platform: Add support for keyboard modifiers in GPM events

Author: magiblot

include/tvision/internal/linuxcon.h

@@ -30,7 +30,9 @@ struct LinuxConsoleInput final : public EventSource
     bool getEvent(TEvent &ev) noexcept override;
     bool hasPendingEvents() noexcept override;
 
-    static ushort getKeyboardModifiers(StdioCtl &io) noexcept;
+    ushort getKeyboardModifiers() noexcept;
+
+    static ushort convertLinuxKeyModifiers(ushort linuxShiftState) noexcept;
 };
 
 class LinuxConsoleStrategy : public ConsoleStrategy

source/platform/gpminput.cpp

@@ -7,6 +7,7 @@
 #include <internal/gpminput.h>
 #include <internal/dispbuff.h>
 #include <internal/linuxcon.h>
+#include <linux/keyboard.h>
 #include <stdlib.h>
 #include <gpm.h>
 
@@ -20,11 +21,11 @@ GpmInput *GpmInput::create(DisplayBuffer &displayBuf) noexcept
     Gpm_Connect conn = {
         .eventMask = GPM_DOWN | GPM_UP | GPM_DRAG | GPM_MOVE,
         .defaultMask = 0, // Disable cursor drawing by the server.
-        /* Disable mouse event reporting when keyboard modifiers are active.
-         * In such case, GPM text selection and copy/paste will be active. */
+        // Report keyboard modifiers except Shift, which terminal emulators
+        // usually reserve for selecting text. Here GPM will do the same.
         .minMod = 0,
-        .maxMod = 0 };
-    // Because we only instantiate GPM in the Linux console, discard the
+        .maxMod = (ushort) ~(1 << KG_SHIFT) };
+    // Because we only instantiate GPM in the Linux console, unset the
     // TERM variable during Gpm_Open so that GPM won't assume it is being
     // ran under xterm (e.g. if TERM=xterm), and 'gpm_fd' won't be -2.
     char *term = newStr(getenv("TERM"));
@@ -82,6 +83,7 @@ bool GpmInput::getEvent(TEvent &ev) noexcept
         ev.what = evMouse;
         ev.mouse.where.x = gpmEvent.x;
         ev.mouse.where.y = gpmEvent.y;
+
         for (const auto &flag : gpmButtonFlags)
             if (gpmEvent.buttons & flag.gpm)
             {
@@ -91,12 +93,17 @@ bool GpmInput::getEvent(TEvent &ev) noexcept
                     buttonState &= ~flag.mb;
             }
         ev.mouse.buttons = buttonState;
+
         if (gpmEvent.wdy)
             ev.mouse.wheel = gpmEvent.wdy > 0 ? mwUp : mwDown;
         else if (gpmEvent.wdx)
             ev.mouse.wheel = gpmEvent.wdx > 0 ? mwRight : mwLeft;
         else
             ev.mouse.wheel = 0;
+
+        ev.mouse.controlKeyState =
+            LinuxConsoleInput::convertLinuxKeyModifiers(gpmEvent.modifiers);
+
         return true;
     }
     return false;

source/platform/linuxcon.cpp

@@ -62,7 +62,7 @@ bool LinuxConsoleInput::getEvent(TEvent &ev) noexcept
     if (input.getEvent(ev))
     {
         auto &keyCode = ev.keyDown.keyCode;
-        ev.keyDown.controlKeyState = getKeyboardModifiers(io);
+        ev.keyDown.controlKeyState = getKeyboardModifiers();
         // Prevent Ctrl+H/Ctrl+I/Ctrl+J/Ctrl+M from being interpreted as
         // Ctrl+Back/Ctrl+Tab/Ctrl+Enter.
         if (keyCode == kbBack || keyCode == kbTab || keyCode == kbEnter)
@@ -83,20 +83,37 @@ bool LinuxConsoleInput::hasPendingEvents() noexcept
     return input.hasPendingEvents();
 }
 
-ushort LinuxConsoleInput::getKeyboardModifiers(StdioCtl &io) noexcept
+ushort LinuxConsoleInput::getKeyboardModifiers() noexcept
 {
     char res = 6;
-    ulong actualModifiers = 0;
     if (ioctl(io.in(), TIOCLINUX, &res) != -1)
+        return convertLinuxKeyModifiers(res);
+    return 0;
+}
+
+ushort LinuxConsoleInput::convertLinuxKeyModifiers(ushort linuxShiftState) noexcept
+{
+    constexpr struct
     {
-        if (res & (1 << KG_SHIFT))
-            actualModifiers |= kbShift;
-        if (res & (1 << KG_CTRL))
-            actualModifiers |= kbLeftCtrl;
-        if (res & (1 << KG_ALT))
-            actualModifiers |= kbLeftAlt;
-    }
-    return actualModifiers;
+        uchar kb;
+        uchar tv;
+    } linuxModifierFlags[] =
+    {
+        {1 << KG_SHIFT, kbShift},
+        {1 << KG_CTRLL, kbLeftCtrl},
+        {1 << KG_CTRLR, kbRightCtrl},
+        {1 << KG_ALT, kbLeftAlt},
+        {1 << KG_ALTGR, kbRightAlt},
+    };
+
+    ushort modifiers = 0;
+    for (const auto &flags : linuxModifierFlags)
+        if (linuxShiftState & flags.kb)
+            modifiers |= flags.tv;
+    // It may be that KG_CTRL was detected, but not KG_CTRLL or KG_CTRLR.
+    if ((linuxShiftState & (1 << KG_CTRL)) && !(modifiers & kbCtrlShift))
+        modifiers |= kbLeftCtrl;
+    return modifiers;
 }
 
 } // namespace tvision