Fix preview command sometimes not executing on Windows

src/manimShell.ts

@@ -17,6 +17,15 @@ const ANSI_CONTROL_SEQUENCE_REGEX = /(?:\x1B[@-Z\\-_]|[\x80-\x9A\x9C-\x9F]|(?:\x
  */
 const IPYTHON_CELL_START_REGEX = /^\s*In \[\d+\]:/gm;
 
+/**
+ * Regular expression to match IPython multiline input "...:"
+ * Sometimes IPython does not execute code when entering a newline, but enters a
+ * multiline input mode, where it expects another line of code. We detect that
+ * this happens and send an extra newline to run the code
+ * See: https://github.com/Manim-Notebook/manim-notebook/issues/18
+ */
+const IPYTHON_MULTILINE_START_REGEX = /^\s*\.{3}:\s+$/m;
+
 /**
  * Regular expression to match a KeyboardInterrupt.
  */
@@ -483,12 +492,13 @@ export class ManimShell {
      * 
      * @param shell The shell to execute the command in.
      * @param command The command to execute in the shell.
+     * @param useShellIntegration Whether to use shell integration if available
      */
-    private exec(shell: Terminal, command: string) {
+    private exec(shell: Terminal, command: string, useShellIntegration = true) {
         this.detectShellExecutionEnd = false;
         Logger.debug("🔒 Shell execution end detection disabled");
 
-        if (shell.shellIntegration) {
+        if (useShellIntegration && shell.shellIntegration) {
             Logger.debug(`💨 Sending command to terminal (with shell integration): ${command}`);
             shell.shellIntegration.executeCommand(command);
         } else {
@@ -657,6 +667,14 @@ export class ManimShell {
                         this.eventEmitter.emit(ManimShellEvent.IPYTHON_CELL_FINISHED);
                     }
 
+                    if (this.isExecutingCommand && data.match(IPYTHON_MULTILINE_START_REGEX)) {
+                        Logger.debug(`💨 IPython multiline detected, sending extra newline`);
+                        // do not use shell integration here, as it might send a CTRL-C
+                        // while the prompt is not finished yet
+                        // \x7F deletes the extra line ("...:") from IPython
+                        this.exec(this.activeShell, "\x7F", false);
+                    }
+
                     if (data.match(ERROR_REGEX)) {
                         Logger.debug("🚨 Error in IPython cell detected");
                         this.activeShell?.show();

src/previewCode.ts

@@ -4,9 +4,8 @@ import { ManimShell } from './manimShell';
 import { EventEmitter } from 'events';
 import { Logger } from './logger';
 
-const PREVIEW_COMMAND = `\x0C checkpoint_paste()\x1b`;
-// \x0C: is Ctrl + L
-// \x1b: https://github.com/bhoov/manim-notebook/issues/18#issuecomment-2431146809
+// \x0C: is Ctrl + L, which clears the terminal screen
+const PREVIEW_COMMAND = `\x0Ccheckpoint_paste()`;
 
 /**
  * Interactively previews the given Manim code by means of the