platform: find a universal solution for consuming unprocessed input

The problem that we fixed for far2l (#49) can be also reproduced with Conpty and win32-input-mode.

I figured out that we can get any terminal to reply to us with a Device Status Report. So use that instead of relying on the far2l protocol.

This commit also fixes a bug when consuming unprocessed input. With a slow connection, we would fail to read the terminal response, which is why we were forced to add a timeout in 08d8357. This was caused by calling NcursesInput::getEvent, which would at times interpret the response sequence as an Alt+Key combination. In order to prevent confusion when debugging, wgetch is now only called directly from NcursesInputGetter.

include/tvision/internal/far2l.h

@@ -10,18 +10,13 @@ class EventSource;
 
 #define far2lEnableSeq "\x1B_far2l1\x1B\\"
 #define far2lDisableSeq "\x1B_far2l0\x1B\\"
-#define far2lPingSeq "\x1B_far2l:FAR=\x1B\\"
-
-enum { pingTimeout = 200 };
 
 ParseResult parseFar2lAnswer(GetChBuf &, TEvent &, InputState &) noexcept;
 ParseResult parseFar2lInput(GetChBuf &, TEvent &, InputState &) noexcept;
 
 bool setFar2lClipboard(StdioCtl &, TStringView, InputState &) noexcept;
 bool requestFar2lClipboard(StdioCtl &, InputState &) noexcept;
 
-void waitFar2lPing(EventSource &, InputState &) noexcept;
-
 } // namespace tvision
 
 #endif // TVISION_FAR2L_H

include/tvision/internal/ncursinp.h

@@ -10,38 +10,47 @@
 #define Uses_TEvent
 #include <tvision/tv.h>
 
+#include <internal/terminal.h>
+
 namespace tvision
 {
 
 class NcursesDisplay;
-struct InputState;
+
+struct NcursesInputGetter final : public InputGetter
+{
+    size_t pendingCount {0};
+
+    int get() noexcept override;
+    void unget(int k) noexcept override;
+};
 
 class NcursesInput : public InputStrategy
 {
     enum : char { KEY_ESC = '\x1B' };
-    enum { readTimeout = 10 };
+    enum { readTimeoutMs = 10 };
 
     StdioCtl &io;
     InputState &state;
     bool mouseEnabled;
+    NcursesInputGetter in;
 
-    static int getch_nb() noexcept;
+    int getChNb() noexcept;
     void detectAlt(int keys[4], bool &Alt) noexcept;
     void parsePrintableChar(TEvent &ev, int keys[4], int &num_keys) noexcept;
     void readUtf8Char(int keys[4], int &num_keys) noexcept;
 
     bool parseCursesMouse(TEvent&) noexcept;
-    void consumeUnprocessedInput() noexcept;
 
 public:
 
     // Lifetimes of 'io', 'display' and 'state' must exceed that of 'this'.
     NcursesInput(StdioCtl &io, NcursesDisplay &display, InputState &state, bool mouse) noexcept;
     ~NcursesInput();
 
-    bool getEvent(TEvent &ev) noexcept;
-    int getButtonCount() noexcept;
-    bool hasPendingEvents() noexcept;
+    bool getEvent(TEvent &ev) noexcept override;
+    int getButtonCount() noexcept override;
+    bool hasPendingEvents() noexcept override;
 };
 
 } // namespace tvision

include/tvision/internal/terminal.h

@@ -11,7 +11,6 @@ namespace tvision
 {
 
 class StdioCtl;
-class EventSource;
 
 struct Far2lState
 {
@@ -27,6 +26,7 @@ struct InputState
     Far2lState far2l;
     bool hasFullOsc52 {false};
     bool bracketedPaste {false};
+    bool gotDsrResponse {false};
     void (*putPaste)(TStringView) {nullptr};
 };
 
@@ -123,7 +123,7 @@ namespace TermIO
     void mouseOn(StdioCtl &) noexcept;
     void mouseOff(StdioCtl &) noexcept;
     void keyModsOn(StdioCtl &) noexcept;
-    void keyModsOff(StdioCtl &, EventSource &, InputState &) noexcept;
+    void keyModsOff(StdioCtl &) noexcept;
 
     void normalizeKey(KeyDownEvent &keyDown) noexcept;
 
