QWasmEventTranslator: replace five QHash with constexpr C arrays

The mapping is static, but a dynamic (even mutable) container was
used.

Fix by using C tables and liner scan, which will be just as fast or
faster than a hash lookup, for the maximum of six entries of each
table.

Change-Id: I899d5b1428dc82cf58862f238595a266aef8279f
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 59 insertions, 5 deletions

diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
index 3895646b89..d165ee5839 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
@@ -779,6 +779,60 @@ quint64 QWasmEventTranslator::getTimestamp()
     return QDeadlineTimer::current().deadlineNSecs() / 1000;
 }
 
+struct KeyMapping { Qt::Key from, to; };
+
+constexpr KeyMapping tildeKeyTable[] = { // ~
+    { Qt::Key_A, Qt::Key_Atilde },
+    { Qt::Key_N, Qt::Key_Ntilde },
+    { Qt::Key_O, Qt::Key_Otilde },
+};
+constexpr KeyMapping graveKeyTable[] = { // `
+    { Qt::Key_A, Qt::Key_Agrave },
+    { Qt::Key_E, Qt::Key_Egrave },
+    { Qt::Key_I, Qt::Key_Igrave },
+    { Qt::Key_O, Qt::Key_Ograve },
+    { Qt::Key_U, Qt::Key_Ugrave },
+};
+constexpr KeyMapping acuteKeyTable[] = { // '
+    { Qt::Key_A, Qt::Key_Aacute },
+    { Qt::Key_E, Qt::Key_Eacute },
+    { Qt::Key_I, Qt::Key_Iacute },
+    { Qt::Key_O, Qt::Key_Oacute },
+    { Qt::Key_U, Qt::Key_Uacute },
+    { Qt::Key_Y, Qt::Key_Yacute },
+};
+constexpr KeyMapping diaeresisKeyTable[] = { // umlaut ¨
+    { Qt::Key_A, Qt::Key_Adiaeresis },
+    { Qt::Key_E, Qt::Key_Ediaeresis },
+    { Qt::Key_I, Qt::Key_Idiaeresis },
+    { Qt::Key_O, Qt::Key_Odiaeresis },
+    { Qt::Key_U, Qt::Key_Udiaeresis },
+    { Qt::Key_Y, Qt::Key_ydiaeresis },
+};
+constexpr KeyMapping circumflexKeyTable[] = { // ^
+    { Qt::Key_A, Qt::Key_Acircumflex },
+    { Qt::Key_E, Qt::Key_Ecircumflex },
+    { Qt::Key_I, Qt::Key_Icircumflex },
+    { Qt::Key_O, Qt::Key_Ocircumflex },
+    { Qt::Key_U, Qt::Key_Ucircumflex },
+};
+
+static Qt::Key find_impl(const KeyMapping *first, const KeyMapping *last, Qt::Key key) noexcept
+{
+    while (first != last) {
+        if (first->from == key)
+            return first->to;
+        ++first;
+    }
+    return {};
+}
+
+template <size_t N>
+static Qt::Key find(const KeyMapping (&map)[N], Qt::Key key) noexcept
+{
+    return find_impl(map, map + N, key);
+}
+
 Qt::Key QWasmEventTranslator::translateDeadKey(Qt::Key deadKey, Qt::Key accentBaseKey)
 {
     Qt::Key wasmKey = Qt::Key_unknown;
@@ -788,25 +842,25 @@ Qt::Key QWasmEventTranslator::translateDeadKey(Qt::Key deadKey, Qt::Key accentBa
 #else
     case Qt::Key_O: // ´ Key_Dead_Grave
 #endif
-        wasmKey = graveKeyTable.value(accentBaseKey);
+        wasmKey = find(graveKeyTable, accentBaseKey);
         break;
     case Qt::Key_E: // ´ Key_Dead_Acute
-        wasmKey = acuteKeyTable.value(accentBaseKey);
+        wasmKey = find(acuteKeyTable, accentBaseKey);
         break;
     case Qt::Key_AsciiTilde:
     case Qt::Key_N:// Key_Dead_Tilde
-        wasmKey = tildeKeyTable.value(accentBaseKey);
+        wasmKey = find(tildeKeyTable, accentBaseKey);
         break;
 #ifndef Q_OS_MACOS
     case Qt::Key_QuoteLeft:
 #endif
     case Qt::Key_U:// ¨ Key_Dead_Diaeresis
-        wasmKey = diaeresisKeyTable.value(accentBaseKey);
+        wasmKey = find(diaeresisKeyTable, accentBaseKey);
         break;
     case Qt::Key_I:// macOS Key_Dead_Circumflex
     case Qt::Key_6:// linux
     case Qt::Key_Apostrophe:// linux
-        wasmKey = circumflexKeyTable.value(accentBaseKey);
+        wasmKey = find(circumflexKeyTable, accentBaseKey);
         break;
         break;
     default: