Support legacy X11 keymaps

Not all X server vendors support the XKB protocol. Furthermore,
while X.org seems to use keycodes that match the usual keyboard
scancodes, other vendors may not do so. This means that using an
XKB keymap suitable for an X.org server results in garbled input
with servers for other vendors.
Both of these issues are addressed by using the core keycode
information as a fallback.

[ChangeLog][X11] Fall back to X11 core keycode information
if an XKB keymap could not be determined through the connection.

Task-number: QTBUG-44938
Change-Id: I64568aa31113d5a3fd90f70c63320a497db21477
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

1 files changed, 317 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.cpp b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
index 2fe3e9332a..9aedee109f 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
@@ -59,6 +59,10 @@
 #undef KeyRelease
 #endif
 
+#if QT_CONFIG(xcb_xlib)
+#include <X11/Xutil.h>
+#endif
+
 #ifndef XK_ISO_Left_Tab
 #define XK_ISO_Left_Tab         0xFE20
 #endif
@@ -678,9 +682,303 @@ void QXcbKeyboard::printKeymapError(const char *error) const
              "directory contains recent enough contents, to update please see http://cgit.freedesktop.org/xkeyboard-config/ .");
 }
 
+#if QT_CONFIG(xcb_xlib)
+/* Look at a pair of unshifted and shifted key symbols.
+ * If the 'unshifted' symbol is uppercase and there is no shifted symbol,
+ * return the matching lowercase symbol; otherwise return 0.
+ * The caller can then use the previously 'unshifted' symbol as the new
+ * 'shifted' (uppercase) symbol and the symbol returned by the function
+ * as the new 'unshifted' (lowercase) symbol.) */
+static xcb_keysym_t getUnshiftedXKey(xcb_keysym_t unshifted, xcb_keysym_t shifted)
+{
+    if (shifted != XKB_KEY_NoSymbol) // Has a shifted symbol
+        return 0;
+
+    KeySym xlower;
+    KeySym xupper;
+    /* libxkbcommon >= 0.8.0 will have public API functions providing
+     * functionality equivalent to XConvertCase(), use these once the
+     * minimal libxkbcommon version is high enough. After that the
+     * xcb-xlib dependency can be removed */
+    XConvertCase(static_cast<KeySym>(unshifted), &xlower, &xupper);
+
+    if (xlower != xupper                                     // Check if symbol is cased
+        && unshifted == static_cast<xcb_keysym_t>(xupper)) { // Unshifted must be upper case
+        return static_cast<xcb_keysym_t>(xlower);
+    }
+    return 0;
+}
+
+static QByteArray symbolsGroupString(const xcb_keysym_t *symbols, int count)
+{
+    // Don't output trailing NoSymbols
+    while (count > 0 && symbols[count - 1] == XKB_KEY_NoSymbol)
+        count--;
+
+    QByteArray groupString;
+    for (int symIndex = 0; symIndex < count; symIndex++) {
+        xcb_keysym_t sym = symbols[symIndex];
+        char symString[64];
+        if (sym == XKB_KEY_NoSymbol)
+            strcpy(symString, "NoSymbol");
+        else
+            xkb_keysym_get_name(sym, symString, sizeof(symString));
+
+        if (!groupString.isEmpty())
+            groupString += ", ";
+        groupString += symString;
+    }
+    return groupString;
+}
+
+struct xkb_keymap *QXcbKeyboard::keymapFromCore()
+{
+    /* Construct an XKB keymap string from information queried from
+     * the X server */
+    QByteArray keymap;
+    keymap += "xkb_keymap {\n";
+
+    const xcb_keycode_t minKeycode = connection()->setup()->min_keycode;
+    const xcb_keycode_t maxKeycode = connection()->setup()->max_keycode;
+
+    // Generate symbolic names from keycodes
+    {
+        keymap +=
+            "xkb_keycodes \"core\" {\n"
+            "\tminimum = " + QByteArray::number(minKeycode) + ";\n"
+            "\tmaximum = " + QByteArray::number(maxKeycode) + ";\n";
+        for (int code = minKeycode; code <= maxKeycode; code++) {
+            auto codeStr = QByteArray::number(code);
+            keymap += "<K" + codeStr + "> = " + codeStr + ";\n";
+        }
+        /* TODO: indicators?
+         */
+        keymap += "};\n"; // xkb_keycodes
+    }
+
+    /* Set up default types (xkbcommon automatically assigns these to
+     * symbols, but doesn't have shift info) */
+    keymap +=
+        "xkb_types \"core\" {\n"
+        "virtual_modifiers NumLock,Alt,LevelThree;\n"
+        "type \"ONE_LEVEL\" {\n"
+            "modifiers= none;\n"
+            "level_name[Level1] = \"Any\";\n"
+        "};\n"
+        "type \"TWO_LEVEL\" {\n"
+            "modifiers= Shift;\n"
+            "map[Shift]= Level2;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Shift\";\n"
+        "};\n"
+        "type \"ALPHABETIC\" {\n"
+            "modifiers= Shift+Lock;\n"
+            "map[Shift]= Level2;\n"
+            "map[Lock]= Level2;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Caps\";\n"
+        "};\n"
+        "type \"KEYPAD\" {\n"
+            "modifiers= Shift+NumLock;\n"
+            "map[Shift]= Level2;\n"
+            "map[NumLock]= Level2;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Number\";\n"
+        "};\n"
+        "type \"FOUR_LEVEL\" {\n"
+            "modifiers= Shift+LevelThree;\n"
+            "map[Shift]= Level2;\n"
+            "map[LevelThree]= Level3;\n"
+            "map[Shift+LevelThree]= Level4;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Shift\";\n"
+            "level_name[Level3] = \"Alt Base\";\n"
+            "level_name[Level4] = \"Shift Alt\";\n"
+        "};\n"
+        "type \"FOUR_LEVEL_ALPHABETIC\" {\n"
+            "modifiers= Shift+Lock+LevelThree;\n"
+            "map[Shift]= Level2;\n"
+            "map[Lock]= Level2;\n"
+            "map[LevelThree]= Level3;\n"
+            "map[Shift+LevelThree]= Level4;\n"
+            "map[Lock+LevelThree]= Level4;\n"
+            "map[Shift+Lock+LevelThree]= Level3;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Shift\";\n"
+            "level_name[Level3] = \"Alt Base\";\n"
+            "level_name[Level4] = \"Shift Alt\";\n"
+        "};\n"
+        "type \"FOUR_LEVEL_SEMIALPHABETIC\" {\n"
+            "modifiers= Shift+Lock+LevelThree;\n"
+            "map[Shift]= Level2;\n"
+            "map[Lock]= Level2;\n"
+            "map[LevelThree]= Level3;\n"
+            "map[Shift+LevelThree]= Level4;\n"
+            "map[Lock+LevelThree]= Level3;\n"
+            "preserve[Lock+LevelThree]= Lock;\n"
+            "map[Shift+Lock+LevelThree]= Level4;\n"
+            "preserve[Shift+Lock+LevelThree]= Lock;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Shift\";\n"
+            "level_name[Level3] = \"Alt Base\";\n"
+            "level_name[Level4] = \"Shift Alt\";\n"
+        "};\n"
+        "type \"FOUR_LEVEL_KEYPAD\" {\n"
+            "modifiers= Shift+NumLock+LevelThree;\n"
+            "map[Shift]= Level2;\n"
+            "map[NumLock]= Level2;\n"
+            "map[LevelThree]= Level3;\n"
+            "map[Shift+LevelThree]= Level4;\n"
+            "map[NumLock+LevelThree]= Level4;\n"
+            "map[Shift+NumLock+LevelThree]= Level3;\n"
+            "level_name[Level1] = \"Base\";\n"
+            "level_name[Level2] = \"Number\";\n"
+            "level_name[Level3] = \"Alt Base\";\n"
+            "level_name[Level4] = \"Alt Number\";\n"
+        "};\n"
+        "};\n"; // xkb_types
+
+    // Generate mapping between symbolic names and keysyms
+    {
+        QVector<xcb_keysym_t> xkeymap;
+        int keysymsPerKeycode = 0;
+        {
+            int keycodeCount = maxKeycode - minKeycode + 1;
+            if (auto keymapReply = Q_XCB_REPLY(xcb_get_keyboard_mapping, xcb_connection(),
+                                               minKeycode, keycodeCount)) {
+                keysymsPerKeycode = keymapReply->keysyms_per_keycode;
+                int numSyms = keycodeCount * keysymsPerKeycode;
+                auto keymapPtr = xcb_get_keyboard_mapping_keysyms(keymapReply.get());
+                xkeymap.resize(numSyms);
+                for (int i = 0; i < numSyms; i++)
+                    xkeymap[i] = keymapPtr[i];
+            }
+        }
+        if (xkeymap.isEmpty())
