic(int mnemonic);
+    int mnemonic() const {
+      return (m_mnemonic & kMnemonicCharMask);
+    }
+    bool mnemonicRequiresModifiers() const {
+      return (m_mnemonic & kMnemonicModifiersMask ? true: false);
+    }
+    void setMnemonic(const int mnemonic,
+                     const bool requireModifiers);
 
     // Assigns mnemonic from the character preceded by the given
     // escapeChar ('&' by default).
-    void processMnemonicFromText(int escapeChar = '&');
+    void processMnemonicFromText(const int escapeChar = '&',
+                                 const bool requireModifiers = true);
 
-    // Returns true if the mnemonic character is pressed.
+    // Returns true if the mnemonic character is pressed (without modifiers).
+    // TODO maybe we can add check for modifiers now that this
+    //      information is included in the Widget
     bool isMnemonicPressed(const ui::KeyMessage* keyMsg) const;
 
     // Signals
@@ -437,7 +446,14 @@ namespace ui {
     Widget* m_parent;             // Who is the parent?
     int m_parentIndex;            // Location/index of this widget in the parent's Widget::m_children vector
     gfx::Size* m_sizeHint;
-    int m_mnemonic;               // Keyboard shortcut to access this widget like Alt+mnemonic
+
+    // Keyboard shortcut to access this widget like Alt+mnemonic.  If
+    // kMnemonicModifiersMask bit is zero, it means that the mnemonic
+    // can be used without Alt or Command key modifiers (useful for
+    // buttons in ui::Alert).
+    static constexpr int kMnemonicCharMask = 0x7f;
+    static constexpr int kMnemonicModifiersMask = 0x80;
+    int m_mnemonic;
 
     // Widget size limits
     gfx::Size m_minSize, m_maxSize;