@@ -141,9 +141,11 @@ namespace TermIO
     ParseResult parseFixTermKey(const CSIData &csi, TEvent&) noexcept;
     ParseResult parseDCS(GetChBuf&, InputState&) noexcept;
     ParseResult parseOSC(GetChBuf&, InputState&) noexcept;
+    ParseResult parseCPR(const CSIData &csi, InputState&) noexcept;
     ParseResult parseWin32InputModeKeyOrEscapeSeq(const CSIData &, InputGetter&, TEvent&, InputState&) noexcept;
 
     char *readUntilBelOrSt(GetChBuf &) noexcept;
+    void consumeUnprocessedInput(StdioCtl &, InputGetter &, InputState &) noexcept;
 }
 
 } // namespace tvision

source/platform/far2l.cpp

@@ -6,10 +6,6 @@
 #include <internal/constmap.h>
 #include <internal/base64.h>
 #include <internal/events.h>
-#include <chrono>
-
-using std::chrono::milliseconds;
-using std::chrono::steady_clock;
 
 #include <time.h>
 
@@ -19,7 +15,6 @@ namespace tvision
 // Request IDs
 const char
     f2lNoAnswer = '\0',
-    f2lPing = '\x04',
     f2lClipGetData = '\xA0';
 
 static char f2lClientIdData[32 + 1];
@@ -157,12 +152,6 @@ ParseResult parseFar2lAnswer(GetChBuf &buf, TEvent &ev, InputState &state) noexc
                     state.putPaste(text);
                 }
             }
-            else if (decoded.size() > 0 && decoded.back() == f2lPing)
-            {
-                ev.what = evNothing;
-                ev.message.infoPtr = &state.far2l;
-                res = Accepted;
-            }
             free(pDecoded);
         }
         free(s);
@@ -295,19 +284,4 @@ bool requestFar2lClipboard(StdioCtl &io, InputState &state) noexcept
     return false;
 }
 
-void waitFar2lPing(EventSource &source, InputState &state) noexcept
-{
-    if (state.far2l.enabled)
-    {
-        TEvent ev {};
-        auto begin = steady_clock::now();
-        do
-        {
-            source.getEvent(ev);
-        }
-        while ( (ev.what != evNothing || ev.message.infoPtr != &state.far2l) &&
-                steady_clock::now() - begin <= milliseconds(pingTimeout) );
-    }
-}
-
 } // namespace tvision

source/platform/ncursinp.cpp

@@ -7,7 +7,6 @@
 
 #include <ncurses.h>
 #include <internal/ncursinp.h>
-#include <internal/terminal.h>
 #include <internal/getenv.h>
 #include <internal/utf8.h>
 #include <internal/stdioctl.h>
@@ -256,19 +255,19 @@ static const auto fromCursesHighKey =
     { "kc2",        {{kbDown},          0} },
 });
 
-static class NcursesInputGetter : public InputGetter
+int NcursesInputGetter::get() noexcept
 {
-    int get() noexcept override
-    {
-        int k = wgetch(stdscr);
-        return k != ERR ? k : -1;
-    }
+    int k = wgetch(stdscr);
+    if (pendingCount > 0)
+        --pendingCount;
+    return k != ERR ? k : -1;
+}
 
-    void unget(int k) noexcept override
-    {
-        ungetch(k);
-    }
-} ncInputGetter;
+void NcursesInputGetter::unget(int k) noexcept
+{
+    if (ungetch(k) != ERR)
+        ++pendingCount;
+}
 