+            return nullptr;
+
+        KeysymModifierMap keysymMods(keysymsToModifiers());
+        static const char *const builtinModifiers[] =
+        { "Shift", "Lock", "Control", "Mod1", "Mod2", "Mod3", "Mod4", "Mod5" };
+
+        /* Level 3 symbols (e.g. AltGr+something) seem to come in two flavors:
+         * - as a proper level 3 in group 1, at least on recent X.org versions
+         * - 'disguised' as group 2, on 'legacy' X servers
+         * In the 2nd case, remap group 2 to level 3, that seems to work better
+         * in practice */
+        bool mapGroup2ToLevel3 = keysymsPerKeycode < 5;
+
+        keymap += "xkb_symbols \"core\" {\n";
+        for (int code = minKeycode; code <= maxKeycode; code++) {
+            auto codeMap = xkeymap.constData() + (code - minKeycode) * keysymsPerKeycode;
+
+            const int maxGroup1 = 4; // We only support 4 shift states anyway
+            const int maxGroup2 = 2; // Only 3rd and 4th keysym are group 2
+            xcb_keysym_t symbolsGroup1[maxGroup1];
+            xcb_keysym_t symbolsGroup2[maxGroup2];
+            for (int i = 0; i < maxGroup1 + maxGroup2; i++) {
+                xcb_keysym_t sym = i < keysymsPerKeycode ? codeMap[i] : XKB_KEY_NoSymbol;
+                if (mapGroup2ToLevel3) {
+                    // Merge into single group
+                    if (i < maxGroup1)
+                        symbolsGroup1[i] = sym;
+                } else {
+                    // Preserve groups
+                    if (i < 2)
+                        symbolsGroup1[i] = sym;
+                    else if (i < 4)
+                        symbolsGroup2[i - 2] = sym;
+                    else
+                        symbolsGroup1[i - 2] = sym;
+                }
+            }
+
+            /* Fix symbols so the unshifted and shifted symbols have
+             * lower resp. upper case */
+            if (auto lowered = getUnshiftedXKey(symbolsGroup1[0], symbolsGroup1[1])) {
+                symbolsGroup1[1] = symbolsGroup1[0];
+                symbolsGroup1[0] = lowered;
+            }
+            if (auto lowered = getUnshiftedXKey(symbolsGroup2[0], symbolsGroup2[1])) {
+                symbolsGroup2[1] = symbolsGroup2[0];
+                symbolsGroup2[0] = lowered;
+            }
+
+            QByteArray groupStr1 = symbolsGroupString(symbolsGroup1, maxGroup1);
+            if (groupStr1.isEmpty())
+                continue;
+
+            keymap += "key <K" + QByteArray::number(code) + "> { ";
+            keymap += "symbols[Group1] = [ " + groupStr1 + " ]";
+            QByteArray groupStr2 = symbolsGroupString(symbolsGroup2, maxGroup2);
+            if (!groupStr2.isEmpty())
+                keymap += ", symbols[Group2] = [ " + groupStr2 + " ]";
+
+            // See if this key code is for a modifier
+            xcb_keysym_t modifierSym = XKB_KEY_NoSymbol;
+            for (int symIndex = 0; symIndex < keysymsPerKeycode; symIndex++) {
+                xcb_keysym_t sym = codeMap[symIndex];
+
+                if (sym == XKB_KEY_Alt_L
+                    || sym == XKB_KEY_Meta_L
+                    || sym == XKB_KEY_Mode_switch
+                    || sym == XKB_KEY_Super_L
+                    || sym == XKB_KEY_Super_R
+                    || sym == XKB_KEY_Hyper_L
+                    || sym == XKB_KEY_Hyper_R) {
+                    modifierSym = sym;
+                    break;
+                }
+            }
+
+            // AltGr
+            if (modifierSym == XKB_KEY_Mode_switch)
+                keymap += ", virtualMods=LevelThree";
+            keymap += " };\n"; // key
+
+            // Generate modifier mappings
+            int modNum = keysymMods.value(modifierSym, -1);
+            if (modNum != -1) {
+                // Here modNum is always < 8 (see keysymsToModifiers())
+                keymap += QByteArray("modifier_map ") + builtinModifiers[modNum]
+                    + " { <K" + QByteArray::number(code) + "> };\n";
+            }
+        }
+        // TODO: indicators?
