Add QKeySequence::Backspace

Handle it in QWidgetTextControl. Add Meta(ctrl) + H
key sequence binding on Mac.

Task-number: QTBUG-32837
Change-Id: Ib1cbb2ce2e20350b4d8c72bd320dff27c1467f2b
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>

src/gui/kernel/qkeysequence.cpp

@@ -289,6 +289,7 @@ void Q_GUI_EXPORT qt_set_sequence_auto_mnemonic(bool b) { qt_sequence_no_mnemoni
     \row    \li DeleteCompleteLine   \li (none)                           \li (none)                 \li Ctrl+U         \li Ctrl+U
     \row    \li InsertParagraphSeparator     \li Enter                    \li Enter                  \li Enter          \li Enter
     \row    \li InsertLineSeparator          \li Shift+Enter              \li Meta+Enter, Meta+O     \li Shift+Enter    \li Shift+Enter
+    \row    \li Backspace             \li (none)                          \li Meta+H                 \li (none)         \li (none)
     \endtable
 
     Note that, since the key sequences used for the standard shortcuts differ
@@ -679,6 +680,7 @@ static const struct {
 
     \value AddTab           Add new tab.
     \value Back             Navigate back.
+    \value Backspace        Delete previous character.
     \value Bold             Bold text.
     \value Close            Close document/tab.
     \value Copy             Copy.

src/gui/kernel/qkeysequence.h

@@ -134,7 +134,8 @@ public:
         Quit,
         FullScreen,
         Deselect,
-        DeleteCompleteLine
+        DeleteCompleteLine,
+        Backspace
      };
 
     enum SequenceFormat {

src/gui/kernel/qplatformtheme.cpp

@@ -320,7 +320,8 @@ const QKeyBinding QPlatformThemePrivate::keyBindings[] = {
     {QKeySequence::FullScreen,              1,          Qt::CTRL | Qt::Key_F11,                 KB_Gnome},
     {QKeySequence::FullScreen,              1,          Qt::Key_F11,                            KB_Win | KB_KDE},
     {QKeySequence::Deselect,                0,          Qt::CTRL | Qt::SHIFT | Qt::Key_A,       KB_X11},
-    {QKeySequence::DeleteCompleteLine,      0,          Qt::CTRL | Qt::Key_U,                   KB_X11}
+    {QKeySequence::DeleteCompleteLine,      0,          Qt::CTRL | Qt::Key_U,                   KB_X11},
+    {QKeySequence::Backspace,               0,          Qt::META | Qt::Key_H,                   KB_Mac}
 };
 
 const uint QPlatformThemePrivate::numberOfKeyBindings = sizeof(QPlatformThemePrivate::keyBindings)/(sizeof(QKeyBinding));

src/widgets/widgets/qwidgettextcontrol.cpp

@@ -1312,8 +1312,10 @@ void QWidgetTextControlPrivate::keyPressEvent(QKeyEvent *e)
     else if (e == QKeySequence::Delete) {
         QTextCursor localCursor = cursor;
         localCursor.deleteChar();
-    }
-    else if (e == QKeySequence::DeleteEndOfWord) {
+    } else if (e == QKeySequence::Backspace) {
+        QTextCursor localCursor = cursor;
+        localCursor.deletePreviousChar();
+    }else if (e == QKeySequence::DeleteEndOfWord) {
         if (!cursor.hasSelection())
             cursor.movePosition(QTextCursor::NextWord, QTextCursor::KeepAnchor);
         cursor.removeSelectedText();