SyncTERM Font Support Detection

* Attempt to detect SyncTERM font support using DSR/CPR
* If a terminal doesn't support DSR/CPR, assume it doesn't support SyncTERM fonts, either.
* Support is also disabled if term simply doesn't ignore the ESC sequence, either

core/ansi_term.js

@@ -59,8 +59,8 @@ exports.resetScreen                 = resetScreen;
 exports.normal                      = normal;
 exports.goHome                      = goHome;
 exports.disableVT100LineWrapping    = disableVT100LineWrapping;
-exports.setSyncTERMFont             = setSyncTERMFont;
+exports.setSyncTermFont             = setSyncTermFont;
-exports.getSyncTERMFontFromAlias    = getSyncTERMFontFromAlias;
+exports.getSyncTermFontFromAlias    = getSyncTermFontFromAlias;
 exports.setSyncTermFontWithAlias    = setSyncTermFontWithAlias;
 exports.setCursorStyle              = setCursorStyle;
 exports.setEmulatedBaudRate         = setEmulatedBaudRate;
@@ -320,7 +320,7 @@ const FONT_ALIAS_TO_SYNCTERM_MAP = {
 
 };
 
-function setSyncTERMFont(name, fontPage) {
+function setSyncTermFont(name, fontPage) {
     const p1 = miscUtil.valueWithDefault(fontPage, 0);
 
     assert(p1 >= 0 && p1 <= 3);
@@ -333,13 +333,13 @@ function setSyncTERMFont(name, fontPage) {
     return '';
 }
 
-function getSyncTERMFontFromAlias(alias) {
+function getSyncTermFontFromAlias(alias) {
     return FONT_ALIAS_TO_SYNCTERM_MAP[alias.toLowerCase().replace(/ /g, '_')];
 }
 
 function setSyncTermFontWithAlias(nameOrAlias) {
-    nameOrAlias = getSyncTERMFontFromAlias(nameOrAlias) || nameOrAlias;
+    nameOrAlias = getSyncTermFontFromAlias(nameOrAlias) || nameOrAlias;
-    return setSyncTERMFont(nameOrAlias);
+    return setSyncTermFont(nameOrAlias);
 }
 
 const DEC_CURSOR_STYLE = {

core/art.js

@@ -351,12 +351,13 @@ function display(client, art, options, cb) {
     });
 
     let initSeq = '';
+    if (client.term.syncTermFontsEnabled) {
         if(options.font) {
             initSeq = ansi.setSyncTermFontWithAlias(options.font);
         } else if(options.sauce) {
             let fontName = getFontNameFromSAUCE(options.sauce);
             if(fontName) {
-            fontName = ansi.getSyncTERMFontFromAlias(fontName);
+                fontName = ansi.getSyncTermFontFromAlias(fontName);
             }
 
             //
@@ -367,7 +368,8 @@ function display(client, art, options, cb) {
             //
             if(fontName && client.term.currentSyncFont != fontName) {
                 client.term.currentSyncFont = fontName;
-            initSeq = ansi.setSyncTERMFont(fontName);
+                initSeq = ansi.setSyncTermFont(fontName);
+            }
         }
     }
 

core/client_term.js

@@ -21,6 +21,8 @@ function ClientTerminal(output) {
     //  convert line feeds such as \n -> \r\n
     this.convertLF      = true;
 
+    this.syncTermFontsEnabled = false;
+
     //
     //  Some terminal we handle specially
     //  They can also be found in this.env{}

core/connect.js

@@ -12,6 +12,28 @@ const async     = require('async');
 
 exports.connectEntry    = connectEntry;
 
+const withCursorPositionReport = (client, cprHandler, failMessage, cb) => {
+    let giveUpTimer;
+
+    const done = function(err) {
+        client.removeListener('cursor position report', cprListener);
+        clearTimeout(giveUpTimer);
+        return cb(err);
+    };
+
+    const cprListener = (pos) => {
+        cprHandler(pos);
+        return done(null);
+    };
+
+    client.once('cursor position report', cprListener);
+
+    //  give up after 2s
+    giveUpTimer = setTimeout( () => {
+        return done(Errors.General(failMessage));
+    }, 2000);
+}
+
 function ansiDiscoverHomePosition(client, cb) {
     //
     //  We want to find the home position. ANSI-BBS and most terminals
@@ -19,29 +41,21 @@ function ansiDiscoverHomePosition(client, cb) {
     //  think of home as 0,0. If this is the case, we need to offset
     //  our positioning to accommodate for such.
     //
-
-
     if( !Config().term.checkAnsiHomePosition ) {
         // Skip (and assume 1,1) if the home position check is disabled.
         return cb(null);
     }
 