+        keymap += "};\n"; // xkb_symbols
+    }
+
+    // We need an "Alt" modifier, provide via the xkb_compatibility section
+    keymap +=
+        "xkb_compatibility \"core\" {\n"
+        "virtual_modifiers NumLock,Alt,LevelThree;\n"
+        "interpret Alt_L+AnyOf(all) {\n"
+            "virtualModifier= Alt;\n"
+            "action= SetMods(modifiers=modMapMods,clearLocks);\n"
+        "};\n"
+        "interpret Alt_R+AnyOf(all) {\n"
+            "virtualModifier= Alt;\n"
+            "action= SetMods(modifiers=modMapMods,clearLocks);\n"
+        "};\n"
+        "};\n";
+
+    /* TODO: There is an issue with modifier state not being handled
+     * correctly if using Xming with XKEYBOARD disabled. */
+
+    keymap += "};\n"; // xkb_keymap
+
+    return xkb_keymap_new_from_buffer(xkb_context,
+                                      keymap.constData(),
+                                      keymap.size(),
+                                      XKB_KEYMAP_FORMAT_TEXT_V1,
+                                      static_cast<xkb_keymap_compile_flags>(0));
+}
+#endif
+
 void QXcbKeyboard::updateKeymap()
 {
     m_config = true;
+    m_keymap_is_core = false;
     // set xkb context object
     if (!xkb_context) {
         if (qEnvironmentVariableIsSet("QT_XKB_CONFIG_ROOT")) {
@@ -714,9 +1012,23 @@ void QXcbKeyboard::updateKeymap()
     }
 #endif
     if (!xkb_keymap) {
-        // Compile a keymap from RMLVO (rules, models, layouts, variants and options) names
+        // Read xkb RMLVO (rules, models, layouts, variants and options) names
         readXKBConfig();
-        xkb_keymap = xkb_keymap_new_from_names(xkb_context, &xkb_names, (xkb_keymap_compile_flags)0);
+#if QT_CONFIG(xcb_xlib)
+        bool rmlvo_is_incomplete = !xkb_names.rules || !(*xkb_names.rules)
+            || !xkb_names.model || !(*xkb_names.model)
+            || !xkb_names.layout || !(*xkb_names.layout);
+        if (rmlvo_is_incomplete) {
+            // Try to build xkb map from core mapping information
+            xkb_keymap = keymapFromCore();
+            m_keymap_is_core = xkb_keymap != 0;
+        }
+#endif
+        if (!xkb_keymap) {
+            // Compile a keymap from RMLVO
+            xkb_keymap = xkb_keymap_new_from_names(xkb_context, &xkb_names,
+                static_cast<xkb_keymap_compile_flags> (0));
+        }
         if (!xkb_keymap) {
             // last fallback is to used hard-coded keymap name, see DEFAULT_XKB_* in xkbcommon.pri
             qWarning() << "Qt: Could not determine keyboard configuration data"
@@ -908,9 +1220,11 @@ xkb_keysym_t QXcbKeyboard::lookupLatinKeysym(xkb_keycode_t keycode) const
     // If user layouts don't contain any layout that results in a latin key, we query a
     // key from "US" layout, this allows for latin-key-based shorcuts to work even when
     // users have only one (non-latin) layout set.
+    // But don't do this if using keymap obtained through the core protocol, as the key
+    // codes may not match up with those expected by the XKB keymap.
     xkb_mod_mask_t latchedMods = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LATCHED);
     xkb_mod_mask_t lockedMods = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LOCKED);
-    if (sym == XKB_KEY_NoSymbol && !m_hasLatinLayout) {
+    if (sym == XKB_KEY_NoSymbol && !m_hasLatinLayout && !m_keymap_is_core) {
         if (!latin_keymap) {
             const struct xkb_rule_names names = { xkb_names.rules, xkb_names.model, "us", 0, 0 };
             latin_keymap = xkb_keymap_new_from_names(xkb_context, &names, (xkb_keymap_compile_flags)0);