 NcursesInput::NcursesInput( StdioCtl &aIo, NcursesDisplay &,
                             InputState &aState, bool mouse ) noexcept :
@@ -288,7 +287,7 @@ NcursesInput::NcursesInput( StdioCtl &aIo, NcursesDisplay &,
     // Make getch practically non-blocking. Some terminals may feed input slowly.
     // Note that we only risk blocking when reading multibyte characters
     // or parsing escape sequences.
-    wtimeout(stdscr, readTimeout);
+    wtimeout(stdscr, readTimeoutMs);
     /* Do not delay too much on ESC key presses, as the Alt modifier works well
      * in most modern terminals. Still, this delay helps ncurses distinguish
      * special key sequences, I believe. */
@@ -303,8 +302,8 @@ NcursesInput::~NcursesInput()
 {
     if (mouseEnabled)
         TermIO::mouseOff(io);
-    TermIO::keyModsOff(io, *this, state);
-    consumeUnprocessedInput();
+    TermIO::keyModsOff(io);
+    TermIO::consumeUnprocessedInput(io, in, state);
 }
 
 int NcursesInput::getButtonCount() noexcept
@@ -314,36 +313,30 @@ int NcursesInput::getButtonCount() noexcept
     return mouseEnabled ? 2 : 0;
 }
 
-int NcursesInput::getch_nb() noexcept
+int NcursesInput::getChNb() noexcept
 {
     wtimeout(stdscr, 0);
-    int k = wgetch(stdscr);
-    wtimeout(stdscr, readTimeout);
+    int k = in.get();
+    wtimeout(stdscr, readTimeoutMs);
     return k;
 }
 
 bool NcursesInput::hasPendingEvents() noexcept
 {
-    int k = getch_nb();
-    if (k != ERR)
-    {
-        ungetch(k);
-        return true;
-    }
-    return false;
+    return in.pendingCount > 0;
 }
 
 bool NcursesInput::getEvent(TEvent &ev) noexcept
 {
-    GetChBuf buf(ncInputGetter);
+    GetChBuf buf(in);
     switch (TermIO::parseEvent(buf, ev, state))
     {
         case Rejected: buf.reject(); break;
         case Accepted: return true;
         case Ignored: return false;
     }
 
-    int k = wgetch(stdscr);
+    int k = in.get();
 
     if (k == KEY_RESIZE)
         return false; // Handled by SigwinchHandler.
@@ -394,7 +387,7 @@ void NcursesInput::detectAlt(int keys[4], bool &Alt) noexcept
  * we check if another character has been received. If it has, we consider this
  * an Alt+Key combination. Of course, many other things sent by the terminal
  * begin with ESC, but ncurses already identifies most of them. */
-    int k = getch_nb();
+    int k = getChNb();
     if (k != ERR)
     {
         keys[0] = k;
@@ -423,7 +416,7 @@ void NcursesInput::readUtf8Char(int keys[4], int &num_keys) noexcept
  * have to predict the number of bytes it is composed of, then read as many. */
     num_keys += Utf8BytesLeft((char) keys[0]);
     for (int i = 1; i < num_keys; ++i)
-        if ( ERR == (keys[i] = wgetch(stdscr)) )
+        if ((keys[i] = in.get()) == -1)
         {
             num_keys = i;
             break;
@@ -472,7 +465,7 @@ bool NcursesInput::parseCursesMouse(TEvent &ev) noexcept
         for (auto &parseMouse : {TermIO::parseSGRMouse,
                                  TermIO::parseX10Mouse})
         {
-            GetChBuf buf(ncInputGetter);
+            GetChBuf buf(in);
             switch (parseMouse(buf, ev, state))
             {
                 case Rejected: buf.reject(); break;
@@ -484,20 +477,6 @@ bool NcursesInput::parseCursesMouse(TEvent &ev) noexcept
     }
 }
 
-void NcursesInput::consumeUnprocessedInput() noexcept
-{
-    // This may be useful if the terminal has sent us events right before we
-    // disabled keyboard and mouse extensions, or if we have been killed by
-    // a signal.
-    TEvent ev;
-    wtimeout(stdscr, 0);
-    auto begin = steady_clock::now();
-    while ( getEvent(ev) &&
-            steady_clock::now() - begin <= milliseconds(readTimeout) )
-        ;
-    wtimeout(stdscr, readTimeout);
-}
-
 } // namespace tvision
 
 #endif // HAVE_NCURSES