-    const done = (err) => {
+    withCursorPositionReport(
-        client.removeListener('cursor position report', cprListener);
+        client,
-        clearTimeout(giveUpTimer);
+        pos => {
-        return cb(err);
+            const [h, w] = pos;
-    };
-
-    const cprListener = function(pos) {
-        const h = pos[0];
-        const w = pos[1];
 
             //
             //  We expect either 0,0, or 1,1. Anything else will be filed as bad data
             //
             if(h > 1 || w > 1) {
-            client.log.warn( { height : h, width : w }, 'Ignoring ANSI home position CPR due to unexpected values');
+                return client.log.warn( { height : h, width : w }, 'Ignoring ANSI home position CPR due to unexpected values');
-            return done(Errors.UnexpectedState('Home position CPR expected to be 0,0, or 1,1'));
             }
 
             if(0 === h & 0 === w) {
@@ -51,15 +65,10 @@ function ansiDiscoverHomePosition(client, cb) {
                 client.log.info('Setting CPR offset to 1');
                 client.cprOffset = 1;
             }
-
+        },
-        return done(null);
+        'ANSI query home position timed out',
-    };
+        cb
-
+    );
-    client.once('cursor position report', cprListener);
-
-    const giveUpTimer = setTimeout( () => {
-        return done(Errors.General('Giving up on home position CPR'));
-    }, 3000);   //  3s
 
     client.term.write(`${ansi.goHome()}${ansi.queryPos()}`);    //  go home, query pos
 }
@@ -82,56 +91,74 @@ function ansiAttemptDetectUTF8(client, cb) {
         return cb(null);
     }
 
-    let posStage = 1;
     let initialPosition;
-    let giveUpTimer;
-
-    const giveUp = () => {
-        client.removeListener('cursor position report', cprListener);
-        clearTimeout(giveUpTimer);
-        return cb(null);
-    };
-
     const ASCIIPortion = ' Character encoding detection ';
 
-    const cprListener = (pos) => {
+    withCursorPositionReport(
-        switch(posStage) {
+        client,
-            case 1 :
+        pos => {
-                posStage = 2;
-
             initialPosition = pos;
-                clearTimeout(giveUpTimer);
 
-                giveUpTimer = setTimeout( () => {
+            withCursorPositionReport(client,
-                    return giveUp();
+                pos => {
-                }, 2000);
+                    const [_, w] = pos;
-
+                    const len = w - initialPosition[1];
-                client.once('cursor position report', cprListener);
-                client.term.rawWrite(`\u9760${ASCIIPortion}\u9760`);    //  Unicode skulls on each side
-                client.term.rawWrite(ansi.queryPos());
-                break;
-
-            case 2 :
-                {
-                    clearTimeout(giveUpTimer);
-                    const len = pos[1] - initialPosition[1];
                     if(!isNaN(len) && len >= ASCIIPortion.length + 6) {  //  CP437 displays 3 chars each Unicode skull
                         client.log.info('Terminal identified as UTF-8 but does not appear to be. Overriding to "ansi".');
                         client.setTermType('ansi');
                     }
+                },
+                'Detect UTF-8 stage 2 timed out',
+                cb,
+            );
+
+            client.term.rawWrite(`\u9760${ASCIIPortion}\u9760`);    //  Unicode skulls on each side
+            client.term.rawWrite(ansi.queryPos());
+        },
+        'Detect UTF-8 stage 1 timed out',
+        err => {
+            if (err) {
+                //  bailing early
+                return cb(err);
             }
+        }
+    );
+
+    client.term.rawWrite(`${ansi.goHome()}${ansi.queryPos()}`);
+}
+
+const ansiQuerySyncTermFontSupport = (client, cb) => {
+    // If we know it's SyncTERM, then good to go
+    if (client.term.termClient === 'cterm') {
+        client.term.syncTermFontsEnabled = true;
         return cb(null);
     }
-    };
 
-    giveUpTimer = setTimeout( () => {
+    //  Some terminals do not properly ignore an unknown ESC sequence for
-        return giveUp();
+    //  setting SyncTERM style fonts. Some draw only a 'D' while others
-    }, 2000);
+    //  show more of the sequence
+    //
+    //  If the cursor remains at 1,1, they are at least ignoring it, if not
+    //  supporting it.
+    //
+    //  We also need CPR support. Since all known terminals that support
+    //  SyncTERM fonts also support CPR, this works out.
+    //
+    withCursorPositionReport(
+        client,
+        pos => {
+            const [_, w] = pos;
+            if (w === 1) {
+                // cursor didn't move
+                client.log.info('Client supports SyncTERM fonts or properly ignores unknown ESC sequence');
+                client.term.syncTermFontsEnabled = true;
+            }
+        },
+        'SyncTERM font detection timed out',
+        cb
+    );
 
-
+    client.term.rawWrite(`${ansi.goto(1, 1)}${ansi.setSyncTermFont('cp437')}${ansi.queryPos()}`);
-
-    client.once('cursor position report', cprListener);
-    client.term.rawWrite(ansi.goHome() + ansi.queryPos());
 }
 
 function ansiQueryTermSizeIfNeeded(client, cb) {
@@ -139,33 +166,26 @@ function ansiQueryTermSizeIfNeeded(client, cb) {
         return cb(null);
     }
 
-    const done = function(err) {
+    withCursorPositionReport(
-        client.removeListener('cursor position report', cprListener);
+        client,
-        clearTimeout(giveUpTimer);
+        pos => {
-        return cb(err);
-    };
-
-    const cprListener = function(pos) {
             //
             //  If we've already found out, disregard
             //
             if(client.term.termHeight > 0 || client.term.termWidth > 0) {
-            return done(null);
+                return;
             }
 
-        const h = pos[0];
-        const w = pos[1];
-
             //
             //  NetRunner for example gives us 1x1 here. Not really useful. Ignore
             //  values that seem obviously bad. Included in the set is the explicit
             //  999x999 values we asked to move to.
             //
+            const [h, w] = pos;
             if(h < 10 || h === 999 || w < 10 || w === 999) {
-            client.log.warn(
+                return client.log.warn(
                     { height : h, width : w },
                     'Ignoring ANSI CPR screen size query response due to non-sane values');
-            return done(Errors.Invalid('Term size <= 10 considered invalid'));
             }
 
             client.term.termHeight  = h;
@@ -179,16 +199,10 @@ function ansiQueryTermSizeIfNeeded(client, cb) {
                 },
                 'Window size updated'
             );
-
+        },
-        return done(null);
+        'No term size established by CPR within timeout',
-    };
+        cb
-
+    );
-    client.once('cursor position report', cprListener);
-
-    //  give up after 2s
-    const giveUpTimer = setTimeout( () => {
-        return done(Errors.General('No term size established by CPR within timeout'));
-    }, 2000);
 
     //  Start the process:
     //  1 - Ask to goto 999,999 -- a very much "bottom right" (generally 80x25 for example
@@ -223,12 +237,11 @@ function connectEntry(client, nextMenu) {
         [
             function basicPrepWork(callback) {
                 term.rawWrite(ansi.queryDeviceAttributes(0));
+                term.write('\nDetecting client features...');
                 return callback(null);
             },
             function discoverHomePosition(callback) {
-                ansiDiscoverHomePosition(client, () => {
+                return ansiDiscoverHomePosition(client, callback);
-                    return callback(null);  //  we try to continue anyway
-                });
             },
             function queryTermSizeByNonStandardAnsi(callback) {
                 ansiQueryTermSizeIfNeeded(client, err => {
@@ -254,7 +267,10 @@ function connectEntry(client, nextMenu) {
             },
             function checkUtf8IfNeeded(callback) {
                 return ansiAttemptDetectUTF8(client, callback);
-            }
+            },
+            function querySyncTERMFontSupport(callback)  {
+                return ansiQuerySyncTermFontSupport(client, callback);
+            },
         ],
         () => {
             prepareTerminal(term);

core/telnet_bridge.js

@@ -199,7 +199,8 @@ exports.getModule = class TelnetBridgeModule extends MenuModule {
                         self.client.removeListener('key press', connectionKeyPressHandler);
                         self.client.log.info(connectOpts, 'Telnet bridge connection established');
 
-                        if(self.config.font) {
+                        //  put the font back how it was prior, if fonts are enabled
+                        if(self.client.term.syncTermFontsEnabled && self.config.font) {
                             self.client.term.rawWrite(setSyncTermFontWithAlias(self.config.font));
                         }